Cranial Nerve Examiantion

TO START

W2I2P4E

  • Wash your hands

  • Wear appropriate PPE

  • Introduce yourself and check patient’s Identity (full name, DOB)

  • Permission: “May I examine the nerves in your head and neck?”

  • Privacy: Ensure curtains to the bay are closed

  • Pain: “Are you in any pain at all?”

  • Position: Sitting opposite you on a chair

  • Equipment: Essential: pen torch, cotton wool. Optional: tuning fork (512Hz), ophthalmoscope, tendon hammer, otoscope, Snellen chart, Ishihara plates, red hatpin

INSPECTION

Surroundings

  • Treatments - oxygen, infusions, feeding tubes, FVC monitor, TPN

  • Paraphernalia - NBM sign, soft diet, walking aids, glasses

Patient

  • Facial droop, wasting, asymmetry, ptosis, ophthalmoplegia 

  • Abnormal movements eg tremor, fasciculations, one-sided weakness

CRANIAL NERVES 

I - Olfactory

  • Ask the patient if they have noticed a change in their sense of taste or smell recently - if yes check for recent cold/COVID

  • Offer to formally assess with distinct scents (e.g. orange) for each nostril

II - Optic

  • Remember AFRO

  • Acuity

    • Ask the patient to cover each eye in turn (keep glasses on if they normally use them) and read a different word on your name badge.

    • If acuity is greatly impaired, test by finger counting, then hand movements, then light perception. 

    • Offer to formally assess acuity with a Snellen Chart (from 6m, or 2m if hand-held), and colour vision with Ishihara plates.

  • Fields

    • Ask the patient to cover one eye and to keep looking at your nose. Cover your own eye on the same side, and sit at the same horizontal level, as if you’re a mirror image.

    • Hold a finger equidistant between yourself and the patient. Move your finger from the edge of the visual field quadrant to the centre and ask them to say yes when they can see your finger. Compare your visual field with theirs in all four quadrants. (Swap your hands in the middle, but tell them to keep theirs where it is)

    • Offer to assess central vision with a red hatpin

  • Reflexes

    • Dim the lights and check pupil size and for asymmetry

    • Accommodation - ask patient to focus on far object then quickly on a near object at the same level. Look for convergence and pupil constriction.

    • Light reflex: ask patient to fixate on a distant target. Shine a light on one eye to see the ipsilateral pupil constrict (direct reflex), then again to see the contralateral eye constrict (consensual reflex). Repeat on other eye.

    • Swinging light test (optional): swing the light from one eye to the other for 3 seconds each. Normally, pupils of both eyes constrict regardless of which eye is stimulated; in a relative afferent pupillary defect (RAPD, classically in MS), the eye with optic nerve disease would paradoxically dilate with light as there is loss of the direct reflex (but an intact consensual reflex).

  • Ophthalmoscopy (offer only)

III, IV, VI - Oculomotor, Trochlear, Abducens

  • Smooth pursuit: Ask the patient to focus on your finger while keeping their head still (steady their head with your other hand if needed). Move your finger slowly in an H shape. Look for nystagmus at the extremes of gaze, and ask the patient if they experience pain/double vision.

    • If there is double vision, cover each eye in turn and ask when the outer image disappears. The outer image is produced by the pathological eye.

  • Saccades: hold up a finger and a pen, and ask the patient to quickly focus on each object alternately.

  • Specific lesions

o   CN III: down and out, ptosis, dilated pupil unresponsive to light or accommodation. Diplopia in all directions of gaze. Parasympathetic functions (i.e. pupils) often affected before extraocular muscles in ‘surgical’ causes, e.g. Posterior Communicating artery aneurysm.

o   CN IV: up and out. Diplopia on looking down (e.g. going down stairs), so compensates by tilting head away from the eye.

o   CN VI: cannot abduct. Diplopia on looking towards the affected eye.

o   INO (internuclear opthalmoplegia): on looking away from the affected side, weak adduction of affected eye and jerky nystagmus of contralateral eye. Typically seen in MS.

V - Trigeminal

  • Sensation

    • Reference touch on sternum, then touch the patient on left/right forehead (V1 – ophthalmic), cheeks (V2 – maxillary) and chin (V3 – mandibular). Stay near midline to avoid C2 dermatome. Ask if it feels normal and same on both sides.

  • Motor

    • “Open your jaw, don't let me close it.” (pterygoids) Open jaw deviates towards the lesion in LMN lesions.

    • “Clench your teeth.” Feel muscle bulk of masseter and temporalis.

  • Reflexes (offer only)

    • Jaw jerk (afferent V3, efferent V3): put finger on chin and tap with tendon hammer; look for closure of mouth. UMN if brisk

    • Corneal reflex (afferent V, efferent VII): touch cornea (not conjunctiva) with cotton wool; look for synchronous blinking

VII - Facial

  • Look for ptosis, droop or asymmetry at rest.

  • Ask patient to make some faces:

    • Raise your eyebrows - Forehead spared in UMN facial nerve lesions due to bilateral innervation (upper spares upper)

    • Scrunch up your eyes - test against resistance 

    • Blow your cheeks out - test against resistance

    • Show me your teeth - (not “smile”)


VIII - Vestibulocochlear

  • Ask patient to close their eyes. Rub your fingers together on one side of their ear and ask them to point to the direction the sound is coming from.

  • Can offer:

    • Weber’s: tuning fork (512Hz) on centre of forehead to lateralise hearing loss, then do Rinne’s on that side.

    • Rinne’s: tuning fork on mastoid process and beside the ear. If louder on bone, conductive hearing loss on that side. If louder in air, sensorineural loss on contralateral ear.

    • Otoscope: look at tympanic membrane

IX, X, XII - Glossopharyngeal, Vagus, Hypoglossal

  • “Open your mouth and say ahh”. Use a pen torch to look for palatal asymmetry (towards the lesion) and uvula deviation (away from the lesion). Look for tongue fasciculations or wasting (MND).

  • “Stick your tongue out and move it side to side.” Look for tongue deviation (towards the lesion)

  • Offer to do gag reflex (afferent IX, efferent X).

  • Specific lesions

    • CN IX: loss of posterior 1/3 taste, dysphagia, no gag reflex.

    • CN X: dysphagia, hoarse voice, autonomic dysfunction, no gag reflex, palatal weakness.

    • CN XII: tongue wasting, deviation towards lesion, fasiculations (LMN); spastic tongue (bilateral UMN).

XI - Spinal Accessory

  • “Shrug your shoulders, don’t let me push them down” – trapezius power. Motor innervation is contralateral.

  • Place your hand on the patient’s right cheek, and ask them to turn towards your hand. Feel the muscle belly of sternocleidomastoid on the left. Repeat on other side. Motor innervation is ipsilateral (ipsilateral SCM turns head to opposite side, as SCM attaches to occiput).





CLOSURE 


Closure

  • Thank the patient, ensure they are comfortable 

  • Remove PPE

  • Clean equipment and wash hands

To complete

  • Full neurological examination (upper and lower limb)

  • Consider other neurological exams

  • Consider additional tests mentioned (e.g. reflexes, ophthalmoscopy) 

💡
In summary, I performed a cranial nerve examination on [name], a [age] year old [sex]. Upon testing, there were no sensory, motor or autonomic deficits in cranial nerves I-XII. In conclusion, this was a normal neurological examination.