Missed limited dorsal myeloschisis: an unfortunate cause for recurrent tethered cord syndrome

Tethered cord secondary to focal nondisjunction of the primary neural tube: experience from a Singapore children's hospital

PURPOSE

Tethered cord due to focal nondisjunction of primary neuralisation (FNPN) is a rare form of spinal dysraphism. We present our institutional experience in managing children diagnosed with FNPN.

MATERIALS AND METHODS

This is a single institution, retrospective study approved by the hospital ethics board. Patients below 18 years of age diagnosed with CDS, LDM or their mixed lesions, and subsequently underwent intervention by the Neurosurgical Service, KK Women's and Children's Hospital, are included.

RESULTS

From 2001 to 2021, 16 FNPN patients (50% males) were recruited. Eight of them had CDS (50.0%), seven had LDM (43.8%), and one patient had a mixed CDS and LDM lesion (6.2%). The average duration of follow up was 5.7 years and the mean age of surgery was 6 months old. Thirteen patients underwent prophylactic intent surgery (81.2%) and three had therapeutic intent surgery (18.8%). All patients did not have new neurological deficit or required repeat surgery for cord retethering. We observed that detethering surgery performed at or less than three months old was associated with having a wound infection (p = .022).

CONCLUSIONS

Our study reports that early recognition and timely intervention are mainstays of management for FNPN. We advocate a multi-disciplinary approach for good outcomes.

Saccular Limited Dorsal Myeloschisis with Spinal Cord Deviation out of the Spinal Canal to the Sac

Saccular limited dorsal myeloschisis (LDM) is characterized by a fibroneural stalk linking the saccular skin lesion to the underlying spinal cord. Since untethering surgery during the early postnatal period is often indicated to prevent sac rupture, saccular LDM should be distinguished from myelomeningocele (MMC) during the perinatal period. We treated two patients with the spinal cord deviation from the spinal canal to the sac, which mimicked a prolapse of the neural placode into the MMC sac. In patient 1, pre- and postnatal magnetic resonance imaging (MRI) revealed that the spinal cord was strongly tethered to the thick stalk. During surgery, the dorsally bent cord and stalk were united, and the border between these two was determined with intraoperative neurophysiological mapping (IONM). In patient 2, the spinal cord was tethered to two slender stalks close to each other, which was visible with the combined use of sagittal and axial postnatal three-dimensional heavily T2-weighted imaging (3D-hT2WI). The preoperative MRI hallmark of saccular LDM is the visualization of a stalk that links the bending cord and sac. Complete untethering surgery to return the cord into the spinal canal and correct its dorsal bending is recommended.

Atlantoaxial limited dorsal myeloschisis: A report of two cases and review of literature

Introduction

Limited dorsal myeloschisis (LDM) is a rare form of spinal dysraphism that is characterised by a distinctive fibroneural stalk connecting the spinal cord to the overlying skin lesion. The skin lesions associated with LDM can appear benign clinically and careful evaluation with an MRI scan is essential for diagnosing LDM and to differentiate this entity from other forms of spinal dysraphism and benign causes of skin lesions.

Research question

There is a lack of reported atlantoaxial LDM in the literature. We sought to report the clinical presentation, radiological features and surgical management of the first two reported atlantoaxial LDM.

Material and methods

Clinical findings and radiological images of the two cases of atlantoaxial LDM that underwent surgical intervention at our institution were retrieved from the medical notes, operative records and imaging system.

Results

Both cases of atlantoaxial LDM (C0-1 and C1-2 respectively) underwent successful resection of the overlying cutaneous lesions and stalks to release the tethered spinal cords.

Discussion

The surgical management of LDM have been associated with good outcomes and consists of resecting the fibroneural stalk close to the underlying cord, releasing the tethered spinal cord and removing the overlying cutaneous lesion.

Conclusion

These are the first two reported cases of atlantoaxial LDM in the literature. We aim to raise awareness of this pathological entity and highlight the importance of establishing the correct diagnosis to guide definitive management, and report the favourable neurological outcome in these cases despite the rostral location.

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Limited dorsal myeloschisis is a rare form of closed spinal dysraphism.

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These are the first two reported cases of atlantoaxial limited dorsal myeloschisis.

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Favourable surgical outcomes can be achieved despite the rostral location.

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Dorsal midline cutaneous lesions should be investigated further with MRI scan.

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The fibroneural stalk connects the overlying cutaneous lesion to the spinal cord.

Embryology of Spinal Dysraphism and its Relationship to Surgical Treatment

Spinal dysraphism is an umbrella term that encompasses a number of congenital malformations that affect the central nervous system. The etiology of these conditions can be traced back to a specific defect in embryological development, with the more disabling malformations occurring at an earlier gestational age. A thorough understanding of the relevant neuroembryology is imperative for clinicians to select the correct treatment and prevent complications associated with spinal dysraphism. This paper will review the neuroembryology associated with the various forms of spinal dysraphism and provide a clinical-pathological correlation for these congenital malformations.

Slender Stalk with Combined Features of Saccular Limited Dorsal Myeloschisis and Congenital Dermal Sinus in a Neonate

Limited dorsal myeloschisis (LDM) and congenital dermal sinus (CDS) originate from incomplete disjunction between the cutaneous and neural ectoderms. Some LDM stalks have been found to have elements of a CDS or dermoid cyst. We surgically treated a saccular lesion in the lumbosacral region of a 7-day-old male neonate. Although fetal magnetic resonance imaging (MRI) failed to reveal a stalk, postnatal MRI including three-dimensional heavily T2-weighted imaging demonstrated a stalk originating from the lumbar cord and extending caudally to enter the lumbosacral meningocele sac. During untethering surgery, we found that the stalk was slender, with a diameter of 0.7-0.8 mm, but otherwise appeared to be a typical LDM stalk. Histopathological examination revealed that the fibrocollagenous stalk contained glial fibrillary acidic protein-immunopositive neuroglial tissues and stratified squamous epithelium. The present report describes the first documented case of a stalk with combined features of saccular LDM and CDS in a neonate. Since cutaneous ectodermal tissue is likely to remain in the remnant stalk, this patient requires careful monitoring to detect the potential development of a dermoid cyst.

A case of prenatally diagnosed limited dorsal myeloschisis with good prognosis

Diagnosis of fetal spinal dysraphism is a challenge. It is difficult to distinguish between a meningocele, myelomeningocele, and a recently described entity called limited dorsal myeloschisis (LDM). Although myelomeningocele is associated with a poor prognosis, LDM can have a good outcome. We present a case of prenatally diagnosed LDM. Because sonographic examination revealed a round, cystic, septated cervical mass without associated cerebral anomalies, the lesion was initially considered an isolated meningocele. Fetal MRI contributed to correct the diagnosis. A diagnostic error can lead to the wrong surgical support or even the termination of pregnancy. Therefore, we highlight the importance of fetal MRI in such cases, particularly when no cerebral abnormalities are observed on sonographic examination.

Neurosurgical pathology of limited dorsal myeloschisis

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.