Neurology · MU Sofia

14. Trigeminal nerve: anatomy, physiology, examination, syndromes

Covers the anatomy of the trigeminal nerve, its three divisions with the areas each supplies, and its sensory and motor functions. It then describes the corneal and jaw jerk reflexes, a step-by-step sensory, corneal and motor examination, and four syndromes: neuropathy, trigeminal neuralgia, motor trigeminal lesion and main sensory nucleus lesion. A diagram of the divisions is included.

Inside: 1 section · 1 labelled picture · 15 flashcards · 2 min

Topic 14 of 88 in the MU Sofia syllabus for Neurology (Medicine, Year 4). The free AceMed note covers it in 1 section, about 290 words (2 min of reading), with 15 flashcards.

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  1. Trigeminal nerve - anatomy, physiology, examination, syndromes

Trigeminal nerve - anatomy, physiology, examination, syndromes

Anatomy

The trigeminal nerve (CN V) is the largest cranial nerve and is a mixed nerve with sensory and motor functions.

Divisions

V1 – Ophthalmic Division (Sensory)

Supplies: Forehead. Scalp. Upper eyelid. Cornea. Dorsum of nose

V2 – Maxillary Division (Sensory)

Supplies: Cheek. Upper lip. Upper teeth. Nasal cavity. Palate

V3 – Mandibular Division (Mixed)

Sensory: Lower lip.Chin. Lower teeth. Anterior 2/3 of tongue (general sensation)

Motor:

  • Muscles of mastication: Masseter. TemporalisM edial pterygoid. Lateral pterygoid

Physiology

Sensory Functions: Touch. Pain. Temperature. Proprioception from the face. Corneal sensation

Motor Functions: Mastication (chewing). Jaw movements

Reflexes

Corneal Reflex

  • Afferent: CN V1. Efferent: CN VII
  • Response: bilateral blinking

Jaw Jerk Reflex

  • Afferent and efferent: CN V
  • Normally absent or minimal

Examination

1. Sensory Examination

  • Test bilaterally in all three divisions: Light touch. Pain (pinprick). Temperature (if necessary)
  • Compare: V1, V2, and V3 territories

2. Corneal Reflex: Touch the cornea gently with cotton.

  • Normal response: Bilateral eyelid closure

3. Motor Examination

Inspection

  • Look for: Temporal wasting. Masseter wasting. Palpation. Ask the patient to clench their teeth.

Palpate: Masseter muscles. Temporalis muscles. Jaw Movement

  • Ask the patient to: Open mouth. Move jaw side to side

Trigeminal Nerve Syndromes

1.Trigeminal Neuropathy

  • Features: Facial numbness.,Reduced facial sensation. Weakness of mastication. Reduced corneal reflex
  • Causes: Tumors. Trauma. Multiple sclerosis

2.Trigeminal Neuralgia (Tic Douloureux): Most common trigeminal disorder.

  • Clinical Features: Sudden severe unilateral facial pain. Electric shock-like attacks. Lasts seconds to minutes
  • Triggered by: Chewing. Talking. Brushing teeth. Touching the face
  • Most commonly affects: V2 and V3 divisions

3.Motor Trigeminal Lesion

  • Features: Weakness of mastication muscles.Jaw deviates toward the affected side on opening. Muscle atrophy
  • Reason: Unopposed action of the normal pterygoid muscle.

4.Lesion of the Main Sensory Nucleus

  • Features: Ipsilateral loss of facial sensation. Reduced corneal reflex

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