Cranial Nerves

Question 1

What bloods should be sent for a confusion screen

Answer 1

“FULL CUG BAT”

F: FBC (e.g. infection, anaemia, malignancy)
U: U&Es (e.g. hyponatraemia, hypernatraemia)
L: LFTs (e.g. liver failure with secondary encephalopathy)
L: caLcium (eg hypercalcaemia)
C: Coagulation/INR (e.g. intracranial bleeding)
U: Urinalysis
G: Glucose (e.g. hypoglycaemia/hyperglycaemia)

B: Blood cultures (sepsis)
A: folAte/hAematinics+ B12 (e.g. B12/folate deficiency)
T: TFTs (e.g. hypothyroidism)

Question 2

What is the order of the cranial nerve exam

Answer 2

Gather equipment
WIPERQQ
Inspection
CN 1, 2, 346, 5, 7, 8, 9&10, 11, 12
Further assessments

Question 3

What tools do you need for the cranial nerve exam (8)

Answer 3

Pen torch
Snellen chart
Ishihara plates
Ophthalmoscope and mydriatic eye drops (if necessary)
Cotton wool
Neuro-tip
Tuning fork (512hz)
Glass of water

Question 4

What should you ask the patient before starting the cranial nerve exam

Answer 4

Ask for name and DOB
Ask for consent
Ask for pain
Ask the patient to sit on a chair, approximately one arm’s length away.

Question 5

What clinical signs should you look for at the start of the CN exam (6)

Give the possible underlying pathology for each

Answer 5

Speech abnormalities: may indicate glossopharyngeal or vagus nerve pathology.

Facial asymmetry: suggestive of facial nerve palsy.

Eyelid abnormalities: ptosis may indicate oculomotor nerve pathology.

Pupillary abnormalities: mydriasis occurs in oculomotor nerve palsy.

Strabismus: may indicate oculomotor, trochlear or abducens nerve palsy.

Limbs: pay attention to the patient’s arms and legs as they enter the room and take a seat noting any abnormalities (e.g. spasticity, weakness, wasting, tremor, fasciculation) which may suggest the presence of a neurological syndrome).

Question 6

How do you assess CN1

Answer 6

Ask the patient if they have noticed any recent changes to their sense of smell.

Olfaction can be tested more formally using different odours (e.g. lemon, peppermint), or most formally using the University of Pennsylvania smell identification test. However, this is unlikely to be required in an OSCE.

Question 7

Give 5 causes of anosmia

Answer 7

Mucous blockage of the nose: preventing odours from reaching the olfactory nerve receptors.

Head trauma: can result in shearing of the olfactory nerve fibres leading to anosmia.

Genetics: some individuals have congenital anosmia.

Parkinson’s disease: anosmia is an early feature of Parkinson’s disease.

COVID-19: transient anosmia is a common feature of COVID-19.

Question 8

How should you assess the second cranial nerve?

Answer 8

remember AFRO
Acuity
Fields (including neglect)
Reflexes (including assessing pupil sizes)
Ophthalmoscopy

Question 9

How do you test visual acuity for the CN exam

Answer 9

Do a gross assessment when they cover each eye - ensure they are wearing their glasses if they use glasses

Offer an official assessment using a Snellen chart

Ask about colour vision

Offer official assessment with Ishihara plates

Question 10

How would you assess visual acuity using a Snellen chart

Answer 10

If the patient normally uses distance glasses, ensure these are worn for the assessment.

1. Stand the patient at 6 metres from the Snellen chart.
2. Ask the patient to cover one eye and read the lowest line they are able to.
3. Record the lowest line the patient was able to read (e.g. 6/6 (metric) which is equivalent to 20/20 (imperial)).
4. You can have the patient read through a pinhole to see if this improves vision (if vision is improved with a pinhole, it suggests there is a refractive component to the patient’s poor vision).
5. Repeat the above steps with the other eye.

Question 11

How do you record the visual acuity of someone after assessing using a Snellen chart

Answer 11

Visual acuity is recorded as chart distance (numerator) over the number of the lowest line read (denominator).

If the patient reads the 6/6 line but gets 2 letters incorrect, you would record as 6/6 (-2).

If the patient gets more than 2 letters wrong, then the previous line should be recorded as their acuity.

When recording the vision it should state whether this vision was unaided (UA), with glasses or with pinhole (PH).

Question 12

What do you do when a patient cannot read the top line of a Snellen chart at 6 (even with pinhole)

Answer 12

1. Reduce the distance to 3 metres from the Snellen chart (the acuity would then be recorded as 3/denominator).
2. Reduce the distance to 1 metre from the Snellen chart (1/denominator).
3. Assess if they can count the number of fingers you’re holding up (recorded as “Counting Fingers” or “CF”).
4. Assess if they can see gross hand movements (recorded as “Hand Movements” or “HM”).
5. Assess if they can detect light from a pen torch shone into each eye (“Perception of Light”/”PL” or “No Perception of Light”/”NPL”).

Question 13

Give 6 causes of decreased visual acuity

Answer 13

Refractive errors
Amblyopia
Ocular media opacities such as cataract or corneal scarring
Retinal diseases such as age-related macular degeneration
Optic nerve (CN II) pathology such as optic neuritis
Lesions higher in the visual pathways

Question 14

How does optic nerve pathology affect visual acuity

Answer 14

Optic nerve (CN II) pathology usually causes a decrease in acuity in the affected eye. In comparison, papilloedema (optic disc swelling from raised intracranial pressure), does not usually affect visual acuity until it is at a late stage.

Question 15

What do you assess after visual acuity when examining CNII

Answer 15

Reflexes:

Direct and consensual pupillary reflexes
Swinging light test
Accommodation reflex

Question 16

What are the afferent and efferent limbs of the pupillary reflexes

Answer 16

The afferent limb functions as follows:
- Sensory input (e.g. light being shone into the eye) is transmitted from the retina, along the optic nerve to the ipsilateral pretectal nucleus in the midbrain.

The two efferent limbs function as follows:
- Motor output is transmitted from the pretectal nucleus to the Edinger-Westphal nuclei on both sides of the brain (ipsilateral and contralateral).
- Each Edinger-Westphal nucleus gives rise to efferent nerve fibres which travel in the oculomotor nerve to innervate the ciliary sphincter and enable pupillary constriction.

Question 17

Which CNII tests assess the afferent and efferent limbs of the pupillary reflexes

Answer 17

• The direct pupillary reflex assesses the ipsilateral afferent limb and the ipsilateral efferent limb of the pathway.
• The consensual pupillary reflex assesses the contralateral efferent limb of the pathway.
• The swinging light test is used to detect relative afferent limb defects.

Question 18

What is the Marcus-Gunn pupil

Answer 18

Relative afferent pupillary defect (Marcus-Gunn pupil): normally light shone into either eye should constrict both pupils equally (due to the dual efferent pathways described above).

When the afferent limb in one of the optic nerves is damaged, partially or completely, both pupils will constrict less when light is shone into the affected eye compared to the healthy eye. The pupils, therefore, appear to relatively dilate when swinging the torch from the healthy to the affected eye. This is termed a relative…. afferent… pupillary defect.

Question 19

What causes Marcus-Gunn pupil

Answer 19

This can be due to significant retinal damage in the affected eye secondary to central retinal artery or vein occlusion and large retinal detachment; or due to significant optic neuropathy such as optic neuritis, unilateral advanced glaucoma and compression secondary to tumour or abscess.

Question 20

What is a unilateral pupillary efferent defect

Answer 20

commonly caused by extrinsic compression of the oculomotor nerve, resulting in the loss of the efferent limb of the ipsilateral pupillary reflexes.

As a result, the ipsilateral pupil is dilated and non-responsive to light entering either eye (due to loss of ciliary sphincter function). The consensual light reflex in the unaffected eye would still be present as the afferent pathway (i.e. optic nerve) of the affected eye and the efferent pathway (i.e. oculomotor nerve) of the unaffected eye remain intact.

Question 21

How do you assess colour vision with Ishihara plates

Answer 21

If the patient normally wears glasses for reading, ensure these are worn for the assessment.

1. Ask the patient to cover one of their eyes.
2. Then ask the patient to read the numbers on the Ishihara plates. The first page is usually the ‘test plate’ which does not test colour vision and instead assesses contrast sensitivity. If the patient is unable to read the test plate, you should document this.
3. If the patient is able to read the test plate, you should move through all of the Ishihara plates, asking the patient to identify the number on each. Once the test is complete, you should document the number of plates the patient identified correctly, including the test plate (e.g. 13/13).
4. Repeat the assessment on the other eye.

Question 22

What can cause colour blindness

Answer 22

Colour vision deficiencies can be congenital or acquired. Some causes of acquired colour vision deficiency include:

Optic neuritis: results in a reduction of colour vision (typically red).
Vitamin A deficiency
Chronic solvent exposure

Question 23

What do you assess in CNII after reflexes in the CN exam

Answer 23

Fields (or you can do before as in AFRO)

Question 24

What do you assess in the fields part of CNII assessment

Answer 24

Visual neglect/inattention
Visual fields
Blind spot

Question 25

Why is neglect often not tested in a CN exam

Answer 25

visual neglect is not caused by optic nerve pathology and therefore this test is often not included in a cranial nerve exam.

Question 26

How do you assess visual neglect

Answer 26

1. Position yourself sitting opposite the patient approximately 1 metre away.
2. Ask the patient to remain focused on a fixed point on your face (e.g. nose) and to state if they see your left, right or both hands moving.
3. Hold your hands out laterally with each occupying one side of the patient’s visual field (i.e. left and right).
4. Take turns wiggling a finger on each hand to see if the patient is able to correctly identify which hand has moved.
5. Finally wiggle both fingers simultaneously to see if the patient is able to correctly identify this (often patients with visual neglect will only report the hand moving in the unaffected visual field – i.e. ipsilateral to the primary brain lesion).

Question 27

How do you assess visual fields

Answer 27

1. Sit directly opposite the patient, at a distance of around 1 metre.
2. Ask the patient to cover one eye with their hand.
3. If the patient covers their right eye, you should cover your left eye (mirroring the patient).
4. Ask the patient to focus on part of your face (e.g. nose) and not move their head or eyes during the assessment. You should do the same and focus your gaze on the patient’s face.
5. As a screen for central visual field loss or distortion, ask the patient if any part of your face is missing or distorted. A formal assessment can be completed with an Amsler chart.
6. Position the hatpin (or another visual target such as your finger) at an equal distance between you and the patient (this is essential for the assessment to work).
7. Assess the patient’s peripheral visual field by comparing to your own and using the target. Start from the periphery and slowly move the target towards the centre, asking the patient to report when they first see it. If you are able to see the target but the patient cannot, this would suggest the patient has a reduced visual field.
8. Repeat this process for each visual field quadrant, then repeat the entire process for the other eye.
9. Document your findings.

Question 28

Name 4 types of visual field defects

Answer 28

Bitemporal hemianopia: loss of the temporal visual field in both eyes resulting in central tunnel vision. Bitemporal hemianopia typically occurs as a result of optic chiasm compression by a tumour (e.g. pituitary adenoma, craniopharyngioma).

Homonymous field defects: affect the same side of the visual field in each eye and are commonly attributed to stroke, tumour, abscess (i.e. pathology affecting visual pathways posterior to the optic chiasm). These are deemed hemianopias if half the vision is affected and quadrantanopias if a quarter of the vision is affected.

Scotoma: an area of absent or reduced vision surrounded by areas of normal vision. There is a wide range of possible aetiologies including demyelinating disease (e.g. multiple sclerosis) and diabetic maculopathy.

Monocular vision loss: total loss of vision in one eye secondary to optic nerve pathology (e.g. anterior ischaemic optic neuropathy) or ocular diseases (e.g. central retinal artery occlusion, total retinal detachment).

Question 29

How do you assess the blind spot in the CN exam

Answer 29

. Sit directly opposite the patient, at a distance of around 1 metre.

2. Ask the patient to cover one eye with their hand.
3. If the patient covers their right eye, you should cover your left eye (mirroring the patient).
4. Ask the patient to focus on part of your face (e.g. nose) and not move their head or eyes during the assessment. You should do the same and focus your gaze on the patient’s face.
5. Using a red hatpin (or alternatively, a cotton bud stained with fluorescein/pen with a red base) start by identifying and assessing the patient’s blind spot in comparison to the size of your own. The red hatpin needs to be positioned at an equal distance between you and the patient for this to work.
6. Ask the patient to say when the red part of the hatpin disappears, whilst continuing to focus on the same point on your face.
7. With the red hatpin positioned equidistant between you and the patient, slowly move it laterally until the patient reports the disappearance of the top of the hatpin. The blind spot is normally found just temporal to central vision at eye level. The disappearance of the hatpin should occur at a similar point for you and the patient.
8. After the hatpin has disappeared for the patient, continue to move it laterally and ask the patient to let you know when they can see it again. The point at which the patient reports the hatpin re-appearing should be similar to the point at which it re-appears for you (presuming the patient and you have a normal blind spot).
9. You can further assess the superior and inferior borders of the blind spot using the same process.

Question 30

What is the final part of the CNII assessment

Answer 30

Offer fundoscopy

Question 31

How do you assess CNIII, IV, and VI

Answer 31

1. Hold your finger (or a pin) approximately 30cm in front of the patient’s eyes and ask them to focus on it. Look at the eyes in the primary position for any deviation or abnormal movements.
2. Ask the patient to keep their head still whilst following your finger with their eyes. Ask them to let you know if they experience any double vision or pain.
3. Move your finger through the various axes of eye movement in a ‘H’ pattern.
4. Observe for any restriction of eye movement and note any nystagmus (which may suggest vestibular nerve pathology or stroke).

REMEMBER Inspect the eyelids for evidence of ptosis which can be associated with:

Oculomotor nerve pathology
Horner’s syndrome
Neuromuscular pathology (e.g. myasthenia gravis)

Question 32

What are the functions of all the extraocular muscles

Answer 32

Superior rectus: primary action is elevation, secondary actions include adduction and medial rotation of the eyeball.

Inferior rectus: primary action is depression, secondary actions include adduction and lateral rotation of the eyeball.

Medial rectus: adduction of the eyeball.

Lateral rectus: abduction of the eyeball.

Superior oblique: depresses, abducts and medially rotates the eyeball.

Inferior oblique: elevates, abducts and laterally rotates the eyeball.

Question 33

What does CNIII palsy look like

Answer 33

Oculomotor palsy (a.k.a. ‘third nerve palsy’) results in the unopposed action of both the lateral rectus and superior oblique muscles, which pull the eye inferolaterally. As a result, patients typically present with a ‘down and out’ appearance of the affected eye.

Oculomotor nerve palsy can also cause ptosis (due to a loss of innervation to levator palpebrae superioris) as well as mydriasis due to the loss of parasympathetic fibres responsible for innervating to the sphincter pupillae muscle.

Question 34

What does CNIV palsy look like

Answer 34

The only muscle the trochlear nerve innervates is the superior oblique muscle.

As a result, trochlear nerve palsy (‘fourth nerve palsy’) typically results in vertical diplopia when looking inferiorly, due to loss of the superior oblique’s action of pulling the eye downwards.

Patients often try to compensate for this by tilting their head forwards and tucking their chin in, which minimises vertical diplopia.

Trochlear nerve palsy also causes torsional diplopia (as the superior oblique muscle assists with intorsion of the eye as the head tilts).

To compensate for this, patients with trochlear nerve palsy tilt their head to the opposite side, in order to fuse the two images together.

Question 35

What does CN VI palsy look like

Answer 35

The abducens nerve (CN VI) innervates the lateral rectus muscle.

Abducens nerve palsy (‘sixth nerve palsy’) results in unopposed adduction of the eye (by the medial rectus muscle), resulting in a convergent squint.

Patients typically present with horizontal diplopia which is worsened when they attempt to look towards the affected side.

Question 36

What is strabismus

Answer 36

Strabismus is a condition in which the eyes do not properly align with each other when looking at an object.

Pathology affecting the oculomotor, trochlear or abducens nerves can cause strabismus.

Question 37

How do you test for strabismus (2)

Answer 37

Light reflex test (a.k.a. corneal reflex test or Hirschberg test)
Cover test

Question 38

What should you assess for the extraocular muscles

Answer 38

Do the H
Look at eyelids
Assessment of strabismus

Question 39

How do you do the light reflex test?

Answer 39

Light reflex test (a.k.a. corneal reflex test or Hirschberg test)
1. Ask the patient to focus on a target approximately half a metre away whilst you shine a pen torch towards both eyes.

2. Inspect the corneal reflex on each eye:

If the ocular alignment is normal, the light reflex will be positioned centrally and symmetrically in each pupil.
Deflection of the corneal light reflex in one eye suggests a misalignment.(strabismus)

Question 40

How do you do the cover test

Answer 40

The cover test is used to determine if a heterotropia (i.e. manifest strabismus) is present.

1. Ask the patient to fixate on a target (e.g. light switch).
2. Occlude one of the patient’s eyes and observe the contralateral eye for a shift in fixation:

If there is no shift in fixation in the contralateral eye, while covering either eye, the patient is orthotropic (i.e. normal alignment).
If there is a shift in fixation in the contralateral eye, while covering the other eye, the patient has a heterotropia.
3. Repeat the cover test on the other eye.

The direction of the shift in fixation determines the type of tropia

Question 41

What result does the cover test give for exotropia

Answer 41

Direction of eye at rest: Temporally (i.e. laterally or outwards)

The direction of shift in fixation of the unoccluded eye when the opposite eye is occluded: Nasally (i.e. medially or inwards)

Question 42

What result does the cover test give for esotropia

Answer 42

Direction of eye at rest: Nasally (i.e. medially or inwards)

The direction of shift in fixation of the unoccluded eye when the opposite eye is occluded: Temporally (i.e. laterally or outwards)

Question 43

What result does the cover test give for hypertropia

Answer 43

Direction of eye at rest: Superiorly (i.e. upwards)

The direction of shift in fixation of the unoccluded eye when the opposite eye is occluded: Inferiorly (i.e. downwards)

Question 44

What result does the cover test give for hypotropia

Answer 44

Direction of eye at rest: Inferiorly (i.e. downwards)

The direction of shift in fixation of the unoccluded eye when the opposite eye is occluded: Superiorly (i.e. upwards)

Question 45

What does CN V3 innervate (motor)

Answer 45

muscles of mastication (masseter, temporal muscle and the medial/lateral pterygoids) as well as the tensor tympani, tensor veli palatini, mylohyoid and digastric muscles.

Question 46

How do you assess sensory element of CN V

Answer 46

Assess the sensory component of V1, V2 and V3 by testing light touch and pinprick sensation across regions of the face supplied by each branch:

Forehead (lateral aspect): ophthalmic (V1)
Cheek: maxillary (V2)
Lower jaw (avoid the angle of the mandible as it is supplied by C2/C3): mandibular branch (V3)

Question 47

How do you assess the motor part of CN V

Answer 47

Muscles of mastication and reflexes (jaw jerk and corneal)

1. Inspect the temporalis (located in the temple region) and masseter muscles (located at the posterior jaw) for evidence of wasting. This is typically most noticeable in the temporalis muscles, where a hollowing effect in the temple region is observed.
2. Palpate the masseter muscle (located at the posterior jaw) bilaterally whilst asking the patient to clench their teeth to allow you to assess and compare muscle bulk.
3. Ask the patient to open their mouth whilst you apply resistance underneath the jaw to assess the lateral pterygoid muscles. An inability to open the jaw against resistance or deviation of the jaw (typically to the side of the lesion) may occur in trigeminal nerve palsy.

Question 48

How do you assess the jaw jerk reflex

Answer 48

The jaw jerk reflex is a stretch reflex that involves the slight jerking of the jaw upwards in response to a downward tap. This response is exaggerated in patients with an upper motor neuron lesion. Both afferent and efferent pathways of the jaw jerk reflex involve the trigeminal nerve.

To assess the jaw jerk reflex:

1. Clearly explain what the procedure will involve to the patient and gain consent to proceed.
2. Ask the patient to open their mouth.
3. Place your finger horizontally across the patient’s chin.
4. Tap your finger gently with the tendon hammer.
5. In healthy individuals, this should trigger a slight closure of the mouth. In patients with upper motor neuron lesions, the jaw may briskly move upwards causing the mouth to close completely.

Question 49

What is the corneal reflex

Answer 49

The corneal reflex involves involuntary blinking of both eyelids in response to unilateral corneal stimulation (direct and consensual blinking). The afferent branch of the corneal reflex involves V1 of the trigeminal nerve whereas the efferent branch is mediated by the temporal and zygomatic branches of the facial nerve.

Question 50

How do you assess the corneal reflex

Answer 50

1. Clearly explain what the procedure will involve to the patient and gain consent to proceed.
2. Gently touch the edge of the cornea using a wisp of cotton wool.
3. In healthy individuals, you should observe both direct and consensual blinking. The absence of a blinking response suggests pathology involving either the trigeminal or facial nerve.

The corneal reflex is not usually assessed in an OSCE scenario, however, you should offer to test it and understand the purpose behind the test.

Question 51

What do you assess for CN VII

Answer 51

The facial nerve (CN VII) transmits motor information to the muscles of facial expression and the stapedius muscle (involved in the regulation of hearing). The facial nerve also has a sensory component responsible for the conveyance of taste from the anterior two-thirds of the tongue.

Question 52

How do you assess the sensory element of CN VII

Answer 52

Ask the patient if they have noticed any recent changes in their sense of taste.

Question 53

How do you assess the motor element of CN VII

Answer 53

Hearing changes
Ask the patient if they have noticed any changes to their hearing (paralysis of the stapedius muscle can result in hyperacusis).

Inspection
Inspect the patient’s face at rest for asymmetry, paying particular attention to:

Forehead wrinkles
Nasolabial folds
Angles of the mouth

Facial movement
Ask the patient to carry out a sequence of facial expressions whilst again observing for asymmetry:

Raised eyebrows: assesses frontalis – “Raise your eyebrows as if you’re surprised.”
Closed eyes: assesses orbicular oculi – “Scrunch up your eyes and don’t let me open them.”
Blown out cheeks: assesses orbicularis oris – “Blow out your cheeks and don’t let me deflate them.”
Smiling: assesses levator anguli oris and zygomaticus major – “Can you do a big smile for me?”
Pursed lips: assesses orbicularis oris and buccinator – “Can you try to whistle?”

Question 54

What does CNVIII do

Answer 54

The vestibulocochlear nerve (CN VIII) transmits sensory information about sound and balance from the inner ear to the brain. The vestibulocochlear nerve has no motor component.

Question 55

How do you perform a gross hearing assessment

Answer 55

1. Position yourself approximately 60cm from the ear and then whisper a number or word.
2. Mask the ear not being tested by rubbing the tragus. Do not place your arm across the face of the patient when rubbing the tragus, it is far nicer to occlude the ear from behind the head. If possible shield the patient’s eyes to prevent any visual stimulus.
3. Ask the patient to repeat the number or word back to you. If they get two-thirds or more correct then their hearing level is 12db or better. If there is no response use a conversational voice (48db or worse) or loud voice (76db or worse).
4. If there is no response you can move closer and repeat the test at 15cm. Here the thresholds are 34db for a whisper and 56db for a conversational voice.
5. Assess the other ear in the same way.

Question 56

How do you perform Rinne’s test

Answer 56

Rinne’s test
1. Place a vibrating 512 Hz tuning fork firmly on the mastoid process (apply pressure to the opposite side of the head to make sure the contact is firm). This tests bone conduction.

2. Confirm the patient can hear the sound of the tuning fork and then ask them to tell you when they can no longer hear it.
3. When the patient can no longer hear the sound, move the tuning fork in front of the external auditory meatus to test air conduction.
4. Ask the patient if they can now hear the sound again. If they can hear the sound, it suggests air conduction is better than bone conduction, which is what would be expected in a healthy individual (this is often confusingly referred to as a “Rinne’s positive” result).

Question 57

Give a Summary of Rinne’s test results

Answer 57

Normal result: air conduction > bone conduction (Rinne’s positive)

Sensorineural deafness: air conduction > bone conduction (Rinne’s positive) – due to both air and bone conduction being reduced equally

Conductive deafness: bone conduction > air conduction (Rinne’s negative)

Question 58

How do you perform Weber’s test

Give the interpretation

Answer 58

1. Tap a 512Hz tuning fork and place in the midline of the forehead. The tuning fork should be set in motion by striking it on your knee (not the patient’s knee or a table).
2. Ask the patient “Where do you hear the sound?”

These results should be assessed in context with the results of Rinne’s test before any diagnostic assumptions are made:

Normal: sound is heard equally in both ears.
Sensorineural deafness: sound is heard louder on the side of the intact ear.
Conductive deafness: sound is heard louder on the side of the affected ear.
A 512Hz tuning fork is used as it gives the best balance between time of decay and tactile vibration. Ideally, you want a tuning fork that has a long period of decay and cannot be detected by vibration sensation

Question 59

What’s Unterberger’s test

Answer 59

Vestibular testing – “Unterberger” or “Turning test”
Ask the patient to march on the spot with their arms outstretched and their eyes closed:

Normal result: the patient remains in the same position.
Vestibular lesion: the patient will turn towards the side of the lesion

Question 60

What is the head-thrust test

Answer 60

Vestibular testing – “Head thrust test” or “Vestibular-ocular reflex”
Before performing this test you need to check if the patient has any neck problems and if so you should not proceed.

1. Explain to the patient that the test will involve briskly turning their head and then gain consent to proceed.
2. Sit facing the patient and ask them to fixate on your nose at all times during the test.
3. Hold their head in your hands (one hand covering each ear) and rotate it rapidly to the left, at a medium amplitude.
4. Repeat this process, but this time turn the head to the right.

The normal response is that ocular fixation is maintained. In a patient with loss of vestibular function on one side, the eyes will first move in the direction of the head (losing fixation), before a corrective refixation saccade occurs towards your nose.

Question 61

What does the CN X innervate

Answer 61

The glossopharyngeal nerve transmits motor information to the stylopharyngeus muscle which elevates the pharynx during swallowing and speech. The glossopharyngeal nerve also transmits sensory information that conveys taste from the posterior third of the tongue. Visceral sensory fibres of CN IX also mediate the afferent limb of the gag reflex.

The vagus nerve transmits motor information to several muscles of the mouth which are involved in the production of speech and the efferent limb of the gag reflex.

The glossopharyngeal and vagus nerves are assessed together because of their closely related functions

Question 62

How do you assess CN X and IX

Answer 62

Ask the patient if they have experienced any issues with swallowing, as well as any changes to their voice or cough.

Inspection
Ask the patient to open their mouth and inspect the soft palate and uvula:

Note the position of the uvula. Vagus nerve lesions result in deviation of the uvula towards the unaffected side.
Ask the patient to say “ahh“:

Inspect the palate and uvula which should elevate symmetrically, with the uvula remaining in the midline. A vagus nerve lesion will cause asymmetrical elevation of the palate and uvula deviation away from the lesion.
Ask the patient to cough:

Vagus nerve lesions can result in the presence of a weak, non-explosive sounding bovine cough caused by an inability to close the glottis.

Swallow assessment

Gag reflex

Question 63

How do you do the swallow assessment

Answer 63

Ask the patient to take a small sip of water (approximately 3 teaspoons) and observe the patient swallow. The presence of a cough or a change to the quality of their voice suggests an ineffective swallow which can be caused by both glossopharyngeal (afferent) and vagus (efferent) nerve pathology.

Question 64

How do you assess CN XI

Answer 64

1. First, inspect for evidence sternocleidomastoid or trapezius muscle wasting.
2. Ask the patient to raise their shoulders and resist you pushing them downwards: this assesses the trapezius muscle (accessory nerve palsy will result in weakness).
3. Ask the patient to turn their head left whilst you resist the movement and then repeat with the patient turning their head to the right: this assesses the sternocleidomastoid muscle (accessory nerve palsy will result in weakness).

Question 65

What does CN XII do

Answer 65

The hypoglossal nerve (CN XII) transmits motor information to the extrinsic muscles of the tongue (except for palatoglossus which is innervated by the vagus nerve). It does not have a sensory component.

Question 66

How do you assess CN XII

Answer 66

1. Ask the patient to open their mouth and inspect the tongue for wasting and fasciculations at rest (minor fasciculations can be normal).
2. Ask the patient to protrude their tongue and observe for any deviation (which occurs towards the side of a hypoglossal lesion).
3. Place your finger on the patient’s cheek and ask them to push their tongue against it. Repeat this on each cheek to assess and compare power (weakness would be present on the side of the lesion).

Question 67

What does hypoglossal nerve palsy look like

Answer 67

Hypoglossal nerve palsy causes atrophy of the ipsilateral tongue and deviation of the tongue when protruded towards the side of the lesion. This occurs due to the overaction of the functioning genioglossus muscle on the unaffected side of the tongue.

Question 68

What should you offer as further tests after the CN exam

Answer 68

Full neurological examination including the upper and lower limbs.
Neuroimaging (e.g. MRI head): if there are concerns about space-occupying lesions or demyelination.
Formal hearing assessment (including pure tone audiometry): if there are concerns about vestibulocochlear nerve function.