Lumbar Sequestrated Disc Fragment Mimicking a Foraminal Schwannoma: An Intraoperative Surprise

Sequestered or extruded lumbar disc fragments may rarely present as mass-like lesions and mimic spinal nerve sheath tumors on magnetic resonance imaging (MRI), particularly when they show contrast enhancement and foraminal extension. We report the case of a 70-year-old man who presented with chronic low back pain and severe right lower limb radiculopathy. MRI of the lumbar spine demonstrated a well-defined contrast-enhancing lesion extending along the right L4 nerve root into the L4-L5 neural foramen, raising the preoperative suspicion of a schwannoma. Because adequate exposure was expected to require ipsilateral facetectomy, contralateral unilateral pedicle screw fixation was planned along with decompression and excision of the lesion. Intraoperatively, the lesion was found to be extradural rather than a nerve sheath tumor and was identified as an sequestrated disc fragment extending through the foramen and compressing the nerve root. Discectomy was performed. The patient experienced marked postoperative relief of radicular pain and was discharged in stable condition on postoperative day 2. This case highlights an important radiological pitfall: migrated or sequestered lumbar disc fragments may closely resemble schwannomas, especially when contrast enhancement and foraminal extension are present. Awareness of this differential diagnosis is essential for surgical planning and patient counseling.