A 20-year-old man with back pain and lower extremity weakness.

A 20-year-old man presented with 1 week of low back pain and progressive lower extremity weakness. Results of cerebrospinal fluid analysis demonstrated elevated total protein and a mildly elevated white blood cell count with lymphocytic predominance. Findings from imaging studies revealed a multifocal, heterogeneously enhancing, intramedullary lesion involving the cervicothoracic spinal cord and nodular enhancement of the cauda equina. The patient eventually underwent spinal surgery for tissue diagnosis. The differential diagnosis, pathologic findings, and diagnosis are discussed.