Cranial Nerve Examination Flashcards
What is the difference between a medical and surgical third nerve palsy? Name some causes of each.
A medical third nerve palsy classically spares the pupil, whereas a surgical third nerve palsy causes pupillary dilation. The pupil is usually sparred in medical causes because the fibres that control the pupil are contained within the outermost layer of the nerve, and are less prone to ischaemia than the inner parts of the nerve. In surgical/compressive causes, the whole nerve is involved.
Medical (classically pupil-sparing), M’s:
Microvascular ischaemia (diabetes)
Migraine
MS/autoimmune disorders
Surgical (classically painful), C’s:
Posterior Communicating artery aneurysm (classic cause)
Cavernous sinus lesion
Cancer (SOL)
Discuss how you would clinically distinguish between an LMN facial nerve lesion and a UMN facial nerve lesion, and comment on why they present differently
An UMN facial nerve lesion spares the forehead, because the nucleus controlling the upper part of the face has bilateral UMN innervation, whereas the lower part of the face has only contralateral UMN innervation.
A LMN facial nerve lesion causes weakness of the whole side of the face, because the LMN innervates the whole side. If this nerve is damaged, there is no innervation at all.
Please list three causes of a unilateral facial nerve lesion, and two causes of bilateral facial nerve lesions.
Causes of a unilateral facial nerve lesion:
Bell’s palsy
Ramsay Hunt syndrome
SOL (e.g. acoustic neuroma, facial nerve tumour, meningioma)
Lyme disease
Nerve infiltration (TB, sarcoidosis, lymphoma)
Parotid tumour/surgery
Causes of bilateral facial nerve lesions:
Lyme disease
Sarcoidosis
Guillain-Barré syndrome
Amyloidosis
What are the stages of diabetic retinopathy and characteristic findings of each stage?
Background: microaneurysms (dots), haemorrhages (blots), hard exudates (lipid deposits)
Pre-proliferative: cotton wool spots (infarcts)
Proliferative: new vessels
Advanced: retinal fibrosis
Maculopathy: macular oedema
What are the grades of hypertensive retinopathy and characteristic findings of each grade?
Grade 1: silver wiring
Grade 2: AV nipping
Grade 3: flame haemorrhages and cotton wool spots
Grade 4: papilloedema
What are the definitions of these pupil abnormalities: miosis, mydriasis, anisocoria?
Miosis: constricted pupil
Mydriasis: dilated pupil
Anisocoria: unequal pipil sizes
What are the definitions of these refractive abnormalities: hyperopia, myopia, presbyopia, astigmatism?
Hyperopia: far (long) sighted – eyeball too short
Myopia: near (short) sighted – eyeball too long
Presbyopia: inability to accommodate for near vision with age due to lens thickening
Astigmatism: deviation in shape of cornea (like back of spoon) resulting in inability to focus light rays from different planes
What is oscillopsia?
Visual disturbance in which there is a to-and-fro movement (oscillation) of the visual fields.
What are the clinical findings of a internuclear ophthalmoplegia due to a right medial longitudinal fasciculus lesion?
Patient can look to the right normally (right eye abducts normally and left eye adducts normally). However, when the patient looks to the left (contralesional side):
– Right eye has adduction deficit (partial/complete)
– Left eye has horizontal abducting saccades/nystagmus
Please list three risk factors for ischaemic stroke
Age, AF, diabetes, hypertension, obesity, hypercholesterolaemia, smoking, obesity, family history
Please list three risk factors for haemorrhagic stroke
Age, anticoagulation, alcohol, hypertension, stress, smoking
Which type of stroke do carotid and vertebral artery dissections cause? When should you suspect dissection as a cause?
– Carotid artery dissection is a cause of anterior circulation stroke
– Vertebral artery dissection is a cause of posterior circulation stroke
– Think about dissection if there is neck pain, the patient is young or there is associated trauma
What is pyramidal weakness?
Pyramidal weakness is weakness that preferentially spares the antigravity muscles, i.e. weakness of upper limb extensors and lower limb flexors resulting in flexed upper limbs and extended lower limbs. It is part of the upper motor neuron syndrome.
How is neurofibromatosis diagnosed?
Diagnosed on clinical features and MRI. Genetic tests also available but may not pick up all cases.
How is neurofibromatosis managed?
– Lifelong annual monitoring: vision, heart and blood pressure, hearing
– Treat complications
– Education
Causes of CN1 palsy
Cauess of CN 2 palsy
Causes of CN3 palsy
Causes of CN 4 palsy
Causes of CN 5 palsy
Causes of CN 6 palsy
Causes of CN 7 palsy
Causes of CN 8 palsy
Causes of bulbar palsy
Why is the pupil spared in diabetic oculomotor palsy?
Features of cerebellopontine angle tumour? Which CNs involved?
Features of Paget’s disease of bone on CN exam? Which CNs involved?
Features of Gradenigo’s syndrome on CN exam? Which CNs involved?
Features of syringobulbia on CN exam? Which CNs involved?
Features of cavernous sinus thrombosis on CN exam? Which CNs involved?
Causes of ANY cranial nerve palsy
∆∆ptosis
Features of CN3 palsy
Actions of the extra-ocular muscles
∆∆ ophthalmoplegia
Describe internuclear ophthalmoplegia
∆∆ internuclear ophthalmoplegia
Interpretation of Rinne and Weber tests
Causes of cerebellar disease?
Classical signs of cerebellar lesion?
Features of cerebellar limb ataxia?
Localising the cerebellar lesion?
∆∆ nystagmus
∆∆ dysarthria
Wernicke’s encephalopathy
Recall 2 causes of pupil asymmetry that you may see on cranial nerve examination
Horner’s: causes small reactive pupil
CN III palsy: causes large pupil
How far away from a Snellen chart should the patient stand for visual acuity testing?
6 metres
In what pathology is RAPD seen?
Optic neuritis (eg MS)
Recall 3 causes of ptosis
CNIII pathology
Horner’s
Myasthaenia gravis
Name the 3 branches of the trigeminal nerve
Ophthalmic
Maxillary
Mandibular
Which branch of the trigeminal nerve has a motor element, and what does it control?
Mandibular
Muscles of mastication
Which cranial nerve forms the afferent and efferent limbs of the corneal reflex?
Afferent = CNV Efferent = CNVII
Which portion of the tongue gets its sensory supply (taste) from the facial nerve?
Anterior two thirds
How can facial nerve palsy affect hearing?
Supplies stapedius muscle. If this is damaged –> hyperacusis
How can the vestibular function of CNVIII be tested?
Turning test - Ask the patient to march on the spot with eyes closed and arms outstretched. If there is a lesion, they will turn towards it.
Recall the direction of deviation of the tongue and the uvula when there is a lesion
Tongue: towards lesion (CNXII)
Uvula: away from lesion (CNX)
How can the olfactory nerve be tested?
Ask them to smell coffee/ nail varnish/ vanilla essence
Must test BOTH nostrils
How can the sensory portion of the optic nerve be tested?
- Assess acuity with Snellen chart (or ask them to read time off clock behind you)
- Assess colour vision using Ishihara plates
- Assess for neglect/ inattention by holding your hands out in periphery of vision and wiggling fields on each side and then both at same time and asking pt which side you are wiggling fingers on
- Assess fields - nb. these are CIRCULAR so you need to start behing the patient and come forwards as well as up and down
How can the motor function of the optic nerve be tested?
Nil
How can the optic nerve reflexes be tested?
- Direct and consensual light reflexes - shine pen torch into eye and assess for constriction of ipsilateral and then contralateral pupil
- Swinging light test (more info on a different card)
- Test accommodation reflex (normal –> BL convergeance and constriction)
How should the swinging light test be performed?
- Ask the patient to look at a far away object to prevent the pupil constricting due to accommodation
- Shine the beam into the first eye for at least 3 seconds, to allow the pupil to stabilise
- Observe the other – eye – does it also constrict?
- Move the beam to the other eye, quickly but not straight across the nose
- Hold for 3 seconds again, note – does the pupil being illuminated stay the same size or get bigger?
- Repeat for the other eye
If a RAPD is present, then when the light is shone into the affected eye the pupils will constrict a little but not fully, due to the afferent defect. When you then shine into the unaffected eye, the pupils will both constrict further.
How can the motor function of the oculomotor nerve be assessed?
Mnemonic: Are Pupils Moving Nice and Smoothly?
- Look for pupil Asymmetry - abnormally large pupil may be due to CN III palsy
- Inspect for Ptosis
- Assess eye Movements (H test)
- Assess for Nystagmus
- Assess for Saccades
How can you assess for nystagmus and saccades?
Get them to follow your finger (smooth pursuit?) until gaze is lateral and then hold to see if there is nystagmus.
To assess for saccades, then get them to look from your hand on one side to your pen on the other very quickly.
How does a trochlear nerve palsy appear?
Vertical diplopia when looking inferiorly due to superior oblique dysfunction
How does an abducens nerve palsy appear?
Due to lateral rectus palsy, there is unopposed adduction which causes a convergent squint
How can eye movements be tested?
Rather than H test, best to check horizontal, then vertical, then down and out eye movements as this isolates the movements controlled by CNIII, IV (down and out) and VI (abduction).
Remember to ask about pain and double-vision – if there is double vision, ask them to cover each eye in turn to see which one produces the more’ real’ image (and therefore which is responsible for creating the ‘false’ 2nd image).
How can the sensory portion of the trigeminal nerve be tested?
Need to test ophthalmic, mandibular and maxillary branches (lateral aspect of forehead, cheek and lower jaw) by lightly touching these areas bilaterally and comparing each side of face.
Nb UMN lesions will be forehead-sparing.
How can the motor function of the trigeminal nerve be assessed?
Palpate the muscles of mastication - temporalis and masseter
How can the trigeminal nerve reflexes be assessed?
Corneal reflex: you need to put the cotton wool over the black bit of the pupil as this is the cornea, not the white bit (sclera) of the eye (CNVII is efferent)
Jaw jerk: put thumb on chin with patient’s mouth open and tap thumb with tendon hammer. Should cause slight closure of the mouth.
How can the sensory portion of the facial nerve be tested?
Ask if any changes in taste
How can the motor function of the facial nerve be assessed?
Ask about any change in hearing (innervates stapedius)
Also facial movements
How can the facial nerve reflexes be tested?
Facial nerve supplies efferent limb of corneal reflex
How can the sensory function of the vestibulocochlear nerve be assessed?
- Check vestibular function - ask patient to march on spot with arms out and eyes closed - if there is a lesion they will turn towards it
- Rinne’s and Weber’s with 512Hz tuning fork
If in both ears, Rinne’s demonstrates air conduction is better than bone condution, what type of hearing loss is it if Weber’s lateralises to one side?
Sensorineural loss in the ear they hear it more quietly in (so opposite side to one Webers lateralises to)
If Rinne’s shows bone conduction is better than air conduction in one ear, and Weber’s lateralises to the same ar, what sort of hearing loss is it?
Conductive
If Rinne’s shows bone conduction is better than air conduction in one ear, and Weber’s lateralises to the opposite ear, what sort of hearing loss is it?
Combined sensorineural and conductive hearing loss in ear where Rinne’s is abnormal
If Rinne’s shows bone conduction is better than air conduction in BOTH ears, and Weber’s does not lateralise, what sort of hearing loss is it?
Conductive loss in both ears
If Rinne’s shows bone conduction is better than air conduction in BOTH ears, and Weber’s lateralises left, what sort of hearing loss is it?
Combined loss in right ear and conductive loss in left
How can the motor function of the glossopharyngeal nerve be assessed?
Ask the patient to swallow some water – if there is a change in voice or a cough, it may suggest an ineffective swallow (afferent CNIX, efferent CNX)
How can the motor function of the vagal nerve be assessed?
Uvula deviation AWAY from the lesion
How can the vagal nerve reflexes be tested?
Gag reflex
How can the motor function of the accessory nerve be tested?
Test sternocleidomastoid and trapezius against resistance
How can the motor function of the hypoglossal nerve be assessed?
Assess for tongue deviation - it will be TOWARDS the lesion
Also assess for wasting/ fasciculations
