Idiopathic herniation of the thoracic spinal cord: report of three cases

STUDY DESIGN: Cases are reported and the literature is reviewed. OBJECTIVE: To present three cases involving idiopathic herniation of the thoracic cord. SUMMARY OF BACKGROUND DATA: Idiopathic spinal cord herniation is a very rare condition. Only 20 cases have been reported. The radiographic and intraoperative findings concerning this herniation remain insufficient, and its pathophysiology is less understood. METHODS: Idiopathic herniation of the thoracic spine was managed operatively in the three cases. The clinical, radiologic, and intraoperative features in these cases are described, and the pathophysiology of this disorder is discussed from a review of the literature. RESULTS: Two of the three patients had a defect in the inner layer of the duplicated ventral dura mater through which the spinal cord was herniated. The third patient had a ventral epidural cyst into which the spinal cord had protruded. Operative reduction of the spinal cord improved motor power in all three patients, although sensory disturbance remained unchanged. CONCLUSIONS: There should be several types of idiopathic spinal cord herniation. This is the first report of this herniation that focuses the abnormalities of the ventral dura mater, together with image and intraoperative findings.