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Dose and diameter relationships for facial, trigeminal, and acoustic neuropathies following acoustic neuroma radiosurgery
Abstract
PURPOSE AND OBJECTIVE: To define the relationships between dose and tumor diameter for the risks of developing trigeminal, facial, and acoustic neuropathies after acoustic neuroma radiosurgery, a large single-institution experience was analyzed.
Two hundred and thirty-eight patients with unilateral acoustic neuromas who underwent Gamma knife radiosurgery between 1987-1994 with 6-91 months of follow-up (median 30 months) were studied. Minimum tumor doses were 12-20 Gy (median 15 Gy). Transverse tumor diameter varied from 0.3-5.5 cm (median 2.1 cm). The relationships of dose and diameter to the development of cranial neuropathies were delineated by multivariate logistic regression.
The development of post-radiosurgery neuropathies affecting cranial nerves V, VII, and VIII were correlated with minimum tumor dose and transverse tumor diameter (P < 0.01 for all except Dmin for VIII where P = 0.10). A comparison of the dose-diameter response curves showed the acoustic nerve to be the most sensitive to doses of 12-16 Gy and the facial nerve to be the least sensitive.
The risks of developing trigeminal, facial, and acoustic neuropathies following acoustic neuroma radiosurgery can be predicted from the transverse tumor diameter and the minimum tumor dose using models constructed from data presently available.
... 4,5,10,13,14,16,17,19 Norén, et al., 16 have prescribed doses of 25 to 35 Gy to the tumor periphery to ensure the arrest of tumor growth; however, the high-dose radiation has led to high morbidity rates because of damage to facial and trigeminal nerves. 3,[12][13][14]16 In addition, possible hearing preservation may be compromised when a higher dose is used. 3,4 The Pittsburgh group has tried to reduce the radiation dose delivered to the tumor margin of 18 to 20 Gy (1987)(1988)) to 14 to 16 Gy (in 1992). ...
... 3,[12][13][14]16 In addition, possible hearing preservation may be compromised when a higher dose is used. 3,4 The Pittsburgh group has tried to reduce the radiation dose delivered to the tumor margin of 18 to 20 Gy (1987)(1988)) to 14 to 16 Gy (in 1992). 3,4,13 There are three major reasons to decrease the margin dose. ...
... 3,4 The Pittsburgh group has tried to reduce the radiation dose delivered to the tumor margin of 18 to 20 Gy (1987)(1988)) to 14 to 16 Gy (in 1992). 3,4,13 There are three major reasons to decrease the margin dose. First, a lower dose reduces the chance of a new cranial neuropathy. ...
Object. The authors conducted a study to determine the optimal radiation dose for vestibular schwannoma (VS) and to examine the histopathology in cases of treatment failure for better understanding of the effects of irradiation.
Methods. A retrospective study was performed of 195 patients with VS; there were 113 female and 82 male patients whose mean age was 51 years (range 11–82 years). Seventy-two patients (37%) had undergone partial or total excision of their tumor prior to gamma knife surgery (GKS). The mean tumor volume was 4.1 cm ³ (range 0.04–23.1 cm ³ ). Multiisocenter dose planning placed a prescription dose of 11 to 18.2 Gy on the 50 to 94% isodose located at the tumor margin. Clinical and magnetic resonance (MR) imaging follow-up evaluations were performed every 6 months.
A loss of central enhancement was demonstrated on MR imaging in 69.5% of the patients. At the latest MR imaging assessment decreased or stable tumor volume was demonstrated in 93.6% of the patients. During a median follow-up period of 31 months resection was avoided in 96.8% of cases. Uncontrolled tumor swelling was noted in five patients at 3.5, 17, 24, 33, and 62 months after GKS, respectively. Twelve of 20 patients retained serviceable hearing. Two patients experienced a temporary facial palsy. Two patients developed a new trigeminal neuralgia. There was no treatment-related death. Histopathological examination of specimens in three cases (one at 62 months after GKS) revealed a long-lasting radiation effect on vessels inside the tumor.
Conclusions. Radiosurgery had a long-term radiation effect on VSs for up to 5 years. A margin 12-Gy dose with homogeneous distribution is effective in preventing tumor progression, while posing no serious threat to normal cranial nerve function.
... This is low compared with facial nerve neuropathy after MS. Yet the incidence of TN after VS RS varies between 0% and 29% across series (14)(15)(16)(17)(18)(19)(20)(21)(22). The lack of detailed guidelines focusing on dosimetry to avoid TN after VS RS may account for this. ...
... Dose that the cisternal portion of the Vth nerve should receive on a limited volume is 11 Gy. This dose is in the range of doses usually considered to be deleterious for cranial nerves in general (2,16,19,21). ...
... Other non-auditory complications of RS have been reported in previous studies, but these studies did not consider the analyzed variables we included, focusing on potential mechanisms of TN after RS. In addition, some of the previous studies were carried out at a time when prescribed doses were higher, dosimetry planning software did not enable all the computations we could perform in this study, and neuroimaging did not enable proper visualization of the Vth nerve (16,32). The Vth nerve is thicker than the VIIth or VIIIth nerve: for this reason, considering only maximal dose to the Vth nerve may not have been as relevant as for the other nerves. ...
Purpose:
To analyze the relationship between dosimetric characteristics and symptoms related to trigeminal neuropathy (TN) observed after radiosurgery (RS) for vestibular schwannomas (VS); to propose guidelines to optimize planification in VS RS regarding TN preservation; and to detail the mechanism of TN impairment after VS RS.
Methods and materials:
One hundred seventy-nine patients treated between 2011 and 2013 for VS RS and without trigeminal impairment before RS were included in a retrospective study. Univariate and multivariate analyses were performed to determine predictors of TN among characteristics of the patients, the dosimetry, and the VS.
Results:
There were 20 Koos grade 1, 99 grade 2, 57 grade 3, and 3 grade 4. Fourteen patients (7.8%) presented a transitory or permanent TN. Between the patients with and without TN after VS RS, there was no significant difference regarding dosimetry or VS volume itself. Significant differences (univariate analysis P<.05, Mann-Whitney test) were found for parameters related to the cisternal portion of the trigeminal nerve: total integrated dose, maximum dose, mean dose, volume of the Vth nerve (Volv), and volume of the Vth nerve receiving at least 11 Gy (VolVcist>11Gy), but also for maximal dose to the Vth nerve nucleus and intra-axial portion (Dose maxVax). After multivariate analysis, the best model predicting TN included VolVcist>11Gy (P=.0045), Dose maxVax (P=.0006), and Volv (P=.0058). The negative predictive value of this model was 97%.
Conclusions:
The parameters VolVcist>11Gy, Dose maxVax, and Volv should be checked when designing dosimetry for VS RS.
... A high rate of functional hearing preservation of 75%, absent facial palsy, and high tumour control rates (97%) were achieved with tumour marginal dose of 10 Gy. [8] Since 1987, the team from the University of Pittsburgh led by Dr. Flickinger et al. had established optimal treatment parameters for the tumour control with facial and hearing preservation. [9] The marginal tumour dose was 12-13 Gy. The actuarial 6 years tumour control rate was 98.6%, with preserved facial nerve function, trigeminal nerve function and hearing preservation rate to be 100%, 95.6% and 78.6% respectively. ...
... More recent reports suggest the primary use of GK therapy for tumours up to a certain size. [9] The technical advancements in neuroimaging have definitely contributed to the further development of GKRS. The introduction of high Tesla MRI, three-dimensional images, constructive interference in steady state and fast imaging employing steady-state acquisition clarify the contrast between the cerebrospinal fluid and the adjacent structures and make their identification much easier. ...
... Leads to high rates of trigeminal, facial and cochlear nerve damage. [9,[19][20][21]24] The Pittsburgh group experience suggests that tumour periphery dose can be safely reduced from 18-20 to 14-16 Gy. [9,16,19] The lower margin dose has fewer chances of cranial neuropathy and hearing loss as well as decreases the theoretical possibility of tumour swelling after treatment. Chung et al. ...
Vestibular schwannomas (VS) are benign tumours arising from the 8th cranial nerve. There are various treatment options for these tumours, which depend upon the tumour size and patient age. However, the surgical treatment has been the conventional method of management of these tumours, since they are frequently detected when quite large in size, especially in our country. Gamma knife radiosurgery (GKRS) is frequently reserved for young patients with small and medium-sized VS (<3 cm) and few symptoms. The tumour control dose is the most important consideration in GKRS, with higher doses having a risk for cranial nerve palsies, whereas lower doses leading to non-treatment of the tumour. The accepted tumour control dose ranges from 12 to 16 Gy among the various series with the tumour control rates of from 87% to 98% considered generally acceptable. The preservation of hearing is an issue worthwhile to be taken into account in GKRS and various series reporting this to range from 40% to 80%. The comparison between microsurgery and GKRS is still debatable because of different indications for both forms of therapies. Microsurgery is chosen for large tumours and GKRS for relatively smaller tumours.
... In GKRS for VS, the prescribed dose is 11-13 Gy at 50% isodose. Any dose exceeding 13 Gy is associated with a higher risk of neuropathy, especially with the loss of functional hearing (70,71). In their short-term follow-up analysis, Massager et al. identified that patients with lower intracanalicular tumor volume (<100 mm 3 ) and lower integrated dose delivered to the intracanalicular part of the tumor (<1.5mJ) had a higher chance of maintaining their hearing at pretreatment levels (72). ...
... The vestibular nerve is sensory and is a radiosensitive structure. Contrary to the facial nerve (motor in nature), the vestibular nerve has a high chance of injury after radiation therapy (71). While treating VS, a radio surgeon must spare the surrounding organs at risk, such as the basal turn of the cochlea and brain stem (74). ...
... One of the three patients who were treated with repeat GKRS developed facial numbness and paresthesia. Trigeminal sensory disturbances or deafferentation pain were observed in Ford, 1998 [21] Excellent-free of cluster headache and took minimal or no medication Good-CHs were reduced in severity and frequency by 50% and preventive and abortive medications were continued Fair-improvement of 25% or less, with continued use of preventive and abortive medications Failure-no relief at all McClelland, 2006 [2] Excellent-free of cluster headache and took minimal or no medication Good-CHs were reduced in severity and frequency by 50% and prophylactic medications were continued Fair-improvement of 25% or less, with continued use of prophylactic medications Failure-no relief at all Donnet, 2006 [1] Excellent-free of cluster headache and took minimal or no medication Good-CHs were reduced in severity and frequency by 50% and prophylactic medications were continued Fair-improvement of 25% or less, with continued use of prophylactic medications Failure-no relief at all Ott, 2010 [12] NS Kano, 2011 [4] BNI score: Grade I (pain free, no use of medication), grade II (occasional pain but off medication), grade IIIa (no pain and continued use of medication required), grade IIIb (some pain, controlled with medication), grade IV (pain improved but not adequately controlled on medication), grade V (no pain relief whatsoever) BNI grades I-IIIb representing favorable pain relief, whereas BNI grades IV and V were defined as treatment failures Content courtesy of Springer Nature, terms of use apply. Rights reserved. ...
... In patients treated with combined targeting of the TN and SPG, the simultaneous ablation of two different points along the trigeminal pathways may also have had a role in causing these excessive sensory disturbances. Finally, in earlier studies, the use of targeting techniques that expose an increased volume and length of the TN or the brainstem to high radiation dose, as compared to contemporary methods, may have contributed to such a high rate of sensory disturbances (Flickinger effect) [21]. As an example, in the study of McClelland et al., an 8-mm collimated isocenter was used to target the trigeminal REZ in 3 patients and a high rate of trigeminal disturbances was observed [10]. ...
Cluster headache (CH) is a severe trigeminal autonomic cephalalgia that, when refractory to medical treatment, can be treated with Gamma Knife radiosurgery (GKRS). The outcomes of studies investigating GKRS for CH in the literature are inconsistent, and the ideal target and treatment parameters remain unclear. The aim of this systematic review is to evaluate the safety and the efficacy, both short and long term, of GKRS for the treatment of drug-resistant CH. A systematic review of the literature was performed to identify all clinical articles discussing GKRS for the treatment of CH. The literature review revealed 5 studies describing outcomes of GKRS for the treatment of CH for a total of 52 patients (48 included in the outcome analysis). The trigeminal nerve, the sphenopalatine ganglion, and a combination of both were treated in 34, 1, and 13 patients. The individual studies demonstrated initial meaningful pain reduction in 60–100% of patients, with an aggregate initial meaningful pain reduction in 37 patients (77%). This effect persisted in 20 patients (42%) at last follow-up. Trigeminal sensory disturbances were observed in 28 patients (58%) and deafferentation pain in 3 patients (6%). Information related to GKRS for CH are limited to few small open-label studies using heterogeneous operative techniques. In this setting, short-term pain reduction rates are high, whereas the long-term results are controversial. GKRS targeted on the trigeminal nerve or sphenopalatine ganglion is associated to a frequent risk of trigeminal disturbances and possibly deafferentation pain.
... While cochlear dose is one of many factors considered, so is the dose received by the relatively radiosensitive vestibulocochlear nerve. 31 Compared to fractionation, single fraction SRS regimens have higher BED delivered to the nerve near the tumor, accelerating vestibulocochlear dysfunction. 32 Cochlear constraints alone do not account for dose received by the vestibulocochlear nerve, and larger tumors will have longer length of nerve treated. ...
... 32 Cochlear constraints alone do not account for dose received by the vestibulocochlear nerve, and larger tumors will have longer length of nerve treated. 31 The reader's cochlear constraints as the sole tool to hearing preservation should be interpreted with significant caution, as the reader fails to address the vestibulocochlear nerve; and as discussed above, both the cochlea and vestibulocochlear nerve benefit from fractionation. ...
... Additional experience with intracranial SRS dose de-escalation to 12-13 Gy in 1 fraction was found to reduce toxicity while maintaining excellent rates of tumor control. 6,11,14 Contemporary reports of outcomes with long-term follow-up and use of lower-dose spinal SBRT in patients with benign tumors have been limited. 15,19 Thus, we aimed to assess the long-term outcomes in patients after spinal SBRT for benign tumors. ...
... 3,5,8,17,18 A greater understanding of the natural history and responsive nature of most benign intracranial lesions has prompted a de-escalation of prescribed SRS doses with similar excellent rates of local control and further avoidance of treatmentrelated toxicity. 6,11,14 The majority of modern series to date have included a large spectrum of dose schedules without a comparison of outcomes between each of them. 3,5,8,17,18 The results of our analysis revealed no significant patient characteristic that was predictive of receiving high-or low-dose SBRT, and we found that patients were less like-ly to receive a high dose when the TrueBeam or Synergy S platform was used (Table 3). ...
OBJECTIVE
Akin to the nonoperative management of benign intracranial tumors, stereotactic body radiation therapy (SBRT) has emerged as a nonoperative treatment option for noninfiltrative primary spine tumors such as meningioma and schwannoma. The majority of initial series used higher doses of 16–24 Gy in 1–3 fractions. The authors hypothesized that lower doses (such as 12–13 Gy in 1 fraction) might provide an efficacy similar to that found with the dose de-escalation commonly used for intracranial radiosurgery to treat acoustic neuroma or meningioma and with a lower risk of toxicity.
METHODS
The authors identified 38 patients in a prospectively maintained institutional radiosurgery database who were treated with definitive SBRT for a total of 47 benign primary spine tumors between 2004 and 2016. SBRT consisted of 9–21 Gy in 1–3 fractions using the CyberKnife (n = 11 [23%]), Synergy S (n = 21 [45%]), or TrueBeam (n = 15 [32%]) radiosurgery platform. For a comparison of SBRT doses, patients were dichotomized into 1 of 2 groups (low-dose or high-dose SBRT) using a cutoff biologically effective dose (BED 10Gy ) of 30 Gy. Tumor control was calculated from the date of SBRT to the last follow-up using Kaplan-Meier survival analysis, with comparisons between groups completed using a log-rank method. To account for potential indication bias, a propensity score analysis was completed based on the conditional probabilities of SBRT dose selection. Toxicity was graded using Common Terminology Criteria for Adverse Events version 4.0 with a focus on grade 3+ toxicity and the incidence of pain flare.
RESULTS
For the 38 patients, the most common histological findings were meningioma (15 patients), schwannoma (13 patients), and hemangioblastoma (7 patients). The median age at SBRT was 58 years (range 25–91 years). The 47 treated lesions were located in the cervical (n = 18), thoracic (n = 19), or lumbosacral (n = 10) spine. Five (11%) lesions were lost to follow-up after SBRT. The median follow-up duration for the remaining 42 lesions was 54 months (range 1.2–133 months). Six (16%) patients (with a total of 8 lesions) experienced pain flare after SBRT; no significant predictor of pain flare was identified. No grade 3+ acute- or late-onset complication was noted. The 5-year local control rate was 76% (95% CI 61%–91%). No significant difference in local control according to dose, fractionation, previous radiation, surgery, tumor histology, age, treatment platform, planning target volume, or spine level treated was found. The 5-year local control rates for low- and high-dose treatments were 73% (95% CI 53%–93%) and 83% (95% CI 61%–100%) (p = 0.52). In propensity score–adjusted multivariable analysis, no difference in local control was identified (HR 0.30, 95% CI 0.02–5.40; p = 0.41).
CONCLUSIONS
Long-term follow-up of patients treated with SBRT for benign spinal lesions revealed no significant difference between low-dose (BED 10Gy ≤ 30) and high-dose SBRT in local control, pain-flare rate, or long-term toxicity.
... Pour Nooebehesht, l'IRM est même meilleure que le scanner ou l'angiographie pour la détermination du volume de la MAV. Le fait de réaliser une balistique de traitement d'un schwannome vestibulaire en fonction des données scanner était un facteur de mauvais pronostique d'après les études multivariées en terme de perte de l'audition (P<0,006) 17, (60% vs 32% p<O,OOl) 18 de complications trigéminales (36% vs 8% p<O,OOOl) ou faciales (27% vs 8% p<O,OOOl) 18 par rapport aux patients traités avec une balistique définie selon des données d'IRM . Des méthodes de fusion d'image entre scanner et IRM ont été proposées afin de se prémunir d'éventuelles erreurs de localisations à l'IRM liées à des artéfacts dus à des distorsions du champ magnétique (qui ont une médiane de 4mm 19,20). ...
... La radiothérapie d'encéphale in-toto a délivré 40 Gy en 20 fractions et a été complétée par une dose de 10 Gy en 5 fractions au lit tumoral. La radiochirurgie a délivré une dose médiane de 21 Gy (14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27). ...
Matériel et Méthodes : de septembre 1992 à décembre 1999, 167 pts ont été traités par radiochirugie en dose unique par un accélérateur linéaire. Les indications étaient une malformation artério-veineuse (MAV) (dose périphérique moyenne de 17 Gy (10-25)) pour 118 pts, un schwannome vestibulaire (SV) (dose périphérique moyenne de 15 Gy (12-20)) pour 23 pts, un méningiome (dose périphérique moyenne de 19 Gy (15-24)) pour 7 pts, une métastase cérébrale (dose périphérique moyenne de 18 Gy (4-25)) pour 19 pts. Résultats : une guérison de la MAV a été obtenue chez 57 pts sur les 102 évalués par angiographie cérébrale (ou IRM pour 2 pts). Le seul facteur pronostique de guérison retrouvé en étude multifactorielle était le faible diamètre principal des cibles uniques de MAV(p=0 .0001 ; OR 0.79 [0.70-0.89] . Le nombre de complications précoces (#lt#3mois) transitoires était de 8. Sur les 114 pts qui ont eu un suivi supérieur à 3mois il y a eu 15 événements tardifs (7 radionécroses symptomatiques, 6 hémorragies et 2 complications non expliquées). La stabilisation a été obtenue pour 22 SV sur 23. Dix pts ont eu des complications à typed'irritation nerveuse. Il y a eu 2 décès (9%) à 11 et 13 mois chez des pts présentant une neurofibromatose de type 2. Une stabilisation a été obtenue pour les 7 méningiomes traités mais avec survenue chez 1 pt d'une radionécrose symptomatique (épilepsie). Il y a eu 9 récidives locales de métastases cérébrales sur 19. On a noté 3 complications précoces (16%) et une complication tardive (6%). La survie globale à 1 an et à 2 ans était respectivement de42% (IC95: 17-68) et 23% (0-47) selon KPL. La survie médiane était de 11 mois.
... The median maximum dose was 38 Gy . The median number of isocenters was 3 (range, [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The median 12-Gy volume, which is the total volume of tissue including the target and receiving ≥12 Gy, was 7.7 mL (range, 0.3-48.7 mL). ...
... We modeled the end point of symptomatic ARE using a previously described actuarial correction averaging method for multivariable logistic regression analysis. 15,16 Patients who developed ARE within 2 years after SRS or had >2-year follow-up were incorporated in the logistic regression model. A value of P<0.05 was used for the statistical significance. ...
... [9,10] Concurrently, the risk of facial and trigeminal neuropathy is associated with the irradiated length of CN and brainstem dose. [11][12][13][14] A few studies have reported retrospective measurement of radiation doses to some of the critical neurological structures (CNSs) such as cochleae, CN and brainstem separately during gamma knife radiosurgery (GKS) of VS. [9,10,[14][15][16] However, dosimetry data on these CNSs from a single treatment plan is rather limited to correlate with the toxicity profile. Radiosurgery treatment planning and delivery techniques of VS is still evolving and need further improvement in regards to reduction of dose to the CNSs without compromising target coverage. ...
... The Pittsburgh group demonstrated that the irradiated length of cranial nerve correspond to subsequent neuropathy. [11,12] In contrast, brainstem dose was demonstrated to be the most significant predictor of trigeminal neuropathy in studies by Foote et al., [13] Recently, Hayhurst and colleagues reported maximum dose to brainstem, trigeminal nerve and dose gradient index besides tumour volume as a predictor of adverse radiation effect (ARE) following GKS for VS. [14] The authors claimed that in those with ARE, the mean maximum brainstem and trigeminal nerve dose was 13.82 Gy and 11.96 Gy compared with 11.16 Gy and 9.12 Gy in those with no ARE. ...
Aim:
To investigate potential sparing of critical neurological structures (CNSs) during radiosurgery of vestibular schwannoma (VS) employing different techniques and dose prescription methods.
Materials and methods:
Fused CT and MRI datasets of eight patients with unilateral VS representing a wide range of target volume (0.48 to 12.08 cc; mean = 3.56 cc), shape and proximity to CNSs such as cochlea, trigeminal nerve and brainstem were re-planned employing static conformal field (SCF), dynamic conformal arc (DCA) and intensity modulated radiosurgery (IMRS) techniques. For every patient, five plans were created for a fixed margin dose of 12 Gy prescribed at 80% in three plans (SCF_80%, DCA_80%, and IMRS_80%) and 50% in another two plans (SCF_50% and DCA_50%). All plans were compared using standard dosimetric indices.
Results:
Primary goal of every plan to cover ≥99% of target volume with 12 Gy was fulfilled for all patients with minimum significant dose to target (D₉₉) ≥11.99 Gy. Best conformity index (CI Paddick = 0.62 ± 0.12) was observed in SCF_80% and DCA_80% plans whereas; sharpest dose gradient index of 3.40 ± 0.40 was resulted from DCA_50%. All five plans resulted similar maximum dose to brainstem (11.04 ± 2.23 to 11.53 ± 1.10 Gy), cochlea (9.02 ± 1.79 to 10.15 ± 1.26 Gy) and trigeminal nerve (11.55 ± 1.38 to 12.19 ± 2.12 Gy). Among 80% prescription plans, IMRS_80% reduces mean and D₅ (P < 0.05) to all CNSs. Prescription of dose at 50% isodose sharpened the dose gradient and significantly (P < 0.05) reduced mean dose and D₅ to all CNSs at the cost of target conformity (P = 0.01). Mean dose to cochlea and trigeminal nerve were least at 4.53 ± 0.86 and 6.95 ± 2.02 Gy from SCF_50% and highest at 6.65 ± 0.70 and 8.40 ± 2.11 Gy from DCA_80% plans respectively.
Conclusion:
This dosimetric data provides a guideline for choosing optimum treatment option and scope of inter institutional dosimetric comparison for further improvement in radiosurgery of Vestibular Schwannoma (VS).
... The incidences of de novo development or worsening of trigeminal neuropathy and facial palsy in contemporary studies using reduced dose GKRS are reportedly 0.9 to 5.5% and 0 to 2.7%, respectively (2,(4)(5)(6)(7)22). Since Flickinger showed a positive correlation between radiation dose and morbidities more than two decades ago (23), the advantages of using lower radiosurgical doses have been widely recognized. Reviews by Sughrue et al. (24) and Yang et al. (25) have suggested that a dose of 13 Gy or less reduces the risk of facial and trigeminal nerve complications following GKRS to treat VSs. ...
Objective:
Gamma knife radiosurgery (GKRS) is commonly used to treat vestibular schwannomas (VSs). The risk of complications from GKRS decreases at lower doses, but it is unknown if long-term tumor control is negatively affected by dose reduction.
Study design:
This was a retrospective case review and analysis of patient data.
Setting:
Tertiary referral center.
Patients:
Patients with VSs who underwent GKRS between 1990 and 2007 at the authors' institution.
Intervention(s):
The subjects were divided into two cohorts based on the prescribed doses of radiation received: a 12 Gy cohort (96 patients) with a follow-up period of 124 months and a >12 Gy cohort (118 patients) with a follow-up period of 143 months.
Main outcome measures:
Tumor control rates at 10 to 15 years, frequency of facial and trigeminal nerve complications, and hearing function.
Results:
The 10 to 15-year tumor control rates were 95% in the 12 Gy cohort and 88% in the > 12 Gy cohort, but the differences were not significant. Compared with the >12 Gy cohort, facial and trigeminal nerve deficits occurred significantly less frequently in the 12 Gy cohort, with the 10-year cumulative, permanent deficit-free rates being 2% and 0%, respectively. Multivariate analyses revealed that treatment doses exceeding 12 Gy were associated with a significantly higher risk for cranial nerve deficits. The percentage of subjects retaining pure-tone average ≤ 50 dB at the final follow-up did not significantly differ between the cohorts (12 Gy cohort, 30% and >12 Gy cohort, 33%; p = 0.823).
Conclusions:
Dose reduction to 12 Gy for GKRS to treat VSs decreased facial and trigeminal nerve complications without worsening tumor control rates.
... Also, given that total dose has previously been shown to be related to toxicity outcomes, we aimed to analyze if there were any differences in BED between SRS and fSRS. 17,18 Both BED10 (p = 0.31) and BED3 (p = 0.23) were not found to be statistically significantly different for SRS and fSRS regimens following two-sample t-test. ...
Purpose: To compare clinical outcomes following stereotactic radiosurgery (SRS) and fractionated stereotactic radiosurgery (fSRS) for vestibular schwannomas (VS).
Materials/Methods: We identified 64 VS patients from the RSSearch Patient Registry (12 treated with SRS and 52 patients treated with fSRS). Potential factors predictive of local control (LC) and toxicity were estimated using the Kaplan-Meier method, Cox proportional hazards model, and binary logistic regressions with propensity score weighting.
Results: SRS (100%) and fSRS (94.2%) resulted in similar LC (p = 0.33). fSRS was associated with a higher likelihood of experiencing toxicities (42.3% vs. 8.3%; p = 0.054 on time-to-event analysis) that was maintained following a propensity-score weighted binary logistic regression (p = 0.037) and propensity-score weighted Cox regression (p = 0.039; hazard ratio (HR) = 8.85 (95% CI: 1.1 – 70.1)).
Conclusion: In a multi-institutional analysis, we note equivalent LC but higher toxicity with fSRS compared to SRS for VS.
... Various authors have suggested that cranial nerve dysfunction, including facial paralysis, following stereotactic radiosurgery correlates strongly with minimum radiation dose as well as total radiation dose [21]. Hypofractionation has additionally been associated with a lower incidence of cranial nerve dysfunction following stereotactic radiation [22]. ...
... 24,41-43 SRS dose reductions from 13-14 to 11-12 Gy in more recent years have resulted in Ͼ90% tumor control rates and Ͻ1% risk for permanent facial nerve palsies. 44,45 Slightly lower doses of 12-13 Gy can be preferentially given to patients with serviceable hearing, and slightly higher doses of 13-14 Gy, to patients with poor hearing prognosis. 43 While hearing preservation rates of 60%-70% were initially reported, longer term follow-up studies of up to 10 years revealed progressive hearing deterioration in most patients. ...
Vestibular schwannomas are the most common cerebellopontine angle tumor. During the past century, the management goals of vestibular schwannomas have shifted from total resection to functional preservation. Current treatment options include surgical resection, stereotactic radiosurgery, and observation. Imaging has become a crucial part of the initial screening, evaluation, and follow-up assessment of vestibular schwannomas. Recognizing and understanding the management objectives, various treatment modalities, expected posttreatment findings, and complications allows the radiologist to play an essential role in a multidisciplinary team by providing key findings relevant to treatment planning and outcome assessment. The authors provide a comprehensive discussion of the surgical management, role of radiation therapy and observation, imaging differential, and pre- and posttreatment imaging findings of vestibular schwannomas.
... The authors discussed that this finding is probably not due to lower vascular density within the dorsal and lateral part compared to the ventral part, as the vascularization of the white matter is quite homogeneous [22]. Clinical data on peripheral neurons showed that sensitive nerves have a higher radiosensitivity than motor nerves [23]; therefore, the sensory quality could affect radiosensitivity too, maybe even within the diameter of the spinal cord. Besides these potential regional differences, the dosimetric factors of the spinal cord seem to be quite complex. ...
Objective
Current constraints aim to minimize the risk of radiation myelitis by the use of restrictive maximal spinal cord doses, commonly 50 Gy. However, several studies suggested that a dose–volume effect could exist. Based on these observations, we evaluated patients receiving potentially excessive doses to the spinal cord within minimal volumes. Patients and methodsPatients receiving radiotherapy between June 2010 and May 2015 using the NovalisTM (Varian, Palo Alto, CA, USA; Brainlab, Heimstetten, Germany) radiosurgery system were retrospectively analyzed. A total of 56 patients with 62 treated lesions that had been prescribed radiation doses close to the spinal cord potentially higher than the common 50 Gy 2‑Gy equivalent-dose (EQD2) constraint were selected for further analysis. Of these patients, 26 with 31 lesions had no history of previous irradiation, while 30 patients with 31 lesions had been previously irradiated within the treatment field. ResultsAccording to different dose evaluation approaches (spinal canal, spinal cord contour), 16 and 10 out of 31 primary irradiated lesions infringed constraints. For the 16 lesions violating spinal canal doses, the maximum doses ranged from 50.5 to 61.9 Gy EQD2. Reirradiated lesions had an average and median cumulative dose of 70.5 and 69 Gy, respectively. Dose drop-off was steep in both groups. Median overall survival was 17 months. No radiation myelitis or radiomorphological alterations were observed during follow-up. Conclusion
This study adds to the increasing body of evidence indicating that excessive spinal cord doses within a minimal volume, especially in a reirradiation setting with topographically distinct high-point doses, may be given to patients after careful evaluation of treatment- and tumor-associated risks.
... 8,11 A second study demonstrated that the length of the cranial nerve that was irradiated corresponded to the subsequent neuropathy. 7,18 In contrast, a final study highlighted that the brainstem radiation dose was the most significant predictor of trigeminal neuropathy. 9,11,27 Our study was slightly different because it evaluated only patients with trigeminal nerve symptoms prior to therapy and then the fate of these symptoms after treatment. ...
OBJECTIVE
The aim of this study was to evaluate the incidence, presentation, and treatment outcomes of trigeminal nerve–mediated symptoms secondary to large vestibular schwannomas (VSs) with trigeminal nerve contact. Specifically, the symptomatic results of pain, paresthesias, and numbness after microsurgical resection or stereotactic radiosurgery (SRS) were examined.
METHODS
The authors conducted a retrospective review of a database for concomitant diagnosis of trigeminal neuralgia (TN) or trigeminal neuropathy and VS between 1994 and 2014 at a tertiary academic center. All patients with VS with TN or neuropathy were included, with the exception of those patients with neurofibromatosis Type 2 and patients who elected observation. Patient demographic data, symptom evolution, and treatment outcomes were collected. Population data were summarized, and outcome comparisons between microsurgery and SRS were analyzed at last follow-up.
RESULTS
Sixty (2.2%) of 2771 total patients who had large VSs and either TN or neuropathy symptoms met inclusion criteria. The average age of trigeminal symptom onset was 53.6 years (range 24–79 years), the average age at VS diagnosis was 54.4 years (range 25–79 years), and the average follow-up for the microsurgery and SRS groups was 30 and 59 months, respectively (range 3–132 months). Of these patients, 50 (83%) had facial numbness, 16 (27%) had TN pain, and 13 (22%) had paresthesias (i.e., burning or tingling). Subsequently, 50 (83%) patients underwent resection and 10 (17%) patients received SRS.
Treatment of VS with SRS did not improve trigeminal symptoms in any patient. This included 2 subjects with unimproved facial numbness and 4 patients with worsened numbness. Similarly, SRS worsened TN pain and paresthesias in 5 patients and failed to improve pain in 2 additional patients. The Barrow Neurological Institute neuralgia and hypesthesia scale scores were significantly worse for patients undergoing SRS compared with microsurgery.
Resection alleviated facial numbness in 22 (50%) patients, paresthesias in 5 (42%) patients, and TN in 7 (70%) patients. In several patients, surgery was not successful in relieving facial numbness, which failed to improve in 17 (39%) cases and became worse in 5 (11%) cases. Also, surgery did not change the intensity of facial paresthesias or neuralgia in 6 (50%) and 3 (25%) patients, respectively. Microsurgery exacerbated facial paresthesias in 1 (8%) patient but, notably, did not aggravate TN in any patient.
CONCLUSIONS
Overall, resection of large VSs provided improved outcomes for patients with concomitant TN, facial paresthesia, and numbness compared with SRS. However, caution should be used when counseling surgical candidates because a number of patients did not experience improvement. This was especially true in patients with preoperative facial numbness and paresthesias, who frequently reported that these symptoms were unchanged following surgery.
... Similar to surgery, the risk of loss of cranial nerve functions after SRS may be proportional to the size of the treated tumor (13). Risk is also proportional to the marginal dose (11,14). ...
Acoustic neuromas are rare, benign intracranial tumours. There are a variety of treatment options, with no clear optimal management strategy and wide variation in treated outcomes. We report the outcomes from a 15 year cohort of patients treated at our centre using fractionated stereotactic radiotherapy (52.5 Gy in 25 fractions).
We analysed a retrospective case series. Patients were identified from patient records and a retrospective review of case notes and imaging reports was undertaken. We assessed tumour response using RECIST criteria and recorded toxicity. Progression-free survival was estimated using the Kaplan-Meier method. The study was conducted according to the STROBE guidelines.
In total, 93 patients were identified; 83 patients had follow-up data, with a median follow-up period of 5.7 years. The overall control rate using RECIST criteria was 92%. Data on complications were available for 90 patients, with six (7%) experiencing a reduction in hearing, one (1%) developing trigeminal nerve dysfunction and one (1%) a deterioration in facial nerve function. Other toxicities included four (4%) patients who developed hydrocephalus, requiring the placement of a shunt and one (1%) patient who developed radiation brainstem necrosis. After further evaluation this patient was deemed to have been treated within acceptable dose constraints.
These data suggest that a good control rate of acoustic neuromas is achievable using fractionated stereotactic radiotherapy to a dose of 52.5 Gy in 25 fractions. Toxicity is considered acceptable but the episode of radiation brainstem necrosis remains of concern and is the subject of further work.
Objectives Local failure of incompletely resected vestibular schwannoma (VS) following salvage stereotactic radiosurgery (SRS) using standard doses of 12 to 13 Gy is common. We hypothesized that dose-escalated SRS, corrected for biologically effective dose, would have superior local control of high-grade VS progressing after subtotal or near-total resection compared with standard-dose SRS.
Design Retrospective cohort study.
Setting Tertiary academic referral center.
Participants Adult patients treated with linear accelerator-based SRS for progressive VS following subtotal or near-total resection.
Main Outcome Measures Dose-escalated SRS was defined by a biologically effective dose exceeding a single-fraction 13-Gy regimen. Study outcomes were local control and neurologic sequelae of SRS. Binary logistic regression was used to evaluate predictors of study outcomes.
Results A total of 18 patients with progressive disease following subtotal (71%) and near-total (39%) resection of Koos grade IV disease (94%) were enrolled. Of the 18 patients, 7 were treated with dose-escalated SRS and 11 with standard-dose SRS. Over a median follow-up of 32 months after SRS, local control was 100% in the dose-escalated cohort and 91% in the standard-dose cohort (p = 0.95). Neurologic sequelae occurred in 28% of patients, including 60% of dose-escalated cohort and 40% of the standard-dose cohort (p = 0.12), although permanent neurologic sequelae were low at 6%.
Conclusions Dose-escalated SRS has similar local control of recurrent VS following progression after subtotal or near-total resection and does not appear to have higher neurologic sequalae. Larger studies are needed.
Minimizing radiation-induced normal tissue damage in the central nervous system (CNS) is a key objective and primary impetus for stereotactic radiosurgery and radiotherapy. The recently published Quantitative Analysis of Normal Tissue Effects in the Clinic (QUANTEC) study provides updated dose/volume/ outcome data on normal tissue tolerance for sixteen anatomic sites, including the CNS. Most of the data used to develop the relationship between dose, volume and normal tissue toxicity derived from large field, conventionally fractionated regimens, and quantitative dose/volume/outcome data at high doses per fraction to limited volumes is much sparser. Nonetheless, QUANTEC provides some limited recommendations for dose constraints in stereotactic radiosurgery/ radiotherapy of the CNS. This paper critically reviews the findings, recommendations and limitations of QUANTEC as they apply to radiosurgery of the CNS, as well as presenting suggestions to establish and validate clinically meaningful dose/volume/toxicity relationships in this setting.
BACKGROUND
Stereotactic radiosurgery is the principal therapeutic alternative to resecting benign intracranial tumors. The goals of radiosurgery are the long-term prevention of tumor growth, the maintenance of patient function, and the prevention of new neurological deficits or adverse radiation effects. Evaluation of long-term outcomes more than 10 years after radiosurgery is needed.
METHODS
We evaluated 285 consecutive patients who underwent radiosurgery for benign intracranial tumors between 1987 and 1992. Serial imaging studies were obtained, and clinical evaluations were performed. Our series included 157 patients with vestibular schwannomas, 85 patients with meningiomas, 28 patients with pituitary adenomas, 10 patients with other cranial nerve schwannomas, and 5 patients with craniopharyngiomas. Prior surgical resection had been performed in 44% of these patients, and prior radiotherapy had been administered in 5%. The median follow-up period was 10 years.
RESULTS
Overall, 95% of the 285 patients in this series had imaging-defined local tumor control (63% had tumor regression, and 32% had no further tumor growth). The actuarial tumor control rate at 15 years was 93.7%. In 5% of the patients, delayed tumor growth was identified. Resection was performed after radiosurgery in 13 patients (5%). No patient developed a radiation-induced tumor. Eighty-one percent of the patients were still alive at the time of this analysis. Normal facial nerve function was maintained in 95% of patients who had normal function before undergoing treatment for acoustic neuromas.
CONCLUSION
Stereotactic radiosurgery provided high rates of tumor growth control, often with tumor regression, and low morbidity rates in patients with benign intracranial tumors when evaluated over the long term. This study supports radiosurgery as a reliable alternative to surgical resection for selected patients with benign intracranial tumors.
Vestibular schwannoma (VS) is a benign neoplasm of Schwann cell origin. It occurs predominantly on the vestibular division of the eighth cranial nerve at the transition with oligodendroglia and at or within the internal auditory meatus. Rarely, tumors arise from cochlear division of the VIII nerve. This slow-growing tumor can become rather large without symptoms other than tinnitus, hearing loss, and/or unsteadiness. Modern neuroimaging permits early-stage tumor diagnosis. The evolution of VS surgical therapy is the illustration of the history of modern neurosurgery.
Object
Stereotactically guided radiosurgery is one of the primary treatment modalities for patients with acoustic neuromas (vestibular schwannomas). The goal of radiosurgery is to arrest tumor growth while preserving neurological function. Patients with acoustic neuromas associated with neurofibromatosis Type 2 (NF2) represent a special challenge because of the risk of complete deafness. To better define the tumor control rate and long-term functional outcome, the authors reviewed their 10-year experience in treating these lesions.
Methods
Forty patients underwent stereotactic radiosurgery at the University of Pittsburgh, 35 of them for solitary tumors. The other five underwent staged procedures for bilateral lesions (10 tumors, 45 total). Thirteen patients (with 29% of tumors) had undergone a median of two prior resections. The mean tumor volume at radiosurgery was 4.8 ml and the mean tumor margin dose was 15 Gy (range 12–20 Gy).
The overall tumor control rate was 98%. During the median follow-up period of 36 months, 16 (36%) tumors regressed, 28 (62%) remained unchanged, and one (2%) grew. In the 10 patients for whom more than 5 years of clinical and neuroimaging follow-up results were available (median 92 months), five tumors were smaller and five remained unchanged. Surgical resection was performed in three patients (7%) after radiosurgery; only one showed radiographic evidence of progression. Useful hearing (Gardner-Robertson Class I or II) was preserved in six (43%) of 14 patients and this rate improved to 67% after modifications made in 1992. Normal facial nerve function (House-Brackmann Grade 1) was preserved in 25 (81%) of 31 patients. Normal trigeminal nerve function was preserved in 34 (94%) of 36 patients.
Conclusions
Stereotactically guided radiosurgery is a safe and effective treatment for patients with acoustic tumors in the setting of NF2. The rate of hearing preservation may be better with radiosurgery than with other available techniques.
High-dose radiation therapy for the treatment of head-and-neck tumors, including those of the central nervous system or acoustic schwannomas, can damage components of the auditory system.
Radiation-induced morbidities to all parts of the auditory system, including external, middle, and inner ear, can occur (e.g. external otitis, cochlear-associated hearing loss), and their incidence/severity is radiation dose-related (both total dose and fraction size).
Timing can be variable and be acute, chronic, and delayed.
The degree of morbidity varies from mild to severe; some are easily manageable while others are irreversible and require rehabilitation.
Chemotherapy can independently cause damage to the cochlea, and be additive to radiation-induced injury; evidence for synergism is lacking.
Controversy exists as to whether traditionally fractionated radiation therapy is safer than hypofractionated radiation therapy when used to treat vestibular schwannomas.
Severe deficiencies in vitamins B1 (thiamine), B6 (pyridoxine), B9 (folate), and B12 cobalamin cause often reversible neurological damage, but their role in development, aging, and dementia are less well established. There is plenty of experimental evidence that thiamine deficiency causes anterograde amnesia in both humans and animals as a result of diencephalic lesions. However, it remains to be determined whether memory functions can be improved with thiamine supplements in young or aged subjects. There is preliminary evidence indicating that thiamine supplements are of value in accelerating information processing. Folate affects myelination in mature and developing organisms. Like thiamine deficiency, folate deficiency causes learning deficits in animals and neuropsychological disorders in humans. Folate replacement therapy is effective in cases when more folate enters the brain and blood levels are low. Subnormal folate and the consequent rise in homocysteine levels are related to poorer cognition, the associations being stronger in non-demented than demented subjects and in specific rather than global evaluations of cognitive function. Like folate deficiency, vitamin B6 deficiency is associated with myelin loss throughout the life-span. However, unlike folate, there is insufficient evidence linking vitamin B6 levels with age-related cognitive decline. Like B6 and B9 deficiencies, vitamin B12 deficiency damages myelin sheaths throughout the lifespan. Like folate, vitamin B12 is associated with specific cognitive abilities in the normal elderly population. However, the evidence linking vitamin B12 administration with cognitive benefits appears insufficient in either demented or non-demented subjects. There is meager evidence of cognitive benefits in Alzheimer's disease or normal aging after the administration of multiple B vitamins. However, such treatment appears to benefit children, though perhaps mostly poorly fed ones. Negative results of B vitamin supplements may be caused by not isolating subjects with marginally low levels of B vitamins, by too short a treatment period, or by overdosing.
It has been long since cerebral arteriovenous malformation (AVM) could be cured by gamma radiosurgery. In this study, it has been found that the complete obliteration of AVM by radiosurgery is depended on the factors such as the size of the nidus, the marginal dose, the location and the age of patients. It is also true that higher the marginal dose, higher the obliteration rate and also higher the risk of radiation injury. Therefore the marginal dose has to be limited by the radiosensitivity (tolerance) of surrounding brain, which means the obliteration rate is largely dependent on the location of AVM. The definition of the eloquent area of AVM by microsurgery is based upon the anatomical and functional importance of the brain. However, the eloquency in radiosurgery is different in that it depends upon radiosensitivity of the surrounding brain around AVM. From this definition, the most eloquent area by radiosurgery is brain around the optic pathway, followed by cochlear nerve, other cranial nerves, brain stem and basal ganglia-thalamus.
We evaluated the results of Gamma Knife radiosurgery for petroclival meningioma in 50 patients (11 males and 39 females). The mean of the patients' age was 55.5 (range: 15 to 79) years old. Stereotactic radiosurgery was performed as a primary treatment in 29 patients. Twenty-one patients had undergone one to five prior resections. Tumors were located at the clivus in 2 patients. In the other 48 cases, tumors were located around the petrous apex or spread over the petro-clival region. Seventeen of the 48 tumors extended into the cavernous sinus. The mean tumor volume was 14.9 (range: 0.7 to 75) ml. The mean maximum dose was 27.2 (range: 18 to 35.7) Gy and the mean tumor margin dose was 13.6 (range: 8.1 to 25) Gy. In a median follow-up period of 36 (range: 6 to 112) months, 20 tumors (40%) decreased in size and 27 tumors (54%) remained unchanged. Only 3 tumors (6%) had radiographic evidence of progression in the treated part of the tumor. Surgical resection was performed in 3 patients after radiosurgery. In 1 patient, a second radiosurgery and then surgical resection was done. A second radiosurgery was also performed in 4 other patients. In 2 of these 4 patients, the second radiosurgery was done for tumor relapse outside the treatment field. The overall tumor control rate was 94%. Cranial nerve deficits without the evidence of tumor growth developed in only 3 patients (6%). Stereotactic radiosurgery was safe and effective in the management of patients with petroclival meningiomas, despite of the proximity of the tumors to critica neural and vascular structures.
Objective:
Head and neck tumors are a heterogeneous group and often invade the skull base. Various radiation techniques can be used for these tumors when surgery is unavailable. This study investigated the indications for gamma knife radiosurgery (GKRS) in benign head and neck tumors.
Methods:
Thirty-seven lesions in 35 patients were treated with GKRS for schwannoma, juvenile nasal angiofibroma, choroidal hemangioma and pleomorphic adenoma. The median follow-up period was 43.0 months (range, 12.2-174.1 months).
Results:
Tumor control was achieved in 35 of 37 lesions (94.6%) at last follow-up after GKRS. Thirty-four lesions (91.9%) decreased, 1 lesion (2.7%) remained stable and 2 lesions (5.4%) increased in size. Clinically, 15 cases (40.5%) showed improvement, 17 cases (45.9%) were stable, 1 case (2.7%) experienced deterioration and 4 cases (10.8%) developed new symptoms. Four of the 5 cases that exhibited deterioration or new symptoms eventually improved.
Conclusion:
GKRS is a reasonable alternative to surgery that can effectively control tumor growth and preserve functions of the head and neck in primary, residual or recurrent benign head and neck tumors.
Despite their benign pathology, acoustic neuromas remain a clinically challenging posterior fossa tumor frequently resulting in hearing loss, tinnitus, vestibular dysfunction, and diminished quality of life. Although advances in microsurgical technique have reduced operative morbidity, a growing number of patients are electing to pursue definitive treatment nonsurgically with stereotactic radiation with outcomes reflecting excellent tumor control and cranial nerve preservation. While stereotactic radiosurgery (SRS) remains the most widely practiced method of stereotactic radiation, an increasing assemblage of institutions have adopted techniques involving fractionation in an effort to improve functional hearing preservation and reduce the morbidity associated with irradiation of large acoustic neuromas. This chapter is devoted to the method of fractionated stereotactic radiotherapy (FSR) for the treatment of acoustic neuromas with a discussion of the radiobiological advantages it provides for preservation of cranial nerve function.
Acoustic schwannomas are benign tumors of the 8 cranial nerve sheath that can affect function of the fifth, seventh, and eighth cranial nerves as well as compress the brainstem. Careful detailed assessment with long observations times is needed with these slow-growing tumors to detect recurrence/progression or complications whenever observation, surgery, or radiation treatment is used for management. Management choices for these tumors have evolved and been refined considerably since the introduction of radiosurgery. This chapter reviews the use of radiosurgery in the management of acoustic schwannomas and covers background information necessary for understanding the optimal management of patients with these tumors.
Facial paralysis following acoustic neuroma (AN) resection can be devastating, but timely and strategic intervention can minimize the resulting facial morbidity. A central strategy in reanimating the paralyzed face after AN resection is to restore function of the native facial muscles using available facial nerves or repurposed cranial nerves, mainly the hypoglossal or masseter nerves. The timing of reinnervation is the single most influential factor that determines outcomes in facial reanimation surgery. The rate of recovery of facial function in the first 6 months following AN resection may be used to predict ultimate facial function. Patients who show no signs of recovery in the first 6 months, even when their facial nerves are intact, recover poorly and are candidates for early facial reinnervation. With delay, facial muscles become irreversibly paralyzed. Reanimation in irreversible paralysis requires the transfer of functional muscle units such as the gracilis or the temporalis muscle tendon unit.
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Vestibular schwannomas (VS) comprise 8% of all intracranial tumors and 90% of cerebellopontine angle and internal auditory canal neoplasms. Secondary to the widespread adoption of screening protocols for asymmetrical hearing loss and the increasing use of advanced imaging, the number of VS diagnosed each year continues to rise, while the average size has declined. Microsurgery remains the treatment of choice for large tumors, however the management of small- to medium-sized VS remains highly controversial with options including observation, radiotherapy, or microsurgery. Within this chapter, the authors provide an overview of the contemporary management of VS, reviewing important considerations and common controversies.
Copyright © 2015 Elsevier Inc. All rights reserved.
A 79-year-old man presented with progressive right facial nerve palsy (FNP). He had pulmonary adenocarcinoma for 12 years and was treated with chemotherapy consisting of carboplatin plus paclitaxel. Neither an intracranial tumor nor cancer cells were detected in the brain image and the cerebrospinal fluid at the onset of FNP. Analysis of a second lumbar puncture demonstrated meningeal carcinomatosis 2 months after the first appearance of FNP symptoms, and the patient’s hearing subsequently became impaired and deteriorated. The patient was transferred to another hospital for end-of-life care 7 months after the first symptoms of FNP. This is a rare case of FNP caused by meningeal carcinomatosis and unusual because FNP preceded impaired hearing.
Objective
To evaluate the effectiveness and long-term outcome of Gamma Knife radiosurgery (GKRS) for tiny vestibular schwannomas (VSs) detected by three-dimensional fast imaging employing steady-state acquisition magnetic resonance (3D-FIESTA MR).
Materials and methods
Between January and December 2004, 3D-FIESTA MR of the brain was performed in patients who had physical health examinations at the Buddhist Tzu Chi General Hospital (Hualien, Taiwan). Tiny intracanalicular VSs (defined as a tumor volume < 0.5 cm2) was detected in 13 patients (8 women and 5 men). The mean age of the patients was 60 years (range, 45–84 years). Hearing function was graded using the Gardner–Robertson (GR) classification. Dose planning was performed on intraoperative stereotactic contrast-enhanced images using multiple 4-mm isocenters. The mean tumor volume was 0.098 cm2 (range, 0.013–0.4 cm2). The mean margin dose was 12.4 Gy (range, 11–14 Gy), and the isodose line was set at a mean of 53.8% (range, 50–70%).
Results
Twelve patients had GR Grade I or II hearing before GKRS, and GR I or II hearing was maintained in 11 patients. Facial and trigeminal nerve functions were preserved in all patients. The tumor control rate was 100% at a mean follow-up period of 9.8 ± 1.1 years (range, 76–126 months). One patient developed acute vertigo 1 day after GKRS, which subsided after short-term use of steroids and did not recur.
Conclusion
With the application of 3D-FIESTA, tiny VSs can be detected early. Because low-dose (12–14 Gy) GKRS is safe and effective for long-term control of the growth of tumors with acceptable preservation rate of hearing function, it may be worthwhile to use 3D-FIESTA to detect tiny VSs and treat the patients using GKRS.
Aims
To evaluate non-auditory toxicity and local control after linear accelerator stereotactic radiosurgery (SRS) for the treatment of vestibular schwannomas.
Materials and methods
The institutional policy was to use SRS for radiologically progressing vestibular schwannomas. Case notes and plans were retrospectively reviewed for all patients undergoing SRS for vestibular schwannomas between September 2002 and June 2012. All patients were surgically immobilised using a BrainLab stereotactic head frame. The treatment plan was generated using BrainLab software (BrainScan 5.03). The aim was to deliver 12 Gy to the surface of the target with no margin. Patients with a minimum of 12 months of follow-up were included for toxicity and local control assessment. Radiological progression was defined as growth on imaging beyond 2 years of follow-up. Overall local control was defined in line with other series as absence of surgical salvage.
Results
Ninety-nine patients were identified. Two patients were lost to follow-up. After a median follow-up interval of 2.4 years, the actuarial radiological progression-free survival at 3 years was 100% and overall local control was also 100%. However, two patients progressed radiologically at 3.3 and 4.5 years, respectively. Twenty-one of 97 (22%) evaluable patients suffered trigeminal toxicity and this was persistent in 8/97 (8%). Two of 97 (2%) suffered long-term facial nerve toxicity (one with associated radiological progression causing hemi-facial spasm alone). One of 97 (1%) required intervention for obstructive hydrocephalus. No statistically significant dosimetric relationship could be shown to cause trigeminal or facial nerve toxicity. However, 7/8 patients with persistent trigeminal nerve toxicity had tumours in contact with the trigeminal nerve.
Conclusions
SRS delivering 12 Gy using a linear accelerator leads to high local control rates, but only prospective evaluation will fully establish short-term toxicity. In this study, persistent trigeminal toxicity occurred almost exclusively in patients whose tumour was in contact with the trigeminal nerve.
Background: The management of tumors located at the skull base pose unique clinical challenges. Recent advances in cranial-based surgical approaches and radiation therapy, including stereotactic radiosurgery (SRS) and fractionated stereotactic radiotherapy (FSRT), have improved our ability to manage these complex tumors. Further study is required to evaluate the safety and efficacy of this technique. We present an evidence-based approach to FSRT for skull base tumors supported by analysis of the published literature. Methods: A comprehensive literature search was conducted from 1980 through December 2006. Patients with primary, residual or recurrent skull base lesions were included in this study. This database query identified 145 related publications. Based on inclusion criteria, 35 FSRT and skull base lesions related publications were identified between 2001 and 2006 by 28 different first authors in 21 different institutions. Results: A total of 1,582 patients with skull base lesions underwent FSRT, including cavernous sinus or other skull base meningiomas (776), schwannomas (208), pituitary adenomas (416), chordoma/chondrosarcoma (58), nasopharyngeal carcinoma (30), craniopharyngioma (71), cavernous hemangioma (1), and chemodectoma (22). Tumor control was 99% for meningiomas, 98% for schwannomas, 97% for pituitary adenomas, 79% for chordomas, 90% for nasopharyngeal carcinomas, 92% for craniopharyngiomas, 95% for cavernous sinus meningiomas, 91% for chemodectomas, and 100% for chondrosarcomas and cavernous hemangiomas. Toxicity was favorable, with 14% of patients developing alopecia, skin erythema, headaches, nausea, and vomiting. Only 0.8% developed late toxicity and were specific to sellar and parasellar tumors. Conclusion: With varying degrees of tumor control rate ranging from 79 to 100% in histologically different skull base tumors, 14% transient complications and 0.8% late toxicity, this analysis provides a framework within which risks and benefits of FSRT for skull base lesions should be considered in individual patients.Copyright © 2010 S. Karger AG, Basel
Vergleicht man die Inzidenzzahlen der letzten Jahre, so findet man eine große Varianz mit Angaben zwischen 9–12 pro 100 000 Einwohner pro Jahr.
Nichtmaligne Erkrankungen weisen zahlreiche Merkmale auf, die berechtigten Anlass zu ihrer Behandlung geben. Sie können invasiv und aggressiv wachsen ohne Metastasen zu setzen wie z.B. beim Desmoid
; sie können kosmetisch entstellend und funktionell sehr störend sein wie beim Keloid
oder der endokrinen Orbitopathie; teilweise können sie sogar lebensbedrohlich sein, z. B. beim therapierefraktären Hämangiom
der Leber (Kasabach-Merritt-Syndrom
) oder dem juvenilen Angiofibrom im Gesichtsbereich bei Kindern und Jugendlichen.
Objective: To analyze the preliminary experience of radiosurgery for Vestibular Schwannomas at the Pontificia Universidad Católica de Chile. Material and methods: Thefirst 17 patients with sporadic Vestibular Schwannomas treated by radiosurgery at our institution are reponed. The marginal dose used was 12 to 12.5 Gy. prescribed at the 70 or 80 isodose Une. Patients were controlled at 6, 12 and 24 months with magnetic resonance, audiometric study and clinical examination. Results: In all of the 17 patients treated a decrease tumor enhancement on MR was demonstrated. In 16 patients (94%) a pattern of central tumor necrosis was observed during the firsyear Actuaría! useful hearing was maintained in 62.5% at 2 year after treatment. Facial nerve function was maintained in all of the 15 patients with normal function at treatment (100%). Trigémina! function was maintained in all of the 14 patients (100%) with previous normal trigeminal function. The mean time to return to work or normal activities was 11.5 days after treatment Conclusions: These preliminary results are comparable with results published in the literature and reinforce the demónstrate role oí radiosurgery in the management oí vestibular schwannomas.
Objective
To evaluate the complications and sequelae of acoustic neuroma surgery, according to tumour size.
Patients and method
A retrospective analysis of 120 patients who underwent microsurgical resection of vestibular schwannomas between November 1994 and September 2006 was undertaken. Tumour size, extent of removal, preservation of facial and cochlear nerves, complications, and sequelae were considered. The degree of hearing preservation after surgery was determined by the Gardner-Robertson classification.
Results
There were 39 small (< 1.5 cm), 59 medium (1.5-3 cm), and 22 large tumours (> 3 cm). Gross total resection was accomplished in 106 cases (88.3 %). The facial nerve was anatomically and functionally preserved in 103 cases on long-term follow-up (85.4 %). The cochlear nerve was functionally preserved (Gardner-Robertson class 1 and 2) in 54.4 % of the small tumours with useful preoperative hearing. Two patients died due to postoperative complications (mortality rate, 1.6 %), and 15 (12.5 %) developed a CSF leak.
Conclusions
Despite the progress in the surgical treatment of acoustic neuromas, a considerable rate of complications and sequelae still remains. Therefore, there is a need to balance pros and cons of surgery in each patient according to the concurrent circumstances, as well as to consider other therapeutic strategies such as radiosurgery or a wait-and-see policy.
The combination of patient fixation and localization systems and computer-assisted three-dimensional treatment planning. has led to sophisticated high-precision external irradiation treatment techniques. Radiosurgery was first described 1951 by Leksell, but not realized for routine clinical use until 1971 with the design of the Gamma Knife system. In the 1980s this method was transferred to modern linear accelerators. The further development led from stereotactic single-dose convergent beam irradiation to fractionated stereotactically guided conformation radiotherapy. Steep decrease of dose allows the selective destruction of small intracranial lesions, while the surrounding brain tissue is optimally protected. Radiosurgery of arteriovenous malformations achieved complete obliteration rates from 71% up to 82% with complication rates df 3%. Local tumor control rates between 85% and 95% were obtained in the treatment of acoustic neurinoma and brain metastases. One of the most important technical advances in radiooncology is the stereotactic fractionated 3D conformation radiotherapy. It allows escalation of radiation dose to the tumor volume without increasing dose to the surrounding healthy tissue. There is a potential benefit in improving local tumor control and cure rates. Therefore, are have selected treatment results of tumors of the cranial base, optic nerve sheath meningiomas, and high-grade gliomas. As conclusion the pros and cons of each treatment method and the clinical results are discussed. In addition, fundamental aspects of radiobiology are described. For high-precision radiotherapy and radiosurgery a multidisciplinary team work is an indispensable prerequisite. This requires a close cooperation between neurosurgeons, neuroradiologists, radiooncologists, and biophysicists.
The radiation oncologist's perspective.During the last decade, stereotactic radiotherapy has widely improved in France. Thus one should study the present situation and its future trend.Quantitative need. — Considering single dose radiotherapy, there are about 900 to 1,000 cases treated per year. However, the trend towards more fractionated treatment will disturb this temporary equilibrium; thus more machine time will be necessary.Qualitative need. — Stereotactic radiotherapy is practiced by multi-disciplinary teams including physicians, physicists and scientific specialists. Radiotherapists and physicist are responsible for treatment planning and evaluation as well as for clinical and methodological research. Accordingly, they should possess computers, treatment planning systems, etc. Such teams are necessary to carry out complex irradiations.General evolution. — Fractionation of irradiation nowadays seems mandatory for most intracranial tumors except metastases and small regular arteriovenous malformations. Heterogeneity of lesion dose is related to the geometry and the physics of convergent fixed or mobile beams. It can be improved and the healthy tissue irradiation can be diminished using the multi-isocentric planning for complex lesion or with micro multi leaf collimators.Modalities of stereotactic radiotherapy according to lesion type. — For neurinomas of the acoustic nerve, fractionated stereotactic radiotherapy yields few of the complications published after single dose stereotactic radiotherapy. The same can be said for meningiomas although some series reported very few complications after single dose stereotactic radiotherapy. Solitary metastases without systemic evolution, not situated on the mid-line, are favorable candidates for palliative single dose stereotactic radiotherapy. The conjunction with total brain irradiation seems to be useful. Small arteriovenous malformations will be treated with single dose stereotactic radiotherapy, whereas voluminous and/or geometrically complex nidus could benefit from protons or photon beams modulated by micro multi leaf collimators and a few fractions.Extra-cranial stereotactic radiotherapy. — Single dose stereotactic radiotherapy and fractionated stereotactic radiotherapy will be used as boost in various situations such as massif facial and in all sorts of tumors in the body specially when lesions are close to critical organs.
Purpose: To report on the clinical outcome of LINAC-based stereotactic radiotherapy (SRT) of uveal melanomas. Additionally, a new prototype (hardware and software) for automated eye monitoring and gated SRT using a noninvasive eye fixation technique is described. Patients and Methods: Between June 1997 and March 2004, 158 patients suffering from uveal melanoma were treated at a LINAC with 6 MV (5 x 14 Gy; 5 x 12 Gy prescribed to 80% isodose) photon beams. To guarantee identical patient setup during treatment planning (CT and MRI) and treatment delivery, patients were immobilized with a BrainLAB thermoplastic mask. Eye immobilization was achieved by instructing the patient to fixate on a light source integrated into the mask system. A mini-video camera was used to provide on-line information about the eye and pupil position, respectively. A new CT and magnetic resonance (MR) compatible prototype, based on head-and-neck fixation and the infrared tracking system ExacTrac, has been developed and evaluated since 2002. This system records maximum temporal and angular deviations during treatment and, based on tolerance limits, a feedback signal to the LINAC enables gated SRT. Results: After a median follow-up of 33.4 months (range, 3-85 months), local control was achieved in 98%. Fifteen patients (9.0%) developed metastases. Secondary enucleation was performed in 23 patients (13.8%). Long-term side effects were retinopathy (n = 70; 44%), cataract (n = 30; 23%), optic neuropathy (n = 65; 41%), and secondary neovascular glaucoma (n = 23; 13.8%). Typical situations when preset deviation criteria were exceeded were slow drifts (fatigue), large sudden eye movements (irritation), or eye closing (fatigue). In these cases, radiation was reliably interrupted by the gating system. In our clinical setup, the novel system for computer-controlled gated SRT of uveal melanoma was well tolerated by about 30 of the patients treated with this system so far. Conclusion: LINAC-based SRT of uveal melanomas provides good local control. The new prototype system improves the quality of treatment and offers the possibility of movement-gated treatments. In an ongoing study, treatment-related side effects are correlated with dose levels. Such correlations can be used to further optimize linac-based SRT of uveal melanoma.
In contrast to photon irradiation, where energy deposition is distributed over a relatively large area, the physical properties of proton irradiation are such that energy deposition occurs within a small target volume. As such, proton beams represent a new platform on which specific delivery of high-dose radiation can be achieved with minimal disruption of normal tissues. Since our understanding of the radiobiology of proton radiation remains incomplete, proton beam treatment planning is based on empirical estimates of tissue effects. Despite such limitations, notable successes have been achieved in the treatment of uveal melanomas, chondrosarcomas, meningiomas, acoustic neuromas, arteriovenous malformations, malignant gliomas, and medulloblastomas.
Hintergrund: Die stereotaktische Radiochirurgie hat sich als Alternative zur Mikrochirurgie in der primären Behandlung von Akustikusneurinomen etabliert. Dennoch wird die Mikrochirurgie in den meisten Fällen als Methode der Wahl angesehen. Im Falle von Rezidivtumoren ist die Resektion erschwert und mit einem deutlich höheren Risiko von Komplikationen behaftet, so dass in diesem Fall der Stellenwert der stereotaktischen Radiochirurgie neu bewertet werden muss. Patienten und Methode: Im Zeitraum von April 1992 bis Juli 1997 wurden 135 Patienten wegen eines Akustikusneurinoms an der Neurochirurgischen Klinik der Karl-Franzens-Universität Graz mit dem γ-Knife therapiert. 12 Patienten aus diesem Kollektiv wurden wegen eines Rezidives nach ein- oder mehrmaliger mikrochirurgischer Resektion behandelt. Die Altersverteilung lag zwischen 38 und 71 Jahren, der Mittelwert bei 57 Jahren. Die Läsionsgröße variierte zwischen 10,5 und 31,2 mm. Die Dosis im Tumorzentrum betrug 22-32,5 Gy. Ergebnisse: Durch die γ-Knife-Therapie konnten alle Rezidivtumore innerhalb eines mittleren Nachuntersuchungszeitraumes von 58,8 Monaten als biologisch inaktiviert angesehen werden. Eine Tumorverkleinerung wurde in 3 Fällen (25 %) erreicht, Nekrosezonen zeigten sich bei 8 Patienten (67 %). Es traten keine zusätzlichen Hirnnervenparesen auf. Schlussfolgerungen: Die γ-Knife-Therapie erwies sich im Falle unserer 12 Patienten als sichere und effiziente Alternative zu einem neuerlichen mikrochirurgischen Vorgehen und könnte als Therapie der Wahl bei Rezidiven nach mikrochirurgischer Resektion eines Akustikusneurinoms angesehen werden.
Radiosurgery in Case of Recurrent Acoustic Neuroma or: The Smart Solution of a Surgical Problem?
Background: Stereotactic radiosurgery has proved to be an effective alternative to microsurgical resection in treatment of acoustic neuroma. Still, microsurgery is considered by many to be the therapy of choice. In case of recurrence microsurgical resection is much more difficult because of scarring and has a higher risk of complications. Therefore in cases of recurrence the role of radiosurgery needed to be evaluated. Patients and Methods: From April 1992 to July 1997 135 patients suffering from acoustic neuroma were treated at the Neurosurgical Department of the University Medical School of Graz by means of the γ-Knife. 12 patients had recurrence after a single or several microsurgical resections. The age distribution was between 38 and 71 years with a mean of 57 years. The diameter of the tumors varied between 10.5 and 31.2 mm. Results: In all 12 cases the tumors could be inactivated biologically in a mean follow-up period of 58.8 months by means of stereotactic radiosurgery. Tumor shrinkage was achieved in 3 cases (25 %), central necrotic areas were observed in 8 cases (67 %). No additional cranial nerve palsies occurred. Conclusions: Stereotactic radiosurgery has proven to be a safe and effective treatment option instead of repeated microsurgery. Stereotactic radiosurgery should be considered as the therapy of choice in cases of recurrent acoustic neuromas.
SUMMARY The radiosurgery term is defined by the treatment with only one dose of ionizing radiation of an injury. This injury must be reached in a precisely way to obtain the result desired for the effect of the radiation in this struc- ture and minimizing the amount of radiation and its effect in circumjacent tissues. The great advance of the radiosurgery is on to the computer science that made possible better examinations of image (CT, MRI, and digital angiography) besides to plan programs that rapidity and security allow to deal with more complex cases with the use of multiple isocenters.
In lifetesting, medical follow-up, and other fields the observation of the time of occurrence of the event of interest (called a death) may be prevented for some of the items of the sample by the previous occurrence of some other event (called a loss). Losses may be either accidental or controlled, the latter resulting from a decision to terminate certain observations. In either case it is usually assumed in this paper that the lifetime (age at death) is independent of the potential loss time; in practice this assumption deserves careful scrutiny. Despite the resulting incompleteness of the data, it is desired to estimate the proportion P(t) of items in the population whose lifetimes would exceed t (in the absence of such losses), without making any assumption about the form of the function P(t). The observation for each item of a suitable initial event, marking the beginning of its lifetime, is presupposed.
For random samples of size N the product-limit (PL) estimate can be defined as follows: List and label the N observed lifetimes (whether to death or loss) in order of increasing magnitude, so that one has \(0 \leqslant t_1^\prime \leqslant t_2^\prime \leqslant \cdots \leqslant t_N^\prime .\) Then \(\hat P\left( t \right) = \Pi r\left[ {\left( {N - r} \right)/\left( {N - r + 1} \right)} \right]\), where r assumes those values for which \(t_r^\prime \leqslant t\) and for which \(t_r^\prime\) measures the time to death. This estimate is the distribution, unrestricted as to form, which maximizes the likelihood of the observations.
Other estimates that are discussed are the actuarial estimates (which are also products, but with the number of factors usually reduced by grouping); and reduced-sample (RS) estimates, which require that losses not be accidental, so that the limits of observation (potential loss times) are known even for those items whose deaths are observed. When no losses occur at ages less than t the estimate of P(t) in all cases reduces to the usual binomial estimate, namely, the observed proportion of survivors.
We reviewed our early experience with the first 26 patients with acoustic neurinomas (21 unilateral, 5 bilateral) treated by stereotactic radiosurgery using the first North American 201-source cobalt-60 gamma knife. Follow-up ranged from 6 to 19 months (median, 13 months). Serial postoperative imaging showed either a decrease in tumor size (11 patients) or growth arrest (15 patients). Loss of central contrast enhancement was a characteristic change (18 patients). Seven patients had good or serviceable hearing preoperatively. In all 7 the preoperative hearing status was retained immediately after radiosurgery. At follow-up, 3 had preserved hearing, 1 had reduced hearing, and 3 had lost all hearing in the treated ear. Hearing in 1 patient that was nonserviceable preoperatively later improved to a serviceable hearing level. Delayed facial paresis developed in 6 patients, and delayed trigeminal sensory loss developed in 7 patients, none of whom had significant deficits before radiosurgery. Both facial and trigeminal deficits tended to improve within 3 to 6 months of onset with excellent recovery anticipated. Lower cranial nerve dysfunction was not observed. All 26 patients remain at their preoperative employment or functional status. At present, stereotactic radiosurgery is an alternative treatment for acoustic neurinomas in patients who are elderly, have significant concomitant medical problems, have a tumor in their only hearing ear, have bilateral acoustic neurinomas, refuse microsurgical excision, or have recurrent tumor despite surgical resection. Although longer and more extensive follow-up is required, the control of tumor growth and the acceptable rate of complications in this early experience testifies to the future expanding role of this technique in the management of selected acoustic neurinomas.
Of 37 patients with 44 intracavernous carotid artery aneurysms (ICCAAns) diagnosed between 1976 and 1988, patients with 20 aneurysms were followed without treatment for 5 months to 13 years (median, 2.4 years). Ten of the 20 ICCAAns were asymptomatic at diagnosis, and 10 were symptomatic. Three of the asymptomatic ICCAAns were symptomatic at follow-up. One of these required clipping because of a progressing cavernous sinus syndrome; the other 2 were minimally symptomatic and have not required treatment. Of the 10 initially symptomatic ICCAAns, 2 had not changed, 4 became more symptomatic, and 4 had symptomatically improved by follow-up. One patient with an ICCAAn that had not changed clinically was lost to follow-up 6 months after diagnosis. Of the 4 ICCAAns that became more symptomatic, 2 continue to be monitored, and 2 required intervention: one with detachable balloon occlusion of the aneurysm with preservation of the internal carotid artery lumen, and the other with gradual cervical internal carotid artery occlusion. The clinical course of this selected group of patients with ICCAAns suggests that the natural history of ICCAAns can be quite variable. Although clinical progression does occur, symptomatic ICCAAns also can improve spontaneously. Therapeutic intervention for asymptomatic ICCAAns should be reserved for patients with aneurysms arising at the anterior genu of the carotid siphon and/or extending into the subarachnoid space, where subarachnoid hemorrhage is most likely. Intervention for symptomatic ICCAAns should be reserved for patients with subarachnoid hemorrhage, epistaxis, severe facial or orbital pain, evidence of radiographic enlargement, progressive ophthalmoplegia, or progressive visual loss.
This paper reviews the principal English literature on hearing preservation in unilateral acoustic neuroma surgery. Seventeen case reports and 13 surgical series are included. In addition, we report ten cases of our own, two with successful hearing preservation. The purpose of this report is to study feasibility, success rate, and associated problems. Previous reports have been compared in terms of criteria that we have selected. A classification system similar to Silverstein's is used. The total number of cases under review is 621, with 221 reported successes. Cases limited to those having a unilateral acoustic neuroma, with valid supportive audiometry, were 394, with 131 successes. The approximate overall rate of success is 33%. There are five cases of hearing preservation with unilateral acoustic neuromas 3 cm or larger when supporting audiometric data are available, the largest being "4-5 centimeters." Problems included mixing of unilateral acoustic neuromas with other types of tumors and failure to include comprehensive data, particularly audiometry. We conclude 1) that hearing preservation is a reasonable goal in unilateral acoustic neuroma surgery, although the number of available candidates is relatively small and 2) that intelligent selection of patients and high quality surgical technique are the keys to success.
To assess the efficacy and toxicity of stereotactic radiosurgery using the gamma knife for acoustic neuromas.
Between January 1990 and January 1993, 36 patients with acoustic neuromas were treated with stereotactic radiosurgery using the gamma knife. The median maximum tumor diameter was 21 mm (range: 6-32 mm). Tumor volumes encompassed within the prescribed isodose line varied from 266 to 8,667 mm3 (median: 3,135 mm3). Tumors < or = 20 mm in maximum diameter received a dose of 20 Gy to the margin, tumors between 21 and 30 mm received 18 Gy, and tumors > 30 mm received 16 Gy. The dose was prescribed to the 50% isodose line in 31 patients and to the 45%, 55%, 60%, 70%, and 80% isodose line in one patient each. The median number of isocenters per tumor was 5 (range: 1-12).
At a median follow-up of 16 months (range: 2.5-36 months), all patients were alive. Thirty-five patients had follow-up imaging studies. Nine tumors (26%) were smaller, and 26 tumors (74%) were unchanged. No tumor had progressed. The 1- and 2-year actuarial incidences of facial neuropathy were 52.2% and 66.5%, respectively. The 1- and 2-year actuarial incidences of trigeminal neuropathy were 33.7% and 58.9%, respectively. The 1- and 2-year actuarial incidence of facial or trigeminal neuropathy (or both) was 60.8% and 81.7%, respectively. Multivariate analysis revealed that the following were associated with the time of onset or worsening of facial weakness or trigeminal neuropathy: (a) patients < age 65 years, (b) dose to the tumor margin, (c) maximum tumor diameter > or = 21 mm, (d) use of the 18 mm collimator, and (e) use of > five isocenters. The 1- and 2-year actuarial rates of preservation of useful hearing (Gardner-Robertson class I or II) were 100% and 41.7% +/- 17.3, respectively.
Stereotactic radiosurgery using the gamma knife provides short-term control of acoustic neuromas when a dose of 16 to 20 Gy to the tumor margin is used. Preservation of useful hearing can be accomplished in a significant proportion of patients.
Currently, microsurgical resection of acoustic neuromas by an experienced, multidisciplinary team is thought to be the treatment of choice. During the past 20 years stereotactic radiosurgery has been used as an alternative to surgical removal. To compare the results of both microsurgery and stereotactic radiosurgery, we conducted a study of 87 patients with unilateral, previously unoperated acoustic neuromas with an average diameter less than 3 cm treated by the neurosurgical service during 1990 and 1991. Preoperative patient characteristics and average tumor size were similar between the treatment groups. State of the art microsurgical or radiosurgical techniques were used by experienced surgeons in both treatment groups. The treatment groups were compared based on cranial nerve preservation, tumor control, postoperative complications, patient symptomatology, length of hospital stay, total management charges, effect on employment status, and overall patient satisfaction. Stereotactic radiosurgery was more effective in preserving normal postoperative facial function (P < 0.05), and hearing preservation (P < 0.03) with less treatment associated morbidity (P < 0.01). Effect on preoperative symptoms were similar between the treatment groups. Postoperative functional outcomes and patients' satisfaction of their tumor management were greater after stereotactic radiosurgery when compared to the microsurgical group, although they did not reach statistical significance (P = 0.07 and P = 0.10, respectively). Patients returned to independent functioning sooner after stereotactic radiosurgery (P < 0.001). Hospital length of stay and total management charges were less in the radiosurgical group (P < 0.001). When compared to microsurgical removal, stereotactic radiosurgery proved to be an effective and less costly management strategy of unilateral acoustic neuromas less than 3 cm in diameter. For many acoustic neuroma patients, stereotactic radiosurgery should be offered as an alternative management strategy.
Presentation of the experiences with 254 acoustic neurinomas, treated at the Karolinska Gamma Knife Center from 1969 to 1991, with a minimum follow-up of 12 months.
Early loss of contrast enhancement on CT or MRI was seen in 70%. Unilateral tumours showed size decrease in 55%, no change in 33%, and increase in 12%. NF 2 tumours had decrease in 33%, no change in 43%, and increase in 24%. Some degree of facial weakness was seen after 17% of treatments, but always with later improvement of function. The incidence of trigeminal neuropathy was 19%. Preservation of hearing was 77%.
Gamma knife treatment is as efficient as microsurgery, but without risk of infection, bleeding or CSF leak. It requires no hospitalisation. The patient can go back to work after a few days. It therefore should be offered as an alternative to every acoustic neurinoma patient.
Stereotactic radiosurgery (SRS) is currently being investigated for treatment of acoustic schwannomas in patients who are not good surgical candidates. The vast majority of the available data is based on gamma knife-treated patients. We present the largest series of patients treated with linear accelerator-based SRS.
Thirty-two patients with acoustic schwannomas were treated with SRS between July 1988 and February 1993; follow-up ranged from 4-59 months. Age ranged from 34-88 years (mean, 62 years). The primary presenting symptom was hearing loss in 30 patients and dementia in two patients. Indications for SRS were age > 65 years (17 patients); recurrence after surgery (13 patients); and medical infirmity (two patients). Dose to the periphery of the lesion ranged from 10-22.5 Gy (mean, 15.5 Gy) specified at the 68-90% isodose line (mean, 80%). Collimator size ranged from 12-35 mm (mean, 23 mm), indicating that the sizes of the tumors were significantly larger than those reported in most gamma knife series.
Follow-up magnetic resonance imaging (MRI) and/or computed tomography (CT) scans revealed the following at 1 year: tumor regression, 12 patients (63%); and no change, seven patients (37%). At 2 years, 11 tumors (73%) were smaller and four tumors (27%) were unchanged. At 3 years, seven patients (78%) had experienced tumor regression and two (22%) had no change. No patient experienced tumor progression after SRS. Seven patients (22%) suffered one or more treatment complications: new onset of 5th and/or 7th cranial nerve deficit (six patients), ataxia (two patients), and/or hydrocephalus necessitating VP shunt (two patients).
Linear accelerator-based SRS provides excellent short-term local control and a relatively low incidence of complications for acoustic schwannomas. Our data compare favorably with results obtained with gamma knife-based SRS. Additional follow-up will be necessary to evaluate the long-term results of treatment.
In order to evaluate the results of radiosurgery for acoustic tumors and to identify optimum treatment parameters, an analysis of tumor control, as well as incidences of hearing loss, facial and trigeminal neuropathies was undertaken. Between August 1987 and August 1991, 134 patients with 136 acoustic tumors received stereotactic gamma knife radiosurgery at the University of Pittsburgh. Median follow-up was 24 months (range: 6-56 months). Tumor volumes ranged from 0.10 to 17.00 cm3 (median = 2.75 cm3). From one to ten isocenters were utilized per tumor treated (median = 3). Minimum tumor doses varied from 12 to 20 Gy (median = 17 Gy). The 4-year actuarial tumor control rate was 89.2 +/- 6.0%. Some degree of hearing (by pure tone audiometry) was preserved in 71.0 +/- 4.4% of patients. The actuarial rates for preservation of either pretreatment hearing level or useful hearing were 34.4 +/- 6.6% and 35.1 +/- 97% respectively. Respectively, the actuarial incidences of postradiosurgery facial and trigeminal neuropathies were 29.0 +/- 4.4% and 32.9 +/- 4.5%, respectively. No significant factors affecting tumor control were identified. Multivariate analysis identified a significantly increased risk of hearing loss in patients with neurofibromatosis (p = 0.0003) as well as decreased risks of facial and trigeminal neuropathies with both decreasing tumor diameter (p = 0.001) and increasing number of isocenters treated (p = 0.003). Radiosurgery is a safe and effective treatment for acoustic neuromas with acceptable morbidity that may be lowered by the use of multiple isocenter treatment techniques and by earlier treatment of small tumors.
To test the hypothesis that length of cranial nerve irradiated is a major factor predicting the risk of cranial nerve injury following radiosurgery and to identify any other significant related treatment factors.
Ninety-two patients (93 acoustic tumors) were treated with a 201 source Cobalt-60 gamma unit from 1987 to 1990 and prospectively followed. The range of minimum tumor dose was 12-20 Gy and maximum dose 24-50 Gy. Univariate and multivariate analyses were used to evaluate any correlations between tumor measurements and treatment factors, with the development of trigeminal and facial neuropathies following radiosurgery.
The risks of trigeminal and facial neuropathy following radiosurgery were associated with the pon-petrous distance and mid porous transverse tumor diameters respectively (anatomically related to the irradiated length of cranial nerves V and VII respectively) in both univariate (p = .002 for V and p = .026 for VII) and multivariate (p = .004 for V and p = .055 for VII) analyses. Tumor volume, other tumor measurements, maximum dose, minimum tumor dose, and tumor dose inhomogeneity were not significantly related to either trigeminal or facial neuropathy in univariate and multivariate analyses.
Within a minimum tumor dose range of 12-20 Gy, the incidence of delayed trigeminal or facial neuropathy depended more on the estimated length of nerve irradiated than the tumor dose or tumor volume. In the future, the risk of delayed facial or trigeminal cranial neuropathy may be reduced significantly by performing radiosurgery when the tumor still has both a small mid-porous transverse diameter and a small pons-petrous distance.
To define changes in treatment technique for vestibular schwannoma radiosurgery and to relate them to changes in outcome, a large single institution experience was reviewed.
Two hundred seventy-three patients with unilateral vestibular schwannomas underwent Gamma knife radiosurgery: 118 with computed tomography (CT) treatment planning during 1987-1991, and 155 with magnetic resonance imaging (MR) treatment planning in 1991-1994. Mean treatment parameters differed between the CT and MR groups: minimum tumor dose (D(min)) was 17 vs. 14 Gy, number of isocenters was 3.4 vs. 5.8, and volume was 3.5 vs 2.7 cc., respectively.
The actuarial 7-year clinical tumor control rate (no requirement for surgical intervention) for the entire series was 96.4 +/- 2.3%, with a radiographic tumor control rate of 91.0 +/- 3.4%; these rates were similar for the CT and MR groups. Significantly lower rates of postradiosurgery facial, trigeminal, and auditory neuropathy were observed in the MR group compared to the CT group. Multivariate analyses found significant independent correlations of increasing rates of facial and trigeminal neuropathy with increasing transverse tumor diameter and D(min), as well as with CT treatment planning (compared to MR). Decreased hearing was similarly correlated with diameter and CT planning but not with D(min).
Changes in radiosurgery technique and the use of lower doses improved the outcome after vestibular schwannoma radiosurgery by decreasing cranial neuropathy rates. MR-based treatment planning appears to have significantly contributed to this improvement. Despite decreases in radiation dose, no change in the high rate of tumor control has yet been observed.
Hearing preservation in unilateral acoustic neuroma surgery
- Gardner
Stereotactic radiosurgery for acoustic neurinomas: early experience
- Linskey