[A case of idiopathic spinal cord herniation with incomplete Brown-Séquard syndrome].

A 50-year-old man was referred to our hospital with myelitis associated with a 10-months history of progressive muscle weakness in the left leg. Neurological examinations demonstrated diffuse muscle weakness of the left leg, touch hypoesthesia of the right leg, reduced pain sensation below the right nipple, left pyramidal sign, and urinary incontinence. On the basis of thoracic spinal MRI and thoracic CT myelography, revealing anterior displacement of the spinal cord and enlargement of the posterior subarachnoid space at the Th4 vertebral level, we diagnosed the patient as having idiopathic spinal cord herniation with incomplete Brown-Séquard syndrome. After microsurgical release of the spinal cord and subsequent covering of the anterior dural defect with an artificial dura mater, the symptoms improved without progression. Clinicians should consider spinal cord herniation as a cause of slowly progressive thoracic myelopathy with Brown-Séquard syndrome.