Cranial Nerve Palsies Flashcards
What are cranial nerve palsies?
They are defined as a lack of nerve function, which may cause partial weakness or complete paralysis of the areas severed by the affected nerve
What are the two functions of CN III?
It innervates four eye extra-ocular muscles to allow superior, inferior and medial eye movement
It innervates the sphincter papillae to produce pupil constriction and accommodation.
What are the eight causes of CN III palsy?
Diabetes Mellitus
Vasculitis (Temporal Arteritis, SLE)
Raised Intracranial Pressure
Posterior Communicating Artery Aneurysm
Cavernous Sinus Thrombosis
Weber’s Syndrome
Amyloid
Multiple Sclerosis
How is a raised intracranial pressure associated with CN III palsy?
It can cause herniation through the tentorium
What cause is indicated when CN III palsy is painful?
Posterior Communicating Artery Aneurysm
What are the five clinical features associated with CN III palsy?
Eye Deviation ‘Down & Out’
Superior Eyelid Ptosis
Pupil Dilatation
Pupillary Light Reflex Loss
Accommodation Loss
Why is ptosis a clinical feature of CN III palsy?
It results in paralysis of the levitator palpebrae superiosis muscle
Why do the eyes deviate down and out in CN III palsy?
This is due to the unopposed actions of the lateral rectus and superior oblique muscles
Why is pupil dilatation a clinical feature of CN III palsy?
This is due to interruption of the parasympathetic fibres to the sphincter pupillae, leaving the dilator pupillae unopposed
Why is accommodation loss a clinical feature of CN III palsy?
This is due to paralysis of the ciliary muscle
In CN III palsy, presenting with a large pupil, what is the most appropriate next step?
Urgent CT Brain
What is the general function of CN IV?
It innervates the superior oblique muscle to allow inferolateral eye movement
What are the four clinical features associated with CN IV palsy?
Vertical Diplopia
Torsional Diplopia
Eye Deviation ‘Upwards & Out’
Head Tilt
When does vertical diplopia occur in CN IV palsy?
When the patient reads a book or goes downstairs
What is vertical diplopia?
It results in defective downward gaze
What is torsional diplopia?
It results in the subjective tilting of objects
What are the two general functions of CN V?
It conveys facial sensation
It innervates the muscles of mastication
What are the five clinical features of CN V palsy?
Trigeminal Neuralgia
Corneal Reflex Loss
Facial Sensation Loss
Mastication Muscle Paralysis
Jaw Deviation
What side does the jaw deviate to in CN V?
It will deviate to the weakest side
What is the general function of CN VI?
It innervates the lateral rectus muscle to allow lateral eye movement
What is a cause of CN VI palsy?
Brain Metastases
What are the three clinical features of CN VI palsy?
Conjugate Lateral Gaze Disorder
Papilloedema
Internuclear Opthalmoplegia
What is another term for conjugate lateral gaze disorder?
Horizontal diplopia
What is conjugate lateral gaze disorder?
It is defined as defective abduction (medial deviation)
Specifically, when individuals look laterally in the direction of the affected eye, the affected eye will not be able to abduct
For example, in a lesion affecting the left eye, when looking to the left, the right eye will adduct and the left eye will remain in the middle as the muscle responsible for making it move laterally is not functioning
What is intranuclear ophthalmoplegia?
It refers to incoordination of eye movements
What are the four general functions of CN VII?
It innervates the muscles of facial expression
It innervates the scalp
It innervates the facial glands
It conveys taste sensation
What are the four UMN causes of CN VII palsy?
Stroke
Brain tumours
Pseudobulbar palsy
Motor neurone disease
What are the nine LMN causes of CN VII palsy?
Otitis media/externa
HIV
Lyme’s disease
Diabetes mellitus
Sarcoidosis
Multiple sclerosis
Gullian barre syndrome
Acoustic neuroma
Parotid tumours
What are the four causes of bilateral CN VII palsy?
Sarcoidosis
Guillain-Barre Syndrome
Lyme’s Disease
Bilateral Acoustic Neuromas (Neurofibromatosis Type II)
What are the six clinical features associated with CN VII palsy?
Facial Paralysis
Facial Weakness
Corneal Reflex Loss
Eye Dryness
Ageusia
Hyperacusis
What are the five types of facial paralysis associated with Bell’s palsy?
Loss of forehead wrinkling
Unable to lift eyebrows
Unable to close eye
Loss of nasolabial fold
Dropping of corner of mouth
What muscle paralysis results in loss of forehead wrinkling?
Frontalis
What muscle paralysis results in drooping of the eyebrow?
Levitator palpebral superioris
What muscle paralysis results in permanent opening of the eye?
Orbicularis oculi
What muscle paralysis results in loss of the nasolabial fold?
Levitator labii superiorois
What muscle paralysis results in drooping of the corner of the mouth?
Oribularis oris
What is hyperacusis?
It s defined as features of everyday sounds seeming much louder than they should
What is ageusia?
It is defined as a decreased sensation of taste
What clinical feature is associated with an UMN lesion of CN VII?
The forehead will be spared, and the patient can move their forehead on the affected side
Why is the forehead spared in an UMN lesion?
This is due to the bihemispheric innervation of the facial nerve nuclei that send axons innervating the frontalis muscle, so that when one hemisphere is damaged the other can continue the function, but not for the lower half of the face
What clinical feature is associated with an LMN lesion of CN VII?
The forehead will not be spared, and the patient cannot move their forehead on the affected side
What is Bell’s palsy?
It is defined as idiopathic facial nerve palsy, in which there is no known cause for the damage caused to the facial nerve
Is Bell’s palsy - acute or chronic?
Acute
Is Bell’s palsy - unilateral or bilateral?
Unilateral
Is Bell’s palsy - UMN or LMN?
LMN
Which age group tends to be affected by Bell’s palsy?
30 - 45 years old
What are the four risk factors of Bell’s palsy?
HSV Infection
Diabetes
Pregnancy
Hypertension
What are the three additional clinical features of Bell’s palsy?
Bell’s phenomenon
Synkinesis
Crocodile tears
What is Bell’s phenomenon?
It refers to the movement of the eyeballs in an upward direction when the eyelids are forcefully closed
What synkinesis?
It occurs when when the damaged axons regrow, however target the wrong muscle
This results in involuntary movement occurring at the same time as a voluntary movement, such as when someone blinks, the corner of their mouth will move upwards at the same time
What is another term for crocodile tears?
Autonomic synkinesis
What is crocodile tears?
This occurs when the axons of the salivary glands regrow to the lacrimal gland
This results in the production of tears whenever someone is hungry or smells food
What are the two treatments for Bell’s palsy?
Prednisolone
Lubricating Eye Drops
What dose of prednisolone is given when Bell’s palsy is detected within 72 hours of onset?
We administer oral prednisolone 50mg/d for ten days
OR
We administer oral prednisolone 60mg/d for five days, followed by a five day reducing regime of 10mg a day
Why do we administer Bell’s palsy patients lubricating eye drops?
In order to prevent the affected cornea from drying out and becoming damaged
How else do we protect the cornea in Bell’s palsy patients?
We advise these patients to cover the affected eye at night
What do we do if Bell’s palsy patients develop eye pain?
A referral to ophthalmology is required to investigate for exposure keratopathy
What is the most appropriate next step in cases where Bell’s palsy shows no improvement after 3 weeks of treatment?
An urgent referral to ENT
What is Ramsay Hunt syndrome?
It is defined as facial nerve palsy caused by the herpes zoster virus (HSV)
Is Ramsay Hunt syndrome - unilateral or bilateral?
Unilateral
Is Ramsay Hunt syndrome - UMN or LMN?
LMN
What additional clinical feature is associated with Ramsay Hunt syndrome?
A painful and tender vesicular rash in the ear canal, pinna and around the ear on the affected side
This rash can extend to the anterior two thirds of the tongue and hard palate
What are the three pharmacological treatment options of Ramsay Hunt syndrome?
Prednisolone
Aciclovir
Lubricating Eye Drops
What is the first line management option of Ramsay Hunt syndrome?
Oral aciclovir for 7 days
AND
Oral prednisolone for 5 days
What is the general function of CN VIII?
To allow hearing and balance
What are the four clinical features associated with CN VIII palsy?
Hearing Loss
Vertigo
Nystagmus
Acoustic Neuromas
What are acoustic neuromas?
They are Schwann cell tumours of the cochlear nerve
What are the three general functions of CN IX?
It innervates the parotid gland to allows salivation and swallowing
It mediates input from the carotid body/sinus
It conveys taste sensation from the posterior third of the tongue
What are the two clinical features associated with CN IX?
Carotid Sinus Hyperreflexia
Gag Reflex Loss
What are the four general functions of CN X?
It allows phonation
It allows swallowing
It conveys taste sensation from the epiglottis and palate
It transmits visceral sensation
What are the two clinical features associated with CN X palsy?
Uvula Deviation
Gag Reflex Loss
What side does the uvula deviate to in CN X palsy?
It will deviate away from the site of lesion
What is the general function of CN XI?
It innervates the sternocleidomastoid and trapezius muscles to allow head and shoulder movement
What are the two clinical features of CN XI palsy?
Head Movement Weakness
Shoulder Movement Weakness
What side does head/shoulder weakness occur on in CN XI palsy?
Contralateral side to lesion
What is the general function of CN XII?
It innervates the intrinsic and extrinsic muscles of tongue to allow tongue movement
What is the clinical feature associated with CN XII palsy?
Tongue deviation
