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