Musculus geniohyoideus
The geniohyoideus is a narrow strap muscle that originates from the medial surface of the mandible near the symphysis and inserts on the basihyoid bone. Its actions are to draw the hyoid apparatus and tongue cranially (forward) and to assist in swallowing and tongue protrusion. Innervation is shared: hypoglossal nerve (CN XII) and the first cervical nerve (C1). It works with the genioglossus and other hyoid muscles to position the tongue and hyoid during eating and swallowing. Because the hyoid apparatus is linked to the larynx and pharynx, these muscles also contribute to upper-airway stability.
Origin: Medial surface of the mandible near the symphysis
Insertion: Basihyoid bone
Action: Draws the hyoid and tongue cranially; assists in swallowing and tongue protusion
Innervation: Hypoglossal nerve (CN XII) and first cervical nerve (C1)
Isolated injury is uncommon. It can be affected by hypoglossal-nerve lesions or by trauma to the mandibular or hyoid region. Dysfunction may contribute to difficulty swallowing or abnormal tongue position.
## Overview Damage to the hypoglossal nerve (cranial nerve XII) paralyzes the tongue and associated muscles (including geniohyoideus), producing severe dysphagia. Food and water return from the nostr
Difficulty swallowing, dropping feed, or abnormal tongue position warrants veterinary examination of the mouth, hyoid region, and neurologic function.
## Overview Damage to the hypoglossal nerve (cranial nerve XII) paralyzes the tongue and associated muscles (including geniohyoideus), producing severe dysphagia. Food and water return from the nostrils, the tongue may hang out or deviate, and aspiration pneumonia is a major risk. Common causes include guttural pouch mycosis and complications of strangles. ## Causes Guttural pouch mycosis, retropharyngeal abscess, trauma, or other lesions affecting cranial nerve XII. ## Diagnosis Clinical signs of tongue paralysis and dysphagia, plus endoscopy of the guttural pouches and pharynx. Neurologic examination confirms hypoglossal involvement. ## Treatment Treatment of the underlying disease (antifungals for guttural pouch mycosis, drainage of abscesses). Supportive feeding (nasogastric or esophagostomy tube) and management of aspiration. Nerve recovery is often incomplete. ## Recovery and Prognosis Guarded. Many horses have permanent deficits. Aspiration pneumonia significantly worsens survival. ## Prevention Prompt treatment of guttural pouch infections and strangles complications. Signs include: food and water returning from the nostrils; tongue hanging out or deviated; inability to swallow; weight loss; aspiration pneumonia risk
Isolated injury is uncommon. It can be affected by hypoglossal-nerve lesions or by trauma to the mandibular or hyoid region. Dysfunction may contribute to difficulty swallowing or abnormal tongue position.
Difficulty swallowing, dropping feed, or abnormal tongue position warrants veterinary examination of the mouth, hyoid region, and neurologic function.
See the Geniohyoideus on our interactive 3D horse model. Open 3D Model