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Original Articles Indian Pediatrics 2000;37: 603-607 |
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Split Cord Malformations - A Clinical Study of 48 Cases |
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Manuscript received:
January 21, 1999; Initial review completed: February 8, 1999;
Key words: Diastematomyelia, Spinal lipoma, Split cord malformations, Tethered cord. Split cord malformations (SCM) are anomalies of the spinal cord in which the cord is split over a portion of its length to form a double neural tube. These malformations may arise alone or in combination with other spinal and extraspinal anomalies(1). Hertwig in 1892 first used the term diastematomyelia (from the Greek diastema meaning cleft and melos meaning medulla) to describe spinal malformations in which the cord is split over a variable distance(2). Herren and Edwards used the term diplomyelia (Greek dipulo meaning double) to describe a complete duplication of a spinal cord segment(3). However, these terms have been used interchangeably by various authors(4,5). Pang and his colleagues suggested that, these confusing and misleading terms should be abandoned and suggested a new classification to deal with all double spinal cord malformations and they also proposed a unified theory of embryogenesis to explain various components of these malformations(6,7). Keeping this new classification in mind, we reviewed and analyzed 48 cases of SCM operated at our institute (over six years). The purpose of this communication is to document these findings.
Patient Population: Forty eight cases operated between January 1992 to December 1997 were reviewed for clinical features, operative details, radiological findings and associated anomalies. After work-up all patients with SCMs were operated upon, even if they were asymptomatic and neurologically intact. MRI was the investigation of choice which had been performed in all patients. Surgical Procedures: In patients with type-1 SCM, laminectomy/laminotomy was per-formed around the attachment of rigid septum. The septum was then removed. After the removal of the septum fibrous adhesions were excised and the dural sleeve was resected. Posterior dural closure was done making a single dural sac. In type-2 SCM, laminectomy/laminotomy was performed at the lower end of the split cord level. The dura was opened and the fibrous septum and paramedian roots tethering the cord were excised. Any associated lesions causing tethering were also corrected at the time of operation. Follow up period ranged from 3 months to 5 years (mean = 2.4 years).
Patients’ age ranged from 16 days to 26 years (mean 6.25 years). The age-wise sex distribution is given in Table I. The mean age of patients with neurological deficit was 6.85 years whereas asymptomatic patients presented at a mean age of 2.03 years. Symptoms and Signs: The presenting symptoms can be summarized in three major categories- motor, sensory and autonomic. The motor deficits consisted of weakness of limbs, atrophy and gait disturbance. The sensory complaints were mainly in terms of dysesthetic pain, hypoesthesia, trophic ulcers and auto-amputation of toes. Bladder and bowel inconti-nence was seen in 13 patients (Table II). Hypertrichiosis was the most common skin (Table II) finding present alone in 12 patients and in combination with other findings in 9 cases. In 32(66%) patients there were some cutaneous markers but only 6 (12%) patients were referred to us when they were less than 1 year of age. Orthopedic deformities were observed in 16 cases. CTEV and unilateral limb shortening were the most common deformities seen in 9 and 7 patients, respectively. Six patients were asymptomatic. Radiological Findings: Plain X-ray films of the spine and chest revealed a number of deformities of the spine (Table III). All patients had a bifid lamina which was not placed at the level of the split cord in all patients. The X-ray chest revealed fused or absent ribs in 2 cases and eventration of diaphragm in 1 patient. The bony spur was seen in 23 patients on plain X-ray among 42 cases of type-1 SCM. MRI revealed an additional lesion causing tethering of the cord in 24 (50%) cases (Table III). Chiari malformation was seen in 6 patients. The dorsolumbar and lumbar region were the most common sites involved in 15 and 14 cases, respectively and the cervical region was involved in 3 cases. Involvement of dorsal and lumbosacral region was seen in 9 and 7 cases, respectively. Operative Findings: Forty two patients had type-1 and 6 had type-2 SCM. A variety of lesions causing tethering of cord were observed (Table IV). Outcome and Complications: Of the symptomatic cases twenty-one (50%) patients showed improvement in neurological status in terms of motor (14 cases) and sensory improve-ment (10 cases). Four patients regained conti-nence and one patient showed significant healing of trophic ulcer. Four patients developed fresh neurological deficits in the postoperative period. Neurological status remained unchanged in 17(40%) cases. Four patients developed CSF leak and 3 had wound infections. All these were managed conserva-tively and healed well. There was no operative or perioperative mortality. Among the asympto-matic patients none developed fresh neuro-logical deficit. However, one developed CSF leak which healed with conservative management.
Table
II:
Clinical Presentation and Cutaneous Markers
Table
III:
Radiological Findings
Table
IV:
Operative Findings
All SCM result from the basic error in the formation of accessory neuroenteric canal between the yolk sac and amnion, which is subsequently invested with mesenchyme to form an endomesenchymal tract that splits the notochord and the neural plate(6). Two types of SCM have been described. Type-1 consists of two hemicords, each contained in its dural tube and separated by a rigid median septum. Type-2 consists of two hemicords contained in a single dural sac separated by a non-rigid, fibrous median septum(6). Split cord malforma-tions are seen more often in females with a female to male ratio of 1.5:1(4,8,9). However, we observed a male preponderance in children which is difficult to explain. Age of the patients with symptomatic SCM (mean-6.85 years) was higher than asymptomatic ones (mean-2.03 yrs.). In conformity with earlier series we also found that skin lesions are very frequent in SCM, hypertrichiosis being the most common finding(4,7-11). We had 66% cases having one or more cutaneous manifestations. Seven cases had midline dimple or dermal sinus. Only those patients which have a dermal sinus above the level of intergluteal fold need to be evaluated by MRI as there is high probability that sinus may extend upto dura or to the spinal cord. Asymmetric weakness of lower limb was the most common clinical manifestation. Sphincteric disturbance has been described in SCM (4,5,7,8,12,13). We observed bladder or bowel dysfunction in 13(27%) patients. Dysesthetic pain has been described as a dominant feature in adults(11,14). All of our adult patients had pain as a predominant complaint. Surgery successfully eliminated pain in 5 out of 6 cases. The common bony deformities include scoliosis, block vertebra, hypoplastic vertebra, kyphosis and fused ribs(4,7,8,10). MRI correctly established the diagnosis in all cases and additional lesions as a cause of tether- ing were demonstrated in 50% cases which required surgery in their own merit. Associated lesions have been reported in upto 85%(7,10), making them significant to be identified at the time of initial investigation, so that surgery can be planned in one stage. Chiari malformations are not frequently reported in literature. Pang et al.(7) and Ersahin et al.(10) did not report a single case with Chiari malformation. In our study, 6 patients had Chiari malformations. This group of patients are prone to postoperative respiratory problems. Miller et al.(15) in serial follow up examina-tions of their patients described neurological deterioration in patients who did not undergo surgery. This deterioration was thought to be due to tethering of the cord. In older asymptomatic patients, sudden onset paraplegia or neurological deficit may appear because of trauma or strenuous exercise(11,16). It is because of this reason that Pang et al. recommended treatment of asymptomatic adults in case they have an active life style(7). Also, once a neurological deficit has appeared there is a low chance of complete recovery. In our study thirty-seven patients had motor deficits but only 17(46%) showed improve-ment. These observations suggest that there may be a case to operate asymptomatic patients to prevent future occurrence of deficits and disabilities in these children and adults. In conclusion SCM is an uncommon malformation of spinal cord that needs to be adequately investigated using MRI. Whole neural axis should be evaluated as the chance of finding associated lesions is high. These tethering lesions should be simultaneously treated at the time of initial surgery. The risk of neurological deficit may increase with age, hence all SCMs should be surgically treated. A good outcome is expected aiming at improvement or stabilization of the deficit.
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