Retained Medullary Cord in Humans: Late Arrest of Secondary Neurulation

Pang, Dachling; Zovickian, John; Moes, Greg S.

doi:10.1227/neu.0b013e31820ee282

Cited by 73 publications

(94 citation statements)

References 72 publications

(93 reference statements)

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“…Morphologically, there was a striking resemblance between the ependyma-lined canal with surrounding neuroglial tissues in our 6 patients with filar- and caudal-type lipomatous malformations and the RMC of the previous reports [8, 9], including ours [10, 11]. Furthermore, the cases were also similar to these previous cases in that there were always neuroglial tissues surrounded by variable amounts of collagenous and adipose tissues [8-11].…”

Section: Discussionsupporting

confidence: 85%

“…Furthermore, the cases were also similar to these previous cases in that there were always neuroglial tissues surrounded by variable amounts of collagenous and adipose tissues [8-11]. The only difference was the amount of adipose tissues; it was apparently greater in the lipomatous malformation than in RMC.…”

Section: Discussionsupporting

confidence: 80%

“…Recently, Pang et al [8] reported the novel entity of a retained medullary cord (RMC) in 7 patients presenting with a robust, elongated cord-like structure continuous from the conus and extending to the dural cul-de-sac. In these cases, intraoperative stimulation indicated that this cord was a “redundant” nonfunctional cord below the true conus [8-11].…”

Section: Introductionmentioning

confidence: 99%

“…In these cases, intraoperative stimulation indicated that this cord was a “redundant” nonfunctional cord below the true conus [8-11]. Pang et al [8] proposed that these cords are portions of the medullary cord and normally regress but can remain because of late arrest of secondary neurulation before the degenerative phase. The central feature in the histopathology of RMC is an ependyma-lined central canal in the dense neuroglial core [8-11].…”

Section: Introductionmentioning

confidence: 99%

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Ependyma-Lined Canal with Surrounding Neuroglial Tissues in Lumbosacral Lipomatous Malformations: Relationship with Retained Medullary Cord

et al. 2018

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Background: An ependyma-lined canal with surrounding neuroglial tissues can be present in lumbosacral lipomatous malformations; however, the precise embryological significance is still unclear. Method: Six out of 50 patients with lipomatous malformations had ependymal structures. We retrospectively analyzed the clinical, neuroradiological, and histological findings of these patients to demonstrate the relationship with the embryological background of the retained medullary cord (RMC), which normally regresses, but was retained here because of late arrest of secondary neurulation. Results: Five (13.9%) of 36 patients with filar and caudal types and 1 of 3 lipomyelomeningoceles had ependymal structures, while none with dorsal and transitional types had these tissues. Histologically, the ependymal structures surrounded by neuroglial tissue and containing various amounts of adipose tissue bear a striking resemblance to the ependymal structures in RMC. Conclusion: The 13.9% incidence of association between the ependymal structures and filar and caudal types is thought to be because of second ary neurulation failure with the same embryological background as that of RMC. Dorsal and transitional types, resulting from primary neurulation failure, therefore, did not have ependymal structures.

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Section: Discussionsupporting

confidence: 85%

Section: Discussionsupporting

confidence: 80%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Ependyma-Lined Canal with Surrounding Neuroglial Tissues in Lumbosacral Lipomatous Malformations: Relationship with Retained Medullary Cord

et al. 2018

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“…No radical resection is recommended unless a retained medullary cord is present between the lipoma and conus medullaris. 17 Type 4 spinal lipoma is nearly synonymous with the filum lipoma. A tiny dimple in the sacrococcygeal region often provides a clue for diagnosis, although its pathological significance is still disputed.…”

Section: Figmentioning

confidence: 99%

New classification of spinal lipomas based on embryonic stage

Morota

Ihara

Ogiwara

2017

PED

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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 spinal dysraphism underwent 699 surgeries between August 2002 and May 2015 at the National Center for Child Health and Development and Tokyo Metropolitan Children's Medical Center. This group of patients had 378 spinal lipomas, including 119 conus spinal lipomas, 27 lipomyelomeningoceles, and 232 filum lipomas, which the authors classified into 4 types based on neural tube formation during embryonic development. Type 1 is defined as pure primary neurulation failure; Type 2 ranges from primary to secondary neurulation failure; Type 3 consists of secondary neurulation failure (early phase); and Type 4 is defined as secondary neurulation failure (late phase). The authors also review embryogenesis in secondary neurulation and analyze the clinical utility of the new classification. RESULTS There were 55 Type 1 spinal lipomas, 29 Type 2, 62 Type 3, and 232 Type 4. All filum lipomas fell into the Type 4 spinal lipoma category. Association with anorectal and/or sacral anomalies was seen in none of the Type 1 cases, 15 (52%) of Type 2, 35 (56%) of Type 3, and 31 (13%) of Type 4. Urogenital anomalies were observed in none of the Type 1 or Type 2 cases, 1 (2%) of Type 3, and 28 (12%) of Type 4. Anomaly syndromes were present in none of the Type 1 cases, 6 (21%) of Type 2, 3 (5%) of Type 3, and 16 (7%) of Type 4. Associated anomalies or anomaly syndromes were clearly observed only for Type 2–4 spinal lipomas encompassing failed secondary neurulation. Radical resection was feasible for Type 1 spinal lipomas. CONCLUSIONS Secondary neurulation of the spinal cord gives rise to the conus medullaris and filum terminale, which are often involved in spinal lipomas. Formation of spinal lipomas seems to be a continuous process overlapping primary and secondary neurulation in some cases. Association with other anomalies was higher in Type 2–4 spinal lipomas, which included failed secondary neurulation, than in Type 1 lipomas, with failed primary neurulation. On the other hand, radical resection was indicated for Type 1, but not for Type 2, spinal lipomas. The new classification of spinal lipomas based on embryonic stage has the potential for clinical use and agrees well with both clinical and surgical findings. The classification proposed here is still preliminary. Further studies and verification are necessary to establish its clinical utility.

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Concepts in the neurosurgical care of patients with spinal neural tube defects: An embryologic approach

Blount

George

Koueik

et al. 2019

Birth Defects Research

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Background: The neural tube defects (NTDs) are a heterogeneous group of structural birth defects that arise from a complex array of multiple genetic and environmental factors and adversely affect the structure and function of the brain and spinal cord. Spinal NTDs are clinically more common than cranial NTDs. There remains a significant gap in linking the multiple NTD phenotypes to current genomic understanding. Methods: This article summarizes the neurosurgical clinical approach to spinal NTDs by correlating each step of embryonic development of the human nervous system with key management concepts for defects that arise at that step. Results: The NTDs are broadly classified as open or closed. Open defects include myelomeningocele (MMC), encephalocele, and anencephaly. Closed defects are also known as occult spinal dysraphism and are characterized by intact skin over the spinal defect. They are more common and often cause neurologic decline from tethered cord syndrome. Failure of primary neurulation gives rise to open myelomeningocele (MMC). Surgical closure of an open MMC focuses on realigning the tissue layers that failed to separate during neurulation. In utero closure is a promising recent technique. Chronic neurosurgical management largely focuses treating hydrocephalus. The Chiari II malformation is uniformly present in MMC patients and may cause brainstem dysfunction. Tethered spinal cord may progressively impair normal neurologic function but typically responds well to surgical untethering. Conclusions: Surgical closure of MMC centers on approximated realignment of embryologically disordered neural tissue. Clinical surgical management decisions in the spinal NTDs remains challenging but standardized principles have emerged. K E Y W O R D S hydrocephalus, myelomeningocele, neurosurgery, spina bifida, spinal lipoma, tethered spinal cord

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Retained Medullary Cord in Humans: Late Arrest of Secondary Neurulation

Cited by 73 publications

References 72 publications

Ependyma-Lined Canal with Surrounding Neuroglial Tissues in Lumbosacral Lipomatous Malformations: Relationship with Retained Medullary Cord

Ependyma-Lined Canal with Surrounding Neuroglial Tissues in Lumbosacral Lipomatous Malformations: Relationship with Retained Medullary Cord

New classification of spinal lipomas based on embryonic stage

Concepts in the neurosurgical care of patients with spinal neural tube defects: An embryologic approach

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