Idiopathic intradural extramedullary epidermoid cyst at the conus medullaris

Abstract

Background: Spinal epidermoid cysts are uncommon, comprising < 1 % of all spinal tumors. Involvement of the conus medullaris and cauda equina is particularly rare, often presenting with nonspecific symptoms and posing diagnostic and surgical challenges. Case Presentation: A 32-year-old woman presented with chronic low back pain and distal limb numbness without weakness or sphincter dysfunction. MRI showed an intradural extramedullary lesion at L1 compressing the conus and displacing cauda equina roots. Gross total excision via hemilaminectomy with neuromonitoring confirmed an epidermoid cyst. Symptoms resolved completely, with no recurrence at 9 months. Clinical Discussion: Spinal epidermoid cysts may mimic other intradural lesions and are best identified with MRI, where DWI improves diagnostic confidence. Reported cases most often present with back pain or sensory disturbance, while delayed diagnosis may result in motor or sphincter involvement. Surgical excision remains the treatment of choice, though capsule adherence can limit removal. Our case illustrates these observations, with complete recovery following timely microsurgical excision. Conclusion: Epidermoid cysts of the conus medullaris region are rare intradural lesions. This case highlights the importance of recognizing their subtle clinical presentation and demonstrates that timely microsurgical excision can achieve symptom resolution with a favourable short-term outcome.