Discrepancy between MRI and intraoperative findings in a rare intramedullary epidermoid cyst: A case report and literature review.

Intramedullary epidermoid cysts are rare, benign spinal tumors originating from ectodermal tissue during embryogenesis, comprising less than 1% of intraspinal lesions and posing diagnostic challenges due to their variable presentation and imaging overlap with other spinal pathologies. This case report describes a 22-year-old female who presented with progressive bilateral lower limb weakness, mid-back pain, and bowel-bladder incontinence, with preoperative MRI revealing a well-circumscribed intradural cystic lesion at the T5-T6 level exhibiting mixed-intensity patterns and a "shouldering effect," initially suggesting an extramedullary location. Surgical exploration, however, confirmed an intramedullary position, and the lesion-characterized intraoperatively as a white, waxy, flaky mass-was excised en-bloc, with histopathology verifying an epidermoid cyst; the patient showed significant neurological recovery by her 12-month follow-up with no recurrence. This case highlights a critical discrepancy between MRI and intraoperative findings, emphasizing the need to integrate clinical, radiological, and surgical observations for accurate diagnosis and management of such rare spinal lesions. It underscores that intramedullary epidermoid cysts, though uncommon, should remain in the differential diagnosis for young adults with progressive neurological deficits, particularly in the thoracic spine, and that complete surgical resection is essential to prevent recurrence. Early diagnosis, meticulous surgical planning, and long-term follow-up are vital for optimizing outcomes, illustrating the importance of adaptability when imaging misaligns with operative reality and reinforcing the value of detailed case reporting to advance understanding of this rare pathology.