Electromyographic analysis of profound facial nerve paralysis following acoustic neuroma resection

The aim of our retrospective study was to determine whether electromyographic findings (motor unit action potentials, MUAPs) can be used in longterm prognosis for profound facial nerve paralysis in patients whose nerve continuity is preserved during surgery for acoustic neuroma. The orbicularis oris, frontal, and orbicularis oculi muscles were examined for the occurrence of MUAPs in 48 such patients. In 30 patients who recovered from complete paralysis within 10 months after surgery, MUAPs in the first two muscles tended to precede the first sign of facial movement. MUAPs appeared in the orbicularis muscle in 80% of these patients at 1 month and in all at 5 months. In the frontal and orbicularis oculi muscles, MUAPs occurred in only 0-20% of these patients in the first month; within 3-5 months the number increased rapidly, and MUAPs were present in 95% of these patients at 10 months. In the remaining 18 patients with long-term complete paralysis (at least 1 year), MUAPs appeared solely in the orbicularis oris muscle: in 20% of these patients in the first month after surgery. While this number slowly rose, there was no period of rapid increase later. We conclude that the occurrence of MUAPs in the orbicularis oris and frontal muscles within 3 months of surgery indicates a good prognosis for reversal of facial nerve paralysis.