The genioglossus is the largest extrinsic tongue muscle and the primary protruder of the tongue. Its fan-shaped attachment from the chin to the entire tongue undersurface and hyoid allows it to protrude, depress, and shape the tongue. The genioglossus is the critical target of hypoglossal nerve stimulation therapy for obstructive sleep apnoea — electrical stimulation during sleep activates it to protrude and stiffen the tongue, keeping the airway open.
| Origin | Superior mental spine on the inner surface of the mandible symphysis |
|---|---|
| Insertion | Inferior tongue surface from tip to root, and the body of the hyoid bone |
| Nerve Supply | Hypoglossal nerve (CN XII) |
| Blood Supply | Deep lingual artery |
| Actions | Protrudes the tongue when both sides act together; Depresses the tongue centre (makes the tongue concave); Ipsilateral tongue deviation when one side acts alone |
|---|
During sleep, the genioglossus normally maintains its tonic activity to keep the tongue from falling posteriorly into the pharynx. In obstructive sleep apnoea this tonic activity is reduced during REM sleep, allowing the tongue to collapse the airway and produce the characteristic apnoeic episodes.
Hypoglossal nerve stimulation (Inspire therapy) delivers electrical impulses to the genioglossus via an implanted electrode on the hypoglossal nerve, synchronised with inspiration to protrude the tongue and maintain pharyngeal airway patency as an alternative to CPAP for obstructive sleep apnoea. Bilateral genioglossus paralysis from hypoglossal nerve lesions produces severe dysarthria and dysphagia from inability to manipulate food and saliva.
The genioglossus is palpable with a finger placed under the chin pressing upward into the floor of the mouth during active tongue protrusion, feeling the broad muscular mass of the tongue floor contracting.
Reduced genioglossus tone during sleep allowing tongue posterior displacement and pharyngeal airway collapse, causing obstructive sleep apnoea managed with CPAP, oral appliances, or hypoglossal nerve stimulation.
