Idiopathic spinal cord herniation causing progressive Brown-Séquard syndrome.

We report a 59-year-old woman with a 2.5 year history of progressive loss of temperature sensation and dysesthesia in the right and weakness in the contralateral lower limb. Magnetic resonance imaging (MRI) and computed tomography myelography of the spinal cord demonstrated transdural herniation and deformation of the spinal cord in the upper thoracic spine. The herniated part of the spinal cord was untethered and replaced, and the anterior dural defect was closed. At a clinical follow-up 3 months later, the motor and sensory functions were almost restored. MRI at this time showed disentanglement of spinal cord adherence.