Neurophysiological Navigation in the Trigeminal Nerve: Use of Masticatory Responses and Facial Motor Responses Evoked by Electrical Stimulationof the Trigeminal Rootlets for RF-Thermorhizotomy Guidance

RF-thermorhizotomy of the trigeminal nerve is an effective and safe treatment of trigeminal neuralgia, provided lesioning of the sensory fibers is performed precisely. To control the accurate placement of the electrode tip, electrical stimulation testing, prior to thermal lesioning, is of prime importance. The clinical observation of direct masticatory responses (DMR) and facial evoked motor responses (EMR) produced by stimulation of the trigeminal rootlets (at 5 Hz) helps to place the electrode tip in the optimal location. The best location is the one where the threshold for eliciting DMR is high and the threshold for evoking facial EMR in the area corresponding to the trigger zone is low. EMR in orbicularis oculi indicates location in V1, levator labii EMR signifies V2 and orbicular oris EMR corresponds to V3.