Motor-evoked potentials of facial musculature in dogs

Motor responses of limb musculature have been elicited by transcranial brain stimulation using electrical and magnetic stimulation. Recording from muscles innervated by cranial nerves has not previously been reported. A unilateral hemispheric craniotomy was performed in 24 dogs. An electric stimulus was delivered directly to the exposed motor cortex via surface electrodes. Evoked electromyographic responses to motor cortex stimulation were recorded from the contralateral orbicularis oculi and orbicularis oris muscles. Preliminary investigation into the use of magnetic stimulation of the motor cortex is compared to direct electrical cortical stimulation. This study demonstrates the potential for magnetic stimulation in the intraoperative and outpatient clinical evaluation of facial nerve disorders. It appears possible, for the first time using magnetic stimulation, to noninvasively stimulate these nerves proximal to the point of injury and to evaluate more central conduction pathways.