Differentials
| Presenting Feature | What might it be? | What might I find? | |
| Ophthalmo-plegia |
CN III palsy (Complete/Partial) |
Causes (P): Microvascular e.g., diabetes, HTN, ischaemia.
Causes (C): Compressive e.g., tumour, trauma, aneurysm, cavernous sinus thrombosis, raised ICP. Deviation of affected eye due to only LR/SO ocular muscles working (down and out), ptosis, dilated pupil if (C). |
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CN IV palsy |
Cause: orbit# but rare to have isolated trochlear nerve palsy.
Palsy of trochlear nerve innervating SO – affected eye unable to look down & out, causing diplopia. |
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CN VI palsy |
Causes: skull fracture, raised ICP (false localising), nasopharyngeal cancer.
Palsy of abducens nerve innervating LR – affected eye unable to aBduct causing conjugate lateral gaze palsy. |
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Internuclear ophthalmoplegia |
Causes: MS, stroke, Lyme disease, TCA overdose, lesion in medial longitudinal fasciculus (connects CN III/IV/VI).
Disordered conjugate lateral gaze palsy – affected eye unable to aDduct, nystagmus of contralateral eye in compensation, convergence/accommodation intact. |
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| Visual field defect |
Optic neuritis |
Causes: MS, SLE, sarcoid, mumps, measles, syphilis.
Unilateral vision loss, may develop from central scotoma. Associated with pain, reduced colour vision & RAPD. |
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Pituitary tumour |
Tend to be benign but can cause hormonal imbalance.
If large enough can compress optic chiasm causing loss of vision in pattern of bitemporal hemianopia. |
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Stroke (MCA/PCA) |
RF: prior CVA, AF, HTN, diabetes, CVD, smoking, obesity.
Limb/facial weakness, dysphasia, ataxia/vertigo. Stroke involving Middle/Posterior CA can cause VF defects. Whole MCA occluded causes homonymous hemianopia. Part MCA occluded causes homonymous quadrantanopia. PCA occlusion causes homonymous hemianopia w/macular sparing. |
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| Facial weakness |
Bell’s Palsy |
Idiopathic unilateral lower motor neurone facial nerve palsy.
Unilateral facial weakness including forehead. At risk of exposure keratopathy to affected eye. |
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Ramsay Hunt syndrome |
Caused by Varicella Zoster virus.
Unilateral lower motor neurone facial nerve palsy. Unilateral facial weakness including forehead plus painful vesicular rash around the ear on the affected side – rash can extend to anterior 2/3 tongue and hard palate. |
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Stroke |
Upper motor neurone facial nerve palsy.
If new onset – treat as stroke until proven otherwise. May have associated limb weakness, dysphasia, ataxia. |
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| Hearing loss |
Conductive Hearing Loss |
Causes: wax, infection, effusion, ETD, perforated TM.
Weber test: sound lateralises to affected ear. Rinne test: bone conduction > air conduction in affected ear. |
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Sensorineural Hearing Loss |
Causes: Sudden SNHL, age, noise exposure, acoustic neuroma.
Weber test: sound lateralises to unaffected ear. Rinne test: air conduction > bone conduction in both ears. |
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Checklist
|
Preparation |
Wash – Name – Explain | |
| Position patient sitting & position yourself opposite them | ||
| Appropriate exposure of face & neck | ||
| General Inspection | Overt facial asymmetry | |
| Overt speech changes | ||
| Clues in bed space | ||
| I – Olfactory | Change to sense of smell | |
| II – Optic | Visual acuity | |
| Near vision | ||
| Colour vision | ||
| Inattention | ||
| Visual fields | ||
| Blind spot | ||
| Pupil size | ||
| Pupil reflexes | ||
| Swinging light test | ||
| Accommodation reflex | ||
| Offer ophthalmoscopy | ||
| III – IV – VI
Oculomotor Trochlear Abducens |
Ptosis | |
| Strabismus | ||
| H-test | ||
| Saccades | ||
| Cover test | ||
| V – Trigeminal | Ophthalmic sensation | |
| Maxillary sensation | ||
| Mandibular sensation | ||
| Temporalis & Masseter wasting | ||
| Temporalis & Masseter palpation | ||
| Jaw opening against resistance | ||
| Offer jaw jerk reflex | ||
| Offer corneal reflex | ||
| VII – Facial | Change to sense of taste | |
| Change to sensitivity of hearing | ||
| Facial tone/symmetry | ||
| Raise eyebrows | ||
| Eyes tightly shut | ||
| Puff out cheeks | ||
| Pursed lips | ||
| Big smile | ||
| VIII – Vestibulocochlear | Change to sense of hearing | |
| Change to balance | ||
| Whisper test | ||
| Rinne test | ||
| Weber test | ||
| Offer head impulse test | ||
| IX – X
Glossopharyngeal Vagus |
Inspect palate and uvula symmetry | |
| Assessment of swallow | ||
| Assessment of cough | ||
| Assessment of speech | ||
| Offer gag reflex | ||
| XI – Accessory | Sternocleidomastoid & Trapezius wasting | |
| Shrug shoulders | ||
| Turn head against resistance | ||
| XII – Hypoglossal | Tongue wasting | |
| Tongue fasciculations | ||
| Tongue deviation on protrusion | ||
| Tongue strength | ||
| Finishing | Re-cover patient | |
| Wash hands |
Explanation
Preparation
Wash, name, explain:
- Wash your hands
- Introduce yourself by name and role
- Check the patient’s name and date of birth
- Explain the procedure and get consent
“I have been asked to examine your cranial nerves. This involves testing some of the nerves in your face, eyes, ears and mouth. You can ask me to stop at any time. Are you happy for me to do that?”
Position the patient sitting on a chair – you will sit opposite them throughout the examination.
Ensure the patient’s face and neck are adequately exposed.
General Inspection
Look at the patient and around the bed space for useful signs:
- Overt facial asymmetry (e.g., Facial droop, ptosis, squint)
- Overt speech disturbance (e.g., Slurred speech, dysphasia)
- Clues around the bed space (e.g., Medications, hearing aids, glasses)
The cranial nerve examination is generally carried out by examining each nerve in turn. Nerves which are examined in a similar way are grouped together; for example cranial nerves III, IV, VI all control eye movements so these are examined together.
You may be asked to perform a generalised cranial nerve examination, or a focused examination relating to a specific symptom (e.g., blurred vision).
I – Olfactory
Ask the patient if they have noticed any changes to their sense of smell.
This is most likely to be sufficient in an OSCE setting, however you could offer formal testing with specific odours testing individual nostrils in turn so that the examiner is aware you have this knowledge.
II – Optic
The key components of testing the optic nerve are:
- Visual acuity
- Near vision
- Colour vision
- Inattention
- Visual field testing
- Blind spot testing
- Pupil inspection
- Pupil reflexes
- Swinging light test
- Accommodation
- Ophthalmoscopy
Check the patient’s visual acuity using a Snellen chart placed 6m away from the patient (or 3m if using a mirror) whilst wearing their usual glasses. Ask the patient to read the line of letters furthest down the chart in the smallest text they can clearly see, testing one eye at a time with the other eye covered. Record the visual acuity as 6/X and repeat with the other eye. A pinhole can be used to repeat visual acuity testing correcting for refractory error.
Offer to check near vision by asking the patient to read a sentence from a book or leaflet. Offer to check colour vision using Ishihara plates.
Check for inattention by asking the patient to focus on your nose and tell you which of your fingers they see moving. Hold up both of your hands to head height at the lateral aspect of the patient’s visual field and wiggle your left and right index fingers in turn then wiggle both together. Inability to notice your finger wiggling on one side is a positive finding and indicates brain injury or stroke.
Carry out visual field testing by comparing the patient’s visual fields to your own when sat opposite approximately 1m away from the patient. Both parties should wear their normal glasses and either use a white pin or your finger to test the visual fields. Ask the patient to focus on your nose and to cover one of their eyes with their hand. Check they can see all of your face with no missing patches. Cover your eye on the same side. Test all 4 quadrants of the visual field by moving the pin or your finger diagonally inwards from each of the 4 corners of the periphery, asking the patient to tell you when they see the object coming into view. Swap eyes and repeat.
Offer to check blind spot using a red pin and moving it slowly laterally from a starting central position equal distance between you and the patient, asking the patient to inform you when the pin disappears.
Examine the patient’s pupils and comment on their approximate size in mm (2-4 mm is normal in a lit room) and whether they are equal in size on both sides. Shine a light into each eye in turn and observe the patient’s direct (pupil constriction in eye light is being shone into) and consensual (pupil constriction in opposite eye in response to light) pupillary reactions.
Perform the swinging light test by rapidly moving your light source between the patient’s right and left eyes ‘swinging’ repeatedly back and forth. A normal response to this test is for both pupils to remain constricted. The test looks for a Relative Afferent Pupillary Defect (RAPD): the pupil in the affected eye constricts more when shining a light in the contralateral eye than when shining it in the affected eye. When testing the direct pupillary reflex, there is a reduced pupil response to shining light in the eye affected. However, the affected eye has a normal pupil response when testing the consensual pupillary reflex. RAPD indicates pathology in the optic nerve or retina.
Accommodation is checked by asking the patient to focus on a target (e.g., pin or finger) which is slowly moved closer to their face. As the target moves closer and eyes converge (move nasally) the pupils should constrict.
Offer ophthalmoscopy to visualise the optic disc and the retina.
III, IV, VI – Oculomotor, Trochlear, Abducens
The efferent limbs of both the pupillary reflex and the accommodation reflex (both explained above) are controlled by the oculomotor nerve.
Inspect the patient’s eyelids for any evidence of ptosis (eyelid drooping). Observe the symmetry of the patient’s eye position, looking for evidence of strabismus (misaligned eye position).
Check eye movements by performing the H–test. Ask the patient to focus on an object (finger, pin, pen) held approx. 30 cm away from their face. Move the object slowly up, down, left and right in a H-shape. Ask the patient to inform you of any diplopia (double vision) or pain on eye movement, observe for any difficulty moving the eye into a certain position (ophthalmoplegia) or nystagmus.
The oculomotor nerve controls all eye movements aside from lateral gaze (lateral rectus – abducens nerve) and inferomedial gaze (superior oblique – trochlear nerve)
Test saccadic eye movements by asking the patient to focus on a target (finger, pin) then rapidly switch their focus to another target a distance away. Observe for speed, accuracy and how smooth these movements are.
Carry out the cover test to check alignment of the eyes. Ask the patient to focus on a distant target (eg spot on the wall) whilst you cover one of their eyes, then switch eyes; alternating the covered eye. When one eye is covered, the contralateral eye should not have to shift to focus on the same target; a shift during the cover test indicates misalignment (e.g., esotropia).
V – Trigeminal
The trigeminal nerve has a sensory and a motor component:
- Sensory – check facial sensation by asking the patient to close their eyes and to inform you if they can feel you touching their face and if it feels equal on both sides. Assess sensation in the areas supplied by the three branches of the trigeminal nerve: ophthalmic (V1) – frontal forehead above eyebrows, maxillary (V2) – over zygomatic bone and mandibular (V3) – chin.
- Motor – assess the temporalis and masseter muscles; inspect for wasting or asymmetry by comparing both sides then palpate whilst asking patient to clench jaw to feel for muscle contraction. Ask the patient to try opening their jaw against resistance to check the pterygoid muscle.
Offer to test the two reflexes associated with the trigeminal nerve:
- Jaw jerk – place your finger on patient’s chin with their mouth open, tap over your finger and observe a subtle jaw closure
- Corneal reflex – touch the cornea gently with gauze or cotton wool and observe blinking in both eyes
VII – Facial
Ask the patient if they have noticed any changes to their taste or hearing sensitivity (anterior 2/3 tongue taste sensation controlled by facial nerve as well as innervation to stapedius (middle ear muscle).
Observe the patient’s face for any droop or asymmetry, especially around the mouth and forehead. Ask the patient to carry out the following facial movements, again observing symmetry and opposing the movements to assess power and motor function of the facial nerve:
- Raise eyebrows
- Scrunch eyes up tight
- Puff out cheeks
- Purse lip
- Big smile
If there is any motor disturbance of the facial nerve, assess for forehead involvement to determine if lesion is upper or lower motor neurone.
VIII – Vestibulocochlear
Ask the patient if they have noted any changes to their sense of hearing or balance.
Carry out a gross hearing assessment using the whisper test. Assessing one ear at a time by masking the contralateral ear by rubbing the tragus and whispering a number, asking the patient to repeat it back to you. Repeat with the other ear.
Perform Rinne and Weber tests using a 512 Hz tuning fork to differentiate between conductive and sensorineural hearing loss.
- Weber test – place tuning fork in middle of patient’s forehead and ask them to identify if the sound is louder on one side or the other, or if it is the same on both sides.
- If a patient has normal hearing the sound will be the same on both sides.
- If the sound literalises, there is either conductive hearing loss on the ipsilateral side or sensorineural hearing loss on the contralateral side.
- Rinne test – place tuning fork on the patient’s mastoid process and then move the tuning fork to the external auditory meatus and ask the patient which sound they hear louder.
- If the patient has normal hearing, air conduction is louder than bone conduction
- An abnormal result (Rinne’s negative) is when bone conduction is better than air conduction. The sound is not heard after removing the tuning fork from the mastoid process and holding it near the ear canal. This suggests a conductive cause for the hearing loss
Offer the head impulse test to check the vestibular–ocular reflex. A normal result is for the patient to be able to maintain central gaze while you gently rotate their head.
IX, X – Glossopharyngeal, Vagus
Ask the patient if they have noted any changes to the swallow, voice, cough, or taste (posterior 1/3 tongue sensation).
Inspect the palate and the uvula position by asking the patient to open their mouth and saying ‘Aaahh’. Observe for any deviation of the uvula at rest, and for symmetrical movement of the palate and uvula on speech. If there is weakness present, the uvula will deviate away from the weaker side.
Ask the patient to swallow a sip of water. Assess for any choking or dysphagia. As the patient to cough and observe for the presence of a strong cough. Assess the patient’s speech for any dysarthria.
Offer to test the patient’s gag reflex, though this is rarely asked for in an OSCE setting.
XI – Accessory
Inspect the patient’s neck for any evidence of trapezius or sternocleidomastoid muscle wasting or asymmetry.
Test the motor function of the trapezius muscle by asking the patient to shrug their shoulders against resistance. Test the motor function of the sternocleidomastoid muscle by asking the patient to turn their head left and right against resistance.
XII – Hypoglossal
Inspect the patient’s tongue with their mouth open to look for any wasting or fasciculations. Ask the patient to stick their tongue out and observe if the tongue deviates to one side (tongue deviates towards the side of weakness).
Ask the patient to press their tongue into each cheek against resistance (your hands pushing their cheeks inward) to check motor function.
Finishing
Thank the patient and allow them to cover themselves. Wash your hands.
Depending on the examination findings you may wish to carry out neurological examination of the upper and lower limbs as well as carry out further investigations including CT or MR scan of the head.
Last updated Dec 2024
Head to members.zerotofinals.com for practice OSCE stations, including an interactive checklist, specific cases and clinical findings.
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