Posterior spinal cord herniation into an extradural thoracic arachnoid cyst: surgical treatment. Case report and review of the literature.

The authors describe the case of a 2-year-old boy who experienced progressive spastic paraparesis for several months. Magnetic resonance imaging revealed an extensive extradural arachnoid cyst at the T3-L1 levels and posterior spinal cord herniation at T3-4. Surgical release of the neck of the hernia and total resection of the arachnoid cyst were performed. The patient had good clinical recovery several weeks after surgical decompression. This case highlights an exceedingly rare type of spinal cord herniation in a pediatric age group, and focuses on the abnormalities of the dorsal dura mater, together with imaging and intraoperative findings.