Spinal Extradural Arachnoid Cyst: Illustrative Case Report and Review of the Literature

Introduction Spinal extradural arachnoid cysts (SEACs) are benign dural outpouchings that can often communicate with the subarachnoid space, allowing cerebrospinal fluid (CSF) to accumulate. Magnetic Resonance Imaging (MRI) often fails to identify the defect which can make accurate localization and surgical planning difficult. Case description We report a case of a 42-year-old female with a large thoracolumbar SEAC (7.1 cm, spanning T11–L1) causing cord compression and neurological deficits. After conservative treatments failed, we performed a single-level T12 laminectomy to fenestrate the cyst and repair a small dural defect at the proximal left T12 nerve root. Intrathecal fluorescein injected via a lumbar drain helped identify the CSF leak. Intraoperative ultrasound confirmed complete cyst evacuation and spinal cord decompression. Postoperatively, the patient’s neurological symptoms improved and there was no evidence of cyst recurrence or CSF leak after 4 weeks on follow-up MRI. Conclusion This case details a surgical approach that opts for limited exposure and defect closure instead of extensive laminectomies and full cyst excision in SEAC management. A multi-level cyst spanning three vertebrae was effectively resolved with a single-level approach focusing on the dural communication. There is consensus on repairing the dural defect, but the necessity of complete cyst wall resection is controversial. This case, combined with emerging evidence, suggests that targeted cyst fenestration with dural defect closure can achieve excellent outcomes in this rare pathology.