Cranial Nerve Examination Flashcards
1
Q
Which 8 pieces of equipment are required for a cranial nerve exam?
For which cranial nerves is each required for?
A
- Pen torch - CN II
- Snellen chart - CN II
- Ishihara plates - CN II
- Opthalmoscope and mydriatic eye drops - CN II
- Cotton wool - CN V
- Neuro-tip - CN V
- Tuning fork (512 Hz) - CN VIII
- Glass of water - CN IX/X
2
Q
How should patient be positioned at start of exam?
A
On chair at 1 arm’s length away
3
Q
What 6 clinical signs are you assessing for during general inspection of a cranial nerve exam?
A
- Speech abnormalities
- Facial asymmetry
- Eyelid abnormalities
- Pupillary abnormalities
- Strabismus
- Limbs
4
Q
Which CN pathology would speech abnormalities indicate?
A
Glossopharyngeal or vagus nerve
5
Q
What CN pathology may facial asymmetry be suggestive of?
A
Facial nerve palsy
6
Q
Which eyelid abnormality may indicate which CN pathology?
A
Ptosis may indicate oculomotor nerve pathology
7
Q
Define mydriasis
A
Mydriasis is the dilation of the pupil
8
Q
Which CN pathology may mydriasis indicate?
A
Oculomotor nerve pathology
9
Q
What is strabismus?
A
A disorder in which both eyes do not line up in the same direction so do not look at the same object at the same time – most common form is ‘crossed eyes’
10
Q
Which CN pathologies may strabismus indicate?
A
CN III (oculomotor), CN IV (trochlear) or CN VI (abducens)
11
Q
How can you assess the limbs during a general inspection of a cranial nerve exam?
A
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 presence of a neurological syndrome
12
Q
What objects and equipment are you looking for during general inspection of a CN exam?
A
- Mobility aids
- Prescription
- Visual aids
- Hearing aids
13
Q
What may walking aids indicate in a CN exam?
A
Gait issues are associated with a wide range of neurological pathologies including Parkinson’s disease, stroke, cerebellar disease and myasthenia gravis
14
Q
What may hearing aids indicate in a CN exam?
A
Often worn by patients with vestibulocochlear nerve issues (e.g. Meniere’s disease)
15
Q
What is Meniere’s disease?
A
A disorder of the inner ear
16
Q
What are the symptoms of Meniere’s disease?
A
- Often unilateral (can spread to both after time)
- Dizziness (vertigo – world spinning around you)
- Hearing loss
- Tinnitus
- Pressure felt deep inside the ear
17
Q
Define vertigo
A
Feeling like room is spinning around you
18
Q
What may the use of visual aids such as visual prisms or occluders indicate?
A
Underlying strabismus
19
Q
Where are the receptors of CN I located?
A
Olfactory receptors in the nasal epithelium
20
Q
Skull foramina of CN I?
A
Cribriform plate in ethmoid bone
21
Q
Describe pathway of olfactory receptors from nasal epithelium to olfactory cortex
A
1) Olfactory receptors in nasal epithelium
2) Axons pass through cribriform plate to olfactory bulb (synapse) and then to olfactory tract
3) Lateral olfactory striae take olfactory in formation to parahippocampal gyrus and amygdala (olfactory cortex)
22
Q
Where is the olfactory cortex located?
A
Inferior surface of the temporal lobe
23
Q
What is the function of CN I?
A
Special sensory - smell
There is no motor component
24
Q
What is the assessment for CN I?
A
Ask patient if they have had any recent changes to sense of smell.
Olfaction can be tested more formally using different odours (e.g. lemon, peppermint) or most formally using University of Pennsylvania smell identification test (but this is unlikely to be required in an OSCE).
25
What are 5 causes of anosmia?
1. Mucous blockage of nose
2. Head trauma
3. Genetics (congenital anosmia)
4. Early feature of Parkinson's disease
5. COVID-19
26
How can head trauma lead to anosmia?
Can result in shearing of olfactory nerve fibres leading to anosmia
27
How can mucous blockage of the nose lead to anosmia?
Preventing odours from reaching olfactory nerve receptors
28
Which CNs are outgrowths of the telecephalon?
CN I and CN II
29
What is the CNS location of CN II?
Retina
30
Describe the pathway of CN II from the retina to the visual cortex
1) Emerge from back of eyes in **retina** and travels back until it reaches the **optic chiasma** (where 2 optic nerves converge)
2) Optic tracts then pass towards back of midbrain and hook upwards to connects with the **lateral geniculate body of the thalamus** (this includes LGN)
3) From LGB there are **optic radiations** – fibres that bring visual information from thalamus to **primary visual cortex** in **occipital lobe**
31
Where is the primary visual cortex located?
Posterior pole of occipital lobe
32
Which skull foramina does CN II pass through?
Optic canal in sphenoid bone
33
What is the function of CN II?
Special sensory - vision (brightness, colour, contrast)
There is NO motor component
34
What 8 aspects are involved in the assessment of CN II?
**_AFRO + Blind spot_**
Pupil Inspection
**A**cuity:
* Snellen chart for visual acuity
* Ishihara plates for colour vision (offer)
**F**ields:
* Visual fields
* Visual inattention
**R**eflexes:
* Direct & consensual
* Swinging light
* Accomodation
**O**phthalmoscopy
+ blind spot (offer)
35
What 3 things are you assessing when inspecting the pupils (CN II)?
1. Pupil size
2. Pupil shape
3. Pupil symmetry
36
How does pupil size change from infancy to adolescence?
Infancy - smaller
Adolescence - bigger
37
What is the normal pupil shape?
Round
38
What can abnormal pupil shape be caused by?
Congenital or due to pathology
39
What are synechiae?
Adhesions formed between adjacent structures within the eye usually a result of inflammation
40
Where are posterior synechiae located?
Adhesions between the **posterior iris** and **anterior lens surface**
41
How can posterior synechiae affect the pupil shape? Why?
Abnormal pupil shape - adhesions prevent dilation
42
What is posterior synechiae associated with?
Uveitis (eye inflammation) caused by e.g. ocular trauma
43
What are peaked pupils in the context of trauma suggestive of?
Globe injury
44
What is a globe injury?
* In ocular trauma, injuries can be classified as either closed globe or open globe
* Globe rupture is where the **integrity of the outer membranes** of the eye are disrupted by **blunt** or **penetrating** trauma
45
What is the effect of a globe injury on the pupil?
Peaked pupil
46
Define anisocoria
Anisocoria is **unequal pupil size**.
47
What can cause anisocoria?
this may be longstanding and non-pathological or relate to actual pathology
48
In pupil asymmetry - if one pupil is more pronounced in bright light, which pupil is abnormal?
The larger pupil
49
In pupil asymmetry - if one pupil is more pronounced in dark, which pupil is abnormal?
The smaller pupil
50
How does oculomotor nerve palsy affect pupil symmetry?
Causes a large pupil in the affected eye
51
How does Horner's syndrome affect pupil symmetry?
Causes a small and reactive pupil in the affected eye
52
Define visual acuity
**the clarity or sharpness of vision**.
53
What piece of equipment is used to assess visual acuity?
A Snellen chart
54
If a patient normally uses **distance** **glasses**, should these be **worn** for the visual acuity assessment?
Yes
55
Describe the steps of assessing visual acuity using a Snellen chart
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.
56
How many metres should the patient stand away from the Snellen chart?
6 metres
57
If reading through a pinhole during visual acuity assessment improves vision, what does this suggest?
it suggests there is a **refractive component** to the patient’s poor vision
58
How is visual acuity recorded?
**Chart distance** (numerator) over the **number of the lowest line read** (denominator).
E.g. 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).
59
If the patient is **unable** to **read** the **top** **line** of the **Snellen** **chart** at **6 metres** (even with pinhole), what steps can be taken?
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”).
60
What are 5 causes of decreased visual acuity?
* Refractive errors
* Amblyopia
* Ocular media opacities e.g. cataract, corneal scarring
* Optic nerve CN II pathology e.g. optic neuritis
* Lesions higher in the visual pathway
61
Define ambylopia
**Impaired** or **dim vision** without obvious defect or change in the eye.
62
How does CN II pathology affect visual acuity?
CN II pathology usually causes a decrease in acuity in the affected eye
63
What is papilloedema?
Optic disc swelling from raised intracranial pressure e.g. head injury, malignant hypertension
64
How does papilloedema affect visual acuity?
Does not affect visual acuity until it is at a late stage
65
What step should first be taken when assessing pupillary reflexes?
With the patient seated, **dim the lights** to allow you to assess pupillary reflexes effectively.
66
What 4 tests are involved in assessment of pupillary reflexes?
1. Direct pupillary reflex
2. Consensual pupillary reflex
3. Swinging light test
4. Accommodation reflex
67
How is a **direct** pupillary light reflex performed?
Shine the light from your pen torch into the patient’s pupil and observe for **pupillary restriction** in the **ipsilateral** eye.
68
What is a normal direct pupillary reflex?
**Constriction** of the pupil that the light is being shone into
69
How is a **consensual** pupillary light reflex performed?
Once again shine the light from your pen torch into the same pupil, but this time observe for pupillary restriction in the **contralateral** eye.
70
What is a normal consensual pupillary reflex?
A normal consensual pupillary reflex involves the **contralateral pupil constricting** as a response to light entering the eye being tested (due to dual efferent pathways)
71
How is a swinging light test performed?
Move the pen torch rapidly between the two pupils
72
What equipment is required for the pupillary reflex tests?
Pen torch
73
What defect is the swinging light test assessing for?
Relative afferent pupillary defect
74
What is a normal result of the swinging light test?
Pupils of both eyes **constrict equally** regardless of which eye is stimulated by the light
75
What is relative afferent pupillary defect (RAPD)?
A condition in which pupils respond differently to light stimuli shone in one eye
76
What is the cause of RAPD?
Unilateral or asymmetrical disease of the **retina** or **optic nerve**
77
What test is used to assess for RAPD?
Swinging light test
78
What is the result of the swinging light test in RAPD?
Pupils dilate when a bright light is swung from unaffected eye to affected eye i.e. less pupil constriction in the eye with retinal/optic nerve disease
79
What is the purpose of the accommodation reflex?
To coordinate visual attention to near objects.
80
How is the accommodation reflex test performed?
1. Ask the patient to focus on a **distant object** (clock on the wall/light switch).
2. Place your finger approximately **20-30cm in front of their eyes** (alternatively, use the patient’s own thumb).
3. Ask the patient to switch from looking at the **distant object** to the **nearby finger/thumb.**
4. Observe the pupils, you should see **constriction** and **convergence bilaterally**.
81
What is the normal result of the accommodation reflex test?
you should see **constriction** and **convergence bilaterally**
82
Each afferent limb of the pupillary light reflex has how many efferent limbs?
2 - one **ipsilateral** and one **contralateral**
83
Which CN is involved in the afferent limb of the pupillary light reflex?
CN II
84
Describe the afferent limb of the pupillary light reflex
Sensory input (e.g. light being shone into eye) is transmitted from the **retina**, along the **optic** **nerve** to the **ipsilateral pretectal nucleus** in the **midbrain**
85
Which CN is involved in the efferent limb of the pupillary light reflex?
CN III
86
Describe the two efferent limbs of the pupillary light reflex
* **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**
87
Which limb of the pupillary light reflex is the direct pupillary light reflex testing?
Assesses the **ipsilateral** **afferent** **limb** and **ipsilateral** **efferent** **limb** of the pathway
88
Which limb of the pupillary light reflex is the consensual pupillary light reflex testing?
the **contralateral efferent limb** of the pathway
89
Which limb of the swinging light test is the direct pupillary light reflex testing?
used to detect **relative afferent limb defects**
90
What is RAPD also known as?
Marcus-Gunn pupil
91
What is limb of the pupillary light reflex is damaged in RAPD/Marcus-Gunn pupil?
The **afferent limb in one of the optic nerves**
92
How does this defect present in RAPD present during a swinging torch test?
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 (RAPD).
93
What is the cause of RAPD?
* Significant retinal damage in the affected eye 2ary to central retinal artery or vein occlusion and large retinal detachment
* Significant optic neuropathy e.g. optic neuritis, unilateral advanced glaucoma and compression 2ary to tumour or abscess
94
How would a **unilateral efferent** defect present?
* Loss of **efferent limb of ipsilateral** pupillary reflexes
* **Ipsilateral pupil is _dilated**_ and _**non-responsive_ to light** entering either eye; due to loss of **_ciliary sphincter function_**
* **Consensual light reflex in unaffected eye would still be present** as the afferent pathway (i.e. optic nerve) of affected eye and efferent pathway (i.e. oculomotor nerve) of unaffected eye remain intact
95
Cause of unilateral efferent defect?
Extrinsic compression of the oculomotor nerve
96
What equipment is required for colour vision assessment?
Ishihara plates
97
Ishihara plates are difficult/impossible to see for those with which defect?
For those with a red-green colour vision defect.
98
Describe the steps of the colour vision assessment
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.
99
What is usually the first page of the Ishihara plates? What does it assess?
The first page is usually the ‘test plate’ which does not test colour vision and instead assesses contrast sensitivity.
100
What are some causes of acquired colour vision deficiencies?
* Optic neuritis: results in a reduction of colour vision (typically red)
* Vitamin A deficiency
* Chronic solvent exposure
101
What vitamin deficiency is often implicated in acquired colour vision deficiencies?
A
102
What is visual neglect/inattention?
a condition in which an individual develops a **deficit** in their **awareness** of **one side** of their **visual** **field**
103
What injury is typically implicated in visual neglect?
**Parietal** lobe injury after a **stroke -** results in an **inability to perceive or process stimuli** on one side of the body
N.B. The side of the visual field that is affected is **contralateral** to the location of the parietal lesion.
104
Why is the visual neglect test not often included in a CN OSCE?
As visual neglect is **not caused by optic nerve pathology**
105
Describe the steps off the visual neglect test
**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).
106
The visual fields assessment relies on comparing the patient's visual fields with your own. Therefore, what 2 aspects is needed for it to work?
* You need to **position** yourself, the patient and the target correctly
* You need to have **normal visual fields** and a **normal-sized blind spot**
107
Describe the steps of the visual fields assessment
This method of assessment relies on **comparing** the **patient’s** visual field with **your own** and therefore for it to work:
* You need to position yourself, the patient and the target correctly (see details below)
* You need to have normal visual fields and a normal-sized blind spot
**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.
108
During the visual field assessment, how do you 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**.
109
Describe bitemporal hemianopia.
What is it caused by?
Loss of temporal visual field in both eyes resulting in central tunnel vision
Cause - typically result of **optic chiasm compression** by a tumour (e.g. pituitary adenoma, craniopharyngioma)
110
What is a homonymous field defect? What are they commonly attributed to?
Affects the **same side** of the visual field in each eye
Commonly attributed to stroke, tumour, abscess (pathology affecting visual fields posterior to the optic chiasm)
111
Heminanopia vs quadrantopia?
Hemianopia → when half the vision is affected
Quadrantopia → when a quarter of the vision is affected
112
What is a scotoma?
An area of absent or reduced vision surrounded by areas of normal vision
113
What can cause a scotoma?
A range of possible aetiologies including demyelinating disease (e.g. multiple sclerosis) and diabetic maculopathy.
114
What is monocular vision loss? What is it caused by?
Total loss of vision in one eye
Caused by **optic nerve** pathology (e.g. anterior ischaemic optic neuropathy) or **ocular diseases** (e.g. central retinal artery occlusion, total retinal detachment)
115
What does everyone have a physiological blind spot?
A physiological blind spot exists in all healthy individuals as a result of the **lack of photoreceptor cells** in the area where the **optic nerve passes through the optic disc**.
116
How does the brain reduce our awareness of our blind spot?
by using information from other areas of the retina and the other eye to mask the defect
117
Describe the steps in assessment of the patient's blind spot
**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.** 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.
118
Where is the blind spot normally found?
The blind spot is normally found just temporal to central vision at eye level.
119
In the context of a cranial nerve examination, why is fundoscopy performed?
To assess the **optic** **disc** for signs of pathology (e.g. papilloedema).
You should offer to perform fundoscopy in your OSCE, however, it may not be required.
120
What is the function of CN III?
* Somatic motor - majority of the extraocular muscles (levator palpebrae superioris, SR, IR, MR, IO)
* Parasympathetic (visceral motor) - sphincter pupillae and ciliary muscle
* Sympathetic - no direct function, but sympathetic fibres run with the oculomotor nerve to innervate the superior tarsal muscle (helps to raise the eyelid).
121
Function of CN IV?
Somatic motor - superior oblique (extraocular muscle)
122
Function of CN VI
Somatic motor - lateral rectus (extraocular)
123
What is the CNS location of CN III?
Pontomesencephalic junction (between midbrain and pons)
124
What is the CNS location of CN IV?
Of CN VI?
IV - dorsal midbrain
VI - pontomedullary junction
125
Which skull foramina does CN III, IV and VI pass through?
Superior orbital fissure
126
What 3 aspects are involved in the assessment of CN III, IV and VI?
1. Eyelid inspection
2. Eye movements
3. Strabismus assessment
127
Why are CN III, IV and VI assessed together?
Similar function
128
What are you assessing the eyelids for in assessment of CN III, IV and VI?
Ptosis
129
What 3 conditions can ptosis be associated with?
1. Horner's syndrome
2. Oculomotor nerve pathology
3. Neuromuscular pathology (e.g. myasthenia gravis)
130
Which CN pathology can ptosis be associated with?
CN III
131
Which CN palsy can abnormalities of eye movements be caused by?
oculomotor, trochlear, abducens, vestibular nerve pathology
132
Describe the steps of assessing eye movements in assessment of CN III, IV and VI
**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).
133
What should you observe for during assessment of eye movements (III, IV, VI)?
* Restriction of eye movement
* Nystagmus (vestibular nerve pathology, stroke)
134
What is the action of:
1. Superior rectus
2. Inferior rectus
3. Medial rectus
4. Lateral rectus
5. Superior oblique
6. Inferior oblique
1. Elevation of eyeball (2ary actions: adduction and medial rotation)
2. Depression of eyeball (2ary: adduction and lateral rotation)
3. Adduction of eyeball
4. Abduction of eyeball
5. Depresses, abducts and medially rotates
6. Elevates, abducts and laterally rotates
135
Which 2 extraocular muscles does CN III not supply?
Superior oblique (IV) and lateral rectus (VI)
136
What does oculomotor nerve palsy result in?
Unopposed action of **lateral rectus** and **superior oblique muscles (which pull the eye inferolaterally)** → ‘down and out’ pupil
137
What does oculomotor nerve palsy result in?
What is the presentation of the patient?
Unopposed action of **lateral rectus** and **superior oblique** muscles (which pull the eye inferolaterally)
Presentation:
* ‘Down and out’ appearance of the affected eye
* Ptosis (due to loss of innervation to levator palpebrae superioris)
* Mydriasis (due to loss of parasympathetic fibres to sphincter pupillae)
138
What is action of levator palpebrae superioris?
The function of the levator palpebrae superioris muscle is **to raise the upper eyelid and to maintain the upper eyelid position**.
139
Define ptosis
drooping of the upper eyelid
140
Define mydriasis
dilation of the pupil of the eye.
141
What is the action of sphincter pupillae?
**constrict the pupil in bright light via the pupillary light reflex or during accommodation**
142
What does trochlear nerve (IV) palsy result in? What is the presentation of the patient?
Loss of superior oblique's action of pulling the eye downwards as well as its assistance with intorsion of the eye as the head tilts.
Presentation:
* **Vertical diplopia** when looking inferiorly - patient's try to compensate by **tilting their head forwards** and **tucking their chin** in which minimises vertical diplopia
* **Torsional diplopia -** patient's try to compensate by tilting their head to the opposite side in order to fuse the two images together
143
Define vertical diplopia
Patients with vertical diplopia complain **of seeing two images, one atop or diagonally displaced from the other**.
144
What CN palsy causes vertical diplopia?
CN IV (trochlear) → causing superior oblique palsy
145
How do patients with vertical diplopia compensate?
by tilting their head forwards and tucking their chin in
146
What CN palsy causes torisonal diplopia?
CN IV (trochlear) → due to superior oblique palsy
147
What does CN VI (abducens) palsy result in? What is the presentation?
Paralysis of the **lateral rectus** muscle results in **unopposed adduction** of the eye (by medial rectus).
Presentation: **horizontal diplopia** which is worsened when they attempt to look towards the affected side
148
Horizontal vs vertical diplopia?
**Vertical diplopia indicates vertical alignment of the images**, which usually suggests pathology in the vertical muscles, including superior oblique, inferior oblique, superior rectus, and inferior rectus.
Horizontal diplopia suggests pathology of the medial or lateral rectus.
149
What is strabismus?
**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.
150
What 2 tests are used to assess strabismus in CN III, IV and VI examination?
1. Light reflex test (corneal reflex test/Hirschberg test)
2. Cover test
151
Describe the steps of the light reflex 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
152
What is a normal result of the light/corneal reflex test?
The corneal/blink/light reflex, is an involuntary blinking of the eyelids elicited by stimulation of the cornea, though could result from any peripheral stimulus (e.g. light). Stimulation should elicit both a direct and consensual response.
If the ocular alignment is normal, the light reflex will be positioned **centrally** and **symmetrically** in each pupil.
153
What would suggest misalignment in the light/corneal reflex test?
Deflection of the corneal light reflex
154
What is the purpose of the ‘cover test’?
The cover test is used to determine if a heterotropia (i.e. manifest strabismus) is present.
155
What is a heterotropia?
Heterotropia is **an upward deviation of the non-fixing eye**.
156
What steps are involved in the cover test?
**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
**3.** Repeat the cover test on the other eye.
157
In the cover test, if there is no shift in fixation in the contralateral eye while covering either eye, the patient is orthotropic. What does this mean?
Normal eye alignment
158
In the cover test, if there is a shift in fixation in the contralateral eye, while covering the other eye, what does this indicate?
Heterotropia
159
The direction of the shift in fixation during the cover test determines the type of tropia:
160
Describe the direction of the:
a) eye at rest
b) shift in fixation of unoccluded eye when opposite eye is occluded
in exotropia
Exotropia → eye turned outward
a) temporally (laterally/outwardly)
b) nasally (medially/inwards)
161
Describe the direction of the:
a) eye at rest
b) shift in fixation of unoccluded eye when opposite eye is occluded
in esotropia
Esotropia → eye turned inward
a) medially
b) laterally
162
Describe the direction of the:
a) eye at rest
b) shift in fixation of unoccluded eye when opposite eye is occluded
in hypertropia?
Hypertropia → eye turned upwards
a) superiorly
b) inferiorly
163
Describe the direction of the:
a) eye at rest
b) shift in fixation of unoccluded eye when opposite eye is occluded
in hypotropia?
Hypotropia → eye turned downward
a) downwards
b) upwards
164
What is the CNS location of CN V?
Dorsal midbrain
165
There are 3 parts to CN V.
Which skull foramina does each pass through?
V1 - superior orbital fissure
V2 - foramen rotundum
V3 - foramen ovale
166
What is the function of each part of CN V?
Somatic sensation from:
* V1 – upper face (scalp and forehead, nose, upper eyelid, conjunctiva and cornea of eye)
* V2 – middle face (lower eyelid, cheek, nares, upper lip, upper teeth and gums)
* V3:
* Lower face (chin, jaw, lower lip, mouth, lower teeth and gums)
* **Somatic motor** to muscles of mastication (masseter, temporal muscle and the medial/lateral pterygoids)
* Tensor tympani (anterior 2/3 tongue), tensor veli palatini, mylohyoid and digastric muscles
167
Which 3 aspects are involved in the assessment of CN V?
1. Sensory assessment
2. Motor assessment
3. Reflexes
168
Describe the steps of the sensory assessment of CN V exam
Ask the patient to **close their eyes** and say ‘yes’ each time they feel you touch their face.
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 branch V1
* Cheek → maxillary branch V2
* Lower jaw (avoid angle of mandible as is supplied by C2/C3) → mandibular branch V3
You should **compare** each region on both sides of the face to allow the patient to identify subtle differences in sensation.
169
Why should you avoid the angle of the mandible in sensory assessment of V3?
as it is supplied by C2/C3
170
Before the light touch and pinprick sensation assessment of CN V on the face, what should you do first? Why?
First, explain the modalities of sensation you are going to assess (e.g. light touch/pinprick) to the patient by demonstrating on their **_sternum_**. This provides them with **a reference of what the sensation should feel like** (assuming they have no sensory deficits in the region overlying the sternum).
171
What component of CN V are you assessing in the motor assessment part?
V3 - muscles of mastication
172
Describe the steps of the motor assessment of CN V exam
**1.** Inspect the **temporalis** (located in the temple region) and **masseter muscles** (located at the posterior jaw) for evidence of wasting.
**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.
173
During the inspection of temporalis and masseter muscles for wasting, where is evidence of wasting most noticeable?
In the temporalis muscles, where a **hollowing effect in the temple region** is observed.
174
What can an ability to open the jaw against resistance or deviation of the jaw (typically to the side of the lesion) indicate?
CN V palsy
175
What 2 reflexes are assessed in the CN V exam?
1. Jaw jerk reflex
2. Corneal reflex
176
What is the jaw jerk reflex?
The jaw jerk reflex is a stretch reflex that involves the slight jerking of the jaw upwards in response to a downward tap
177
What CN is involved in the jaw jerk reflex?
Both afferent and efferent pathways of the jaw jerk reflex involve the trigeminal nerve.
178
Who is the jaw jerk reflex exaggerated in?
patients with an **upper** motor neuron lesion
179
Describe the steps of assessing 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**
180
What is the corneal reflex?
The corneal reflex involves involuntary **blinking** of both eyelids in response to unilateral corneal stimulation (direct and consensual blinking).
181
What is the afferent and efferent branch of the corneal reflex pathway?
Afferent - V1 trigeminal
Efferent - temporal & zygomatic branches of CN VII
182
Describe the steps of the corneal reflex in assessment of CN V
**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.
183
What is the CNS location of CN VII (facial)?
Pontine-medulla junction
184
What skull foramina does CN VII enter/exit via?
Enter - internal acoustic meatus
Exit - stylomastoid foramen
185
What is the function of CN VII?
Motor - **muscles of facial expression** and the **stapedius** muscle
Sensory - conveyance of taste from anterior 2/3 of tongue
186
What 2 aspects are involved in the assessment of CN VII?
1. Sensory
2. Motor
187
What does the sensory assessment of CN VII involve?
Ask the patient is they have noticed any recent changes in their **sense of taste**.
188
What 3 aspects does the motor assessment of CN VII involve?
1. Hearing changes
2. Inspection of the face
3. Facial movement
189
Why are you asking about hearing changes in the motor assessment of CN VII?
Ask the patient if they’ve noticed any changes to the hearing.
## Footnote
Paralysis of the stapedius muscle can result in hyperacusis (noise sensitivity)
190
What are you inspecting the face for in CN VII assessment?
Inspect the patient’s face at rest for asymmetry, paying particular attention to:
* Forehead wrinkles
* Nasolabial folds
* Angles of the mouth
CN VII controls muscles of facial expression
191
During the ‘facial movement’ aspect of CN VII examination, ask the patient to carry out a sequence of facial expressions while observing for asymmetry.
What are these 5 facial expressions? What muscle does each assess?
* **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?”*
192
how does facial nerve palsy present?
with **unilateral weakness** of **the** [**muscles of facial expression**](https://geekymedics.com/muscles-of-facial-expression/)
193
Is facial nerve palsy caused by upper or lower motor neuron lesions?
Can be caused by both
194
What is the most common cause of LMN facial palsy?
Bell's palsy
195
How does facial palsy caused by LMN lesion (i.e. Bell's palsy) present?
Weakness of **all ipsilateral muscles of facial expression:**
* Orbicularis oculi muscle and facial muscles involved
* Unable to close eyes
* Weakness of angle of mouth
* Cannot elevate eyebrows
196
What is the most common cause of UMN facial palsy?
Stroke
197
How does an UMN facial palsy present (i.e. stroke)?
**Unilateral facial muscle weakness**, however, the **upper facial muscles are partially spared** because of **bilateral** cortical representation (resulting in forehead/frontalis function being somewhat maintained).
* Can elevate eyebrows
* Contralateral lower quadrant weakness (corner of mouth drops)
198
CNS location of CN VIII (vestibulocochlear)?
Cerebellopontine angle
199
Which skull foramina does CN VIII pass through?
Internal acoustic meatus
200
What is the function of CN VIII?
Hearing and balance from inner ear to brain (special sensory)
201
What 5 aspects are involved in the examination of CN VIII?
1. Gross hearing assessment
2. Rinne's test
3. Weber's test
4. Vestibular testing - Unterberger/Turning test
5. Vestibular testing - Head thrust test/Vestibular-ocular reflex
202
What is involved in the ‘gross hearing assessment’ of the CN VIII exam?
1. Ask the patient if they’ve noticed any change in the hearing recently.
2. Explain that you are going to say three words or three numbers and you’d like the patient to repeat them back to you (choose two-syllable words or bi-digit numbers).
203
Describe the steps of the gross hearing assessment
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.
