Functions of the Trigeminal Nerve
The trigeminal nerve (CN V) serves two primary functions: providing general sensation to large portions of the head and neck, and delivering branchial motor innervation to the muscles of mastication. 1
Sensory Functions
The trigeminal nerve is the largest cranial nerve and provides comprehensive sensory coverage through its three main divisions 1, 2:
Ophthalmic division (V1) - Provides sensory innervation to the upper face, forehead, scalp, and portions of the nasal cavity 3
Maxillary division (V2) - Innervates the midface including the cheek region, oral cavity, and teeth 2, 3
Mandibular division (V3) - Supplies sensation to the mandibular and temporal regions, as well as portions of the oral cavity 3
The sensory function encompasses detection of touch, pain, temperature, and proprioception from the face, scalp, nasal cavity, oral cavity, teeth, and dura mater of the middle cranial fossa 2, 4. Sensory signals travel from peripheral receptors through the trigeminal ganglia to second-order neurons in the trigeminal brainstem sensory nuclear complex, then ascend via the trigeminothalamic tract to reach the thalamus and cortex for interpretation 5.
Motor Functions
The mandibular division (V3) is unique among the three branches as it contains both sensory and motor fibers 2:
Branchial motor innervation - Controls the muscles of mastication, enabling chewing function 1, 4
Motor abnormalities manifest as weakness when chewing food, representing dysfunction of this motor component 1
Clinical Manifestations of Dysfunction
When the trigeminal nerve is affected by pathology, symptoms depend on the involved segment and division 1:
Sensory disturbances include trigeminal neuralgia (tic douloureux), facial numbness, or altered sensation in specific facial regions 1, 5
Motor abnormalities present as weakness or difficulty with mastication 1
Cheek sensory deficits specifically indicate V2 (maxillary) involvement 3
MRI is the preferred imaging modality for investigating trigeminal nerve pathology, with high-resolution 3T magnets providing superior anatomic detail of the complex branching patterns 1, 4.