Clinical neuroscience

Question 1

Examination of CN I (olfactory)

Answer 1

Function is sensory (smell)

each nostril is tested separately, easily recognised substance is used such as pepermint oil

Question 2

Examination of CN II

Answer 2

Function is vision/sense of sight

1. Observe
   - level of eyelid - Ptosis (CN 3 lesion, myasthenia, Horners syndrome)
   - Lid retraction
   - position of eye
   - exophthalmos (graves, tumor)
   - Enopthalmos (horners syndrome)
2. acuity
   - use visual acuity cards (snellen chart) paitent may use glasses

• ask what is the smallest line you can read if less that 6/60
• counting fingers
• followed by hand waving
• then perception of light and dark

3. gross visual fields/visual inattention:
   - finger confrontation
4. visual fields:
   - test with a red pin: white objects more easily seen than red
   - central vision = colour: rods
   - Peripheral vision = black and white: rods
   - therefore earlier peripheral loss is easily detected with a pin
5. blind spot (red pin)
6. pupils
   -afferent - optic nerve
   9efferent - PNS component of CN 3
   - 20% difference in size - normal
   - >20% difference is significant Anisocoria
   test for the following
   -light reflex - direct
   - consensual
   - swinging light test
   - a normal pupil always constricts to light
   - abnormal pupil dilates to light indicating an afferent pupillary defect i.e. Marcus Gunn papillary sign, caused by optic neuritis or compression of the optic nerve
7. Fundoscopy
   - fundus of the eys is examined with the aid of an Opthalmoscope
   - red reflex
   - retina: locate vessel: follow the vessels to the disc, and then the periphery
   - You may need to dilate the pupil with tropic amide (this is not done in a paitent with glaucoma)

Question 3

Examination of the CN III, IV and VI

all tested together
CN 3 (oculomotor)
CN 4 (trochlear)
CN6 (Abducens)

This is because they subserve motor functions to the extrinsic muscles of the eyes (for eye movement)

Answer 3

1.Observe:
–position of head (head tilted away from the side of a CN 4 lesion).
–eyelid (ptosis suggest CN 3 lesion or a Horner’s) –eye position (one eye looking up or down suggests skew deviation).

2. Screen: Instruct patient to “look up, look down, look to the left, look to the right”
3. Pursuit movements: –Ask patient to follow the movement of a pin (‘H’ direction) with their eyes only (head should be steady).
4. Saccadic movements:–“finger to fist”: Ask patient to follow your finger and fist in alternating manner while you switch your right finger around the left fist.
5. Accommodation: “Look in to the distance … now at my finger”

Question 4

Examination of CN V: Trigeminal

Answer 4

CN V performs sensorimotor functions–Motor to temporalis and masseter –Sensory to face.
Perform the following tests:

1. Corneal reflex (CN5 to feel CN7 to blink)
2. Sensation•Test pin-prick/soft-touch in each of the three anatomical divisions -ophthalmic, maxillary and mandibular).

Perform the following tests:–Motor•“Clench your jaw” Palpate temporalis/masseter bulk. •Strength of jaw opening. “Hold your jaw open” Look for deviation to the side of weakness.•Jaw-jerk reflex.

Question 5

Examination of CN VII facial

Functions:–Sensory, motor, autonomic functions–Motor functions to the facial musculature and the Tensor tympani and stapedius–Taste: via chordae tympani to the anterior 2/3 of the tongue.

Answer 5

Perform the following tests:

1. “Smile”
2. “Show me your teeth”
3. “Screw up your eyes”
4. “Look up to the ceiling”
5. “Whistle”
6. “Blow out your cheeks”
7. Tap your fingers at each ear

Question 6

Examination of CN VIII: Vestibulocochlear

Functions auditory/vestibular functions

Answer 6

Perform the following tests:

1. Hearing: Whispering numbers (at arm’s length whilst occluding the opposite ear).
2. Weber’s: 512 Hz tuning fork held on the centre of the head. “Where is it louder?”
3. Rinne’s: 512 Hz tuning fork held on the mastoid then in front of the ear to test bone and air conduction respectively. Normally air conduction better than bone conduction.

NB: Vestibular component is usually tested with the gait, not a part of Cranial Nerves Examination

Question 7

Examination of CN IX and X

tested tigether

CN IX: Glossopharyngeal
function
- sensory: posterior 1/3 of tongue, soft palate, pharynx. c
-motor: stylopharyngeus

CN X: Vagus

function:
- sensory: external ear
- motor: palate, pharynx, larynx (via recurrent laryngeal)

Answer 7

Perform the following tests:
1.Ask patient to ‘Cough’ (check for voice quality)
2.”Say Ahh” -Observe soft-palate movement.
•If normal uvula stays in midline
•If weak uvula deviates (pulled over) to the normal side.
3. Gag reflex test (bilaterally)
•Sensory -CN IX
•Motor –CN X

Question 8

Examination of CN XI: spinal accessory

function
-motor: supplies - ipsilateral trapezium and ipsilateral sternomastoid muscles

Answer 8

Perform the following tests:

1. Shoulder elevation (trapezius)
2. Lateral head rotation (opposite sternomastoid)
3. Pushing forehead forward against resistance (check bilateral sternomastoid for weakness, myopathy)

Question 9

Examination of CN XII: Hypoglossal

function 
-motor to tongue

Answer 9

Perform the following tests:

1. Observe the tongue (mouth open position)
2. Ask patient to stick out the tongue: Tongue points toward (pushed to) the weak side.
3. Test tongue strength