Thoracic myelopathy due to an intramedullary herniated nucleus pulposus: first case report and review of the literature.

Background And Importance: Herniation of intervertebral discs is relatively common. Migration usually occurs in the ventral epidural space; very rarely discs migrate in the subdural space. No cases of intradural intramedullary disc have been reported in humans.

Clinical Presentation: A case of a herniated intervertebral disc directly into the spinal cord parenchyma is presented. The patient presented with 2 weeks of progressive bilateral lower extremity numbness and weakness, saddle hypoesthesia, urinary dysfunction and gait disturbance. Spine magnetic resonance imaging (MRI) with gadolinium revealed a solitary well-defined intramedullary lesion (T7-T8 level) with ring enhancement and focal cord expansion with significant surrounding edema. Metastatic workup and neural axis imaging was negative. A thoracic laminectomy and myelotomy was performed; the lesion was pearlescent and well circumscribed. It was densely adherent to the ventral pia and gross totally removed. Pathology was consistent with nucleus pulposus.

Conclusion: Intradural intramedullary migration of a herniated intervertebral disc is extremely rare but should be considered in the differential. It may present in a variety of clinical scenarios, including thoracic myelopathy, and mimic intramedullary spinal cord tumor.