Spontaneous thoracic spinal cord herniation--case report.

A 54-year-old female presented with spontaneous thoracic spinal cord herniation manifesting as chronic progressive motor weakness in both legs. Spastic paraparesis (4/5) and pathological reflexes such as ankle clonus were noted. She also had mild bladder dysfunction but no bowel dysfunction. She had no sensory disturbance, including tactile and pinprick sense. Magnetic resonance (MR) imaging revealed that the atrophic spinal cord was displaced into the ventral extradural space at the T4-5 intervertebral level with markedly dilated dorsal subarachnoid space. Computed tomography obtained after myelography showed no evidence of intradural spinal arachnoid cyst. She underwent surgical repair of the spinal cord herniation via laminectomy, and spinal cord herniation through the ventral dural defect was confirmed. Postoperative MR imaging revealed improvement of the spinal cord herniation, but her symptoms were not improved. Spontaneous spinal cord herniation is a rare cause of chronic myelopathy, occurring in the upper and mid-thoracic levels, and the spinal cord is usually herniated into the ventral extradural space. Early differential diagnosis from intradural spinal arachnoid cysts is important for a satisfactory outcome.