Cranial nerves Flashcards
What is the first thing you should do before examining the cranial nerves?
Perform a general inspection of patient head and neck - scars? facial asymmetry? ptosis? proptosis? skew deviation of the eyes? inequality of pupils - size/shape/symmetry? abnormality of speech or voice?
How do you test CN1/olfactory?
Only usually tested if patient reports an alteration in sense of smell
Use olfactory testing bottles ie coffee
Test each nostril separately by blocking the other
How do you test visual acuity? (CN2/optic)
If patient wears glasses, should keep on.
Test each eye separately using a Snellen chart, standing at 6m away.
Recorded as chart distance is m (numerator) over the lowest line read (denominator).
If patient makes some errors on a largely correct line, recorded as ie 6/6 (-2)
If unavailable, basic assessment made by getting them to state the number of fingers you’re holding up
How do you test a visual field? (CN2/optic)
Sit opposite with about an arms length between you and your patient
Ask patient to cover one eye, you cover the mirror image and look into each others eye
Slowly move a red neurotip (shows up) from a point outside your own visual field horizontally into it
Ask patient to say when they first see it, when it disappears and when it reappears again
Repeat in vertical axis to gauge size of zone
Repeat with other eye
How do you test for inattention/visual extinction?
CN2/optic
Hold you hands up in the periphery of a patients vision, one on each side
Wiggle your index fingers up and down randomly and get patient to identify which one or both are moving
Visual inattention is present when patient can identify movement individually but will ignore one side when both moved together
How do you test for direct and consensual light reflexes? (CN2/optic afferent + CN3 efferent)
Ask patient to look straight ahead, bring the light source in from the side and shine it into their eye
Look for constriction of pupil
Repeat process again looking at other eye for consensual reflex
How do you test for accommodation?
CN2/optic
Ask patient to focus on a distant point then to focus on your finger held approximately 30cm from their nose
A normal reaction will involve the constriction of both pupils
How do you test CN3/oculomotor, CN4/trochlear and CN6/abducens?
Look for ptosis
Ask patient to keep head still and follow your finger with their eyes
Slowly trace an H shape with an additional central line with your finger
Ask if the patient experiences any double vision and observe for any nystagmus if moved far to the periphery
How do you test the sensory division of CN5/trigeminal?
Get patient to shut eyes
Touch a wisp of cotton to each side of the face in the three dermatomes representing the opthalmic/maxillary/mandibular divisions
Ask if they can feel the stimulus and if they notice any difference between the strength of the sensation on either side of their body
How do you test the motor division of CN5/trigeminal?
Ask patient to clench their jaw
Palpate the masseter and temporalis muscles for wasting on both sides
How do you test CN7/facial?
Inspect forehead wrinkles/nasolabial folds/angles of mouth for asymmetry
Ask patient to raise eyebrows - assess symmetry
Ask patient to scrunch eyes up whilst you try to open them - assess power
Ask patient to blow out cheeks - assess power
Ask patient to smile - assess asymmetry
Ask patient to purse lips - assess symmetry
Ask patient to show teeth - assess symmetry
How do you test CN8/vestibulocochlear?
Cover opposite ear with your hand and whisper a number to your patient
Ask them to repeat it
Repeat in other ear
How do you perform Rinnes and Weber’s tests? (CN8/vestibulocochlear)
Rinnes - Place a vibrating tuning fork on the mastoid process then transfer it to the external acoustic meatus: if conduction is normal = louder at external meatus, conductive loss = louder on mastoid, sensorineural = both reduced by similar amount
Weber’s - place a vibrating tuning fork against the forehead in the midline (maybe get patient to block ears): if normal = even loudness, sensorineural = louder in normal ear
How do you test CN9/glossopharyngeal, CN10/vagus?
Ask patient say ‘ahh’
Observe uvula and soft palate moving upwards and any deviation (away from side of lesion)
Ask patient if they have any difficulty swallowing (no need to conduct gag reflex), can get patient to swallow some water and look for coughing/delayed swallow (IX afferent/X efferent)
Ask patient to cough - a bovine (non-explosive) cough suggests vagal palsy
Note hoarseness of voice
How do you test CN11/accessory?
Ask patient to shrug shoulders against you pushing down to test trapezius
Ask patient to turn head to side and resist you pushing it to the other to test SCM
