Cranial nerves examination

Question 1

what equipment is required for the cranial nerves examination?

Answer 1

• pen torch
• Snellen chart
• Ischihara plates
• opthalmoscope and mydriatic eye drops
• cotton wool
• neurotip
• tuning fork (512Hz)
• glass of water

Question 2

what is looked for in general inspection?

Answer 2

• speech abnormalities
• facial asymmetry
• eyelid abnormalities
• pupillary abnormalities
• strabismus
• limbs
• walking aids
• hearing aids
• visual aids
• prescriptions

Question 3

how is the olfactory nerve (CN I) tested?

Answer 3

1. ask patient if they have noticed any recent changes to their sense of smell
2. can be tested more formally using different odours (e.g. lemon or peppermint) or using the University of Pennsylvania smell identification test

Question 4

what are some causes of anosmia?

Answer 4

• mucous blockage of the nose
• head trauma
• genetics
• Parkinson’s disease

Question 5

how is the optic nerve (CN II) tested?

Answer 5

1. assess pupil size
2. assess pupil shape
3. assess pupil symmetry
4. assess and record visual acuity
5. direct pupillary reflex
6. consensual pupillary reflex
7. swinging light test
8. accommodation reflex
9. Ischihara plates
10. visual neglect/inattention
11. visual field assessment
12. blind spot assessment
13. fundoscopy

Question 6

how is visual acuity assessed?

Answer 6

1. use a Snellen chart
2. if patient usually uses distance glasses, ensure they’re worn
3. ask patient to cover one eye and read the lowest line they’re able to
4. record the lowest line the patient was able to read (e.g. 6/6 (metric) is equivalent to 20/20 (imperial))
5. you can have the patient read through a pinhole to see if this improves vision
6. repeat with other eye

Question 7

how is visual acuity recorded?

Answer 7

1. chart distance in metres (numerator) over the number of the lowest line read (denominator)
2. if patient reads the 6/6 line but gets 2 letters incorrect, you would record it as 6/6 (-2)
3. if patient gets more than 2 letters wrong, the previous line should be recorded as their acuity
4. when recording the vision state whether this vision was unaided (UA), with glasses or with a pinhole (PH)

Question 8

what are further steps for patients with poor vision in visual acuity?

Answer 8

1. reduce the distance to 3 metres from chart (3/denominator)
2. reduce the distance to 1 metre from chart (1/denominator)
3. assess if they can count the number of fingers you’re holding up (CF)
4. assess if they can see gross hand movements (HM)
5. assess if they can detect light from a pen torch shone into each eye (PL or NPL; perception of light)

Question 9

what are causes of decreased visual acuity?

Answer 9

• refractive errors
• amblyopia
• ocular media opacities e.g. cataract or corneal scarring
• retinal diseases such as age-related macular degeneration
• optic nerve pathology e.g. optic neuritis
• lesions higher in the visual pathways

Question 10

how is the direct pupillary reflex tested?

Answer 10

1. dim lights and shine the light from the pen torch into their pupil and observe for pupillary restriction in the ipsilateral eye
2. a normal direct pupillary reflex involves constriction of the pupil that the light is being shone into

Question 11

how is the consensual pupillary reflex tested?

Answer 11

1. dim lights and shine the light from the pen torch into their same pupil, but this time observe for pupillary restriction in the contralateral eye
2. a normal consensual pupillary reflex involves the contralateral pupil constricting as a response to light entering the eye being tested

Question 12

how is the swinging light test performed?

Answer 12

move the pen torch rapidly between the two pupils to check for a relative afferent pupillary defect

Question 13

how is the accommodation reflex tested?

Answer 13

1. ask patient to focus on a distant object
2. place your finger 20-30cm in front of their eyes
3. ask patient to switch from looking at the distant object to the nearby finger/thumb
4. observe the pupils, you should see constriction and convergence bilaterally

Question 14

how can you use the Ishihara plates to test colour vision?

Answer 14

1. ask patient to cover one of their eyes
2. ask patient to read the numbers on the Ishihara plates; the first page does not test colour vision and assesses contrast sensitivity
3. if patient can read the test plate, move through all the plates, asking patient to identify the number on each
4. once complete, document the number of plates identified correctly, including the test plate
5. repeat on other eye

Question 15

what are some causes of colour vision deficiencies?

Answer 15

• optic neuritis
• vitamin A deficiency
• chronic solvent exposure