Stereotactic radiosurgery in two cases of presumed fourth cranial nerve schwannoma.

A 47-year-old woman and a 45-year-old man with gradually progressive fourth cranial nerve palsy underwent stereotactic radiosurgery for presumed fourth cranial nerve schwannomas with the gamma knife at a marginal tumor dose of 14 and 13 Gy, respectively. In one patient, the ocular misalignment disappeared; in the other patient, it stabilized. MRI showed shrinkage of the tumors. These patients represent the second and third reported cases of presumed fourth cranial nerve schwannoma treated with radiosurgery and the first cases with substantial follow-up information.