Summary of findings
Do not read out twelve nerves in turn. Say which nerves are affected, on which side, whether the lesion is upper or lower motor neurone, and where one lesion could explain all of it.
Good afternoon, sir. I examined the cranial nerves of a middle-aged man. There is a left lower motor neurone facial weakness involving the forehead, with loss of the nasolabial fold and inability to bury the eyelashes. The left corneal reflex is reduced and there is diminished sensation over all three divisions of the left trigeminal nerve. Hearing is reduced on the left, with Rinne positive in both ears and Weber lateralising to the right — a left sensorineural deafness. There is nystagmus on looking to the left and an ataxic gait with a tendency to fall to the left. The other cranial nerves are intact and the fundi are normal. These findings localise to the left cerebellopontine angle, affecting the fifth, seventh and eighth nerves with cerebellar involvement, most likely a vestibular schwannoma. I would like to complete my examination by testing the limbs for cerebellar signs and long tract signs, and by asking about tinnitus and the rate of onset.
| Test | Normal | What an abnormal result means |
|---|---|---|
| Rinne | Air conduction louder than bone conduction (positive) | Negative — bone louder — means conductive deafness in that ear |
| Weber | Heard in the midline | Lateralises to a conductive loss, away from a sensorineural loss |
| Swinging torch | Both pupils constrict equally | A pupil that dilates on illumination is a relative afferent pupillary defect — optic nerve or severe retinal disease |
| Jaw jerk | Absent or just present | Brisk in a bilateral upper motor neurone lesion above the pons — pseudobulbar palsy |
| Tongue protrusion | Midline | Deviates towards the weak side in a twelfth nerve lesion |
| Uvula on saying "ah" | Midline | Deviates away from the weak side in a tenth nerve lesion |
Differential diagnoses
- Isolated lower motor neurone seventh nerve palsy — Bell's palsy, herpes zoster oticus, otitis media, parotid tumour, sarcoidosis, HIV seroconversion, Lyme disease. See Facial nerve palsy
- Third nerve palsy with a fixed dilated pupil — posterior communicating artery aneurysm or uncal herniation until proved otherwise; a pupil-sparing palsy suggests diabetic or hypertensive microvascular infarction
- Cerebellopontine angle syndrome (V, VII, VIII and cerebellar signs) — vestibular schwannoma, meningioma, cholesteatoma, tuberculoma
- Cavernous sinus syndrome (III, IV, V1, V2, VI) — cavernous sinus thrombosis, pituitary apoplexy, carotid aneurysm, nasopharyngeal carcinoma, mucormycosis in poorly controlled diabetes
- Jugular foramen syndrome (IX, X, XI) — glomus tumour, metastasis, skull base tuberculosis
- Multiple lower cranial nerve palsies with a neck mass — nasopharyngeal carcinoma, lymphoma, skull base metastasis
- Bulbar and pseudobulbar palsy — motor neurone disease, brainstem stroke, myasthenia gravis, Guillain–Barré syndrome
- Bilateral facial weakness — Guillain–Barré syndrome, sarcoidosis, Lyme disease, HIV, leprosy
The full anatomical breakdown, including visual field defects and eye movement disorders, is in Cranial nerve lesions.
Investigations
- Capillary glucose, HbA1c and blood pressure — microvascular palsies in diabetes and hypertension
- Full blood count, ESR, urea and electrolytes, HIV test, syphilis serology
- MRI of the brain with gadolinium, including internal auditory meati for a cerebellopontine angle lesion; CT where MRI is unavailable, with dedicated skull base views
- CT angiography or MR angiography urgently for a painful third nerve palsy with a dilated pupil
- Lumbar puncture after imaging — malignant meningitis, tuberculous meningitis, Guillain–Barré syndrome, cryptococcal disease
- Pure tone audiometry for asymmetrical sensorineural deafness
- Nasopharyngoscopy and biopsy when multiple lower cranial nerves are involved
- Chest X-ray and serum ACE where sarcoidosis is suspected
- Acetylcholine receptor antibodies and repetitive nerve stimulation for fatigable weakness — see Myasthenia gravis
Treatment
- Treat the cause: prednisolone within 72 hours for Bell's palsy, antituberculous treatment for skull base or meningeal tuberculosis, surgery or radiotherapy for a schwannoma, urgent neurosurgical referral for an aneurysm
- Protect the eye in any facial palsy or fifth nerve sensory loss — artificial tears by day, ointment and taping at night, and an urgent ophthalmology referral for exposure keratitis
- Assess swallowing in every bulbar palsy before allowing oral intake; nasogastric feeding if unsafe
- Speech and language therapy, physiotherapy and psychological support
- Treat blood pressure, diabetes and HIV as the underlying driver
Examiner questions
References
- Longo DL, Fauci AS, Kasper DL, Hauser SL, Jameson JL, Loscalzo J, et al., eds. Harrison's Principles of Internal Medicine. 22nd ed. New York: McGraw Hill; 2025.