Rapid expansion of a ventral arachnoid cyst after syringo-subarachnoid shunting in the thoracic spinal cord: Case report

Background: Intradural spinal arachnoid cysts have rarely been reported in association with intramedullary cysts. These associated lesions most commonly occur in the thoracic spine. Case Description: We reported an unusual balance of cerebrospinal fluid dynamics between an initially occult arachnoid cyst and syringomyelia. The arachnoid cyst was not allowed to express itself until the syrinx was decompressed with a syringo-subarachnoid shunt. Conclusion: Only one other report in the literature described a similar case; however, our case is the first to be confirmed by intraoperative ultrasound.