Organ
Facial motor nucleus
Pontine neurons that move the face
High-yield
A lesion of the nucleus or its outgoing fibers can weaken the upper and lower face on the same side. A lesion above the nucleus commonly affects the opposite lower face more strongly, with relative forehead preservation.
Overview
Motor neurons in the caudal pons send facial-nerve axons to muscles derived from the second pharyngeal arch. The axons first loop around the abducens nucleus, then turn toward their exit near the pontomedullary junction. Cortical commands reach the nucleus from both hemispheres, but the balance differs between muscles: opposite-hemisphere control is particularly important for the lower face.
Reference facts
- Location
- Ventral and lateral tegmentum of the caudal pons
- Parts
- Groups of motor neurons serving different facial muscles; upper-face control has substantial bilateral cortical input, while lower-face control is predominantly contralateral
- Relations
- Outgoing axons form the internal genu around the abducens nucleus; together these structures underlie the facial colliculus on the fourth-ventricle floor
- Function
- Drives facial-expression muscles, stapedius, stylohyoid and the posterior belly of digastric
Clinical correlation
Facial weakness involving the forehead can arise from a facial-nerve disorder or a pontine lesion. Forehead weakness can also occur with cerebral stroke, so this sign alone cannot distinguish stroke from Bell palsy. Associated neurologic findings and the full clinical assessment matter.
Frequently asked questions
Where is the facial motor nucleus located?
The facial motor nucleus lies ventral and lateral tegmentum of the caudal pons.
What does the facial motor nucleus do?
Drives facial-expression muscles, stapedius, stylohyoid and the posterior belly of digastric.
What are the parts of the facial motor nucleus?
Groups of motor neurons serving different facial muscles; upper-face control has substantial bilateral cortical input, while lower-face control is predominantly contralateral.