- The hypoglossal nerve, CN XII provides motor innervation to the tongue.
- Normally, a horse resists the tongue being retracted from the mouth.
- The horse will quickly return the tongue after it is pulled out to the side.
- Horses with hypoglossal weakness appear differently.
- The tongue may protrude from the mouth.
- Chronic unilateral hypoglossal lesions may result in unilateral tongue atrophy.
- Bilateral hypoglossal lesions may result in difficulty prehending food.
- Horses with cerebral dysfunction may have signs corresponding to tongue weakness.
- However, tongue atrophy is not present in these animals.