Surgical Techniques in Upper Airway Stimulation

During the 1980‘s first approaches for electrical stimulation of the pharyngeal airway had been investigated [1, 2]. The thought was to increase genioglossus muscle neuromuscular activity. Already during these times Eisele et al. hypothesized that pharyngeal occlusion during sleep in patients with obstructive sleep apnea (OSA) is caused by decreased activity in the genioglossus muscle. Electrical stimulation of the muscle could result in an improvement tone of the muscle and restore pharyngeal patency during sleep [3]. It is mainly the pioneering work by the group of Schwarz, Eisele and Smith, who figured out that hypoglossal nerve stimulation directly instead of genioglossus muscle stimulation could be superior. Several different investigators have explored different electrical approaches to stimulation the pharynx. Surface electrodes have been placed on the upper neck skin in an attempt to move the tongue forward [4, 5]. Another group placed surface transoral electrodes into the region of the hypoglossal nerve [6]. Also percutaneous electrodes placed into the region of the hypoglossal nerve have been tried [7, 8]. Major drawbacks of these studies were that it was not clear if the genioglossus muscle was selectively stimulated with the electrodes. Consequently, many patients woke up from arousals during sleep, which occurred with these stimulation techniques. The authors concluded that the pharyngeal patency improvement was caused because of the arousals during stimulation. So, it was clear, that a direct stimulation of the hypoglossal nerve is needed to activate the main airway opener - the genioglossus muscle.