Ventral Transdural Herniation of the Thoracic Spinal Cord: Surgical Treatment in Four Cases and Review of Literature

Summary

 Background. A specific cause of progressive Brown-Sequard syndrome has been identified: a ventral herniation of the thoracic spinal cord through the dural sleeve on one side.

Method. Four female patients who were affected by a progressive Brown Sequard syndrome related to a transdural spinal cord herniation have been investigated and were submitted to surgery and postoperative evaluation.

Findings. The MRI scan showed atrophy and forward displacement of the spinal cord on one side and adhesion of the spinal cord to the dura mater. CT myelography demonstrated the disappearance of the premedullar rim at the level of the herniation and the shadow of the extradural herniation. Surgical treatment consisted in the excision of the arachnoid cyst when there was one, section of the dentate ligament, release of the adhesions, detachment of the spinal cord from the hernial orifice, and lastly suture of the dural tear or placement by a patch. Follow-up examination showed motor improvement with persistent sensory deficit in two cases and stabilisation in two cases.

Interpretation. The cause of the dural tear, either traumatic or congenital could not be confirmed in the four cases. Symptoms probably occur when herniation fills the orifice and strangulation happens which explains the late appearance and progressive evolution of this myelopathy. Mobilisation of the herniated spinal cord back into the intradural space can be achieved by surgery and may stop the evolution of the symptoms and signs.