Examination of Cranial Nerves Flashcards

1
Q

What are the two questions we must ask when examining a patient for cranial nerves?

A

Is it a single nerve or multiple nerves involved?

Single = it it a lesion in the CNS or PNS?

Multiple = CNS lesion or from systemic disease?

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What do we test for using the cranial nerves?

A
  1. Smell
  2. Sight
  3. Face
  4. Hearing and balance
  5. The mouth
  6. Neck and shoulders
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What could be some causes of bilateral and unilateral los of smell?

A

Bilateral - trauma, Parkinsons disease, COVID 19

Unilateral - frontal lobe lesion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How do we examine the eye?

A
  • Inspection
  • Pupillary reactions
  • Visual activity
  • Visual fields
  • Eye movements
  • Fundoscopy

Inspection = look at the appearance of pupils and the iris and the eye lids. Example of a finding is a cataracts.

Pupillary reactions = moving torch from side to side and checking for the direct pupil opening or closing and the consensual reaction of the other eye. Cover each eye when examining the other.
Ask patient to focus on an object and hope to see pupils constricting.
Afferent pathway through optic nerve and the efferent though the oculomotor nerve.
Consensual light reaction in other eye is due to the optic nerve connecting in the Edinger-Westphal nucleus in the brain, whose axons run to both the right and left oculomotor nerve so both eyes will constrict

Visual acuity - use Snellen charts to ask patient to read from (letter). Can assess colour vision through the Ishihara phases (to identify numbers in the middle).

Visual fields -
Different lesions you may find here. Number 2 is a very common one causing bitemporal hemianopia. This is where you have a lesion in the optic chiasma.

Fundoscopy - ask patient to focus on object in the distance and you put the optomoscope to your eye and assess patients risk eye with your left eye and vice versa.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How do we examine cranial nerves 3, 4 and 6?

A

Ask patient to focus on your finger and then move your finger into different places. Make sure they dont move their head.

Eye movement pathology.
All extraocular muscles are innervated by cranial nerve 3 - oculomotor.
Oblique superior muscle - innervated by the trochlear nerve
Abducens - lateral rectus muscle innervation

Oculomotor Nerve (CN III): controls most of the eye’s movements, including constriction of the pupil and maintaining an open eyelid by innervating the levator palpebrae superioris muscle.

Can work out what nerve is causing the problem due to what issues the patient has with their eyes. i.e. if patient can’t move eye to side, audience nerve innervating the lateral rectus muscle has a lesion.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are some rules of double vision?

A
  • Maximal in direction of gaze of affected muscle

- False image (outer image, arises in the affected eye)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What are some common causes of a lesion in cranial nerves 3,4 and 6?

A

Diabetes
Trauma
Tumors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do we examine the trigeminal nerves?

A

Touch patients face lightly in different places. Check for strength of chewing muscles too.

Also need to check the cornea reflex to check the two nerves. Need to be unconscious patient.

Inferior Alveolar Nerve injury, (a branch of the mandibular division of the trigeminal). Common with implants and root treatments -Third molar (or wisdom teeth surgery) related inferior alveolar nerve injury is reported to occur in up to 3.6 % of cases permanently and 8% of cases temporarily.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

How do we check the facial nerve?

A

Ask patients to scrunch eyes, wrinkle forehead, blow out cheeks and to smile.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

How is the cranial nerve 8 examined?

A

Use a turning fork of different hz. Induce vibration in the tuning fork and then put it close to the ear of the patient on the mastoid process.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How do we examine the mouth and tongue?

A
  • Ask about taste
  • Listen to the voice
  • Inspection
  • Uvula
  • Gag reflex
  • Tongue

Assessing these nerves is by inspecting the uvula and its position regarding the midline. Lesion in either of these nerves will cause a diversion of this from the midline.

Hyposglossal nerve - motor innervation to the tongue. Need to inspect tongue and check position.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What do we see with a hypoglossal nerve palsy?

A

Tongue moves to the left
Tongue has a lesion on the left of it
Reduced movements of tongue

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

How do we check for cranial nerve 11?

A

Cranial nerve 11 = involved in movement of the neck.
Innervates the sternocleidomastoid and the trapezius muscle.

Ask patient to shrug their shoulders and turn head left to right.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly