A Case of Unruptured Dissecting Vertebral Artery Aneurysm with Monitoring Evoked Potentials of the Hypoglossal Nerve and the Vagus Nerve.

There are a few reports monitoring evoked poten- tials(EP)of the hypoglossal nerve and the vagus nerve for operation of posterior fossa neoplasms. However, there is no report monitoring EP of their nerves for operation of vertebral artery aneurysm. The author reports a case of unruptured right dis- secting vertebral artery aneurysm with monitoring EP of the hypoglossal nerve with needle electrodes placed in the tongue, and EP of the vagus nerve with electromyographic tracheal tube. A 53-year-old woman underwent right occipital artery-posterior inferior cerebellar artery anastomosis (OA-PICA) and proximal clipping of a right dissecting vertebral artery aneurysm. General anesthesia was induced with remifentanil, propofol and suxametho- nium, and was maintained with oxygen, air, remifen- tanil and propofol. The author monitored EP of the hypoglossal nerve and the vagus nerve, somatosen- sory evoked potentials and motor evoked poten- tials. When the manipulation reached brainstem, EP of the hypoglossal nerve and EP of the vagus nerve appeared respectively. Thereafter, the manipulation was meticulously advanced preventing the damage of their nerve induced surgically. Her operative course was uneventful. It is a useful method to monitor EP of the hypoglos- sal nerve and the vagus nerve in a case of OA-PICA and proximal clipping of dissecting vertebral artery aneurysm.