Spinal extradural arachnoid cyst: a case report.

Spinal arachnoid cyst is a rare cause of myelopathy secondary to spinal cord compression. We report a case presenting extradural arachnoid cyst of probable traumatic origin leading to irreversible neurological deficits including paraparesis and neurogenic bladder. The patient presented progressive paraparesis and voiding difficulty. Magnetic resonance imaging (MRI) of the spine revealed long segmental cystic lesion of cerebrospinal fluid (CSF) signal intensity at dorsal extramedullary space of T11 to L3 level suggesting arachnoid cyst with diffuse cord compression. On the operation, an ovoid shaped dural defect was identified at right sided dorsolateral aspect of the dura mater between nerve root sleeves at T11 and T12 level. The patient was treated by microsurgical repair of the dural defect and intraoperative findings revealed no further leakage of CSF. The neurological status of the patient was stationary on follow-up examination postoperatively. We postulate that delayed-onset post-traumatic extradural arachnoid cyst should be taken into consideration on the differential diagnosis of intrapinal cysts.