Surgical Management of Thoracic Arachnoid Cyst Causing Spinal Cord Compression: A Case Report.

Spinal arachnoid cysts are rare intradural spinal canal collections of cerebrospinal fluid enclosed by an arachnoid membrane, often associated with congenital or acquired dural defects, most frequently located in the thoracic spine, although they may also occur at lumbar or cervical levels. Symptomatic arachnoid cysts typically cause progressive neurological deficits secondary to spinal cord or nerve root compression. We report the case of a 29-year-old woman presenting with a 1-year history of progressive low back pain, lower limb weakness, and persistent pain unresponsive to conservative management. Magnetic resonance imaging (MRI) demonstrated an extramedullary, extradural cystic lesion extending from T9 to L2, causing significant spinal cord displacement, consistent with an arachnoid cyst. The patient underwent microsurgical decompression consisting of a laminectomy and cyst fenestration under microscopic visualization, resulting in symptomatic relief. Postoperative imaging confirmed resolution of the spinal cord compression. This case underscores the necessity of timely diagnosis and surgical intervention in symptomatic spinal arachnoid cysts to prevent permanent neurological sequelae. MRI remains essential for accurate diagnosis, and early surgical treatment offers a favorable prognosis with low recurrence risk.