Lumboperitoneal shunt combined with myelotomy for treatment of syringohydromyelia.

This study was undertaken to investigate whether a direct communication between the fourth ventricle and the syrinx exists in the majority of patients with syringohydromelia and whether intraspinal pressure plays a role in the pathogenesis of this disorder. A series of 13 patients with syringohydromyelia delineated by magnetic resonance (MR) imaging was reviewed, and the intracranial pressure (ICP) and lumbar spinal pressure (LSP) were recorded concomitantly in three patients. Lumboperitoneal shunting was performed in seven patients, six of whom also underwent myelotomy of the caudal spinal cord. Magnetic resonance imaging visualized a cerebrospinal fluid (CSF) channel connecting the fourth ventricle with the syrinx in only one of the 13 patients, and in the remaining 12 patients it revealed a long segment of the spinal cord free of syrinx below the fourth ventricle. This finding is in accordance with recent MR studies of syringohydromyelia. The concomitant recording of ICP and LSP in our patients who had myelomeningocele and Chiari II malformation showed findings contradicting the reports of Williams. Lumbar spinal pressure was equal to ICP under steady-state conditions, and was elevated by straining or crying more markedly than ICP. Craniospinal pressure dissociation with ICP greater than with LSP, as described by Williams, was not observed. Lumboperitoneal shunting concomitant with myelotomy and syringopleural shunting 1 month after myelotomy resulted in marked and sustained shrinkage of the syrinx and neurological improvement in four patients. It was concluded that the majority of patients with syringohydromyelia and Chiari malformation lack a direct communication connecting the fourth ventricle with the syrinx. The results suggest that CSF moves under pressure into the spinal cord, contributing to the formation and maintenance of the syrinx, and that LP shunting combined with myelotomy can effect shrinkage of the syrinx.