Electroneurography: preoperative facial nerve assessment in acoustic neuroma surgery: a preliminary study.

Preservation of facial nerve function during acoustic tumor resection is an important goal. Patients with acoustic tumors who present with facial weakness may be at increased risk of postoperative facial paralysis. Subclinical tumor involvement of the facial nerve may be more frequent than is commonly recognized. A preliminary study was undertaken to assess the incidence of subclinical involvement of the facial nerve and to discern if such involvement had prognostic implications. Preoperative facial electroneurography (ENoG) was performed in thirteen patients undergoing surgical resection of acoustic tumors. Three of thirteen patients demonstrated preoperative facial weakness and ENoG was abnormal in all three of these patients. Of the ten patients with normal facial function preoperatively, eight revealed amplitude reduction on ENoG testing. Further study is required to discern the prognostic value of preoperative ENoG abnormalities.