Giant intradural extramedullary arachnoid cyst of the thoracic spine.

Spinal intradural arachnoid cysts (ACs) are found frequently in the thoracic region, and often extend over four or five vertebral levels. We present a 28-year-old patient who had a giant thoracic congenital intradural extramedullary AC (T1-T12) with a 10-month history of pain, paresthesia, paraparesis and gait ataxia. A T3 to T6 laminectomy was performed.