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BDS2; CHHD > Examination of Cranial Nerves > Flashcards

Examination of Cranial Nerves Flashcards

1. To list all the cranial nerves 2. To demonstrate a good knowledge of all cranial nerve anatomy and functions 3. To effectively identify and recognise the signs, symptoms and specific facial manifestations of common cranial nerve lesions

1
Q

List the cranial nerves in order

A 
I = Olfactory 
II = Optic 
III = Oculomotor 
IV = Trochlear
V = Trigeminal 
VI = Abducens
VII = Facial 
VIII = Vestibulocochlear
IX = Glossopharyngeal 
X = Vagus 
XI = Accessory 
XII = Hypoglossal
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2
Q

What type of nerve is CN I

A

Olfactory nerve is a sensory nerve

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3
Q

Which foramen does CN I emerge from

A

Olfactory nerve emerges from the cribriform palate of ethmoid bone

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4
Q

How is CN I examined

A

Use cloves as a stimulant as they preserve scent
Test one nostril at a time by occluding the opposite side
Patient shouldn’t be able to see stimulus
Ask the patient to describe the smell

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5
Q

What is the normal response to CN I examinations

A

Being able to perceive the smell with either nostril

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6
Q

What is the abnormal response to CN I examination and what could be the cause of this

A
  1. Unilateral loss of smell = SIGNIFICANT
    - Structural brain lesion affecting the olfactory bulb/tract
    - Local causes e.g. deviated septum, blocked nasal passage
  2. Bilateral loss
    - Rhinitis (runny nose)
    - Damage to the cribriform plate
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7
Q

What type of nerve is CN II

A

Optic nerve is a sensory nerve

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8
Q

Which foramen does CN II emerge from

A

Optic nerve emerges from optic foramen

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9
Q

Name the four tests for CN II

A
  1. Visual acuity (image sharpness)
  2. Visual fields (wideness of view)
  3. Pupil reflex (reaction to light)
  4. Accomodation (lens’ adaptation to distance)
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10
Q

How is visual acuity examined

A

CN II Optic nerve examination measured using the Snellen’s test and the acuity is recorded using d/D

  • Patient is placed 6m from the test types (d=6)
  • Each eye is tested separately
  • Normal eye acuity = 20/20
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11
Q

What does 20/20 vision mean

A

The patient can read at 20’ with the same accuracy as a person with normal vision

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12
Q

What does 20/200 vision mean

A

The patient can read at 20’ what a normal person can read from 200’ making the patient legally blind due to very poor acuity

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13
Q

Why would a pituitary tumour affect the visual field

A

The pituitary sits close to optic chiasm, so if there is a tumour here it will compress and damage the nasal part of the visual field because fibres decussate at the optic chiasm

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14
Q

How are visual fields examined

A

CN II Optic nerve examination assessed by confrontation (examiner compares the patient’s visual field to their own - assuming theirs is normal)

  • Test each eye separately with the test object (finger/pin)
  • Place yourself 1m away from the patient and tell them to look directly ay you
  • The test object is presented equidistant from the patient’s and examiner’s eye
  • Ask the patient to say now when they first see the target
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15
Q

What is being observed when testing the pupillary light reflex

A

The size, shape and symmetry of the pupils (this regulates the amount of light)

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16
Q

What are the different roles of the afferent and efferent nerves in the pupillary light reflex

A 
Afferent = Optic nerve detects light 
Efferent = Oculomotor nerve causing constriction/dilation
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17
Q

How is the pupillary light reflex examined

A
  • Dim the lights and ask the patient to look into the distance
  • Shine a bright light obliquely (approaching laterally) into the pupil
  • Observe for the direct response (same eye) and consensual response (opposite eye)

Observe for ptosis
Observe the pupils for size (measure diameter, irregularities and asymmetry)

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18
Q

What does ptosis suggest

A

This is drooping of the eyelid which could indicate damage to the oculomotor nerve

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19
Q

What implicates an afferent defect in the pupillary light reflex

A

If the direct and consensual reflexes are absent when light is shown in the bad eye

If the direct and consensual reflexes are intact when light is shone in the good eye

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20
Q

What implicates an efferent defect in the pupillary light reflex

A

If the direct reflex is absent but the consensual reflex is present when shone in the bad eye

If the direct reflex is present but the consensual response absent when shone in good eye

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21
Q

What is relative afferent pupillary defect (RAPD)

A

This is an asymmetric pupillary reaction to light when it is shined back and forth (swinging light) between the eyes

When the light is shone onto the stronger optic nerve side, there will be greater constriction, and when swung onto the weaker side there will be slight dilation in comparison

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22
Q

What is RAPD a sign of

A

Relative afferent pupillary defect suggests asymmetric optic nerve disease or damage

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23
Q

How is the accommodation reflex tested

A

CN II Optic nerve examination which involves asking the patient to look into the distance and then at the tip of their nose

Accommodation is signified by the following

  • Diverging when looking far
  • Converging when looking near
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24
Q

What are the extra ocular muscle cranial nerves, what type of nerves are these, where do they emerge from and what do they do

A

CN III Oculomotor
CN IV Trochlear
CN VI Abducens

These are motor nerves emerging from the supra-orbital fissures responsible for moving the eye

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25
Q

Which muscles do CN III, CN IV and CN VI innervate and what is their action when stimulated

A

LR6 SO4

Lateral rectus (pulls away from nose) = Abducens
Medial rectus (pulls towards nose) = Oculomotor 
Superior rectus (pulls upwards) = Oculomotor 
Inferior rectus (pulls downwards) = Oculomotor 
Superior oblique (inwards + downward rotation) = Trochlear 
Inferior oblique (upwards + outward rotation) = Oculomotor
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26
Q

How are extra-ocular movements tested

A

CN III Oculomotor, CN IV Trochlear, CN VI Abducens examination

Place yourself 1m infront of patient
Ask patient to look to each side, up and down following a ‘H’ pattern by making them follow your finger/pen with their eyes without moving their head
Pause at the ends of each direction of gaze to observe for nystagmus

27
Q

What are the possible abnormal findings when conducting an examination of extra-ocular movements and what do each of them signify

A
  1. Ptosis = weakness in elevator muscle causing a droopy eyelid
    - Myasthenia gravis and CN III Palsy (Superior rectus)
  2. Strabismus = ‘lazy eye’ where the eyes are not properly aligned when looking at an object (squint)
    - This can cause double vision
  3. Nystagmus = abnormal repetitive jerky movements of the eye which are uncontrolled meaning that the patient cannot focus
    - Due to abnormal stimulation of the semi-circular canal which balances images
    - This is why the eyes typically flip backwards towards the semi-circular canal
28
Q

What does CN III Palsy cause

A

Palsy of the oculomotor nerve causes

  1. Ptosis (elevator palpebrae superiors)
  2. Large pupil (affects pupillary constrictor - efferent)
  3. Eye is down + out (unopposed action of LR6 + SO4)
29
Q

What does CN IV Palsy cause

A

Palsy of the trochlear nerve causes

Diplopia on looking down (vertical-diplopia) - due to weakened depression from SO4, the bad eye will sit slightly higher than the good one

30
Q

What does CN VI Palsy cause

A

Horizontal diplopia (lateral rectus affected)

31
Q

Name a syndrome which has clinical findings presenting similar to CNIII Palsy

A

Horner’s Syndrome (rare)

This can occur as a result of surgery/trauma to the neck/lung, or due to breast cancer infiltrating the superior cervical sympathetic ganglion

32
Q

What are the characteristics of Horner’s Syndrome

A

Ptosis - levator palpebrae affected causing drooping
Anhydrosis - absence of sweat due to SNS damage
Miosis - excessive pupil constriction
Enopthalmous - retruded eyeball

33
Q

What are the branches of CN V and where does each branch emerge from

A

Trigeminal Nerve has the following branches

  • Ophthalmic emerging from supra-orbital fissure
  • Maxillary emerging from foramen ovale
  • Mandibular emerging through foramen rotundum (sensation to post. 1/3 tongue)
34
Q

What are the functions of CN V

A

Trigeminal nerve has the following functions

  • V1 - V3 = Sensory
  • V3 = Motor (muscles of mastication)
35
Q

What are the muscles of mastication and what are they innervated by

A
  1. Temporalis
  2. Masseter
  3. Lateral pterygoid
  4. Medial pterygoid
36
Q

How is the sensory function of CN V examined

A

CN V Trigeminal nerve sensation is assessed by touching a cotton wisp to the forehead, cheek and chin on both sides of the face

  • Other tests include: Corneal reflex, pain and temperature
  • The angle of jaw is avoided as this is innervated by upper cervical roots
37
Q

How is the motor function of CN V examined

A

CN V Trigeminal nerve motor function is assessed by

  1. Palpating temporals and masseter muscles on either side when the patient clenches their teeth
  2. Asking patient to open their mouth and repeat this against resistance. Observe for any deviations of the jaw to one side
  3. With their mouth open, ask the patient to protrude their jaw to either side against resistance
  4. The jaw-jerk reflex is elicited by placing an index finger over the middle of the patient’s chin with the mouth slightly open and the jaw relaxed, the index finger is then tapped with a reflex hammer in a downward stroke
38
Q

What are the extra cranial branches of CN VII

A

CN VII Facial nerve has intracranial and extra cranial branches, the latter is divided into

  1. Temporal branch
  2. Zygomatic branch
  3. Buccal branch
  4. Marginal mandibular branch
  5. Cervical branch
39
Q

What are the functions of CN VII

A

CN VII Facial nerve is responsible for

  1. Sensory - taste to anterior 2/3 of tongue
  2. Motor - muscles of facial expression
  3. Autonomic function - PsNS to glands
    - lacrimal
    - submental
    - submandibular
40
Q

How is the sensory function of CN VII examined

A

CN VII Facial nerve sensation is taste which is assessed by

  • Protruding tongue which is lightly held
  • Placing a small solution to one side of the anterior 2/3 of tongue using a saturated cotton applicator
  • With the tongue still protruded, ask the patient to point to a sign displaying one of the possible four tastes (sweet, sour, salty, bitter)
  • Give the patient a sip of water and repeat the test using an alternate stimulus
41
Q

How is the motor sensation of CN VII examined

A

CN VII Facial nerve motor functioning involves the muscles of facial expression

Observe for asymmetry which indicated widening of the palpebral fissure of flattening of the Nasolabial fold

  • Ask the patient to wrinkle their forehead by raising their eyebrows and closing their eyes tightly
  • Observe for asymmetry of ability to bury eyelashes and palpate for differences of ability to resist eye opening
  • Ask the patient to show their teeth, puff out their cheeks and appose their lips

Although the patient may have an asymmetric face, there should be no facial weakness

42
Q

Outline the significance of abnormal responses to examination of the motor sensation by CN VII

A

CN VII Facial nerve motor functioning abnormalities can suggest

  1. Lower motor neurone lesion - causing weakness of the entire side of face with equal involvement of upper and lower facial muscles
  2. Upper motor neurone lesion of the contralateral supra nuclear pathway - resulting in weakness of the lower muscles of facial expression
    - The upper muscles of facial expression (frontal + orbicularis oculi) are less affected because the facial nucleus that innervates them receives partial input from the ipsilateral hemisphere

Upper spares upper, Lower takes it all

43
Q

What are the causes of CN VII palsy (LMN lesions)

A
  • Infections e.g. Varicella Zoster (Shingles), Ottitis media, Ramsey Hunt Syndrome
  • Bell’s palsy (post viral infection)
  • Injection into parotid gland
  • Malignant tumour of the parotid gland
  • Lyme disease
44
Q

What are the causes of CN VII palsy (UMN lesions)

A
  • CVAs like stroke
  • Brain tumours
  • Traumatic brain injuries
  • Cerebral palsy
45
Q

What can cause bilateral CN VII palsy

A
  1. Guillain-Barre’s syndrome = autoimmune condition of peripheral nervous system
  2. Moebius syndrome = congenital bilateral facial nerve weakness/ paralysis resulting from underdevelopment of the nerve (CN VI + other CNs can also be affected)
46
Q

What does Bell’s palsy present with

A
  • Patient cannot wrinkle brow
  • Ptosis (droopy eyelid)
  • Inability to puff cheeks
  • Drooping mouth - unable to smile/pucker
47
Q

What does Ramsay-Hunt syndrome present with

A
  • Vesicular rash on external ear
  • Lower motor neurone paralysis of facial nerve
  • Loss of taste sensation over anterior 2/3 of tongue
48
Q

What is the role of CN VIII

A

CN VIII Vestibulo-cochlear nerve has two parts

  1. Vestibular nerve
    - Transmits sensory information by vestibular hair cells in the semilunar canal
    - Gives sensation of the body position and gaze stability for balancing
  2. Cochlear nerve
    - Auditory sensory information from cochlear for hearing
49
Q

How is CN VIII examined and what is the normal response to this testing

A

CN VIII Vestibulo-cochlear nerve is examined using the Rinne + Weber tests for hearing

Normal response:
Rinne - air conduction > bone conduction (front + back ear)
Weber - patients will hear equally from both ears or respond with they are unsure (which side is sound from)

  • The conductive part of the ear receives sound (conductive defects occur here)
  • The neurophase is where the cochlear nerve relates information to the brain (sensory neural defects occur here)
50
Q

What do abnormal responses to CN VIII examination suggest

A

CN VIII Vestibulo-chochlear nerve abnormal responses include

RHINE
- Bone conduction > Air condition = Conductive hearing loss or sensorineural deafness

WEBER

  • Abnormal if patient lateralises to one ear = Conductive hearing loss
  • Sound is heard best by the non-involved ear = Sensoineural deafness
51
Q

What is the function of CN IX, where does it emerge and how can it be tested

A

CN IX Glossopharyngeal nerve has motor, autonomic, general sensory and special sensory functions, and it emerges from the jugular foramen

The following can be used to test CN IX function
Sensory = Gag reflex, taste sensation
Motor = Swallowing motion

52
Q

What is the function of CN X

A

CN X Vagus nerve has the following functions

  1. Motor
    - voluntary muscles of the pharynx and most of larynx
  2. Autonomic
    - parasympathetic component of smooth muscle of viscera of thorax and abdomen
  3. Sensory
    - visceral sensory information from thorax and abdomen
    - chemoreceptors of aortic bodies
53
Q

How can CN IX and CN X be examined and what is the abnormal response

A

CN IX Glossopharyngeal nerve and CN X Vagus nerves are examined together by

  • Checking palatal elevation by having the patient sustain “aaahhh”; observe for palatal movement rather than uvula, elevation should be symmetrical
  • Assess the gag reflex by gently stroking the soft palate on each side

Abnormal response = unilateral palatal weakness where the palate fails to elevate on the weak side and the gag reflex is absent on that side

54
Q

What is the function of CN XI

A

CN XI Accessory nerve supplies voluntary motor innervation to the sternocleidomastoid and trapezius muscles

55
Q

How is CN XI examined

A

CN XI Accessory nerve is assed by

  • observing for atrophy/ asymmetry of muscles
  • observing for quickness of shoulder shrug
  • shrugging shoulders against resistance
  • asking patient to flex their head forward against resistance placing opposite hand against back of head for support
56
Q

What is the function of CN XII

A

CN XII Hypoglossal nerve has motor innervation to all tongue muscles except the palatoglossus muscle (CNX)

57
Q

Which foramen does CN XII emerge from

A

CN XII Hypoglossal nerve emerges from foramen magnum

58
Q

How is CN XII examined

A

CN XII Hypoglosal nerve is examined by

  • protruding tongue
  • pushing tongue against cheek and with resistance from outside using your hand

LMN lesion can cause tongue to deviate to the affected side

59
Q

Suggest the cranial nerve which is most likely to be affected in the following scenario:

Patient presented with headache and vomiting. On examination, the jaw moves to the left when opened. There is one sided reduction in facial sensation with loss of corneal reflex.

A

CN V Trigeminal nerve

60
Q

Suggest the cranial nerve which is most likely to be affected in the following scenario:

A 65-year-old patient was walking the garden when he noticed a drooping weakness of the left side of the face and he is unable to raise the left eyebrow

A

CN VII Facial nerve

61
Q

Suggest the cranial nerve which is most likely to be affected in the following scenario:

A patient complains of impairment of taste and smell. On formal testing, sense of smell is lost, and taste is mildly reduced

A

CN I Olfactory nerve

62
Q

Suggest the cranial nerve which is most likely to be affected in the following scenario:

A 74-year-old presents with headache and dizziness and instability of gait. The patient’s tongue deviates to the left when it is protruded. The patient cannot easily move their tongue from left to right

A

CN XII Hypoglossal nerve

63
Q

Suggest the cranial nerve which is most likely to be affected in the following scenario:

A 32-year old male with IDDM presents with diplopia on looking to the right and is unable to abduct the right eye

A

CN VI Abducens nerve

BDS2; CHHD (32 decks)

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