[The terminal hypoglossal nerve and its anatomical variability].

Upper airway stimulation plays an increasingly important role in the treatment of obstructive sleep apnea (OSA). The target of stimulation is the hypoglossal nerve (N. XII), which-as a pure motor nerve-innervates the intrinsic and extrinsic tongue muscles. By selectively stimulating individual nerve fibers, the upper airway can be opened by protruding the tongue. The N. XII has a number of anatomical variants, which are decisive during surgical implantation of these pacemaker systems. Intraoperative neuromonitoring is very helpful in this regard. Accurate placement of the stimulation electrode for selective upper airway stimulation requires knowledge of N. XII anatomy, intraoperative neuromonitoring, and accurate assessment of muscle contractions and tongue movements.