Sacral Intradural Arachnoid Cyst of Cauda Equina: A Case Report and Review of the Literature

This report presents the case of a 36-year-old man complaining of chronic low back pain and numbness along the posterolateral surface of the right leg. Magnetic resonance imaging (MRI) revealed a disc degeneration and protrusion at the L₅-S₁ level and an extensive fluid-equivalent formation with a craniocaudal dimension of 8 cm at the S₁-S₅ level. Initially, due to the minimal clinical complaints, the cyst was considered asymptomatic. Two months later, the patient presented to the clinic with polyradiculopathy across S₁-S₅ dermatomes bilaterally, paresis of the tibial nerves, and retention of the pelvic-reservoir functions. Follow-up MRI confirmed the previous study, but visualized S₁-S₅ root compression. Given the presence of cauda equina syndrome, the patient was considered a surgical candidate. A cyst measuring 8 cm in craniocaudal length and 3 cm in width was found intradurally. Microsurgical resection of the cyst was performed. Histological examination confirmed the diagnosis of an arachnoid cyst. Postoperatively, due to recurrence, a lumbo-peritoneal shunt was implanted, after which the patient's neurological status significantly improved. Follow-up examination after 72 months revealed mild motor and sensory deficits. Maximal safe resection of the cyst is the most effective therapeutic approach that leads to the elimination of complaints and absence of recurrences. In cases with recurrence, a lumbo-peritoneal shunt may be considered.