The intermediate type split cord malformation: hypothesis and case report

Gastrulation and Split Cord Malformation

Split cord malformation (SCM) is a rare form of closed spinal dysraphism, in which two hemi-cords are present, instead of a single spinal cord. SCM is categorised into type 1 and type 2. Type 1 SCM is defined by the presence of a bony or osseocartilaginous spur between the hemi-cords, whereas type 2 SCM has no bony spur, and the two hemi-cords are contained within a single dura. In this chapter, we present the putative mechanisms by which SCM arises, including gastrulation defects and Pang's unified theory. The typical and rare clinical presentations and variations are described. Finally, we outline the step-by-step surgical approach to both SCM 1 and 2 and the overall prognosis of both conditions.

Type 1.5 Split Cord Malformation : A New Theory of Pathogenesis

To report two cases of type 1.5 split cord malformation (SCM), a subtype of SCM with combined characteristics of types I and II and to review the relevant literature and propose a new possible pathogenetic theory for type 1.5 SCM. A 52-year-old woman had hemicords within a single dural sac with a dorsal bony septum at the L5 level. A 9-year-old boy had hemicords within a single dural sac with a ventral bony septum and fibrous extension at the L3 level. Both patients underwent microsurgical treatments for removing the bony septum, detethering the spinal cord, and sectioning the filum terminale. The surgical procedure revealed an extradural partial bony septum and hemicords within an intact single dural sac in each patient. Both patients were discharged from the hospital without de novo nerve dysfunction. Published cases have validated that types I and II SCM can overlap. We recommend recent type 1.5 SCM as a normative terminology for this overlapping SCM and report two rare cases of this SCM. We propose an associated pathogenesis consisting of uneven distribution and regression to explain type 1.5 SCM. Furthermore, we postulate that the amount of condensing meninx primitiva might determine whether the left bony septum has fibrous extensions to the opposite dura in type 1.5 SCM.

Split Cord Malformation Type 2 with Double Dorsal Lipoma: A Sequela or a Chance

An 11-month-old baby girl, with normal perinatal history, presented with a congenital lumbosacral swelling and a sacral dimple. Imaging revealed a split cord malformation (SCM) type 2 at L1–L3 with a lipomeningocoele extending intradurally and tethering both the hemicords, the conus was noted to be at L4. She underwent excision of the lipoma and detethering of the hemicords. Intraoperatively, the split cord was seen from L1 to L3 with an aberrant median vessel passing between the hemicords. Two lipomas were seen separately attached to each of the hemicords, the lipomas were dissected off the hemicords, and the hemicords were neurulated. The case helps revisit the unified theory proposed by Pang for SCM as well as the theory of premature disjunction in the pathogenesis of lipomeningocoele. Formation of the endomesenchymal tract splits the developing cord into two, whereas the premature detachment of neuroectoderm from the cutaneous ectoderm can lead to lipomeningocoeles. The present case is only the fourth case ever reported of an SCM type 2 with double lipoma. In the case report, we discuss the embryological basis of this condition and surgical nuances of management.

Type 1.5 Split Cord Malformations: An Uncommon Entity

BACKGROUND

Split cord malformations (SCMs) are among the rare congenital spinal anomalies. In 1992, Pang et al. proposed the unified theory of embryogenesis and explained the formation of SCM type 1 and 2. This theory has been widely accepted in the neurosurgical literature, backed by several studies. However, there have been reports in the literature that defy both the classification as well as the formation of SCMs, based on the unified theory of embryogenesis. We report a case of SCM that does not fit into this classification scheme and try to elucidate its embryologic basis, with review of the relevant literature. We also attempt to include this variety into the existing classification system of SCMs.

CASE DESCRIPTION

An 11-year-old boy presented with low backache after trivial trauma. He was neurologically intact. Imaging showed low-lying tethered cord and a midline ventral bony spur (D12, L1) with a single dural sac encasing both the hemicords. Surgical exploration showed a ventral bony spur with 2 hemicords, enclosed in a single dural tube. Excision of the bony spur and detethering of the filum terminal were performed. The postoperative course was uneventful and the patient was discharged satisfactorily.

CONCLUSIONS

SCMs possibly represent a continuum of changes beginning at the gestational age of days 20-30. Terminology such as mixed or intermediate type is used to denote SCMs that show features of both type 1 and type II. We prefer using type 1.5 SCMs for all such cases, thereby avoiding confusion and maintaining uniformity in the nomenclature. However, further experimental studies are required to substantiate our understanding of these complex embryologic anomalies on the basis of current hypotheses.

Neural tube dysraphism: review of cutaneous markers and imaging

Neural tube dysraphisms are congenital anomalies resulting from impaired formation of structures along the craniospinal axis during central nervous system development. When these malformations are large or lack a skin covering, they are easily recognized, whereas smaller or skin-covered malformations may not be readily apparent. Due to the intimate embryologic origin of the skin and nervous system, these occult malformations are often heralded by associated cutaneous abnormalities. In this article, the common clinical presentations and cutaneous markers of craniospinal dysraphism are reviewed, along with the recommended imaging modalities.

Split cord malformation types I and II: a personal series of 131 patients

PURPOSE

A personal series of 131 patients with split cord malformation (SCM) operated on is presented.

METHODS

Age, gender, symptoms and signs, radiological and operative findings, complications, associated anomalies, outcome, and pathological specimens were analyzed.

RESULTS

There were 88 girls (73 %) and 43 boys (27 %). The female predominance was slightly more remarkable in type I SCMs than in type II SCMs. The presenting symptoms can be summarized as skin lesions, spina bifida aperta, scoliosis or kyphoscoliosis, sphincter disturbance, foot deformities and weakness, and/or atrophy in the lower extremities. The ages of patients with neurological deficits and orthopedic deformities were significantly older than those without deficits (P = 0.030). The duration of symptoms was longer in the patients with neurological deficits and orthopedic deformities than that in those without deficits (P = 0.00095). In six patients, composite SCMs were present. Only one patient with a type II SCM did not have an associated spinal cord lesion. A type I SCM was more frequently encountered in patients with spina bifida (P < 0.0005). Transient postoperative complications were seen in 29 patients (22 %). There was no permanent complication. Retethered cord syndrome developed in five patients with a type I SCM.

CONCLUSIONS

The risk of neurological and orthopedic deficits increases with the age of the patient. The risk of permanent deficit after surgery is very low. The whole spine must be examined for additional lesions. All patients should be surgically treated when diagnosed, especially before the development of orthopedic and neurological manifestations, and all associated lesions should also be treated at the same session.

Sprengel's deformity and spinal dysraphism: connecting the shoulder and the spine

BACKGROUND AND PURPOSE

Sprengel's deformity, a rare congenital malformation of the scapula, may be observed in combination with spinal dysraphism. The co-occurrence of these malformations suggests an unknown shared etiology. Therefore, we reviewed the medical records of eight children presenting with both malformations and performed a review of the literature.

PATIENTS AND METHODS

Databases from four university medical centers were searched for children presenting between 1992 and 2012 with spinal dysraphism and a Sprengel's deformity.

CONCLUSION

The combination of spinal dysraphism and Sprengel's deformity is rare, and is associated with segmentation defects of the spine and ribs. Although the etiology of both spinal dysraphism and Sprengel's deformity remains unclear, all deformities of the spine, ribs, and shoulder might result from a common genetic defect affecting somitogenesis.

Split cord malformation: experience from a tertiary referral center

AIM

To present clinical, radiological, and follow-up features of 34 cases with spinal split cord malformation (SCM) treated in a tertiary referral center between April 2000 and March 2012.

METHODS

A total of 59 patients were treated due to SCM between April 2000 and March 2012 at the Gazi University Faculty of Medicine, Division of Pediatric Neurosurgery. Data for each patient were evaluated retrospectively, and age, sex, clinical findings, radiological findings, complications, and surgical results were recorded. Patients with a follow-up period of less than 6 months, patients harboring an open spinal dysraphism, and patients who had had their index surgery in another clinic were excluded, thus leaving a total of 34 patients for further analysis.

RESULTS

There were 19 females and 15 males ranging in age from 2 months to 15 years (mean 5.04 years). In this cohort, skin stigma was the most common reason (76.5%) to seek medical care. Of the cases, 22 (64.7%) had lumbar SCM and 12 (35.3%) had thoracic SCM. There were no cervical SCM. Twenty-one (61.8%) of the cases had type 1 SCM and 13 (38.2%) had Type 2 SCM. Of the patients, 21 (61.8%) had a detectable neurological deficit at initial evaluation. There were no differences between patients with and without a neurological deficit regarding age, sex, type, and level of SCM. Overall evaluation of patients regarding their final neurological status revealed that 16 (47.1%) patients improved, 4 (11.8%) deteriorated, and 14 (41.2%) remained stable.

CONCLUSIONS

In our opinion, all patients diagnosed with either type of SCM should be surgically treated to prevent further neurological deterioration. The results of this study, together with previously published data, confirm the effectiveness and safety of surgical intervention in SCM.

Mixed split cord malformation: are we missing something?

BACKGROUND

The new classification for split cord malformation, based on the unified theory of embryogenesis includes two types Type I and II defined on the basis of the nature of the medium septum and the state of the dural tube. According to this, these are the only two essential features needed for typing and there is never an overlap between the two main forms. We have described two cases that defy this theory.

CASE REPORT

We present two patients with split cord malformation who appear to have a combination of features specific to Type I and Type II. Both patients had a partial bony spur within a single dural sac.

CONCLUSION

An overlap between the two forms of split cord malformation does exist. The role of meninx primitiva in the formation of median bony septum is debatable.

Histological study of paramedian dorsal root ganglia in an infant with split cord malformation. Case report

The authors present a histological study of resected tissue obtained from an 18-month-old girl with split cord malformation Type II whose right foot was smaller than her left. Magnetic resonance imaging revealed duplication of the spinal cord below the level of L-1. On laminectomy it was discovered that the cord was tethered in the lumbosacral region. The resected tissue contained the cluster of paramedian dorsal root ganglia unique to this congenital anomaly. On histological examination, the ganglion cells expressed not only neuronal markers but also a marker for muscle cells indicative of pathological development of the midline structure. Further histological study is necessary to gain a deeper insight into this congenital disease and to obtain additional information for use in surgical planning.