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Secondary neurulation (indicated by lighter shading). At the end of primary neurulation (indicated by darker shading), the caudal neuropore closes, and the caudal eminence forms distal to the neural tube. The caudal eminence undergoes cavitation and connects to the neural tube at the junctional region, fusing with the neural tube and regressing to form the filum terminale. When the transition from primary to secondary neurulation overlaps, junctional neurulation results. During the period of secondary neurulation, separation of the cloaca starts at postovulatory Week 5. Formation of the external genitalia begins at postovulatory Week 7. The simultaneity of these processes corresponds with the frequency of associated anomalies occurring in each type of spinal lipoma.
Source publication
OBJECTIVE
Spinal lipomas are generally thought to occur as a result of failed primary neurulation. However, some clinical features cannot be explained by this theory. The authors propose a novel classification of spinal lipomas based on embryonic changes seen during primary and secondary neurulation.
METHODS
A total of 677 patients with occult spi...
Contexts in source publication
Context 1
... of the mechanism and process of caudal neural tube formation have become known only during the past few decades (Fig. 7). Primary neurulation, announced by the appearance of the neural groove and folds, starts after about 17-18 postovulatory days (PODs) in the normal hu- man embryo. 13 Fusion of the neural folds begins approxi- mately after POD 22. Initiation of neural tube fusion is be- lieved to start at multiple sites simultaneously with bi-or ...
Context 2
... and formation of the caudal eminence; the second is the cavitation of the caudal emi- nence and connection to the closed primary neural tube (spinal cord); the third consists of the fusion of the hollow secondary neural tube and the primary neural tube; and the fourth is the regression of the secondary neural tube to the filum terminale (Fig. ...
Context 3
... Week 5, reaching the cloacal membrane at postovulatory Week 8, thus separat- ing the cloaca from the rectum and anal membrane poste- riorly and from the urogenital sinus and membrane ante- riorly. 22 Organogenesis proceeds thereafter. Formation of external genitalia begins at postovulatory Week 7, after separation of the anal and urethral folds (Fig. 7). 23 It should be remembered that the caudal eminence is located dorsal to the cloaca; the chronological and anatomical coinci- dence with secondary neurulation can lead to interactions resulting in complex anomalies such as caudal agenesis. 14 ...
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Background
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Citations
... Afterward, a new class was added known as chaotic lipoma with its developmental origin occurring at junctional neurulation [11,12]. The most recent model for classification of spinal lipomas according to the embryological origin, Morota classification, divided spinal lipomas into 4 types [13]. In type 1 the etiology is due to primary neurulation failure. ...
Lipomas are benign lesions composed of typical fatty tissue (i.e., fat cells). They are uncommon to occur in the spinal cord or the filum terminale, the fibrous tissue that connects to the bottom of the spinal cord. A spinal cord lipoma is a fatty tumor that develops within the properly positioned spinal cord and constitutes approximately 1% of all spinal tumors. It is classified as a developmental tumor because it is produced by an embryological development error in which normal fat tissue becomes adherent to embryonic spinal cord tissue. The exact pathogenesis of such lesions is unknown. Many theories seek to explain their etiology and origin. Intradural spinal lipomas are big, bulky, and completely intradural lesions. Intradural lipomas are rare (4% of all lipomas) and mostly seen in the thoracic area. They are, however, seen in all spinal regions, with the cervical region appearing to be the most prevalent in children. Clinical pictures differ from one patient to another. Some may be asymptomatic, and others may develop worsening neurological symptoms. Symptoms of intradural lipoma are produced by the mass’s growth and its compression of the spinal cord while it grows because of fatter deposition in the lipoma. The earlier to diagnose intradural lipomas, the better. There are Multiple imaging modalities could be used to visualize intradural lipomas. There is controversy about the best management of intradural lipoma, but the primary aim of surgery is decompression and debulking of the spinal cord to ease the clinical manifestations.
... In particular, complex lumbosacral spinal cord lipomas (CSL) are lipomas with active involvement of the conus medullaris, and or cauda equina [3]. Research insights reveal that a series of sequential errors during embryogenesis lead to their development [2,4]; and that CSL differ morphologically amongst themselves and have variable clinical outcomes [5][6][7]. Cumulative literature on various aspects of CSL such as its natural history [8][9][10], subtype classification [5][6][7], clinical presentation, surgical principles [6], and treatment outcomes [6,9,11], have led to better understanding of this condition. Under such circumstances, we are now aware that outcomes focused on long-term neurological, urological and avoidance of re-tethering are essential indicators of successful treatment [6,9,12]. ...
... Research insights reveal that a series of sequential errors during embryogenesis lead to their development [2,4]; and that CSL differ morphologically amongst themselves and have variable clinical outcomes [5][6][7]. Cumulative literature on various aspects of CSL such as its natural history [8][9][10], subtype classification [5][6][7], clinical presentation, surgical principles [6], and treatment outcomes [6,9,11], have led to better understanding of this condition. Under such circumstances, we are now aware that outcomes focused on long-term neurological, urological and avoidance of re-tethering are essential indicators of successful treatment [6,9,12]. ...
... In recent years, there is growing evidence that TR/ NTR and prophylactic surgery for selected CSL patients have long-term neurological, urological, and functional benefits [12,25,[30][31][32]. Nonetheless, there is still a lack of consensus with regards to firstly, the extent of resection of the lipoma; next, the best approach for asymptomatic patients [3,8,10] and lastly, the individual definition and classification of the different CSL subtypes [5,7,25,30]. Also, there are topics of debate specific to CSL. ...
Background: Total/near-total resection (TR/NTR) of complex lumbosacral lipomas (CSL) is reported to be associated with better long-term functional outcomes and lower symptomatic re-tethering rates. We report our institutional experience for CSL resection in affected children. Methods: This is a single-institution, retrospective study. Inclusion criteria consist of patients with CSL with dorsal, transitional and chaotic lipomas based on Pang et al's classification. The study population is divided into 2 groups: asymptomatic patients with a normal preoperative workup referred to as 'prophylactic intent' and 'therapeutic intent' for those with pre-existing neuro-urological symptoms. Primary aims are to review factors that affect post-operative clean intermittent catheterization (CIC), functional outcomes based on Necker functional score (NFS), and re-tethering rates. Results: 122 patients were included from 2000 to 2021. There were 32 dorsal lipomas (26.2 %), 74 transitional lipomas (60.7 %), and 16 chaotic lipomas (13.1 %). 82 % patients achieved TR/NTR. Favourable NFS at 1-year was 48.2 %. The re-tethering rate was 6.6 %. After multivariable analysis, post-operative CIC was associated with median age at surgery (p = 0.026), lipoma type (p = 0.029), conus height (p = 0.048) and prophylactic intent (p < 0.001). Next, extent of lipoma resection (p = 0.012) and the post-operative CSF leak (p = 0.004) were associated with re-tethering. Favourable NFS was associated with lipoma type (p = 0.047) and prophylactic intent surgery (p < 0.001). Conclusions: Our experience shows that TR/NTR for CSL is a feasible option to prevent functional deterioration and re-tethering. Efforts are needed to work on factors associated with post-operative CIC.
... They were first described by Virchow in 1857, but it was not until 1982 that the first classification was made by Chapman [1]. Since then, different classifications have been described, including that made in 2009 by Pang [2], in which he described chaotic lipomas for the first time, and subsequently the classification by Morota in 2017 [3]. ...
... He differentiated between dorsal, terminal and transitional and later added what he described as chaotic lipoma [2,9]. Finally, it is the 2017 classification of Morota [3] that we believe represents the greatest change compared to those previously described. It is based on the formation of the spinal cord during embryogenesis, from the first to the second neurulation, and results in four types. ...
Purpose
Recent years have seen a paradigm shift towards total/near-total resection in spinal cord lipoma surgery. As this procedure is technically challenging, surgical candidates need to be selected appropriately through accurate image assessment and classification. The purpose of this paper is to describe a surgical series of paediatric spinal cord lipomas, their diagnosis, results and complications.
Methods
We undertook a retrospective review of paediatric patients with spinal cord lipomas who underwent surgery between 2008 and 2022. The variables studied were age, gender, preoperative symptoms according to the Necker Functional Score (NFS), type of lipoma according to Morota’s classification, functional and radiological surgical outcomes using the cord-sac ratio (CSR), need for re-operation, complications and follow-up.
Results
A total of 25 patients (average age 36 months) underwent surgery. According to Morota’s classification, MRI showed 13 type 1 lipomas, two type 2, two type 3 and eight type 4. The preoperative NFS was 16.06, with urological abnormalities being the most frequent manifestation. Total/near-total resection was attempted since 2015. Five patients with type 1 lipoma required re-operation due to clinical deterioration with suspected retethering, all of them with a CSR > 0.3. The series average CSR was 0.417.
Conclusions
This paper highlights the importance of proper classification for a correct surgical approach to obtain favourable results and minimise possible complications. Based on our experience, given our results regarding the percentage of fistulae and retethering rates, we limited radical resection to symptomatic type 1 lipomas. Our future aim is to obtain better CSR rates and to decrease the retethering percentage.
... Lumbosacral lipoma is classified into five types, the dorsal, caudal, transitional, lipomyelomeningocele, and filar, based on MRI findings, showing different surgical anatomies [11]. In addition, there is a newer classification based on the embryonic stage, which affects the surgical objectives and strategies [12,13]. As a method of imaging, CISS is a useful method that can clearly visualize the anatomical relationship among the lipoma, nerve roots, and spinal cord. ...
Untethering surgery for lumbosacral lipoma is a preventive procedure, and avoidance of complications and good long-term outcomes are required. We introduced presurgical interactive virtual simulation (IVS) applying three-dimensional multifusion images using a haptic device aimed at improving operative outcomes.
Fourteen patients with newly diagnosed lumbosacral lipoma were recruited and underwent preoperative IVS. The median age at surgery was 8 months. A three-dimensional image analysis system was used to extract and fuse structures necessary for surgery, such as the lipoma, spinal cord and skin, from CT and MRI, and create three-dimensional multifusion images. The created images were individually converted to standard triangulated language format and loaded onto a workstation (Geomagic freeform™) that could be freely transformed, and the laminectomy range and lipoma extraction procedure were examined. Presurgical IVS was performed, and the actual surgery was performed.
The disease types were dorsal, caudal, lipomyelomeningocele, transitional, and filum in 5, 5, 2, 1, and 1 patients, respectively. The surgical procedure and extent of the laminectomy were as planned for all patients. Resection of the lipomas tended to be less than expected preoperatively because of positive reactions on intraoperative monitoring. No postoperative complications were observed. The median postoperative follow-up period was 29 months, and there were no reoperations during the observation period.
Although there are various types of lumbosacral lipoma, surgery can be safely performed by performing presurgical IVS. The short-term course is good; however, long-term follow-up is necessary for the appearance of neurological symptoms associated with growth and re-tethering.
... The term "chaotic" was introduced to describe a variation, typically of transitional lipoma, in which the attachment of the lipoma extends beyond the dorsal root entry zone and thus precludes complete safe resection [10]. In contrast to these morphologically based classifications, Morota et al. proposed a schema based upon presumed embryogenesis and used this to help explain the association with malformations of the cloacal region [11]. ...
... Per series, the presence of a meningocele (1 patient), dorsal dermal sinuses (7 patients), or sacral agenesis (24 patients) did not significantly influence neurological outcome (likely owing to low numbers) [3,9,11,23,28]. Two papers commented on the significance of syrinxes in relation to outcome [2,24]. Wykes et al. 2012 reported MRI findings of a syrinx significantly influenced neurological outcome (univariate analysis) [2]. ...
Objective
Conus region lumbosacral lipomas (LSLs) are highly heterogeneous in their morphology, clinical presentation, and outcome, with an incompletely understood natural history and often treacherous surgical anatomy. This systematic review aims to critically evaluate and assess the strength of the current LSL evidence base to guide management strategies.
Methods
According to a systematic review following PRISMA guidelines, a search was conducted using the key term “lumbosacral lipoma” across MEDLINE (OVID), Embase, Cochrane Library, and PubMed databases from January 1951 to April 2021. All studies containing ten or more paediatric conus lipomas were included. Data heterogeneity and bias were assessed.
Results
A total of 13 studies were included, containing 913 LSLs (predominantly transitional type—58.5%). Two-thirds (67.5%) of all patients (treated and non-treated) remained clinically stable and 17.6% deteriorated. Neuropathic bladder was present in 8.6% at final follow-up. Of patients managed surgically, near-total resection vs. subtotal resection deterioration-free survival rates were 77.2–98.4% and 10–67% respectively. 4.5% (0.0–27.3%) required re-do untethering surgery. Outcomes varied according to lipoma type. Most publications contained heterogeneous populations and used variable terminology. There was a lack of consistency in reported outcomes.
Conclusion
Amongst published series, there is wide variability in patient factors such as lipoma type, patient age, and methods of (particularly urological) assessment. Currently, there is insufficient evidence base upon which to make clear recommendations for the management of children with LSL. There is an imperative for neurosurgeons, neuroradiologists, and urologists to collaborate to better standardise the terminology, assessment tools, and surgical interventions for this challenging group of conditions.
... Because of the various clinical significance and morphologies among CSD subtypes, the classification and treatment of CSDs have been previously considered. [1][2][3][4] Although most classifications are based on morphology, Morota et al. proposed a new classification of spinal lipoma based on the embryological stage when the de-velopmental failures occur, which includes four types: Type 1, primary neurulation failure only; Type 2, failed neurulation between the primary and secondary neurulations; Type 3, early-phase secondary neurulation failure; and Type 4, late-phase secondary neurulation failure. 1) Filum terminale lipoma (FTL), one of the subtypes of CSDs, is equivalent to Type 4 spinal lipoma according to Morota's classification. ...
... Although some skin stigmata, such as subcutaneous masses and human tails, are undoubtedly recognized as strongly associated stigmata, 18) the association of mild ones, such as simple dimples and deviated gluteal clefts, is debatable because some studies included them in associated stigmata, but others did not. 1,12,19) In general, sacral dimples are a common skin stigma, which can be generally found in 2%-4% of neonates. 12,13) Deformed gluteal clefts are also commonly confirmed and reported as low-risk skin stigmata if isolated. ...
Closed spinal dysraphism (CSD) encompasses a heterogeneous group of spinal cord deformities, which can be accompanied by several types of skin stigmata. These skin stigmata may include inconspicuous features, such as sacral dimples and deformed gluteal clefts, but the association between such mild skin stigmata and CSD is uncertain. This study aimed to reevaluate the indication for magnetic resonance imaging (MRI) in patients with skin stigmata while considering the indication for surgery. A retrospective analysis was conducted on magnetic resonance images of 1255 asymptomatic children with skin stigmata between 2003 and 2015. Skin stigmata classification was based on medical chart data. All subtypes of CSDs except for filum terminale lipomas (FTL), FTL thicker than 2 mm or with low conus medullaris, were considered to meet the surgical indication. CSD prevalence was estimated while considering the surgical indications and assessed after excluding all FTL cases. Skin stigmata were classified into seven types, dimple, deformed gluteal cleft, hair, subcutaneous mass, appendage, discoloration, and protruding bone, and included 1056 isolated and 199 complex ones. The prevalence of CSD was 19.5%, 6.8%, and 0.5% among patients with isolated dimples (n = 881) and 13.9%, 5.8%, and 0.7% among those with isolated deformed gluteal clefts (n = 136) for all cases, surgical indications, and patients without FTL, respectively. Dimples and deformed gluteal clefts had a low prevalence of CSD requiring surgical intervention, and cases without FTL were rare. Asymptomatic patients with mild skin stigmata may not require immediate MRI.
Fullsize Image
... e most likely reason why the histopathological coexistence of TMCC and RMC tissues has rarely been reported, as in these cases, is that the tethering tract caused by secondary neurulation failures, such as RMC and caudal lipoma, is rarely continuous from the skin lesion to the spinal canal through the myofascial defect and spina bifida, [13] unlike the primary neurulation failure, and few histopathological studies on the epidural stalk have been performed. Both patients in the present study had a continuous tract from the skin lesion to the spinal canal through a myofascial defect and sacral hiatus. ...
Background
The retained medullary cord (RMC), caudal lipoma, and terminal myelocystocele (TMCC) are thought to originate from the failed regression spectrum during the secondary neurulation, and the central histopathological feature is the predominant presence of a central canal-like ependyma-lined lumen (CC-LELL) with surrounding neuroglial tissues (NGT), as a remnant of the medullary cord. However, reports on cases in which RMC, caudal lipoma, and TMCC coexist are very rare.
Case Description
We present two patients with cystic RMC with caudal lipoma and caudal lipoma with an RMC component, respectively, based on their clinical, neuroradiological, intraoperative, and histopathological findings. Although no typical morphological features of TMCC were noted on neuroimaging, histopathological examination revealed that a CC-LELL with NGT was present in the extraspinal stalk, extending from the skin lesion to the intraspinal tethering tract.
Conclusion
This histopathological finding indicates the presence of TMCC that could not be completely regressed and further supports the idea that these pathologies can be considered consequences of a continuum of regression failure during secondary neurulation.
... Junctional neurulation is the recently established embryonic stage of spinal cord formation and bridges between the primary and secondary neurulation stages [17][18][19]. Failure of this process leads to a new category of SBO which includes complex forms of spinal lipoma [20][21][22] (Fig. 2). ...
... Junctional neurulation spans from the beginning of the terminal stage of primary neurulation to the early stage of secondary neurulation [19,22]. Its embryonal role is the fusion of the primary neural tube and CCM. ...
... RR: radical resection; STR: subtotal resection; PR: partial resection neurological deficits. Spinal lipomas originating in this stage are, in general, huge in size, complex in anatomy, and usually one of the most formidable subjects of surgery among the spinal lipomas, as well as other congenital anomalies in the lumbosacral region [22]. Segmental spinal dysgenesis, once called "junctional neural tube defect," is another pathology caused by failed CCM fusion during junctional neurulation [20,21] (Fig. 4). ...
The technical evolution of the surgery for spina bifida occulta (SBO) over the course of a half-century was reviewed with special foci placed on the spinal lipoma and tethered spinal cord. Looking back through history, SBO had been included in spina bifida (SB). Since the first surgery for spinal lipoma in the mid-nineteenth century, SBO has come to be recognized as an independent pathology in the early twentieth century. A half-century ago, the only option available for SB diagnosis was the plain X-ray, and pioneers of the time persevered in the field of surgery. The classification of spinal lipoma was first described in the early 1970s, and the concept of tethered spinal cord (TSC) was proposed in 1976. Surgical management of spinal lipoma with partial resection was the most widely practiced approach and was indicated only for symptomatic patients. After understanding TSC and tethered cord syndrome (TCS), more aggressive approaches became preferred. A PubMed search suggested that there was a dramatic increase of publications on the topic beginning around 1980. There have been immense academic achievements and technical evolutions since then. From the authors’ viewpoint, landmark achievements in this field are listed as follows: (1) establishment of the concept of TSC and the understanding of TCS; (2) unraveling the process of secondary and junctional neurulation; (3) introduction of modern intraoperative neurophysiological mapping and monitoring (IONM) for surgery of spinal lipomas, especially the introduction of bulbocavernosus reflex (BCR) monitoring; (4) introduction of radical resection as a surgical technique; and (5) proposal of a new classification system of spinal lipomas based on embryonic stage. Understanding the embryonic background seems critical because different embryonic stages bring different clinical features and of course different spinal lipomas. Surgical indications and selection of surgical technique should be judged based on the background embryonic stage of the spinal lipoma. As time flows forward, technology continues to advance. Further accumulation of clinical experience and research will open the new horizon in the management of spinal lipomas and other SBO in the next half-century.
... A 16-year-old female patient received surgery for a type 2 spinal lipoma (lipomyelomeningocele) at age 25 days [11]. Subsequently, she underwent two operations for TCS at age 4 years and 7 years at another hospital. ...
... We previously applied this technique in an adult case of retained medullary cord with satisfactory outcomes. In certain cases where radical resection of a spinal lipoma is performed, the addition of ventral anchoring is indicated during the initial repair surgery [11,13,15]. Ventral anchoring is an orthodox, neurosurgical approach for preventing TSC recurrence and the need for repeated operations. ...
Objective
Retethering is not an unusual operation for a congenital lumbosacral dysraphic spinal lesion. The present study aimed to assess a new surgical technique for preventing retethering.
Surgical technique
After untethering the spinal cord, the pia mater or scar tissue at the caudal end of the conus medullaris is anchored to the ventral dura mater loosely using 8–0 thread, and the dura mater is closed directly. This technique is called ventral anchoring.
Results
Ventral anchoring was performed in 15 patients (aged 5 to 37 years old, average age: 12.1 years old) between 2014 and 2021. All but one patient showed improvement or stabilization of the preoperative symptoms. No complication directly related to the procedure was observed. Postoperative MRI demonstrated that the dorsal subarachnoid space was restored in 14 patients but was undetectable or absent in three patients on follow-up MRI. No patients have experienced a recurrence of the tethered cord syndrome during the follow-up period.
Conclusion
Ventral anchoring is effective for restoring the dorsal subarachnoid space after untethering the spinal cord. This preliminary study suggested that ventral anchoring has the potential to prevent the postoperative radiographic recurrence of tethered spinal cord in patients with a congenital lumbosacral dysraphic spinal lesion.
... [20] e present case is associated with a fatty terminal filum and sacral bony malformation, which are thought to be related to secondary neurulation failure but not primary neural tube closure. [16,23] To the best of our knowledge, the association of fully formed heterotopic or ectopic DRG with secondary neurulation disorders has not been reported; hence, its impact on the embryopathogenesis is uncertain. From the neuroimaging finding of the present case that the dorsal nerve roots entangled with the ectopic DRG possibly connected to the normally positioned DRGs in the root sleeves, we speculated that some of the ganglion cells might have successfully migrated to the future formation site of the root sleeves and developed to the DRGs, while some cells might have been left behind at the intradural region and develop into the ectopic DRG. ...
Background
A heterotopic dorsal root ganglion (DRG) is sometimes observed in the vicinity of dysplastic neural structures during surgery for open spinal dysraphism; however, it is rarely associated with closed spinal dysraphism. Distinguish from neoplasms by preoperative imaging study is difficult. Although the embryopathogenesis of a heterotopic DRG has been speculated to be migration disorder of neural crest cells from primary neural tube, its details remain unelucidated.
Case Description
We report a pediatric case with an ectopic DRG in cauda equina associated with a fatty terminal filum and bifid sacrum. The DRG mimicked a schwannoma in the cauda equina on preoperative magnetic resonance imaging. Laminotomy at L3 revealed that the tumor was entangled in the nerve roots, and small parts of the tumor were resected for biopsy. Histopathologically, the tumor consisted of ganglion cells and peripheral nerve fibers. Ki-67 immunopositive cells were observed at the periphery of the ganglion cells. These findings indicate the tumor comprised DRG tissue.
Conclusion
We report detailed neuroradiological, intraoperative and histological findings and discuss the embryopathogenesis of the ectopic DRG. One should be aware of the possibility of ectopic or heterotopic DRGs when cauda equina tumors are observed in pediatric patients with neurulation disorders.
