Physiology of hypoglossal nerve stimulation

Abstract

The base of tongue plays an important role in the pathophysiology of obstructive sleep apnea (OSA), and addressing the tongue base can be an alternative for continuous positive airway pressure and some surgeries done such as uvulopalatopharyngoplasty to treat OSA. One of the options to address the tongue base to treat the OSA is stimulation of human hypoglossal nerve with implantable devices. Thus, one needs to know the physiology of the human hypoglossal nerve to understand the mechanism of such devices. The human hypoglossal nerve is the primary motor nerve that innervates 7 of the 8 extrinsic and intrinsic muscles of the tongue on each side, except palatoglossus muscle, which is innervated by the ipsilateral vagus nerve. At the level of the hyoid bone, the human hypoglossal nerve (the proximal and midthird) is normally unfasciculated, becoming fascicular only in its distal third where it branches. The lateral branch has many small, independent branches that supply the styloglossus, hyoglossus, and inferior longitudinalis muscles. The medial branch innervates the genioglossus, superior longitudinalis, transversalis, and verticalis muscles.