Transdural medullary hernia
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Extremely rare but its incidence is probably underestimated. Rare cause of progressive myelopathy. Hernia of the spinal cord through a defect in the dura mater.
There are cases:
- idiopathic: more often in women, between T4 and T7 (favoring effect: dorsal kyphosis). Cause: posterior arachnoid cyst ? repetitive, calcified herniation eroding the dura mater?
- post-surgical
- post-traumatic
Clinical signs are caused by strangulation of the spinal cord and correspond to a Brown-Sequard syndrome of gradual onset: spastic monoparesis, unilateral piriformis syndrome, pain, ataxia, hypertonic disorders.
Diagnostic MRI: angulation of the spinal cord that is anterior in case of herniated thoracic or posterior in case of cervical hernia.
Treatment: surgery of the dura or enlargement of the dural defect to release the spinal cord.
Anesthetic implications:
nobody knows whether a neuraxial block might exacerbate the neurologic clinical picture. One English neurosurgeon is convinced that a spinal block or an epidural block (including a blood patch) is contraindicated.
References :
- Goetti R, Wille D, Ktrezschmar U, Klein A, Scheer I.
Idiopathic spinal cord herniation.
JAMA Neurol 2013 ; 70 :125.
- Malmood A, Ramaswamy K.
Idiopathic thoracic spinal cord herniation : the unknown anaesthetic implications.
Anaesth Intensive Care 2015 ; 43 : 787-8
Updated: September 2018