Intraoperative neurophysiological monitoring of accessory and hypoglossal nerves during surgery for vestibular schwannoma with brainstem involvement: a case report

Abstract

In brainstem surgery, neurophysiological monitoring of each lower cranial nerve (LCN) can minimize the risk of postoperative complications. This case report describes the intraoperative monitoring of the cranial nerves XI - XII during surgery for vestibular schwannoma located from the left cerebellopontine angle to the brainstem. An abrupt decrease of the left accessory (CN XI) and hypoglossal (CN XII) motor evoked potentials (MEP) was observed during the dissection of the tumor attached to the branch of the left LCNs. The patient developed pharyngeal dysphagia, tongue deviation, and left trapezius weakness after surgery. Intraoperative decrement of transcranial MEP in CN XI and CN XII may be a predictor of postoperative, sustained dysphagia. For surgery of cerebellopontine angle tumor, monitoring of LCNs using transcranial MEP should be performed especially if the tumor locates close to the brainstem.