Motor nucleus of the trigeminal nerve

Motor nucleus of the trigeminal nerve

Diagram of the cranial nerve nuclei showing the trigeminal nerve (V) and its motor nucleus.
Latin	nucleus motorius nervi trigemini
Part of	Trigeminal nerve
System	Nervous system

The motor nucleus of the trigeminal nerve is a collection of motor neurons located in the pons of the brainstem. It is responsible for innervating the muscles of mastication and other muscles derived from the first pharyngeal arch.

Anatomy

The motor nucleus of the trigeminal nerve is situated in the upper part of the pons, medial to the principal sensory nucleus of the trigeminal nerve. It lies near the midline, ventral to the fourth ventricle. The nucleus is composed of large multipolar neurons that give rise to the motor fibers of the trigeminal nerve (cranial nerve V).

Location

The motor nucleus is located in the tegmentum of the pons, specifically at the level of the middle cerebellar peduncles. It is positioned anterior to the superior cerebellar peduncle and lateral to the medial longitudinal fasciculus.

Function

The primary function of the motor nucleus of the trigeminal nerve is to provide motor innervation to the muscles involved in mastication. These muscles include the masseter, temporalis, medial pterygoid, and lateral pterygoid muscles. Additionally, the nucleus innervates the tensor tympani, tensor veli palatini, mylohyoid, and the anterior belly of the digastric muscle.

Neural Pathways

The axons of the motor neurons in the motor nucleus of the trigeminal nerve exit the brainstem and join the mandibular division of the trigeminal nerve (V3). These fibers travel through the foramen ovale to reach their target muscles.

Corticobulbar Tract

The motor nucleus receives bilateral input from the corticobulbar tract, which originates in the primary motor cortex of the cerebral cortex. This bilateral innervation ensures that damage to one hemisphere of the brain does not completely paralyze the muscles of mastication.

Clinical Significance

Lesions affecting the motor nucleus of the trigeminal nerve or its axons can lead to weakness or paralysis of the muscles of mastication. This can result in difficulty chewing and a deviation of the jaw towards the affected side when the mouth is opened.

Trigeminal Neuralgia

While primarily a sensory disorder, trigeminal neuralgia can sometimes involve the motor components of the trigeminal nerve, leading to muscle spasms or weakness.

Development

The motor nucleus of the trigeminal nerve develops from the basal plate of the embryonic neural tube. It is associated with the first pharyngeal arch, which gives rise to the muscles it innervates.

See Also

• Trigeminal nerve
• Cranial nerve nuclei
• Pons
• Mastication