Mixed split cord malformation: are we missing something?

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.

Chinese expert consensus on diagnosis and management of split cord malformation

Split cord malformation (SCM) is a neural tube defect that the spinal cord is longitudinally separated into two hemicords with individual functions, which causes severe spinal cord impairment and sensorimotor deficit. As a kind of myelodysplasia and a special type of tethered cord syndrome, SCM is not widely understood, and common issues in the diagnosis and treatment of SCM should be clarified. In this paper, the Chinese Split Cord Malformation Working Group made a consensus for SCM on embryopathogenesis and types, clinical presentations, neuroimaging assessment, indications and principle of the surgery, surgical techniques and nuances, and prognosis and follow up.

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.

Historical Perspective of Split Cord Malformations: A Tale of Two Cords

INTRODUCTION

Our appreciation and understanding of what is now known as the split cord malformation (SCM) have a long history. The oldest known example of SCM is from roughly AD 100. Other isolated examples can be found in the large body of work of the pathologists of the 1800s, where the SCMs were found incidentally during autopsies.

CONCLUSIONS

SCM has a rich history and has intrigued physicians for over 200 years. Many well-known figures from the past such as Chiari and von Recklinghausen, both pathologists, made early postmortem descriptions of SCM. With the advent of MRI, these pathological embryological derailments can now often be detected and appreciated early and during life. Our understanding and ability to treat these congenital malformations as well as the terminology used to describe them have changed over the last several decades.

Diastematomyelia with hemimyelomeningocele: An exceptional and complex spinal dysraphism

Variations in split cord malformation (SCM) have been described earlier. However, a true hemimyelomeningocele (HMM) as only congenital malformation is extremely rare and is reported infrequently in published literature. We are reporting the case of a 3-month-old girl child who presented with a swelling on the lower back since birth. Magnetic resonance imaging revealed a type 1 SCM with right hemicord forming a HMM. Precise diagnosis and thorough anatomical detail of dysraphism is essential for optimal, individualized neurosurgical management.

Cutting filum terminale is very important in split cord malformation cases to achieve total release

AIM

Split cord malformations (SCMs) are rare congenital anomalies of the vertebrae and the spinal cord. Tethered cord syndrome (TCS) is a clinical condition of various origins that arises from tension on the spinal cord. Radiographic findings may include and/or associate split cord malformations and the other neural tube defects. However, the spinal cord can even be tethered by a filum terminale with normal appearance and normal level conus medullaris in magnetic resonance imaging (MRI). The aim of our study is to show whether SMC patients with normal or abnormal MRI findings had all histological abnormal filum terminale and also to show that the standard SCM repairing operation without cutting filum will not achieve total release.

MATERIAL AND METHODS

We have reviewed 33 SCM patients between July 2005 and December 2013. They were operated by adding untethering procedure of filum terminale following standard surgical intervention, and a part of the filum was taken for histopathological examination even though MRI did not show the presence of abnormality of filum terminale.

RESULTS

We found that abnormal filum terminale with a normal appearance may had dense collagen fibers, wide and numerous capillaries, and hyaline formation, while normal filum terminale is a mixture of collagen fibers and blood vessels. We did not obtain positive Verhoeff elastic fiber staining. The elastic fibers had disappeared in all fila terminalia, except control cadaver group.

CONCLUSION

Our results showed that all fila of SCM patients had loss of elastic fibers and increased of hyalinization, which means loss of elasticity of filum terminale. Less severe traction may remain asymptomatic in childhood and present with neurological dysfunction later in life. For this reason, surgical procedure of SCM patients including releasing of filum terminale seems more beneficial for the patients and be better for long term.

Concurrent split cord malformation and teratoma: dysembryology, presentation, and treatment

Split cord malformation (SCM) is a rare form of spinal dysraphism in which the spinal cord is divided in the sagittal plane, forming a double neural tube. In addition to being associated with a variety of malformations, SCM may occur with spinal cord tumors, with only exceptional cases involving teratomas. As only eight patients with a teratoma associated with SCM have been reported, their presentation characteristics and treatment are currently unclear. We review the literature of all patients with SCM with concurrent spinal teratoma, discuss the potential dysembryology, and report the first case of SCM with concurrent spinal teratoma in an elderly patient. The mean age of those with concurrent SCM and teratomas was 39.4 years, with 55.6% occurring in females. The lumbar spine was the most frequent location for teratomas (66.7%), with the Type II malformation more commonly occurring with these tumors (75%). The duration of symptoms varied widely, ranging from 1 month to 5 years, with the average duration being nearly 2 years. Back pain (87.5%) and lower extremity weakness (75%) were the most common presenting symptoms. As SCM may be associated with progressive neurological deterioration and teratomas can contain immature or malignant components, surgery should be attempted with the goal of gross total resection. Nonetheless, in patients with a concurrent tumor and spinal dysraphism, spinal teratomas should be considered in the differential diagnosis. Gross total resection of these lesions may be safely achieved even in the presence of SCM using intraoperative electrophysiologic monitoring.

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.

Split cord malformation Type II with twin dorsal lipomas

Although uncommon, variations in split cord malformation (SCM) have been described. However, a combination of SCM Type II and dorsal lipomas has not been reported. The authors describe the case of a 6-year-old girl who presented with a 1-year history of spastic paraparesis associated with a lipomatous swelling on her lower back. Radiology revealed a Type II SCM with a dorsal lipoma at that level. Intraoperatively, the authors observed a dorsal lipoma for each hemicord; these were excised, and the septum causing the split was cut. Premature separation of the cutaneous and neural ectoderm is predetermined for each neural fold, and a split at this level would give rise to SCM with twin dorsal lipomas, one for each hemicord.

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.