Trigeminal nerve (CN V)
Nerve · CN V Mixed
The largest cranial nerve: a large sensory root and a small motor root leave the lateral mid-pons, and the trigeminal (Gasserian) ganglion in Meckel's cave gives ophthalmic (V1), maxillary (V2) and mandibular (V3) divisions that leave the skull through three separate foramina. Sensory to the face, scalp to the vertex, cornea, mouth, nasal cavity and dura; motor to the muscles of mastication via V3 only.
Traced from the start
- Pons
- Trigeminal nerve (CN V)
Detail
- Sensory
- Face (three divisions), cornea, oral and nasal cavities, teeth, anterior two-thirds of tongue (general sensation), temporomandibular joint, anterior and middle cranial fossa dura
- Motor
- Masseter, temporalis, medial and lateral pterygoids, tensor tympani, tensor veli palatini, mylohyoid, anterior belly of digastric (all through V3)
- Nuclei
- Mesencephalic (proprioception from jaw), principal sensory (touch, pons), spinal trigeminal (pain and temperature, extends to C2), motor nucleus (pons)
- Reflexes
- Corneal reflex: afferent V1, efferent VII. Jaw jerk: afferent and efferent V3, brisk with bilateral upper motor neurone lesions
When it goes wrong
Trigeminal neuralgia from a loop of the superior cerebellar artery compressing the root entry zone (or a demyelinating plaque in a young patient with multiple sclerosis)
Paroxysms of unilateral electric-shock pain in V2 or V3 lasting seconds, triggered by chewing, talking, shaving or touching the face, with a normal examination; carbamazepine is first line and MRI excludes a structural cause
Lateral medullary infarct or syringobulbia damaging the spinal trigeminal nucleus and tract
Ipsilateral loss of facial pain and temperature sensation with touch preserved (dissociated sensory loss)
Cerebellopontine angle tumour compressing the sensory root
Ipsilateral facial numbness and an absent corneal reflex, often the first sign after hearing loss
Practise this structure
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