STUDY DESIGN: Retrospective case series. OBJECTIVE: To determine the clinical significance and prognosis of idiopathic syringomyelia. SUMMARY OF BACKGROUND DATA: With the widespread use of magnetic resonance imaging, cases of syringomyelia are found occasionally. However, the clinical significance and optimum treatment strategy for idiopathic syringomyelia remain unclear, because there are few reports on details of this condition. METHODS: The clinical records and magnetic resonance images of 15 patients with idiopathic syringomyelia were reviewed to determine the changes in patient's neurologic status assessed by the Japanese Orthopedic Association scores for cervical myelopathy and the distribution of the syringomyelia on magnetic resonance imaging. Twelve cases were treated conservatively (conservative group) and syringo-subarachnoid shunt was performed in the remaining 3 cases (surgical group). The follow-up period ranged from 7 to 20 years (mean: 10.5 y). RESULTS: The localized type of idiopathic syringomyelia, which extended under 3 vertebras (mean: 2.1 vertebras), was observed in the 12 patients of the conservative group. There were no significant changes in either the size of the syringomyelia or the severity of the neurologic deficits during the follow-up period (mean: 10 y). In contrast, the extended type, which distributed over 4 or more vertebras (mean: 10.2 vertebras), was observed in the 3 patients of the surgical group. Because of severe and progressive neurologic deficits, syringo-subarachnoid shunt was performed and the surgery successfully prevented further neurologic deterioration. The mean Japanese Orthopedic Association score of the surgical group was significantly lower than that of the conservative group, both at the time of the initial examination and at the final follow-up. CONCLUSIONS: There are 2 types of idiopathic syringomyelia. One is a "localized" type, which might represents congenital enlargement of the central canal of the spinal cord, and can be managed conservatively. The other is an "extended" type, which causes progressive neurologic dysfunction, and should be treated surgically to prevent further neurologic deterioration. Further study should be needed to clarify the mechanism of the extended type of idiopathic syringomyelia.
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