Structure and Function of the Facial Motor Nucleus
- The nucleus is located in the ventrolateral pontine tegmentum.
- Its axons form the motor component of the facial nerve.
- Neurons in the dorsal region innervate muscles of the upper face, while neurons in the ventral region innervate muscles of the lower face.
- The facial motor nucleus is part of the special visceral efferent (SVE) cell column.
- It innervates muscles derived from pharyngeal arches.
- It receives cortical input from the primary motor cortex.
- Upper motor neurons send axons that synapse on neurons in the facial motor nucleus.
Cortical Input to the Facial Motor Nucleus
- Cells of the facial motor nucleus receive cortical input from the primary motor cortex.
- Upper motor neurons descend through the internal capsule.
- Neurons in the dorsal aspect receive inputs from both sides of the cortex.
- Neurons in the ventral aspect mainly receive contralateral inputs.
- Both sides of the brain control the muscles of the upper face.
Clinical Significance of Facial Motor Nucleus Lesions
- An upper motor neuron lesion to fibers innervating the facial motor nucleus results in central seven.
- The syndrome is characterised by spastic paralysis of the contralateral lower face.
- A lower motor neuron lesion to the facial motor nucleus results in paralysis on the same side of the injury.
- Idiopathic palsy is the term used when the cause cannot be identified.
- Bells palsy is the term used when the cause is known.
Mechanism of Facial Nerve Upper vs Lower Motor Neuron Lesions
- Lesions within the corticobulbar tract are upper motor neuron lesions.
- Lesions affecting the individual branches are lower motor neuron lesions.
- The facial nerve branches leave the facial motor nucleus via different routes.
- The temporal branch receives motor input from both hemispheres.
- The zygomatic, buccal, mandibular, and cervical branches receive input from only contralateral hemispheres.
Additional Details about the Facial Motor Nucleus
- The nucleus has a dorsal and ventral region.
- Its axons travel dorsally and loop around the abducens nucleus.
- It is considered along with the trigeminal motor nucleus, nucleus ambiguus, and spinal accessory nucleus.
The facial motor nucleus is a collection of neurons in the brainstem that belong to the facial nerve (cranial nerve VII). These lower motor neurons innervate the muscles of facial expression and the stapedius.
| Facial motor nucleus | |
|---|---|
 Plan of the facial and intermediate nerves and their communication with other nerves. ("Nucleus of Facial N." labeled at upper left.) | |
 Diagram of brain stem showing the nuclei of the cranial nerves | |
| Details | |
| Part of | Medulla oblongata |
| Artery | AICA |
| Vein | Anterior medullary |
| Identifiers | |
| Latin | Nucleus nervi facialis |
| MeSH | D065828 |
| NeuroNames | 586 |
| NeuroLex ID | birnlex_903 |
| TA98 | A14.1.05.412 |
| TA2 | 5939 |
| FMA | 54572 |
| Anatomical terms of neuroanatomy | |
