SN7
SHORT NOTE
5M
Describe the trigeminal nerve with its divisions and distribution. Add a note on the associated parasympathetic ganglia.
Origin and Divisions
The trigeminal nerve (V) is the largest cranial nerve and the great sensory nerve of the face and head, and the motor nerve of mastication.
- Arises from the pons by a large sensory and a small motor root
- The sensory root expands into the trigeminal (Gasserian) ganglion in Meckel cave on the petrous temporal bone
- It is the nerve of the first pharyngeal arch
| Division | Exit from the skull | Nature |
|---|---|---|
| Ophthalmic (V1) | Superior orbital fissure | Sensory only |
| Maxillary (V2) | Foramen rotundum | Sensory only |
| Mandibular (V3) | Foramen ovale | Mixed — sensory and motor |
Distribution
| Division | Chief branches | Area supplied |
|---|---|---|
| V1 | Frontal (supra-orbital, supratrochlear), lacrimal, nasociliary | Forehead, upper eyelid, cornea and conjunctiva, dorsum of the nose, frontal and ethmoidal sinuses, part of the dura |
| V2 | Infra-orbital, zygomatic, superior alveolar, palatine, nasal | Lower eyelid, cheek, upper lip, upper teeth, maxillary sinus, palate |
| V3 | Auriculotemporal, lingual, inferior alveolar, buccal; motor branches | Lower lip and chin, lower teeth, anterior two-thirds of the tongue (general sensation), temple, external auditory meatus, TMJ |
- Motor fibres travel only in V3, supplying the four muscles of mastication (masseter, temporalis, medial and lateral pterygoid), and also mylohyoid, anterior belly of digastric, tensor tympani and tensor veli palatini
Associated Ganglia
| Ganglion | Topographically with | Functionally with | Supplies |
|---|---|---|---|
| Ciliary | V1 (nasociliary) | Oculomotor (III) | Sphincter pupillae, ciliary muscle |
| Pterygopalatine | V2 | Facial (VII) — greater petrosal | Lacrimal gland, nasal and palatine glands |
| Submandibular | V3 (lingual) | Facial (VII) — chorda tympani | Submandibular and sublingual glands |
| Otic | V3 | Glossopharyngeal (IX) — lesser petrosal | Parotid gland |
Reflexes and Testing
- Corneal reflex — afferent V1, efferent VII (orbicularis oculi). Its loss is an early sign of an acoustic neuroma
- Jaw jerk — both afferent and efferent are V3; exaggerated in an upper motor neurone lesion above the pons
- Sensory testing over the three territories; motor testing by clenching the teeth (feeling masseter and temporalis) and by opening the jaw against resistance
- The jaw deviates toward the paralysed side on opening, since the intact lateral pterygoid pushes it across
Applied Aspects
- Trigeminal neuralgia (tic douloureux) — paroxysms of severe lancinating pain in the distribution of V2 or V3, triggered by touch, chewing or a cold draught; often from vascular compression of the root. Treated with carbamazepine, then microvascular decompression
- Herpes zoster ophthalmicus — involves V1; vesicles on the tip of the nose (Hutchinson sign) indicate nasociliary involvement and a real risk to the eye
- Inferior alveolar nerve block is given at the lingula near the mandibular foramen; it anaesthetises the lower teeth of that side, and the lingual nerve is usually blocked with it
- Loss of the corneal reflex with facial numbness and deafness suggests a cerebellopontine angle tumour involving V, VII and VIII
- Referred pain is common within the trigeminal territory — dental disease presents as earache, and sinusitis as toothache, because the same division supplies both
All questions in Head & Neck
- Q1Describe the triangles of the neck with their boundaries and contents. Add a note on the posterior triangle and its applied anatomy. ★
- Q2Describe the thyroid gland under relations, blood supply and nerve relations. Add a note on the applied anatomy of thyroidectomy. ★
- Q3Describe the parotid gland under bed, structures within it, duct and nerve supply. Add a note on its applied anatomy. ★
- Q4Describe the larynx under cartilages, cavity, muscles and nerve supply. Add a note on vocal cord palsy. ★
- Q5Describe the cavernous sinus with its contents and connections. Add a note on cavernous sinus thrombosis and the dangerous area of the face. ★
- SN1Describe the course and branches of the facial nerve. Differentiate upper from lower motor neurone facial palsy. ★
- SN2Describe the temporomandibular joint with its movements. Add a note on its dislocation. ★
- SN3Describe the submandibular gland with its relations, duct and nerve supply. ★
- SN4Describe the layers of the deep cervical fascia and the fascial spaces of the neck. ★
- SN5Describe the tongue with its papillae, muscles and nerve supply. Add a note on hypoglossal nerve palsy. ★
- SN6Describe the layers of the scalp with their clinical importance. ★
- SN7Describe the trigeminal nerve with its divisions and distribution. Add a note on the associated parasympathetic ganglia.