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Limited dorsal myeloschisis with no extradural stalk linking to a flat skin lesion: a case report

December 2018
Child's Nervous System 34(12)

December 2018
34(12)

DOI:10.1007/s00381-018-3938-z

Authors:

Takato Morioka

Hachisuga Hospital

Show all 5 authorsHide

Background: Limited dorsal myeloschisis (LDM) is characterized by a fibroneural stalk linking the skin lesion to the underlying spinal cord. CASE PRESENTATION : A 7-month-old girl with a lumbosacral "cigarette-burn" flat skin lesion underwent untethering surgery. The intradural tethering stalk appeared to originate at the dural wall and join the cord with no extradural stalk linking to the skin lesion. Histological examination of the intradural stalk revealed glial fibrillary acidic protein-immunopositive neuroglial tissues in the fibrocollagenous band, which is the central histopathological feature of an LDM stalk. Conclusion: It is conceivable that the LDM stalk in our patient was originally linked to the skin lesion and subsequently regressed and was replaced by mature adipose tissue. We should be mindful of possible variations in the morphological features of LDM.

(a) Photograph showing a “cigarette-burn” flat skin lesion with surrounding abnormal hair. (b) Serial sagittal (slice thickness 0.4 mm) and (c) axial views (slice thickness 1.97 mm) of three-dimensional heavily T2-weighted images (3D-hT2WI) with fat suppression show an intradural tethering stalk (red arrows) starting at the lower part of L4 level and joining the lower-lying conus at L3 level; however, the images show no extradural stalk continuous with the skin lesion (indicated with asterisk). A large syringomyelic cavity with continuity with the central canal is seen at L1 and L2 levels. Although thickened filum terminale is noted (yellow arrows), in (d), the axial view of 3D-T1 weighted image (slice thickness 1.97 mm) shows no fatty filum

…

(a) Schematic drawing and (b) microscopic view of the operative findings. (a-1, b-1) Following laminoplastic laminotomy at L2–5, a tiny dural protrusion is noted at the lower level of L4. (a-2, b-2) Upon opening the dura, the small-diameter stalk starts at the dural wall and joins the dorsal surface of the lower-lying conus at the L3. A glomus of vascular channels around the stalk-cord attachment is seen, and the syringomyelic wall is noted just rostral to the stalk-cord attachment. Thickened terminal filum is continuous with the lower-lying conus. (a-3, b-3) The intradural stalk is disconnected from the dura and the cord to untether the cord, and the stalk is then removed. The stalk is divided into two parts (the stalk-dura attachment and intradural stalk) and submitted for histological examination. The syringomyelic wall is opened to make a stoma for syringostomy, and the wall of the syringomyelia is submitted for histological examination. The terminal filum is resected as column and submitted for histological examination.

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Histopathological findings of the resected specimens. Each section except for (a) is indicated in Fig. 2(a-3). (a) The image shows no fibrocollagenous tract continuous with the skin tissue, which had finely jagged squamous epithelium; however, subcutaneous mature fibroadipose tissue (fat) is noted. (b–f) Longitudinal section of the intradural tract showing a fibrocollagenous tract embedded with glial fibrillary acidic protein (GFAP)-immunopositive neuroglial tissues (c–e) and peripheral nerve fibers with ganglion cells (f). (g–i) Longitudinal sections of the stalk-dura attachment show dense fibrocollagenous tissue (shown in Mason’s trichrome staining (M-T) in (h)) embedded with peripheral nerve fibers with ganglion cells (i) and an arachnoid tissue (j). (k, l) The wall of the syringomyelia consists of GFAP-positive neuroglial tissues. (m–o) Longitudinal section of the filum showing fibrocollagenous tracts embedded with a large amount of mature adipose tissue (fat), neuroglial tissue (n), and peripheral nerve fibers with ganglion cells (o). Large vessel (Ves) is also noted

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CASE REPORT

Limited dorsal myeloschisis with no extradural stalk linking to a flat skin

lesion: a case report

Akiko Hiraoka

&Takato Morioka

&Nobuya Murakami

&Satoshi O. Suzuki

&Masahiro Mizoguchi

Received: 6 July 2018 / A ccepted: 27 July 2018 / Published online: 6 August 2018

#Springer-Verlag GmbH Germany, part of Springer Nature 2018

Abstract

Background Limited dorsal myeloschisis (LDM) is characterized by a fibroneural stalk linking the skin lesion to the underlying

spinal cord.

Case presentation A 7-month-old girl with a lumbosacral Bcigarette-burn^flat skin lesion underwent untethering surgery. The

intradural tethering stalk appeared to originate at the dural wall and join the cord with no extradural stalk linking to the skin lesion.

Histological examination of the intradural stalk revealed glial fibrillary acidic protein-immunopositive neuroglial tissues in the

fibrocollagenous band, which is the central histopathological feature of an LDM stalk.

Conclusion It is conceivable that the LDM stalk in our patient was originally linked to the skin lesion and subsequently regressed and

was replaced by mature adipose tissue. We should be mindful of possible variations in the morphological features of LDM.

Keywords Glial fibrillary acidic protein .Fibroneural stalk .Untethering

Introduction

Limited dorsal myeloschisis (LDM) was first described as a dis-

tinct clinicopathological entity by Pang et al. in 2010 [7]. LDMs

are characterized by two invariable features: a focal closed neural

tube defect and a fibroneural stalk linking the skin lesion to the

underlying spinal cord [7,8]. The embryogenesis of LDM is

hypothesized to be incomplete disjunction between cutaneous

and neural ectoderms, which prevents complete midline skin

closure and allows a persistent fibroneural stalk between the

disjunction site and the dorsal neural tube [2,7,8]. LDMs are

categorized based on their external skin manifestations as saccu-

lar and non-saccular (flat) [7,8]. Saccular LDM consists of a

skin-based cerebrospinal fluid sac topped by a squamous

epithelial dome; flat LDM has a squamous epithelial flat surface

or sunken crater or pit, typically called a Bcigarette-burn^skin

lesion [3,4]. In all LDMs, the fibroneural stalk is tethered to the

cord, and recommended treatment consists of untethering the

stalk from the cord [7,8]. Recently, we treated a patient with flat

skin lesion, in whom the intradural LDM stalk appeared to start

at the dural wall and joined the cord with no extradural stalk

linking to the skin lesion. We also discuss the detailed histopath-

ological analysis of the stalk.

Case report

At birth, a baby girl was noted to have a lumbosacral

Bcigarette-burn^flat skin lesion with surrounding abnormal

hair (Fig. 1(a)). There is no history of discharge or local infec-

tion at the site of the skin lesion. She was neurologically nor-

mal. At 5 months of age, magnetic resonance imaging (MRI)

including three-dimensional T1-weighted spoiled gradient-

recalled echo and three-dimensional heavily T2-weighted im-

ages [6] demonstrated an intradural tethering tract (Fig. 1(b,

c)), originating at the dural wall of the lower part of L4 level

and joining the lower-lying conus at the L3 level; however,

there is no extradural stalk continuous with the skin lesion. A

large syringomyelic cavity with continuity with the central

canal was noted at the L1-L2 level (Fig. 1(b, c)). Although

*Takato Morioka

takato@ns.med.kyushu-u.ac.jp

Department of Pediatric Neurology, Fukuoka Children’s Hospital,

Fukuoka, Japan

Department of Neurosurgery, Fukuoka Children’s Hospital, 5-1-1

Kashii-teriha, Higashi-ku, Fukuoka 813-0017, Japan

Department of Neuropathology, Graduate School of Medical

Sciences, Kyushu University, Fukuoka, Japan

Department of Neurosurgery, Kitakyushu Municipal Medical Center,

Kitakyushu, Japan

Child's Nervous System (2018) 34:2497–2501

https://doi.org/10.1007/s00381-018-3938-z

Content courtesy of Springer Nature, terms of use apply. Rights reserved.

Focal Spinal Nondisjunction in Primary Neurulation : Limited Dorsal Myeloschisis and Congenital Spinal Dermal Sinus Tract

Article

Full-text available

Mar 2021

Spinal dysraphic lesions due to focal nondisjunction in primary neurulation are commonly encountered in paediatric neurosurgery, but the "fog-of-war" on these conditions was only gradually dispersed in the past 10 years by the works of the groups led by the senior author and Prof. Kyu-Chang Wang. It is now clear that limited dorsal myeloschisis and congenital spinal dermal sinus tract are conditions at the two ends of a spectrum; and mixed lesions of them with various configurations exist. This review article summarizes the current understanding of these conditions' embryogenetic mechanisms, pathological anatomy and clinical manifestations, and their management strategy and surgical techniques.

Clinicopathological findings of limited dorsal myeloschisis associated with spinal lipoma of dorsal-type

Article

Full-text available

May 2020

Purpose Limited dorsal myeloschisis (LDM) is thought to arise from focal incomplete disjunction between the cutaneous and neural ectoderm during primary neurulation, while spinal lipoma of dorsal-type (dorsal lipoma) arises from premature disjunction. Thus, simultaneous occurrence of an LDM and dorsal lipoma are not surprising, and may represent slightly different perturbations of disjunction caused by the same insult in neighboring loci. However, the clinicopathological findings of the LDM with dorsal lipoma have not been fully determined. Methods Of 21 patients with LDM, 3 (14.3%) had dorsal lipoma. We retrospectively analyzed the clinicopathological findings of these 3 patients, especially the histopathological distribution of the fibrocollagenous LDM tract and fibroadipose tissue of the lipoma. Results Patients 1 and 2 had flat skin lesions, while patient 3 had a human tail-like cutaneous appendage. In the tethering stalks linking the skin lesion at the lumbosacral lesion to the low-lying conus medullaris of the three patients, fibrocollagenous tissues embedding adipose tissues at the subcutaneous site, and with abundant adipose tissues at the extradural site, were changed to fibroadipose tissue at the intradural site. While glial fibrillary acidic protein-immunopositive neuroglial tissues were observed in 2 (patients 1 and 2), peripheral nerve fibers were observed in every stalk. Smooth muscle fibers were noted in patient 1, while a large amount of striated muscle fibers were seen in patients 2 and 3. Conclusion These cases showed various tissues with different origins in the stalk. There may also be a seamless continuation between fibrocollagenous LDM tissue at the distal site and lipomatous tissue at the proximal site. Peripheral nerve fibers and smooth muscle fibers of neural crest origin may be dragged into the stalk during incomplete disjunction, while the striated muscle fibers of mesodermal origin may enter the stalk along with the lipomatous tissues during premature disjunction.

Ectopic dorsal root ganglion in cauda equina mimicking schwannoma in a child

Article

Full-text available

Jan 2023

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.

Limited dorsal myeloschisis without extradural stalk continuity to coexisting congenital dermal sinus

Article

Full-text available

Aug 2022
CHILD NERV SYST

Limited dorsal myeloschisis (LDM) is characterized by a fibroneural tethering stalk linking the skin lesion to the underlying spinal cord. LDM without an extradural stalk is rare. A full-term boy was noted at birth to have a dimple in the upper back (dorsal skin of the lower thoracic region). Computed tomographic scan showed spina bifida at the T9–12 vertebral level and osteochondral tissue at the T10 level. Magnetic resonance imaging (MRI) demonstrated a tiny dorsal lipoma at the T8 vertebral level, but the intradural tethering tract was not apparent. At 18 days of age, the congenital dermal sinus (CDS) tract started from the dimple and terminated at the osteochondral tissue, without continuity of the dura mater, and the osteochondral tissues were resected. At age 2 years 8 months, he developed spastic paresis of the right foot. On MRI, the tethering tract from the dorsal lipoma became apparent. During the second surgery at age 2 years 11 months, the intradural stalk started from the dorsal lipoma and joined the inner surface of the dura mater was untethering from the cord. Postoperatively, right spastic paresis was improved. Histological examination of the intradural stalk revealed the distribution of S100-immunopositive peripheral nerve fibers, which is one of the histopathological hallmarks of LDM. We speculated that the extradural stalk with coexisting CDS originally linked from the skin lesion subsequently regressed and was replaced by fibroadipose tissue with osteochondral tissue migration. Intradural exploration should always be seriously considered in these disorders of persisting neurocutaneous connection.

Surgical histopathology of a filar anomaly as an additional tethering element associated with closed spinal dysraphism of primary neurulation failure

Article

Full-text available

Jul 2021

Background Closed spinal dysraphism of primary neurulation failure could be associated with filar anomalies, such as filar lipoma or thickened and tight filum terminale (TFT), resulting from impaired secondary neurulation. Retained medullary cord (RMC) is a remnant of the cavitary medullary cord originating from the secondary neurulation failure. Some filar lipomas are known to contain a central canal-like ependyma-lined lumen with surrounding neuroglial tissues (E-LC w/NGT), that is, a characteristic histopathology of RMC. To clarify the embryological background of these filar anomalies, we evaluated the histopathological findings. Methods Among 41 patients with lesions of primary neurulation failure who underwent initial untethering surgery, the filum including cord-like structure (C-LS) was additionally resected in 10 patients (five dorsal and transitional lipomas; five limited dorsal myeloschisis). We retrospectively analyzed the clinical, neuroradiological, intraoperative, and histopathological findings. Results Among 10 patients, two patients were diagnosed with RMC based on morphological features and intraoperative neurophysiological monitoring. The diagnosis of filar lipoma was made in six patients, since various amounts of fibroadipose tissue were histopathologically noted in the filum. Two patients were diagnosed with TFT, since the filum was composed solely of fibrocollagenous tissue. E-LC w/NGT was noted not only in both C-LSs of RMCs but also in two out of six fila both with filar lipomas and fila with TFTs. Conclusion These findings provide further evidence for the idea that entities, such as filar lipoma, TFT, and RMC, can be considered consequences of a continuum of regression failure occurring during late secondary neurulation.

Focal Spinal Nondisjunctional Disorders: Including a Discussion on the Embryogenesis of Cranial Focal Nondisjunctional Lesions

Chapter

Aug 2023
Adv Tech Stand Neurosurg

The publication of a comprehensive report on limited dorsal myeloschisis by the senior author (DP) in 2010 has brought full attention to the concept of limited myeloschisis that he first formulated in 1992 and ignited interests in the whole spectrum of focal spinal nondisjunctional disorders. Now that focal nondisjunctional disorders have become well known, new clinical reports on these conditions or relevant subjects are frequently seen. Here we present an updated review on the full spectrum of focal spinal nondisjunctional disorders and extend the scope to include a discussion on the embryogenesis of cranial focal nondisjunctional malformations.KeywordsLimited dorsal myeloschisisDermal sinus tractDermoidNondisjunctionDysraphismFocal spinal nondisjunctional disordersFocal cranial nondisjunctional disordersEncephalocele

Surgical Pathoembryology and Treatment of Limited Dorsal MyeloschisisLimited dorsal myeloschisisの病態と外科治療

Article

Jan 2021

Limited dorsal myeloschisis (LDM), first proposed by Pang et al., is thought to originate from a small segmental failure of the dorsal closure of the neural folds during primary neurulation. The disjunction between the cutaneous and neural ectoderm is impaired at the focal limited nonclosure site. This results in a retained fibroneural stalk linking the skin lesion and the dorsal spinal cord, which results in tethering of the cord. Based on skin manifestations, LDMs were originally categorized as saccular and nonsaccular (flat). Saccular LDM consists of a skin-based cerebrospinal fluid sac topped by a squamous epithelial dome, whereas the flat LDM has a squamous epithelial flat surface or a sunken crater or pit typically called a “cigarette-burn” skin lesion. Recently, we reported a human tail-like cutaneous appendage as an additional morphological type of skin lesion. The recommended treatment consisted of prophylactic untethering of the stalk from the cord. Because of the shared origin of LDM and congenital dermal sinus (CDS), CDS elements may be found within the fibroneural LDM stalk with a 10-20% possibility. When part of the CDS invested in the intradural stalk is left during untethering surgery, inclusion tumors such as dermoid cysts may develop in the patient. Although the central histopathological finding of LDM stalk is the presence of glial fibrillary acidic protein (GFAP) -immunopositive neuroglial tissues in the fibrocollagenous tract, immunopositivity for GFAP was observed in 50-60% of pathologically examined cases. The presence of neural crest cells, such as peripheral nerve fibers and melanocytes, also assists in the histopathological diagnosis of LDM. In this case report, the diagnostic and surgical strategies of LDM are discussed accordingly.

Congenital Dermal Sinus Elements in Each Tethering Stalk of Coexisting Thoracic Limited Dorsal Myeloschisis and Retained Medullary Cord

Article

Dec 2020

Introduction: The embryogenesis of limited dorsal myeloschisis (LDM) likely involves impaired disjunction between the cutaneous and neural ectoderms during primary neurulation. Because LDM and congenital dermal sinus (CDS) have a shared origin in this regard, CDS elements can be found in the LDM stalk. Retained medullary cord (RMC) is a closed spinal dysraphism involving a robust, elongated, cord-like structure extending from the conus medullaris to the dural cul-de-sac. Because the RMC is assumed to be caused by impaired secondary neurulation, concurrent RMC and CDS cannot be explained embryologically. In the present article, we report a case in which CDS elements were noted in each tethering stalk of a coexisting LDM and RMC. Case presentation: A 2.5-month-old boy with left clubfoot and frequent urinary and fecal leakage had 2 tethering tracts. The upper tract, which ran from the thoracic tail-like cutaneous appendage, had CDS elements in the extradural stalk and a tiny dermoid cyst in the intradural stalk immediately after the dural entry. In the lower tract, which ran from the lumbosacral dimple, the CDS as an extradural stalk continued to the RMC at the dural cul-de-sac. Both stalks were entirely resected through skip laminotomy/laminectomy at 1 stage to untether the cord and resect the CDS elements. Conclusion: Surgeons should be aware that CDS elements, in addition to LDM, may coexist with RMC that extends out to the extradural space.

Limited Dorsal Spinal Nondisjunctional Disorders: Limited Dorsal Myeloschisis, Congenital Spinal Dermal Sinus Tract, and Mixed Lesions

Chapter

Jun 2020

Neurosurgical Pathology and Management of Limited Dorsal Myeloschisis Associated with Congenital Dermal Sinus in Infancy

Article

Jul 2020

Background: Because of the shared origin of limited dorsal myeloschisis (LDM) and congenital dermal sinus (CDS), CDS elements may be found within the fibroneural LDM stalk. When part of the CDS invested in the intradural stalk is left during untethering surgery, inclusion tumors such as dermoid cysts may develop. However, the most appropriate surgical strategy for LDM with CDS is still under debate. Methods: Of 19 patients with LDM, 3 (15.8%) had histologically verified CDS elements. We retrospectively analyzed the clinicopathological findings of these patients. Results: In patient 1, the entire stalk including a tiny dermoid cyst at the intradural stalk could be resected through two-level laminectomy during untethering at 6 months of age. In patients 2 and 3, the stalk appeared to be a typical LDM stalk during the initial surgery at 18 and 7 days, respectively; however, CDS was histologically diagnosed in the proximal severed end of the stalk. Postoperative three-dimensional heavily T2-weighted imaging demonstrated spherical enlargement of the remnant stalk, and the entire length of the remnant stalk including newly developed dermoid was resected during the second surgery at 3 years 11 months and 11 months, respectively. Histopathologically, glial fibrillary acidic protein-immunopositive neuroglial tissues and CDS elements were mainly located at the proximal and distal sites of the stalk, respectively, supporting the "dragging down and pulling up" theory. In patients 2 and 3, however, the proximal head of the dermoid cyst passed the distal head of the neuroglial tissues and located at the stalk-cord attachment. Conclusion: Surgeons should be aware of the approximately 10% possibility of the coexistence of CDS when managing infant LDM. However, the recommendation for excision of the entire length of the LDM stalk in all patients should be more carefully made because such a strategy may result in an unnecessary extent of laminotomy/laminectomy for most patients with pure LDM. However, once the postoperative histological examination reveals coexistence of CDS in the resected proximal part of the stalk, the entire length of the remnant stalk should be excised as soon as possible.

Surgical histopathology of limited dorsal myeloschisis with flat skin lesion

Article

Full-text available

Jan 2019
CHILD NERV SYST

PurposeLimited dorsal myeloschisis (LDM) is characterized by two invariable features: a focal closed neural tube defect and a fibroneural stalk linking the skin lesion to the underlying spinal cord. Although detailed histopathological findings of the LDM stalk were originally described by Pang et al., the precise relationship between the histopathological findings and clinical manifestations including intraoperative findings has not been fully determined. Methods We retrospectively analyzed the histopathological findings of the almost entire stalk and their relevance to the clinical manifestations in six Japanese LDM patients with flat skin lesions. ResultsGlial fibrillary acidic protein (GFAP)-immunopositive neuroglial tissues were observed in three of the six patients. Unlike neuroglial tissues, peripheral nerve fibers were observed in every stalk. In four patients, dermal melanocytosis, “Mongolian spot,” was seen surrounding the cigarette-burn lesion. In three of these four patients, numerous melanocytes were distributed linearly along the long axis of the LDM stalk, which might represent migration of melanocytes from trunk neural crest cells during formation of the LDM stalk. Conclusion Immunopositivity for GFAP in the LDM stalk was observed in as few as 50% of our patients, despite the relatively extensive histopathological examination. We confirm that the clinical diagnosis of LDM should be made based on comprehensive histopathological examination as well as clinical manifestations. The profuse network of peripheral nerve fibers in every stalk and the high incidence of melanocyte accumulation associated with dermal melanocytosis might assist the histopathological diagnosis of LDM.

Neurosurgical pathology of limited dorsal myeloschisis

Article

Full-text available

Feb 2018
CHILD NERV SYST

Purpose: The term limited dorsal myeloschisis (LDM) was used by Pang et al. (2010) to describe a distinct clinicopathological entity. LDMs are characterized by two invariable features: a focal-closed neural tube defect and a fibroneural stalk that links the skin lesion to the underlying spinal cord. Methods: We retrospectively analyzed the neurosurgical pathologic findings of four LDM patients. Results: Case 1 had a saccular skin lesion with nonterminal abortive myelocystocele at T11-12. Cases 2, 3, and 4 had a non-saccular (flat) skin lesion in the lumbosacral region. The morphologic features of the lesion in case 2 were those of meningocele manque. Cases 3 and 4 had accompanying non-LDM anomalies, caudal-type lipoma and type II split-cord malformation with neurenteric cyst, respectively. At preoperative diagnosis of the LDM stalk, magnetic resonance imaging, including 3D heavily T2-weighted image was useful; however, minute findings were often missed in the complicated cases 3 and 4. All patients had a favorable outcome following untethering of the stalk from the cord. The central histopathological feature of the LDM stalk is neuroglial tissue in the fibrocollagenous band; however, the stalk in cases 2 and 4 did not have glial fibrillary acidic protein-immunopositive neuroglial tissues. Conclusions: Therefore, the diagnosis of LDM should be made based on comprehensive evaluation of histologic and clinical findings.

New classification of spinal lipomas based on embryonic stage

Article

Full-text available

Jan 2017

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.

Usefulness of three-dimensional T1-weighted spoiled gradient-recalled echo and three-dimensional heavily T2-weighted images in preoperative evaluation of spinal dysraphism

Article

Full-text available

May 2013
CHILD NERV SYST

Purpose: The aim of this study was to evaluate the usefulness of three-dimensional T1-weighted spoiled gradient-recalled echo (3D T1-GRE) images for the preoperative anatomical evaluation of lumbosacral lipoma, thick filum terminale, and myelomeningocele as a means of compensating for the drawbacks of 3D heavily T2-weighted (3D hT2-W) images. Methods: Nine patients with lumbosacral lipomas, one patient with tight filum terminale, and five patients with myelomeningoceles were included in this study. 3D T1-GRE images were compared with 3D hT2-W images or conventional magnetic resonance images in terms of delineation of lipomas and other structures in the patients with lipomas and tight filum terminale. For patients with myelomeningoceles, 3D T1-GRE images were compared with 3D hT2-W images in terms of artifacts in the cerebrospinal fluid (CSF) space. Results: The 3D T1-GRE images demonstrated lipomas with good contrast to the spinal cord and CSF space and more clearly delineated the anatomical relationship between lipomas and these structures than did the 3D hT2-W images. The 3D T1-GRE images delineated dural defects through which extradural lipomas penetrated into the intradural space. The 3D T1-GRE images also demonstrated the presence or absence of lipomas in the filum terminale and the absence of artifact in the myelomeningoceles. Furthermore, they were useful for differentiating artifacts observed on the 3D hT2-W images from nerve elements. Conclusions: The complementary use of 3D T1-GRE and 3D hT2-W images may compensate for the drawbacks of 3D hT2-W images and may eventually improve lesion visualization and surgical decision making.

Congenital Dermal Sinus and Limited Dorsal Myeloschisis: "Spectrum Disorders" of Incomplete Dysjuction Between Cutaneous and Neural Ectoderms

Article

Mar 2018
NEUROSURGERY

Background: The existence of tethering tracts in spinal dysraphism, other than congenital dermal sinus (CDS), has been recognized and has been summated into an integrated concept of limited dorsal myeloschisis (LDM). Objective: To elucidate the underlying embryology of LDM in relation to CDS by focusing on the pathological features of special cases of tethering tracts. Methods: Out of 389 spinal dysraphism patients who were operated on from 2010 to 2016, 5 patients who had tethering tracts composed of both CDS and LDM (or "probable LDM" if only fibrous tissue was found) were identified. Their clinical presentation, radiological images, operative findings, and pathology were thoroughly reviewed. Results: Three nonsaccular-type patients harbored stalks in which the squamous epithelial lined sinus (CDS) was found in the distal portion, and fibroneural (LDM) or fibrous (probable LDM) tissue in the proximal part. Two patients had saccular lesions, and a stalk was found inside the sac, connecting a small pit on the skin to the spinal cord. The tracts were pathologically identical to a CDS. Conclusion: This study reports the coexistence of CDS and LDM (or probable LDM) components. These unique cases support the hypothesis that the CDS and LDM are among a spectrum of an anomaly that is caused by failure of complete dysjunction between cutaneous and neural ectoderms. Neurosurgeons should be aware of the possibility of coexisting "CDS" components in cases suggestive of LDM. In such cases, not only untethering but also meticulous removal of the squamous epithelium is critical.

Congenital Dermal Sinus and Limited Dorsal Myeloschisis: “Spectrum Disorders” of Incomplete Dysjuction Between Cutaneous and Neural Ectoderms

Article

Mar 2018

BACKGROUND The existence of tethering tracts in spinal dysraphism, other than congenital dermal sinus (CDS), has been recognized and has been summated into an integrated concept of limited dorsal myeloschisis (LDM). OBJECTIVE To elucidate the underlying embryology of LDM in relation to CDS by focusing on the pathological features of special cases of tethering tracts. METHODS Out of 389 spinal dysraphism patients who were operated on from 2010 to 2016, 5 patients who had tethering tracts composed of both CDS and LDM (or “probable LDM” if only fibrous tissue was found) were identified. Their clinical presentation, radiological images, operative findings, and pathology were thoroughly reviewed. RESULTS Three nonsaccular-type patients harbored stalks in which the squamous epithelial lined sinus (CDS) was found in the distal portion, and fibroneural (LDM) or fibrous (probable LDM) tissue in the proximal part. Two patients had saccular lesions, and a stalk was found inside the sac, connecting a small pit on the skin to the spinal cord. The tracts were pathologically identical to a CDS. CONCLUSION This study reports the coexistence of CDS and LDM (or probable LDM) components. These unique cases support the hypothesis that the CDS and LDM are among a spectrum of an anomaly that is caused by failure of complete dysjunction between cutaneous and neural ectoderms. Neurosurgeons should be aware of the possibility of coexisting “CDS” components in cases suggestive of LDM. In such cases, not only untethering but also meticulous removal of the squamous epithelium is critical.

Modification of surgical procedure for “probable” limited dorsal myeloschisis

Article

Feb 2017

OBJECTIVE Since the entity limited dorsal myeloschisis (LDM) was proposed, numerous confusing clinical cases have been renamed according to the embryopathogenesis. However, clinical application of this label appears to require some clarification with regard to pathology. There have been cases in which all criteria for the diagnosis of LDM were met except for the presence of a neural component in the stalk, an entity the authors call “probable” LDM. The present study was performed to meticulously review these cases and suggest that a modified surgical strategy using limited laminectomy is sufficient to achieve the surgical goal of untethering. METHODS The authors retrospectively reviewed the imaging findings, operative notes, and pathology reports of spinal dysraphism patients with subcutaneous stalk lesions who had presented to their institution between 2010 and 2014. RESULTS Among 33 patients with LDM, 13 had the typical nonsaccular lesions with simple subcutaneous stalks connecting the skin opening to the spinal cord. Four cases had “true” LDM meeting all criteria for diagnosis, including pathological confirmation of CNS tissue by immunohistochemical staining with glial fibrillary acidic protein. There were also 9 cases in which all clinical, imaging, and surgical findings were compatible with LDM, but the “neural” component in the resected stalk was not confirmed. For all the cases, limited exposure of the stalk was done and satisfactory untethering was achieved. CONCLUSIONS One can speculate based on the initial error of embryogenesis that if the entire stalk were traced to the point of insertion on the cord, the neural component would be proven. However, this would require an extended level of laminectomy/laminotomy, which may be unnecessary, at least with regard to the completeness of untethering. Therefore, the authors propose that for some selected cases of LDM, a minimal extent of laminectomy may suffice for untethering, although it may be insufficient for diagnosing a true LDM.

Limited dorsal myeloschisis: A not-so-rare form of primary neurulation defect

Article

Sep 2013
CHILD NERV SYST

Limited dorsal myeloschisis (LDM) is a distinctive form of spinal dysraphism characterized by two constant features: a focal "closed" midline skin defect and a fibroneural stalk that links the skin lesion to the underlying cord. The embryogenesis is hypothesized to be incomplete disjunction between cutaneous and neural ectoderms, thus preventing complete midline skin closure and allowing persistence of a physical link (fibroneural stalk) between the disjunction site and the dorsal neural tube. We utilize the experience gained from the management of 63 patients with LDM to illustrate these features. All patients were studied with MRI or CT myelogram, operated on, and followed for a mean of 9.4 years. There were 11 cervical, 16 thoracic, 8 thoracolumbar, and 28 lumbar lesions. Two main types of skin lesion were: saccular (26 patients; consisting of a skin base cerebrospinal fluid sac topped with squamous epithelial dome or a thin membranous sac) and nonsaccular (37 patients; with a flat or sunken squamous epithelial crater or pit). The internal structure of a saccular LDM could be a basal neural nodule, a stalk that inserts on the dome, or a segmental myelocystocoele. In nonsaccular LDMs, the fibroneural stalk has variable thickness and complexity. All fibroneural stalks contain glioneuronal tissues accompanied by variable quantities of nerves and mesodermal derivatives. In all LDMs, the fibroneural stalk was tethering the cord. Twenty-nine patients had neurological deficits. There was a positive correlation between neurological grade and age suggesting progression with chronicity. Treatment consisted of detaching the stalk from the cord. Most patients improved or remained stable. LDMs were associated with three other dysraphic malformations in more than coincidental frequencies: six LDMs were contiguous with dorsal lipomas, four LDMs shared the same tract or traveled in parallel with a dermal sinus tract, and seven LDMs were related to a split cord malformation. The embryogenetic implications of these associations are discussed. LDM is a distinctive clinicopathological entity and a tethering lesion with characteristic external and internal features. We propose a new classification incorporating both saccular and flat lesions.

Limited Dorsal Myeloschisis: A Distinctive Clinicopathological Entity

Article

Dec 2010
NEUROSURGERY

Limited dorsal myeloschisis (LDM) is a distinctive form of spinal dysraphism characterized by 2 constant features: a focal "closed" midline defect and a fibroneural stalk that links the skin lesion to the underlying cord. The embryogenesis is hypothesized to be incomplete disjunction between cutaneous and neural ectoderms, thus preventing complete midline skin closure and allowing persistence of a physical link (fibroneural stalk) between the disjunction site and the dorsal neural tube. To illustrate these features in 51 LDM patients. All patients were studied with magnetic resonance imaging or computed tomography myelography, operated on, and followed for a mean of 7.4 years. There were 10 cervical, 13 thoracic, 6 thoracolumbar and 22 lumbar lesions. Two main types of skin lesion were saccular (21 patients), consisting of a skin-base cerebrospinal fluid sac topped with a squamous epithelial dome, and nonsaccular (30 patients), with a flat or sunken squamous epithelial crater or pit. The internal structure of a saccular LDM could be a basal neural nodule, a stalk that inserts on the dome, or a segmental myelocystocele. In nonsaccular LDMs, the fibroneural stalk has variable thickness and complexity. In all LDMs, the fibroneural stalk was tethering the cord. Twenty-nine patients had neurological deficits. There was a positive correlation between neurological grade and age, suggesting progression with chronicity. Treatment consisted of detaching the stalk from the cord. Most patients improved or remained stable. LDM is a distinctive clinicopathological entity and a tethering lesion with characteristic external and internal features. We propose a new classification incorporating both saccular and flat lesions.

Limited dorsal myeloschisis with no extradural stalk linking to a flat skin lesion: a case report

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