Mapping of Hypoglossal Nerve Branches for Stimulator Implant Surgeries Amy Arnold, BS, CNIM & W. Bryan Wilent, PhD, DABNM*
Background Hypoglossal Nerve Branches After Cuff Implanted A new treatment for obstructive After cuff implanted, surgeon will turn on sleep apnea is hypoglossal nerve tEMG Responses the stimulator and should see repetitive stimulation. The geinioglossus artifact (33 Hz) when initially turned on muscle, innervated by a branch of with low current. the hypoglossal, is responsible for Styloglossus Genioglossus protruding the tongue, upper Response just airway dilation, and stiffening of the 0.4 mA Hyoglossus on Hyo- anterior pharyngeal wall. Hyo-Styloglossus Styloglossu Relaxation of this muscle during
REM sleep contributes to
obstructive sleep apnea. Trapezius
When current is increased, will see Selective stimulation of the of the repetitive EMG (note: display gain not hypoglossal nerve branch Genioglossus optimized and EMG responses clipped) innervating the Genioglossus Large response geniogilossus , which has minimal on muscle afferents, just prior and during the 0.4 mA Geniolglossus
inspiratory phase of respiration can Goal of surgery: Implant stimulator cuff around Hyo-Styloglossus
reduce apnea episodes . bracnh of Hypoglossal nerve that innervates the Small response Genioglossis muscle specifically. on Hyo-
Trapezius Styloglossus Goal of IONM: Help surgeon identify the different Implant branches of the Hypoglossal nerve. .
Genioglossus Summary Response just Monitoring is to optimize the placement of Stim Lead 0.4 mA on the stimulator cuff around the branch Generator IONM Plan Recording: Longer needles are preferred Key is Hyo-Styloglossus Genioglossus innervating Genioglossus muscles. placing electrodes into the Genioglossus and the other pair into Hyoglossus and/or Styloglossus such that they If the nerve is isolated and stimulated don’t fall out. Trapezius is primarily a control for sEMG. Trapezius properly (watch for current shunting) responses should ideally be seen on just Breathing Sitmulation: A Medtronic Bipolar with anode and the Genioglosus. After placing the cuff and Sensor Lead cathode denoted is preferred making sure anode is Ideally, this is what you want, response turning it on, obvious 33 Hz tEMG proximal when stimulating. Here, a concentric bipolar from just on Genioglossus muscle responses should be seen. . was used and works just fine.
Parameters 100 us pulse width, 0-2.0 mA, 4.7 Hz.