Resection of brachial plexus schwannomas while monitoring transcranial motor evoked potentials: report of two cases.

A schwannoma is a benign nerve sheath tumor treated by enucleation, which carries the risk of intraoperative nerve injury that is observed after awakening. Transcranial motor evoked potential (TcMEP) monitoring has been established as an effective method to predict and prevent intraoperative neurological complications during brain and spinal surgery. However, there have been few reports on its application in head and neck surgeries. We performed enucleation to relieve the symptoms due to schwannomas in the neck of two women, aged 25 years and 70 years. Both women presented with a left cervical mass, paresthesia of the left upper limb, and a Tinel-like sign without muscle weakness. TcMEPs were recorded before beginning surgery, during surgery, and immediately before completing surgery. The dissecting lines were decided using the stimulator attached to the dissecting instrument, which helped warn the surgeon regarding risky areas. Histopathological examinations confirmed the diagnosis of schwannoma. There was no significant difference in the pre- and postoperative TcMEP recordings, and no postoperative motor deficits were identified. Intraoperative TcMEP monitoring is expected to be useful in preventing operative complications while treating head and neck schwannomas.