Presurgical electrophysiological findings in acoustic nerve tumours.

The clinical involvement of the facial nerve is a rare finding among the initial symptoms of acoustic neurinomas. However, compression of the facial nerve is a common intraoperative finding. Blink reflex was recorded in 20 patients affected by cerebellar-pontine angle tumor confirmed at surgery. Recordings were also made of the M-response of the facial nerve from the naso-labial folds. In 6 cases jaw reflex was also recorded. In summary, these electrophysiological studies revealed a facial nerve damage in 13 and a trigeminal nerve dysfunction in 2 out of 18 clinically unaffected patients. The combined study of the 3 tests proved to be useful when the blink reflex showed an isolated R1 delay, that is, in cases in which the level of damage along the trigemino-facial reflex arc cannot be defined by the recording of the blink reflex alone.