Chapter 16 - Bringing the masseter reflex into the operating room

Abstract

The masseter reflex is a monosynaptic proprioceptive reflex that provides fundamental feedback information about masticatory behavior. Abnormal masseter reflex has been reported ipsilateral to midbrain lesions. In a previous study, we provided evidence of the feasibility of eliciting the H-reflex in the masseter muscle in patients under general anesthesia for intraoperative monitoring purposes. For eliciting the masseter H-reflex, we electrically stimulated the masseteric nerve, a branch of the trigeminal nerve innervating the masseter muscle, by inserting a pair of monopolar electromyography needles or hook wire electrodes under the zygomatic arch, anteriorly to the temporomandibular joint. H-reflexes were recorded by subdermal needles inserted in the ipsilateral masseter and temporalis muscles. The H-reflex recorded from the masseter muscle may be an important tool for monitoring lesions involving the midbrain and mid-pons, but the utility of this method needs surgical and monitoring validation before assessing its value in the operating room.