Thoracic Spinal Intradural Arachnoid Cyst With a Fulminant Course

Background: Spinal arachnoid cysts are rarely occurring benign cerebrospinal fluid-containing lesions that can occur anywhere along the spinal axis but are principally seen in the thoracic spine. They occur either ventrally or dorsally and can be extradural, intradural extramedullary, or intramedullary. They may be asymptomatic or can present with insidious pain and neurologic symptoms related to spinal cord and/or nerve root compression. Case Report: A 49-year-old male developed sudden midback pain with rapid progression to gait instability, urinary retention, and paraplegia within 10 hours. His presentation for neurosurgical care was delayed because of lack of funds and unfavorable insurance policies. At presentation 3 months after the onset of symptoms, magnetic resonance imaging of his spine showed a ventrolateral intradural extramedullary cystic lesion at T5-T6 with severe cord compression. He underwent T5-T6 and T6-T7 laminectomies with a limited left sixth rib costotransversectomy for microsurgical resection of the cyst. Postoperatively, the patient reported improvement in bladder and bowel control, but his paraplegia persisted. Conclusion: Arachnoid cysts are mostly benign lesions; however, they may have disastrous outcomes if not promptly addressed with the necessary urgency when symptoms are progressive, as in our patient.