Motor Impairment following Blockade of the Infraorbital Nerve: Implications for the Use of Anesthetization Techniques in Speech Research

Infraorbital nerve blocks were performed bilaterally in three subjects as a partial test of the hypothesis that some portion of the motor innervation to die facial muscles is provided in the trigeminal nerve. To ascertain the influence of this anesthetic procedure, the magnitude and rate of upper lip displacement (for speech and nonspeech tasks), the magnitude and rate of upper lip depression force, and diadochokinetic rate were transduced and recorded, both pre- and postanesthesia. All measures, along with bilateral muscle action potentials from orbicularis oris superior obtained for all force and displacement tasks, were reduced in magnitude as a function of the anesthetic condition. These findings, along with results from previous speech anesthetic studies, were interpreted to suggest that anesthesia of the infraorbital nerve produces measurable, if not substantial motor weakness in the supraoral musculature. The implications for previous studies, where anesthesia techniques have been employed, are discussed.