The trigeminal nerve is the largest cranial nerve and the primary sensory nerve of the face, providing cutaneous sensation to the entire face from the vertex to the jaw and proprioception from the masticatory muscles. Its sensory nucleus extends from the midbrain to the upper cervical cord — the longest cranial nerve nucleus — explaining why face pain can be referred to the upper neck and vice versa. Trigeminal neuralgia is the most severe facial pain syndrome.
| Origin | Trigeminal ganglion (Gasserian ganglion) in Meckel's cave on the petrous temporal bone |
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Trigeminal neuralgia produces the most severe paroxysmal facial pain known, triggered by innocuous stimuli such as light touch, eating, or wind. Carbamazepine is the first-line treatment. Microvascular decompression of a blood vessel compressing the trigeminal root at the brainstem is the most durable surgical treatment. The corneal reflex (V1 afferent, CN VII efferent) is the most sensitive test of early V1 trigeminal dysfunction. Herpes zoster of the trigeminal nerve (V1) produces ophthalmic shingles with corneal involvement.
Paroxysmal severe facial pain from vascular compression of the trigeminal root at the brainstem, managed with carbamazepine and microvascular decompression for drug-refractory cases.
V3 branch damage during mandibular third molar extraction producing ipsilateral lower lip and chin numbness that may be permanent when the nerve is transected rather than stretched.
