Cranial Nerve Exam Flashcards
What is CN I (1)?
Olfactory Nerve
What is CN II (2)?
Optic nerve
What is CN III (3)?
Occulomotor nerve
What is CN IV (4)?
Trochlear nerve
What is CN V (5)?
Trigeminal nerve
What is CN VI (6)?
Abducens nerve
What is CN VII (7)?
Facial nerve
What is CN VIII (8)?
Vestibulocochlear nerve
What is CN IX (9)?
Glossopharyngeal Nerve
What is CN X (10)?
Vagus nerve
What is CN XI (11)?
Spinal accessory nerve
What is CN XII (12)?
Hypoglossal nerve
How should you first assess a patient’s cranial nerves?
General inspection
What is the pathology?
Bell’s Palsy (unilateral facial nerve weakness)
What is the pathology?
Stroke (UMN lesion affecting the facial muscles)
How can Bell’s be differentiated from a facial stroke?
Forehead sparing in stroke
Why is there forehead sparing in stroke?
Bilateral UMN supply to the superior part of the facial nerve nucleus
What should be looked for in eyes on general inspection?
- Strabismus
- Ptosis
- Asymmetrical pupil
What is this sign?
Ptosis
What is this sign?
(Not the ptosis)
Miosis (pupil constricted)
What is this sign?
Mydriasis (pupil dilation)
How can you distinguish unilateral miosis from unilateral mydriasis?
The normal pupil should be more constricted in brighter light
What abnormality of speech is relevant to a cranial nerve exam?
Dysarthria (problems with articulation)
What signs of cranial nerve problems can be seen around the bedside?
- Glasses
- Hearing aids
How can the function of the olfactory nerve be assessed?
Ask if they have had any changes to their sense of smell
What are the aspects of a full optic nerve assessment?
(Doing all of these in an exam is excessive unless specifically asked to)
- Pupil inspection
- Visual acuity
- Pupillary reflexes
- Colour vision
- Visual fields
- Fundoscopy
What are the essential aspects of an optic nerve assessment?
- Pupil inspection
- Visual acuity (brief tests of ability to read/see)
- Visual fields
- Fundoscopy (may not be needed)
- Pupillary reflexes (also CN III)
What aspects of optic nerve assessment can be modified or excluded for OSCE purposes?
- Visual acuity - not always necessary to do full Snellen chart
- Colour vision - exclude in most exams
What is the pathology*?
Anisocoria (unequal pupil size) - in this case, mydriasis
*Up to 20% of people are born with very mild anisocoria
(Fun Fact: David Bowie developed anisocria when a friend damaged his iris in a fight)
What is the type of anisocoria and what is the likely cause?
Mydriasis - CN III lesion
What is the type of anisocoria and what is the likely cause?
Miosis - Horner’s syndrome
How can visual acuity be tested in an OSCE?
Ask the patient to cover one eye at a time and read a part of a book or magazine
Should patients be given their glasses when testing visual acuity?
Yes
What can be used to more formally test visual acuity?
Snellen chart
If performing fundoscopy as part of a cranial nerve exam, what aspects should be included?
- Red reflex
- Retinal visualisation
Which eye should be used to look in the patients left eye?
Left (and vice versa)
How can visual fields be assessed?
- Sit/stand level with the patient
- Ask them to cover one eye and cover/close your corresponding eye
- Hold finger at the edge of your visual fields (2/4/8/10 o’clock positions) midway between you and the patient and ask the patient if they can see your finger moving
- Repeat with the other eye
What shows a visual field defects in a cranial nerve exam?
Needing to move your finger in from where you can see it so that the patient can see it
What is the name of and what can cause this sort of visual field defect?
- Monocular blindness
- Optic nerve or retinal lesion
What is the name of and what can cause this sort of visual field defect?
- Bitemporal hemianopia
- Lesion at the optic chiasm
What can cause a lesion at the optic chiasm?
Pituitary tumour
What is the name of and what can cause this sort of visual field defect?
- Right homonymous hemianopia
- Lesion of the optic tract
How should CN 3,4 and 6 be tested?
Testing ocular movements
What shape should a patient be made to follow to test ocular movements?
H shape
What should be observed for on eye movement testing?
- Restricted movement
- Nystagmus
What is shown here?
Nystagmus
Palsy of which nerve is seen here?
Abducens
Palsy of which nerve is seen here?
Oculomotor nerve
Palsy of which nerve is seen here?
Trochlear nerve
Which tests for
What are the tests of pupillary reflexes?
- Accommodation reflex
- Direct pupillary reflex
- Consensual pupillary reflex
- Swinging light test
How is the accommodation reflex tested?
- Ask patient to look into the distance
- Hold a pen a few cm in front of their nose
- Ask them to look at the tip of the pen
What should be seen on normal accommodation?
- Convergence of the eyes
- Constriction of the pupils
How are the direct light reflexes tested?
- Hold hand down midline
- Shine light into one eye and observe it for constriction
- Repeat with the other eye
How are the consensual light reflexes tested?
- Hold hand down midline
- Shine light into one eye and observe the other for constriction
- Repeat with the other eye
How is the swinging light test performed?
- Swing pen torch from one eye to the other
- Observe for dilation of the pupils when light shone in one pupil
What does the swinging light test assess for?
RAPD (relative afferent pupillary defect or Marcus Gunn Pupil)
What does dilation of pupils when swinging light onto a pupil?
The pupil that the light is being shone into has an RAPD
Which nerves are involved in the light reflexes?
2 and 3
If there is absence of direct reflex but presence of consensual, which nerve is affected?
2
If there is absence of direct and consensual reflexes in one eye, which nerve is affected?
3
If there is loss of consensual reflex only which nerve is affected?
The contralateral 2nd nerve
How is the sensory aspect of the 5th nerve tested?
- Test light touch in the opthalmic, maxillary and mandibular divisions
- Compare left to right
Which muscles are supplied by the motor aspect of the trigeminal nerve?
Muscles of mastication
How is the temporalis muscles tested?
Ask patient to clench teeth whilst feeling temple area
How is the masseter muscle tested?
Ask patient to clench teeth whilst feeling over cheeks
How are the pterygoid muscles tested?
Ask the patient to open their mouth and resist you closing
If there is pterygoid weakness, what will be seen on examination?
Deviation to the side of weakness when opening the mouth
How is the facial nerve tested?
Ask the patient to perform specific movements of the muscles of facial expression
What muscles should be tested when assessing the function of the facial nerve?
- Frontalis
- Orbicularis oculi
- Orbicularis oris
- Buccinator
How is the frontalis muscle tested?
Ask the patient to raise their eyebrows
What unilateral weakness of the frontalis muscle suggest?
LMN lesion
What does unilateral weakness of all muscles of facial expression except frontalis suggest?
UMN lesion
How is orbicularis oculi tested?
Ask the patient to screw their eyes closed and resist you opening
How is orbicularis oris tested?
Ask the patient to grin 😀
How is the buccinator muscle tested?
Ask the patient to puff out their cheeks and resist you pushing them in
How can the vestibulocochlear nerve be tested?
- Whisper a number in the paitent’s ear and ask them to repeat it
- Weber’s test
- Rinne’s test
What is Weber’s test?
- Place a tuning fork on the patient’s forehead
- Ask them which ear it localises to if any
What does localisation of Weber’s test suggest?
Asymmetrical hearing loss
Where does the sound localise to in an asymmetrical sensorineural hearing loss in Weber’s test?
The unaffected ear
Where does the sound localise to in an asymmetrical conductive hearing loss in Weber’s test?
Affected ear
What is Rinne’s test?
- Place the tuning fork on the mastoid process and ask them to tell you when it stops
- Move fork to in front of ear and ask if they can still hear it
What result of Rinne’s suggests conductive hearing loss?
Unable to hear once moved from mastoid
What suggests sensorineural loss in Rinne’s test?
Able to hear sound when moved from mastoid process (in the ear that sound localised away from in Weber’s test - will show the same Rinne result in normal ear)
What are the Bulbar cranial nerves?
9, 10, 12
How should the bulbar nerves be tested?
- Cough
- Articulation
- Examine pharynx
- Tongue movements
What cranial nerve is tested by asking the patient to cough?
10 (vagus)
How can articulation be tested?
Ask the patient to say the days of the weeks
What nerves are involved in articulation?
- (7)
- 10
- 12
How is the pharynx examined?
- Use a tongue depressor and pen torch
- Ask the patient to say ahh and observe uvula
- Remove tongue depressor
- Ask to swallow
Where does the uvula deviate in a CN IX or X lesion?
Away from the lesion on saying ahh
What is not normally tested in a conscious patient?
Gag reflex
How is CN 12 tested?
- Ask the patient to stick their tongue out
- Observe for wasting
- Move side to side
- Push tongue into side of cheek and apply resistance
What indicates a CN 12 lesion?
Deviation towards the lesion
How is the CN 11 tested?
- Ask patient to shrug their shoudlers against resistance
- Ask the patient to turn their head against resistance
Which muscle provides shoulder shrugging?
Trapezius
Which muscle provides head turning?
Sternocleidomastoid
What additional tests can be considered after a cranial nerve exam?
- Neuro exam of the limbs
- Gait and balance
- CT/MRI head
What is shown here?
Left CN XII lesion
What is shown here?
Left CN IX or X lesion
