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HUMAN HEALTH AND DISEASE > Neurology II: Cranial Nerves & Their Disorders > Flashcards

Neurology II: Cranial Nerves & Their Disorders Flashcards

1
Q

What do the cranial nerves form a part of?

A

The peripheral nervous system (PNS)

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2
Q

What are the 12 cranial nerves?

A

I - (Olfactory)
II - (Optic)
III - (Oculomotor)
IV - (Trochlear)
V - (Trigeminal)
VI - (Abducens)
VII - (Facial)
VIII - (Auditory or Vestibulocochlear)
IX - (Glossopharyngeal)
X - (Vagus)
XI - (Spinal Accessory)
XII - (Hypoglossal)

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3
Q

Describe the structure of the olfactory nerve.

A

-Shortest cranial nerve
-Unmyelinated
-Sensory component only

Specialised epithelium at the top of the nasal cavity contains olfactory nerve fibres

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4
Q

What can damage to the olfactory nerve result in and how can damage be caused?

A

Damage to the olfactory nerve can cause altered sense of smell, or complete loss of sense of smell (anosmia).

Causes include head injuries, tumours and neurodegenerative disorders

(Temporary changes to smell can be caused by infection)

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5
Q

What is the function of the olfactory nerve?

A

Sense of smell

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6
Q

How would you test to see if the patient’s olfactory nerve is functioning well?

A

Ask about any recent changes to sense of smell

Then, with the patient’s eyes closed, ask them to occlude one nostril and identify the smell (e.g. coffee, vanilla)
Repeat on the other sid

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7
Q

The optic nerve only has a sensory component, true or false?

A

true

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8
Q

What is the function of the optic nerve?

A

Transmission of sensory information from the retina to the primary visual cortex of the brain

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9
Q

What are some potential causes of optic nerve defects?

A

Trauma
Tumour (e.g. pituitary adenoma)
Multiple sclerosis (optic neuritis-inflammation damages optic nerve)
Stroke

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10
Q

What do you have to test in order to examine the optic nerve?

A

Visual acuity

Visual fields

Pupillary reflexes

Fundoscopy

Fundoscopy is performed with an ophthalmoscope & it allows visualisation of the retina and optic disc (optic nerve head) but this is rarely carried out in dental setting

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11
Q

How can visual acuity be formally assessed?

A

Snellen chart (letters with diff sizes) with the patient sat 6 metres away.

Colour vision is also assessed using Ishihara plates (numbers in different colours)

Dental setting: Ask the patient to read from a printed page (glasses, contact lenses should be worn)

Test one eye at a time

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12
Q

How can visual fields be formally assessed?

A

Tested through confrontation: sit facing each other with a distance of ~an arm’s length

Have the patient looking directly at your eye or nose and test each quadrant in the patient’s visual field by having them count the number of fingers that you are showing

This relies on the examiner having normal visual fields & blind spots

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13
Q

What are some common visual field defects?

A

Monocular blindness (e.g. trauma)

Bitemporal hemianopia (classically seen in acromegaly) leads to impaired peripheral vision

Homonymous hemianopia (e.g. stroke)

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14
Q

How is the pupillary reflex tested?

A

Pupillary Reflex
Darkened room

  1. Direct reflex – Shine the pen torch into one eye. Look for pupillary constriction of
    ipsilateral eye (i.e. the eye you are shining the light into)
  2. Consensual reflex – shine the light into the same eye as previously, but this time, observe the contralateral eye for pupillary constriction

3.Now repeat for the other eye (direct and consensual reflex)

What is being tested:
Afferent (sensory) pathway - optic nerve

Efferent (motor) pathway - oculomotor nerve

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15
Q

If you had a left optic nerve lesion, what would happen when testing the pupillary reflex?

A

Shine a pen torch into the left eye:

Left direct reflex lost (the left pupil will not constrict)

Left consensual reflex maintained (left pupil will constrict when light shone in the right eye)

Right direct pupillary response is maintained

Right consensual reflex is lost (right pupil will not constrict when light is shone into left eye)

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16
Q

If you had a left oculomotor nerve lesion, what would happen when testing the pupillary reflex?

A

Shine a pen torch into the left eye:

Left direct reflex lost

Left consensual reflex lost

Right direct reflex maintained

Right consensual reflex maintained

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17
Q

Which cranial nerves are usually assessed together and why?

A

III (oculomotor), IV(trochlear), & VI (abducens)

All 3 have a motor function and supply the extra-ocular muscles

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18
Q

What does the oculomotor nerve supply?

A

Supplies medial, superior & inferior rectus, inferior oblique, levator palpebrae superioris

Also supplies parasympathetic fibres involved in pupillary constriction

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19
Q

What does the trochlear nerve supply?

A

Superior oblique

20
Q

What does the abducens nerve supply?

A

Lateral rectus

21
Q

What will palsies of cranial nerves III, IV, & VI result in?

A

Diplopia - double vision

22
Q

What are potential causes of palsy in the oculomotor nerve and how does it manifest?

A

Causes: diabetes, increased intra-cranial pressure

Manifestation: eye is fixed down and out, unless looking towards the affected side

Additional signs: ptosis (drooping), dilated pupil (mydriasis)

23
Q

What is a potential cause of palsy in the trochlear nerve and how does it manifest?

A

Cause: trauma

Manifestation: eye cannot move down and in (vertical diplopia when looking inferiorly)

24
Q

What are potential causes of palsy in the abducens nerve and how does it manifest?

A

Causes: stroke, multiple sclerosis

Manifestation: cannot look to the affected side

25
Q

How do you test for these palsies?

A

Usually performed alongside cranial nerve II, after visual fields

Ask the patient to follow a pen as you draw out the letter H

Ensure they keep the head still and only move the eyes

26
Q

Does the trigeminal nerve have both sensory and motor function?

A

yes

27
Q

What are some potential causes of trigeminal nerve palsy?

A

Upper motor neurone lesions (i.e. within the brain cortex) include tumours, multiple sclerosis

Lower motor neurone lesions (affecting the peripheral nerve fibres) include cavernous sinus lesions, iatrogenic damage to IAN/lingual nerve

28
Q

How do you test the sensory component of the trigeminal nerve?

A

Sensory component divided into ophthalmic (V1), maxillary (V2) and mandibular (V3) divisions

Tested through light touch and pin prick (use a Neurotip)

Corneal reflex (V1) not routinely tested

29
Q

How do you test the motor component of the trigeminal nerve?

A

Motor component supplies muscles of mastication

Inspect temporalis/masseter for wasting

Palpate temporalis/masseter muscle bulk with patient clenching

Ask the patient to open the jaw against resistance from your hand

(Jaw jerk reflex- not routinely performed)

30
Q

What functions does the facial nerve have?

A

Sensory for taste to the anterior 2/3rds via chorda tympani

Motor to the muscles of facial expression, nerve to stapedius

Secretomotor to lacrimal, submandibular & sublingual salivary glands

31
Q

What are potential causes of facial nerve palsy?

A

Upper motor neurone lesions: stroke

Lower motor neurone lesions: Bell’s palsy, parotid tumour

Remember that in lower motor neurone lesions, the entire half of the face is affected

In upper motor neurone lesions, the forehead is spared (as there is bilateral innervation from the cortex)

32
Q

How do you test the facial nerve?

A

Ask about changes to sense of taste

Ask about hearing (hyperacusis)

Facial movements (tested against resistance)- raise eyebrows, close eyelids, puff out cheeks, purse the lips, show your teeth

33
Q

What is the function of the vestibulocochlear nerve?

A

It has a sensory function

Is involved in hearing and balance

34
Q

What are some common causes of vestibulocochlear nerve defects?

A

Acoustic neuroma (tumour that develops on vestibular nerve)

Paget’s disease (bones grow larger+weaker)

35
Q

How do you test the vestibulocochlear nerve?

A

Ask about changes to hearing

Whisper into the ear (choose a bi-digit number or two syllable word) and ask the patient to repeat

Rinne and Weber test are performed using a tuning fork to assess for sensorineural vs conductive deafness

36
Q

What are the functions of the glossopharyngeal nerve?

A

Sensory and motor functions

-Principal role is sensory to tonsillar fossa and pharynx

-Taste to the posterior 1/3rd of the tongue

-Parasympathetic innervation to the parotid glands

37
Q

What are some potential causes of glossopharyngeal nerve palsy?

A

Trauma, tumour, diphtheria

(IX nerve problems usually occur alongside CN X problems)

38
Q

What will patients with a glossopharyngeal nerve palsy have?

A

Impaired gag reflex

(Testing gag reflex is not routinely performed)

39
Q

What is the function of the vagus nerve?

A

Motor function supplying the pharynx, larynx and soft palate.

40
Q

What are some causes of vagus nerve palsy?

A

Trauma, brainstem lesion

41
Q

How do you test the vagus nerve (and glossopharyngeal nerve)?

A

Ask the patient to say ‘ah’ to visualise the uvula and soft palate.

If a deficit is present, the uvula will deviate towards the unaffected side

Gag reflex (not performed routinely)

42
Q

What is the function of the accessory nerve (also known as spinal accessory nerve)?

A

Motor function to muscles of the neck

43
Q

What is the most common cause of accessory nerve palsy?

A

Stroke

44
Q

How do you test the accessory nerve?

A

Inspect for wasting of trapezius/sternocleidomastoid

Shrug shoulder against resistance (test one side at a time)

Turn the head against resistance

45
Q

What is the function of the hypoglossal nerve?

A

Motor function to the tongue

46
Q

What are some causes of hypoglossal nerve palsy?

A

Trauma, brainstem lesions

47
Q

How do you test the hypoglossal nerve?

A

Ask the patient to protrude their tongue

The tongue should look symmetrical and there should not be any deviation on protrusion

If a lesion is present, the tongue deviates to the side of the lesion

There may also be muscle wasting on the side of the lesion and fasiculation (involuntary twitching)

HUMAN HEALTH AND DISEASE (58 decks)

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