Trigeminal nerve (CN V)
Brief overview
The trigeminal nerve is the principal sensory nerve of the face and anterior scalp and carries motor fibres to the muscles of mastication. Its three divisions-ophthalmic (V1), maxillary (V2) and mandibular (V3)-have relatively little dermatome overlap, so lesions produce well‑localised deficits.
In emergency care the priorities are accurate mapping of sensory and motor findings, recognising red flags that require urgent imaging or specialist referral, and distinguishing classical trigeminal neuralgia from secondary causes (tumour, infection, trauma).
Anatomy and function (clinical focus)
- Components: predominantly sensory; motor fibres run with V3.
- Sensory modalities: fine touch, position, pain and temperature from the face, oral mucosa, teeth, nasal cavity, sinuses and part of the meninges. No gustatory fibres.
- Motor supply (V3): muscles of mastication-masseter, temporalis, medial and lateral pterygoids-and smaller muscles (tensor veli palatini, mylohyoid, anterior belly of digastric, tensor tympani).
- Foramina and routes:
- V1 (ophthalmic) → superior orbital fissure.
- V2 (maxillary) → foramen rotundum.
- V3 (mandibular) → foramen ovale.
- Trigeminal (Gasserian) ganglion lies in Meckel’s cave; central processes enter the pons.
- Corneal reflex: afferent limb is V1; efferent limb is facial nerve (VII).