Cranial nerves exam Flashcards
What are you looking for on general inspection in a cranial nerve exam?
- Facial asymmetry (facial nerve palsy)
- Eye lid abnormality (oculomotor nerve pathology
- Pupil abnormality (oculomotor nerve pathology)
- Limb abnormalities (spasticity, weakness, wasting, tremor = neurological syndrome)
- Walking/hearing/visual aids
How do you examine cranial nerve 1 (olfactory)?
- Ask the patient if they have noticed any changes to their sense of smell
- If required, test different odours (e.g. coffee, peppermint) in each nostril
- Causes of anosmia = mucous blockage, head trauma, genetics, Parkinson’s disease, Covid-19
What are the different components of testing cranial nerve 2 (optic)?
Visual acuity
Visual fields
Visual inattention/neglect
Pupillary light reflexes
Accommodation
How do you test visual acuity?
- Stand the patient 6m away from a Snellen chart (wearing glasses if normally used)
- Ask them to cover 1 eye and read the lowest line possible
- Visual acuity is recorded as chart distance over lowest line read (e.g. reading the 6th line at 6m = 6/6 or 20/20)
- If a Snellen chart is not available ask them how many fingers you are holding up, or reading different sized fonts from a magazine/newspaper
- reduced visual acuity = cataract/corneal scarring, macular degeneration, optic nerve pathology
How do you asses visual fields?
- Sit directly opposite the patient, about 1m away
- Ask the patient to cover one eye, and mirror the patient to cover your eye as well
- Ask the patient to focus on your nose without moving their head or eyes, also focus on the patients face
- Compare the patients visual fields with your own by holding a test object at equal distance between you and the patient, and bringing it form the periphery and moving towards the centre
- Ask the patient to say when they first see it, then repeat in each quadrant on each eye
- If you can see the test object and the patient can’t, this suggests a visual field defect (e.g. pathology in the visual pathway)
How do you test for visual inattention/neglect?
- Sit opposite the patient. about 1m away, and ask the patient to focus on your nose
- Hold your hands up in the peripheries of the patient visual fields
- Wiggle a finger and ask the patient to point to which hand has moved, then wiggle both
- If the patient has visual inattention, they will correctly report both sides individually but ignore the side with an affected visual field when both hands are moved
How do you asses pupillary light reflexes?
With the lights dimmed, ask the patient to look forwards, shine the pen torch in their pupil and observe:
- the direct response in the ipsilateral eye
- the consensual response in the contralateral eye
Also use the swinging light reflex to check for a relative afferent pupillary defect
How do you asses accommodation?
- Ask the patient to focus on a distant object, then switch to a nearby object
- Observe the pupils which should constrict and converge
How do you asses cranial nerves 3, 4, and 6 (oculomotor, trochlear, and abducens)?
- Ask the patient to keep their head still and follow your finger (30cm away) as you move in a ‘H’ and ‘I’ pattern
- Observe for any nystagmus and restricted eye movements, and ask if they experienced any diplopia
- CN3 palsy = affected eye is ‘down and out’ (unopposed action of lateral rectus and superior oblique)
- CN4 palsy = vertical diplopia when looking down
- CN6 palsy = convergent squint and horizontal diplopia (unopposed adduction of the eye)
How do you asses cranial nerve 5 (trigeminal)?
Sensory:
- use cotton wool to lightly touch the forehead (ophthalmic), cheek (maxillary), and lower jaw (mandibular)
- compare each region on both sides
Motor:
- ask the patient to clench their teeth and palpate the masseter and temporalis muscles
- ask them to open their mouth against resistance (deviation occurs towards the side of paralysed pterygoid muscle)
Jaw jerk reflex:
- ask the patient to open their mouth and place your finger horizontally across the patients chin
- tap your finger with the tendon hammer, and any brisk closure is pathological (UMN lesion)
How do you asses cranial nerve 7 (facial)?
Sensory:
- ask if the patient has had any changes to their taste
Motor:
- ask the patient to carry out facial expressions (raised eyebrows, closed eyes, blown out cheeks, smiling, pursed lips)
- observe any asymmetry (lower face only = UMN lesion, upper and lower face = LMN lesion)
How do you asses the hearing aspect of cranial nerve 8 (vestibulocochlear)?
Gross hearing assessment:
- Stand behind the patient and block the hearing in the other ear (by covering or rubbing)
- Whisper a word/number from 60cm away and ask them to repeat it
- If they can’t hear it, move closer or use a louder voice
Rinne’s test:
- Place a vibrating 512Hz tuning fork on the mastoid process to test bone conduction
- When the patient can no longer hear it move the tuning fork in front of the ear (testing air conduction) and ask if they can still hear it
- Normal = air conduction > bone conduction, conductive deafness = bone > air, sensorineural deafness air > bone but both reduced
Weber’s test:
- Place a vibrating 512Hz tuning fork in the middle of the forehead and ask where the patient hears the sound
- Normal = equal in both ears, conductive deafness = louder in affected ear, sensorineural deafness = louder in intact ear
How do you asses the vestibular aspect of cranial nerve 8 (vestibulocochlear)?
Ask the patient if they have had any dizziness
Unterberger/Turning test:
- ask the patient to march on the spot with their arms outstretched and eyes closed
- normal = patient stays in the same position, vestibular lesion = patient turns towards side of lesion
Vestibular-ocular reflex
- sit facing the patient and ask them to focus on your nose
- hold their head and rotate it rapidly to one side and the other
- their eyes should be able to stay fixed on your nose, if not this suggest loss of vestibular function
How do you asses cranial nerves 9 and 10 (glossopharyngeal and vagus)?
- Ask the patient if they have had any difficulty swallowing or changes to their voice
- Ask the to say “ahh” and inspect the palate and uvula (vagus nerve lesion = deviation away from lesion)
- Ask the patient to cough (vagus nerve lesion = weak, non-explosive bovine cough
- An absent gag reflex would suggest glossopharyngeal nerve lesion, but is not routinely performed
How do you asses cranial nerve 11 (accessory)?
- Inspect for sternocleidomastoid or trapezius muscle wasting
- Ask the patient to lift their shoulders and turn their head against resistance
- Weakness suggests accessory nerve palsy
