Rapid enlargement of a syringomyelia cavity following syringo-subarachnoid shunt: case report.

We describe a patient who presented with syringomyelia 20 years following an operation for foramen magnum meningioma. A syringo-subarachnoid shunt was placed, which connected the syrinx and the cerebello-pontine angle cistern. Following shunt placement, the patient's symptoms rapidly progressed, and magnetic resonance imaging (MRI) revealed enlargement of the syrinx. The symptoms improved with a decrease in syrinx size after placement of a syringo-peritoneal shunt in combination with revision of the syringo-subarachnoid shunt, changing the position of the subarachnoid tip to the caudal spinal subarachnoid space. The mechanism of rapid enlargement of the syrinx cavity following placement of the syringo-subarachnoid shunt is discussed.