Electromyographic facial nerve monitoring during resection for acoustic neurinoma under moderate to profound levels of peripheral neuromuscular blockade.

The facial nerve is monitored intra-operatively using electromyography to identify and prevent damage during the excision of an acoustic neurinoma. In order to determine whether a profound level of peripheral neuromuscular blockade could be achieved without compromising facial electromyographic monitoring, 11 patients undergoing resection of acoustic neurinoma were studied. After induction of anaesthesia, an infusion of atracurium was administered to reduce the integrated electrically evoked muscle potential (EEMP) of the hypothenar eminence by 70-100%. The facial nerve was directly stimulated in the surgical field and the facial evoked muscle potentials (EMPs) were recorded. Even under complete peripheral neuromuscular blockade (i.e. no electrically evoked muscle potential measurable over the hypothenar eminence, no palpable hypothenar muscle response) it was possible to evoke facial muscle electromyographic responses by stimulation of the facial nerve.