Intraoperative monitoring during surgery for hypoglossal schwannoma.

A 54-year-old man presented with an intracranial schwannoma of the hypoglossal nerve between the medulla and the left hypoglossal canal. The condylar fossa approach was used with intra-operative electromyography (EMG) monitoring of the lower cranial nerves. The tumor was then removed carefully without decreasing the tongue EMG responses. EMG monitoring enabled us to remove the tumor while maintaining the function of the hypoglossal nerve. Tongue EMG was easily recorded by stimulating the hypoglossal nerve fibers, which was useful in identifying the hypoglossal nerve and evaluating its function. This suggests that tongue EMG is a useful monitoring tool to enhance neurological outcome following removal of tumors in this region.