Neurology exam signs - Cranial Nerves Flashcards
How would you test the olfactory nerve?
- Test each nostril with smelling salts if available
- Ask if noticed any change in smell
What mnemonic would you use for remembering what to examine when assessing the optic nerve?
- Acuity
- Fields
- Reflexes
- Optic disc
How would you assess visual acuity?
- Snellen chart
- Near vision
- Volour vision
How far away is a snellen chart read from?
6 metres
How would you record acuity?
- If patient gets >2 wrong, use previous line as acuity
- If patient gets 2 wrong, use that line
What would you use to assess colour vision?
Ishihara plates
How would you assess visual fields?
- Visual inattention
- Visual fields
- Blind spots
When assessing inattention, what does inattention on one side mean?
Identification of one hand when both are moving
- Means there is a contralateral parietal lesion
Where would a lesion be if someone had bitemporal hemianopia?
Optic chiasm
Where would a lesion be if someone had monocular field loss?
Intra-ocular pathology or ipsilateral optic nerve pathology
Where might someone have a lesion if they had homonymous hemianopia?
Contralateral optic tract/radiation lesion, or occipital cortex if macular sparing is present
How would you assess blind spots?
- Hold red pin between you and patient
- Check they can see in the middle
- Move horizontally, mapping blind spots
What would a central scotoma indicate?
Optic nerve lesion
What would a large blind spot indicate?
Papilloedema
What reflexes would you assess when assessing the optic nerve?
- Accommodation
- Direct and consensual pupillary reflexes
- Swinging light test
How would you interpret pupils that were symmetrical, but when light is shone in one eye, neither pupils constrict?
Afferent lesion (optic nerve) in the eye the light was shone in
How would you interpret a persistenly dilated pupil in one eye, while the other is reactive to light?
Efferent lesion (occulomotor nerve) in the dilated pupil eye
How would you interpret pupils becoming more dilated when light is shone in one eye than the other?
https://www.youtube.com/watch?v=HSYo7LhfV3A
That eye is relatively less sensitive to light, indicating a relative afferent pupillary defect
How would you examine the optic disc?
Opthalmoscopy
How would you examine CN III, IV, and V?
- Inspect
- H-test
- Saccades test
What would horizontal nystagmus on H-testing of CN III, IV and VI indicate?
- Cerebellar pathology
- Vestibular pathology
If there was complex opthalmoplegia on H-testing of CN III, IV and VI, what would you consider doing?
Get patient to raise eye for 20 seconds and test for fatiguability - myaesthenia gravis
How would you remember the different muscles for each eye movement?
- SR, LR and IR are all on the lateral side of the eye, from top to bottom
- IO, MR and SO and on the medial side of the eye, from top to bottom
How would you remember which nerves supply which muscles in the eye?
SO4LR6, and all other are 3
- Superior Oblique CN 4
- Lateral Rectus CN 6
How would the eye sit with a CNIII lesion?
Down and out
What nerve lesion would be present if the eye could not move inferiorly when facing medially?
CN 4 - Trochlear nerve supplying Superior oblique
What nerve lesion would be present if the eye could not move laterally?
CN 6 - Abducens nerve supplying lateral rectus
What would you think of as casues of complex opthalmoplegia?
- Graves
- Mitochondrial disfunction
- Myaesthenia
- Brainstem lesion
How would you inspect the trigeminal nerve?
- Temporalis/masseter wasting
- Sensory
- Jaw clench and open against resistnace
- Corneal reflex
- Jaw jerk
What are the components to the corneal reflex?
- Afferent - CN V, V1
- Efferent - CN VII