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Prognostic variables and outcome in relation to different bleeding patterns in arteriovenous malformations

Authors:
Nazife Dinc at Friedrich Schiller University Jena
Nazife Dinc
Sae-yeon Won at University Medical Center Rostock
Sae-yeon Won
Johanna Quick at University Hospital Frankfurt
Johanna Quick
Joachim Berkefeld
Joachim Berkefeld
Joachim Berkefeld
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Abstract and Figures

Subarachnoid hemorrhage as bleeding pattern occurs rarely in ruptured arteriovenous malformations (AVM). The aim of the present study is to evaluate different bleeding patterns in hemorrhages due to an AVM and their impact on outcome in terms of risk and treatment stratification. We evaluated 158 patients with ruptured AVMs who were admitted to our neurosurgical department from 2002 to 2017. We compared different bleeding patterns, such as intracerebral hemorrhage (ICH), subarachnoid hemorrhage (SAH), or both (ICH + SAH) and evaluated predictive variables for outcome in the last follow-up. ICH was found in 48.7% of patients, isolated SAH in 20.9% of patients, and both in 30.4% of patients. The mean parenchymal blood volume was 34.5cm³. 38.6% of the patients had AVM-associated aneurysms, mostly located pre-nidal (77%). AVMs with ruptured aneurysms often resulted in ICH with SAH component (p < 0.001) and SAH pattern occurred more often infratentorial (p = 0.003). In a multivariate logistic regression model, poor clinical state on admission (WFNS IV-V) (p < 0.01), eloquence, infratentorial location (p = 0.05), and presence of ICH with SAH component (p = 0.02) were the most relevant predictors of a poor outcome after AVM rupture. Bleeding pattern in AVM hemorrhage depends on angioarchitectural and hemodynamic features and SAH component predicts outcome negatively. AVM-associated pre-nidal aneurysms may harbor a higher risk for rupture and SAH pattern when located infratentorial. Treatment decisions and risk stratifications should be considered in view of these findings.
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ORIGINAL ARTICLE
Prognostic variables and outcome in relation to different bleeding
patterns in arteriovenous malformations
Nazife Dinc
1
&Sae-Yeon Won
1
&Johanna Quick-Weller
1
&Joachim Berkefeld
2
&Volker Seifert
1
&Gerhard Marquardt
1
Received: 15 January 2019 /Revised: 12 February 2019 /Accepted: 25 February 2019 / Published online: 5 March 2019
#Springer-Verlag GmbH Germany, part of Springer Nature 2019
Abstract
Subarachnoid hemorrhage as bleeding pattern occurs rarely in ruptured arteriovenous malformations (AVM). The aim of the
present study is to evaluate different bleeding patterns in hemorrhages due to an AVM and their impact on outcome in terms of
risk and treatment stratification. We evaluated 158 patients with ruptured AVMs who were admitted to our neurosurgical
department from 2002 to 2017. We compared different bleeding patterns, such as intracerebral hemorrhage (ICH), subarachnoid
hemorrhage (SAH), or both (ICH + SAH) and evaluated predictive variables for outcome in the last follow-up. ICH was found in
48.7% of patients, isolated SAH in 20.9% of patients, and both in 30.4% of patients. The mean parenchymal blood volume was
34.5cm
3
. 38.6% of the patients had AVM-associated aneurysms,mostly located pre-nidal (77%). AVMs with ruptured aneurysms
often resulted in ICH with SAH component (p< 0.001) and SAH pattern occurred more often infratentorial (p= 0.003). In a
multivariate logistic regression model, poor clinical state on admission (WFNS IV-V) (p< 0.01), eloquence, infratentorial
location (p= 0.05), and presence of ICH with SAH component (p= 0.02) were the most relevant predictors of a poor outcome
after AVM rupture. Bleeding pattern in AVM hemorrhage depends on angioarchitectural and hemodynamic features and SAH
component predicts outcome negatively. AVM-associated pre-nidal aneurysms may harbor a higher risk for rupture and SAH
pattern when located infratentorial. Treatment decisions and risk stratifications should be considered in view of these findings.
Keywords Arteriovenous malformation .Subarachnoid hemorrhage .Hemorrhage pattern
Introduction
Outcome in hemorrhage due to an arteriovenous malforma-
tion (AVM) is infrequently devastating and depends on bleed-
ing pattern. While recent studies suggest that AVM hemor-
rhage is not as devastating as previously presumed compared
to aneurysmal subarachnoid hemorrhage (SAH), which is
more often lethal, AVM rupture tends to result in more neu-
rological deficits [1]. In addition to several negative prognos-
tic factors such as older age [2], poor initial admission state
[3], hematoma volume [4], and infratentorial location [5,6], a
subarachnoid component seems to impact outcome signifi-
cantly. Intraparenchymal hematoma is the most common
pattern in AVM-associated hemorrhage [7]. SAH due to an
AVM is described to amount 9% and literature therefore is
rare. The objective of our single-center study is to assess
how far subarachnoid component in AVM-associated hemor-
rhage impacts the final outcome negatively.
Materials and methods
Study design
The study was performed in accordance with our institutional
ethical review board. A retrospective review of patients with
ruptured brain arteriovenous malformation (AVM) who were
registered and evaluated at our neurosurgical department from
2002 to 2017 and entered into our prospectively maintained
database was carried out. The onset of hemorrhage was con-
sidered as the day at which the patient was admitted to our
emergency service. The diagnosis AVM was confirmed with
magnetic resonance imaging (MRI) or digital subtraction an-
giography (DSA). Different bleeding patterns such as
*Nazife Dinc
nazife.dinc@kgu.de
1
Department of Neurosurgery, Goethe University Hospital Frankfurt,
Schleusenweg 2-16, 60528 Frankfurt, Germany
2
Department of Neuroradiology, Goethe University Hospital,
Frankfurt, Germany
Neurosurgical Review (2019) 42:731–736
https://doi.org/10.1007/s10143-019-01091-7
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
... It can also be used for measuring depression severity [19]. It consists of 9 items, and the total score can be classified as minimal (0-4), mild (5-9), moderate (10)(11)(12)(13)(14), or severe (15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27) depressive symptoms [19]. ...
... It is remarkable that the self-proclaimed items "health" and "life satisfaction" of the QOLS were scored higher in patients with ICH, despite their shortcomings in the mRS. Treatment modality, bleeding volume and bleeding pattern neither had a significant impact on the QOLS even though in the literature, patients with subarachnoid components have higher outcome impairment [14,30,31,45]. These findings contradict the current literature concerning the impact of ICH on the QoL which could be due to several potential biases: It is possible that the unruptured AVMs are likely to be more symptomatic and tend to seek medical help and get the diagnosis compared to non-symptomatic patients who get the diagnosis after haemorrhage. ...
Long-term follow-up in patients with brain arteriovenous malformation based on the Quality of Life Scale and socioeconomic status
Article
Full-text available
  • Sep 2022
  • NEUROSURG REV
Objective Intracranial haemorrhage (ICH) is associated with permanent neurological disability resulting in deterioration of the quality of life (QoL). Our study assesses QoL in patients with ruptured arteriovenous malformation (AVM) in long-term follow-up at least five years after ICH and compares their QoL with the QoL of patient with non-ruptured AVM.Methods Using the Quality of Life Scale (QOLS), the Patient Health Questionnaire (PHQ-9) for depressive symptoms, and the socioeconomic status (SES), a prospective assessment was performed. The modified Rankin Scale (mRS) was assessed for outcome.ResultsOf 73 patients, 42 (57.5%) had ruptured (group 1) and 31 (42.5%) a non-ruptured AVM (group 2). Mean follow-up time was 8.6 ± 3.9 years (8.5 ± 4.2 years in group 1 and 8.9 ± 3.7 years in group 2). Favourable outcome (mRS 0–1) was assessed in 60 (83.3%) and unfavourable in 12 (16.7%) patients. Thirty-one of 42 patients (73.8%) in group 1 and 29 of 30 patients in group 2 (96.7%) had favourable outcomes. Mean QOLS was 85.6 ± 14.1 (group 1 86.1 ± 15.9, group 2 84.9 ± 11.4). Patients in group 1 did not show a significant difference in QoL compared to patients in group 2 (p = 0.23). Additional analyses in group 2 (rho = − 0.73; p < 0.01) and in untreated AVM patients (rho = − 0.81; p < 0.01) showed a strong correlation between QOLS and PHQ-9.Conclusion Long-term follow-up showed no difference in the QoL between patients with and without ICH caused by brain AVM. Outcome- and QoL-scores were high in both groups. Further studies are necessary to evaluate depression and anxiety symptoms in patients with AVM.
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... On physical examination, auscultation typically demonstrates a bruit, which is due to abnormally high blood flow. Pulsation is a feature of AVMs as well (72). In this patient, an ultrasound revealed a vascular malformation in the musculature of the right neck/shoulder, with a clear communication with the right common carotid artery. ...
How we approach localized vascular anomalies
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  • Apr 2021
Vascular anomalies are a group of disorders divided into two distinct subtypes: vascular tumors and vascular malformations. Vascular tumors are proliferative in nature, while malformations are non-proliferative. Simple, localized vascular malformations refer to a group of malformations that are localized to a single area of involvement. These simple malformations include capillary, lymphatic, venous, and arteriovenous malformations. The pediatric hematologist and oncologist is becoming increasingly involved in the diagnosis and management of these disorders. This review presents four cases as a means to discuss the diagnosis, clinical and imaging features, and management strategies of simple, localized vascular malformations.
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How we approach localized vascular anomalies
Article
  • Sep 2022
Vascular anomalies are a group of disorders divided into two distinct subtypes: vascular tumors and vascular malformations. Vascular tumors are proliferative in nature, while malformations are nonproliferative. Simple, localized vascular malformations refer to a group of malformations that are localized to a single area of involvement. These simple malformations include capillary, lymphatic, venous, and arteriovenous malformations. The pediatric hematologists and oncologists are becoming increasingly involved in the diagnosis and management of these disorders. This review presents four cases as a means to discuss the diagnosis, clinical and imaging features, and management strategies of simple, localized vascular malformations.
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Toll-like receptor-4 pathway as a possible molecular mechanism for brain injuries after subarachnoid hemorrhage
Article
  • Jan 2020
Subarachnoid hemorrhage (SAH) is known as an acute catastrophic neurological disease that continues to be a serious and significant health problem worldwide. The mechanisms contributing to brain injury after SAH remain unclear despite decades of study focusing on early brain injury (EBI) and delayed brain injury (DBI). Neuroinflammation is a well-recognized consequence of SAH and may be responsible for EBI, cerebral vasospasm, and DBI. Toll-like receptors (TLRs) play a crucial role in the inflammatory response by recognizing damage-associated molecular patterns derived from the SAH. TLR4 is the most studied Toll-like receptor and is widely expressed in the central nervous system (CNS). It can be activated by the extravasated blood components in myeloid differentiation primary response-88/Toll/interleukin-1 receptor-domain-containing adapter-inducing interferon-β (MyD88/TRIF)-dependent pathway after SAH. Transcription factors, such as nuclear factor-κB (NF-κB), mitogen-activated protein kinase (MAPK) and interferon regulatory factor (IRF), that regulate the expression of proinflammatory cytokine genes are initiated by the activation of TLR4, which cause the brain damage after SAH. TLR4 may therefore be a useful therapeutic target for overcoming EBI and DBI in post-SAH neuroinflammation, thereby improving SAH outcome. In the present review, we summarized recent findings from basic and clinical studies of SAH, with a primary focus on the biological characteristics and functions of TLR4 and discussed the mechanisms associated with TLR4 signaling pathway in EBI and DBI following SAH.
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Arterial aneurysms associated with arteriovenous malformations of the brain: classification, incidence, risk of hemorrhage, and treatment—a systematic review
Article
Full-text available
  • Nov 2016
  • ACTA NEUROCHIR
Background: Aneurysms associated with brain arteriovenous malformations (bAVMs) influence the natural history of these lesions and pose important therapeutic challenges. However, the epidemiology, natural history, and appropriate management of the aneurysms associated with bAVMs are not completely understood due to the paucity of large and uniform studies. We performed a systematic review of published series examining the association between aneurysms and bAVMs with the purpose of clarifying the prevalence, risk of hemorrhage, and appropriate management of these lesions. Method: PRISMA/MOOSE guidelines were followed. We conducted a comprehensive literature search of three databases (PubMed, Ovid MEDLINE, and Ovid EMBASE) on aneurysms associated with bAVMs. Only studies examining consecutive case series of aneurysms associated with bAVMs were included. From the collected studies, we extracted data regarding prevalence of bAVM-associated aneurysms, risk of aneurysm rupture in relation to bAVM location and aneurysm characteristics, and treatment-related outcomes. Results: Our systematic review included 44 articles with a total of 10,093 bAVMs. The proportion of bAVMs with an associated aneurysm was 20.2 % (95 % CI = 19.4-20.9 %). Among ruptured bAVMs with associated aneurysms, the aneurysm was the source of hemorrhage in 49.2 % (95 % CI = 43.7-54.7 %) of cases. Flow-related aneurysms were the most common source of aneurysm rupture (78.5 %, 95 % CI = 70.6-84.9 %). Infratentorial bAVM-associated aneurysms presented a higher risk of rupture (60 %, 95 % CI = 47.4-71.9 %) when compared with supratentorial lesions (29 %, 95 % CI = 21.4-38.5 %). Endovascular treatment of aneurysms associated with bAVMs had a cure rate of 80.0 % (95 % CI = 73.3-85.3 %), complication rate of 8.7 % (95 % CI = 5.5-13.1 %), and a good neurological outcome rate of 78.8 % (95 % CI = 72.5-83.9 %). Conclusions: Twenty percent of bAVMs harbored arterial aneurysms. The presence of aneurysm increases the risk of bleeding of the bAVM, especially when flow-related or infratentorially located. Aneurysms associated with bAVMs should be treated promptly. Selective endovascular treatment of bAVM-associated aneurysms appears safe and effective.
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Associated Aneurysms in Infratentorial Arteriovenous Malformations: Role of Aneurysm Size and Comparison with Supratentorial Lesions
Article
Full-text available
  • Jan 2016
Background: The natural history and treatment of brain arteriovenous malformations (AVMs) is the object of ongoing debates and discussions. To capture the entirety of these complex lesions, associated vascular pathologies, such as associated aneurysms (AAs), have to be implemented in future risk stratification models, as they are believed to represent additional risk factors for intracranial hemorrhage. The present study aims to determine AA characteristics in posterior fossa AVMs and to compare with AAs accompanying supratentorial AVMs, with special focus on aneurysm size. Methods: Patients with cerebral AVMs, treated in our department between 1990 and 2013, were analyzed retrospectively. Only patients with flow-related AAs of the feeding arteries were evaluated. Thus, patients harboring intranidal, venous or remote aneurysms were excluded. Results: Of 485 patients with cerebral AVM, 76 patients harbored an AVM of the posterior fossa. Among those, 22 individuals exhibited a total of 35 AAs (n = 8 patients with multiple AAs). Most common location of AAs was the posterior inferior cerebellar artery (n = 20, 57%) and mean AA diameter was 7.9 mm (SD 5.5). In the subgroup of patients with a single AA, mean aneurysm size in posterior fossa AVMs was with 7.8 mm (SD 6.0; range 2-25 mm) significantly larger than the mean size of AAs with supratentorial AVMs (4.8 mm, SD 3.0; range 2-20 mm; p = 0.048). Intracranial hemorrhage was found in 18 of 22 patients (82%) with infratentorial AVMs, and of these, 11 patients suffered from aneurysm rupture. In 14 patients bearing a single AA, 8 (57%) had sustained hemorrhage from aneurysm rupture. The mean diameter of AAs was as supposed in the ruptured group with 9.8 mm (SD 6.9; range 4-25 mm) significantly larger than in the unruptured AA group exhibiting a mean of 5.0 mm (SD 3.3; range 2-10 mm; p = 0.038). Patients with posterior fossa AVMs and AAs were significantly older as compared to those patients with supratentorial lesions (57.1, SD 12.6 vs. 45.8 years, SD 15.9 years; p = 0.004), which was also evident in the subgroup of patients with single AAs (55.2, SD 11.7 vs. 45.8 years, SD 14.9 years; p = 0.038). Conclusions: AAs of posterior fossa AVMs are larger in diameter than aneurysms accompanying supratentorial AVMs. AA size influences risk for hemorrhage, which, together with the high number of hemorrhagic events in posterior fossa AVMs, justifies treating these pathologies. The higher age of patients with AVMs of the posterior fossa might be one reason for larger AAs in this cohort, when compared to patients with supratentorial AVMs and AAs.
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The Effect of Flow-Related Aneurysms on Hemorrhagic Risk of Intracranial Arteriovenous Malformations
Article
  • Aug 2018
  • NEUROSURGERY
Background: Previous reports indicated an association between hemorrhagic presentation and flow-related aneurysms in arteriovenous malformation (AVM) patients. However, it remains unclear whether these flow-related aneurysms result in the hemorrhage of AVM. Objective: To characterize this hemorrhage risk using our institutional experience over 25 yr. Methods: We retrospectively reviewed records of patients at our institution diagnosed with AVM from 1990 to 2015. Patients without associated aneurysms (AVM only) and those with flow-related aneurysms (AVM-FA) were compared. Those with intranidal or unrelated aneurysms were excluded. Annual risk of AVM-related hemorrhage was calculated using the birth-to-treatment approach and compared using Poisson rate ratio test. Results: Among 526 patients, there were 457 AVM only patients and 69 with flow-related aneurysms. AVM-FA patients were older (P = .005). AVMs with flow-related aneurysms were more likely located in the cerebellar vermis and hemispheres (P = .023 and .001, respectively). Presence of flow-related aneurysms increased the risk of presentation with subarachnoid hemorrhage (P < .001). Interestingly, no significant differences in presenting hemorrhage due to AVM rupture were found (P > .356). The majority of aneurysms were untreated (69.5%), and only 8 (9.8%) had ruptured presentation. At follow-up (mean = 5.3 yr), patients with flow-related aneurysms were less likely to develop seizures (P = .004). The annual risk of AVM hemorrhage was 1.33% and 1.05% for AVM only patients and AVM-FA patients, respectively (P = .248). Conclusion: Despite increased risk of subarachnoid hemorrhage at presentation, there was no increased likelihood of rupture in AVMs with flow-related aneurysms. More studies are warranted, as clarifying the competing risks of AVM vs aneurysm rupture may be critical in determining optimal treatment strategy.
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Posterior fossa AVMs: Increased risk of bleeding and worse outcome compared to supratentorial AVMs
Article
  • Apr 2018
Infratentorial AVMs are often considered as potentially hazardous as they are thought to present more often with hemorrhage, may harbor AVM-associated aneurysms more frequently and to be associated with poor outcome. The aim of our study is to compare features of supratentorial and infratentorial AVMs. We retrospectively analyzed 316 consecutive patients with cerebral AVM presenting to our neurovascular center between 2005 and 2015. Location and angioarchitecture of the AVM including AVM-associated aneurysms, bleeding events, and outcome during follow up were analyzed. Outcome was assessed using the modified Rankin Scale (mRS) and stratified into favorable (mRS 0–2) and unfavorable (mRS 3–6). 41.6% of the patients with a supratentorial AVM (stAVM) and 69.2% of the patients with an infratentorial AVM (itAVM) were presented with a hemorrhage initially (p < .001). Patients with itAVMs were older at presentation (mean 48.1 vs. 37.9 years, p < .001). ItAVMs furthermore were smaller (95.1% <3 cm nidus-diameter, p < .001) and had lower Spetzler-Martin-Grades (p = .04). Associated aneurysms were more frequent in itAVMs (38.5% vs. 20.7%, p < .004) and were associated with an increased risk of hemorrhage at presentation (30.9% vs. 18.7%, p = .013). Outcome was poor in 10.8% of the patients with stAVM and in 28.3% of patients with itAVM (p < .001). The risk of a new hemorrhage-associated deficit was significantly higher in itAVMs (p < .001). Most posterior fossa AVMs are associated with an increased hemorrhage rate. Thus they are a predictor for poor outcome and should be treated even if unruptured to maintain good neurological function.
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Hemodynamics Associated With Intracerebral Arteriovenous Malformations: The Effects of Treatment Modalities
Article
  • Dec 2017
  • NEUROSURGERY
The understanding of the physiology of cerebral arteriovenous malformations (AVMs) continues to expand. Knowledge of the hemodynamics of blood flow associated with AVMs is also progressing as imaging and treatment modalities advance. The authors present a comprehensive literature review that reveals the physical hemodynamics of AVMs, and the effect that various treatment modalities have on AVM hemodynamics and the surrounding cortex and vasculature. The authors discuss feeding arteries, flow through the nidus, venous outflow, and the relative effects of radiosurgical monotherapy, endovascular embolization alone, and combined microsurgical treatments. The hemodynamics associated with intracranial AVMs is complex and likely changes over time with changes in the physical morphology and angioarchitecture of the lesions. Hemodynamic change may be even more of a factor as it pertains to the vast array of single and multimodal treatment options available. An understanding of AVM hemodynamics associated with differing treatment modalities can affect treatment strategies and should be considered for optimal clinical outcomes.
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Basal subarachnoid hemorrhage by rupture of arteriovenous malformation at the cerebellopontine angle: Basal SAH by rupture of AVM at CPA
Article
  • Apr 2017
  • NEUROPATHOLOGY
A man in his late forties had lived as a recluse for more than ten years. He was found dead in his room. At autopsy, subarachnoid hemorrhage (SAH) was detected at the base of the brain, which weighed 1333 g. The cerebellar tonsil was swollen. The cerebral ventricle was enlarged and filled with blood. A hematoma was observed in the upper part of the left side of the cerebellar hemisphere. The location and size of SAH in this case indicated that the rupture of a cerebral aneurysm (CA) had occurred; however, CA was not detected. A mass of blood vessels buried in the hematoma was observed at the left cerebellopontine angle (CPA). The vascular lesion showed round-shaped blood vessels as well as flat-shaped vessels with the appearance of veins, but with elastic fibers indicative of arteries. The lesion was considered to be the nidus and was 5-8 mm in size. Feeding arteries appeared to be from the anterior inferior cerebellar artery (AICA). However, the draining vein and anastomotic parts of the artery and vein were not confirmed. Based on these histopathological features, this vascular lesion was diagnosed as arteriovenous malformation (AVM). A differential diagnosis between AVM at CPA and CA is needed in order to identify the source of non-traumatic SAH.
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A proposed grading system for arteriovenous malformations
Article
  • Oct 1986
  • J NEUROSURG
✓ An important factor in making a recommendation for treatment of a patient with arteriovenous malformation (AVM) is to estimate the risk of surgery for that patient. A simple, broadly applicable grading system that is designed to predict the risk of morbidity and mortality attending the operative treatment of specific AVM's is proposed. The lesion is graded on the basis of size, pattern of venous drainage, and neurological eloquence of adjacent brain. All AVM's fall into one of six grades. Grade I malformations are small, superficial, and located in non-eloquent cortex; Grade V lesions are large, deep, and situated in neurologically critical areas; and Grade VI lesions are essentially inoperable AVM's. Retrospective application of this grading scheme to a series of surgically excised AVM's has demonstrated its correlation with the incidence of postoperative neurological complications. The application of a standardized grading scheme will enable a comparison of results between various clinical series and ...
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Increased prevalence and rupture status of feeder vessel aneurysms in posterior fossa arteriovenous malformations
Article
  • Oct 2015
  • J Neurointerv Surg
Background Posterior fossa arteriovenous malformations (AVMs) are considered to have a higher risk of poor outcome, as are AVMs with associated aneurysms. We postulated that posterior fossa malformations may be more prone to associated feeder vessel aneurysms, and to aneurysmal source of hemorrhage. Objective To examine the prevalence and hemorrhagic risk of posterior fossa AVM-associated feeder vessel aneurysms. Methods A retrospective review of AVMs was performed with attention paid to location and presence of aneurysms. The hemorrhage status and origin of the hemorrhage was also reviewed. Results 571 AVMs were analyzed. Of 90 posterior fossa AVMs, 34 (37.8%) had aneurysms (85% feeder vessel, 9% intranidal, 15% with both). Of the 481 supratentorial AVMs, 126 (26.2%) harbored aneurysms (65% feeder vessel, 29% intranidal, 6% both). The overall incidence of feeder aneurysms was higher in posterior fossa AVMs, which were evident in 34.4% of infratentorial AVMs compared to 18.5% of supratentorial malformations (p<0.01). The presence of intranidal aneurysms was similar in both groups (9.2% vs 8.8%). Feeder artery aneurysms were much more likely to be the source of hemorrhage in posterior fossa AVMs than in supratentorial AVMs (30% vs 7.6%, p<0.01). Conclusions Posterior fossa AVMs are more prone to developing associated aneurysms, specifically feeder vessel aneurysms. Feeder vessel aneurysms are more likely to be the source of hemorrhage in the posterior fossa. As such, they may be the most appropriate targets for initial and prompt control by embolization or surgery due to their elevated threat.
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