Delayed-Onset Leg Weakness Caused by Posterior Migration of a Herniated Disc to the Thecal Sac Mimicking Epidural Hematoma in a Flexion-Distraction Injury of the Lumbar Spine: A Case Report

ABSTRACT

STUDY DESIGN: Case report. OBJECTIVES: To document the first known case of posterior migration of a herniated disc in a lumbar flexion-distraction injury. SUMMARY OF LITERATURE REVIEW: Lumbar disc herniation is sometimes confused with epidural hematoma, especially when the disc migrates posterior to the thecal sac. There has been no report of posterior migration of a herniated disc after a lumbar flexion-distraction injury. MATERIALS AND METHODS: A 47-year-old woman with no pertinent medical history was diagnosed with a flexion-distraction injury of the L2–L3 vertebrae after a motor vehicle accident. The patient had no neurological deficit initially. Magnetic resonance imaging (MRI) showed a space-occupying lesion with T2 hyperintensity and T1 isointensity on the dorsal side of the thecal sac at L2–L3. After posterior lumbar fixation and fusion, progressive leg weakness occurred 1 week postoperatively. RESULTS: A second operation revealed no evidence of epidural hematoma, but a sequestrated disc. Decompression and sequestrectomy were performed, and the patient's neurological status had recovered fully at 4 months postoperatively. CONCLUSIONS: This case highlights the potential for posterior migration of a herniated disc with flexion-distraction injuries of the thoracolumbar spine. Discontinuity of the posterior annulus fibrosus on MRI may aid the distinction of posterior migration of a herniated disc from epidural hematoma. Because posterior migration of a herniated disc is associated with progressive neurological deficits, surgeons must consider decompression surgery when such herniation is suspected, even in the absence of neurological symptoms.