Activation patterns of the tongue muscles with selective stimulation of the hypoglossal nerve

The upper airways were imaged in anesthetized beagles to investigate the effect of selective stimulation of the hypoglossal nerve (HG) with a multi-contact peripheral nerve electrode. A fiberscope lead (diam. 5 mm) was inserted through the proximal end of the tracheostomy and fixed at 1 cm behind the uvula to image the oro- and nasopharynx while the head was fixed at either 30° or 60° from the horizontal with the mouth open or closed. Images of the tongue were recorded with a camera in open mouth positions. These images show that stimulations delivered through the electrode contacts placed around the HG nerve trunk can generate several different activation patterns of the tongue muscles. Some of these patterns translate into a substantial increase in the pharyngeal opening size while some others decrease it. The activation patterns vary as a function of the head position and the lower jaw. These results suggest that selective stimulation of the HG nerve can be a useful technique to maximize the effects of HG nerve stimulation in removing the obstructions in sleep apnea patients.