Lumbar Spinal Osteoblastoma Mimicking a Dumbbell Radicular Schwannoma

Spinal dumbbell tumors originate from nerve roots, usually growing within the spinal canal, the neural foramen and the extraforaminal compartment in the paraspinal region. We report a case of a 20-year-old man who presented with back pain radiating to his left lower limb mostly when in a supine position. Magnetic resonance imaging of the lumbar spine showed a dumbbell lesion at the L5-S1 neural foramen, with enlargement of the foramen and extension into the left paraspinal compartment. Although MR imaging studies were strongly suggestive of a dumbbell radicular schwannoma, the histological diagnosis was an osteoblastoma of the lumbar spine originating from the left L5 pedicle with intra-canalicular, intraforaminal and extracanalicular extension. The presentation, imaging studies, intervention, pathology and differential diagnosis are described.