Cranial Nerve Lesions Flashcards
Which two extraocular muscle are NOT innervated by the oculomotor nerve
Lateral rectus
Superior oblique
What muscle is responsible for lifting the upper eyelid and what nerve innervates it
- Levator palpebrae
- Oculomotor
How does a 3rd nerve palsy present
- Ptosis and squint
- Fixed dilated, non-reactive pupil
- Eye pulled down and out
- Diplopia
How does a 3rd nerve palsy cause a dilated, non-reactive pupil
The oculomotor nerve carries parasympathetic fibres that innervate the circular muscles of the iris
What does a 3rd nerve palsy that spares the pupil suggest (2)
Microvascular cause
* DM
* HTN
* Ischaemia
Give 5 causes of third nerve palsy
- diabetes mellitus
- vasculitis e.g. temporal arteritis, SLE
- raised ICP can cause a third nerve palsy due to uncal herniation
- posterior communicating artery aneurysm (pain)
- cavernous sinus thrombosis
What extraocular muscle does the trochlear nerve supply
Superior oblique
What are 3 functions of the superior obliques
- Primary: Intorsion
- Depression
- Abduction
How does a trochlear nerve palsy present
- Affected eye deviates upwards and slightly out
- Affected eye elevates further as it moves medially
- Vertical diplopia
What extraocular muscle does the abducens nerve supply
Lateral rectus
How does a 6th nerve palsy present
- Affected eye turns inwards at primary position
- Unable to abduct affected eye but can adduct
- Horizontal diplopia when looking far away or in the direction of the affected eye
How may patients with a 4th nerve palsy compensate for vertical diplopia
Head tilt to better align the eyes and reduce the diplopia
4 ways a trigeminal nerve palsy may present
- paralysis of chewing muscles
- deviation of jaw to weak side
- Loss of corneal reflex (afferent)
- trigeminal neuralgia
5 ways a facial nerve palsy may present
- Ipsilateral paralysis of face
- Facial droop
- increased sensitivity to sound
- Loss of taste
- loss of corneal reflex (efferent)
What does the facial nerve supply sensory innervation to
Anterior 2/3 of the tongue
Give 4 causes of bilateral facial nerve palsy
- sarcoidosis
- Guillain-Barre syndrome
- Lyme disease
- bilateral acoustic neuromas
Give 5 causes of a unilateral facial nerve palsy
- Bell’s palsy
- Ramsay-Hunt syndrome (due to herpes zoster)
- acoustic neuroma
- parotid tumours
- HIV
How could you differentiate between a facial nerve palsy caused by an UMN lesions and a LMN lesion
- UMN lesion ‘spares’ upper face i.e. forehead
- LMN lesion affects all facial muscles
3 ways a vestibulocochlear palsy may present
- Hearing loss
- Tinnitus
- Loss of balance, vertigo
Give 4 way a 9th/10th cranial nerve palsy may present
- Difficulty swallowing
- loss of gag reflex
- Deviation of uvula away from the side of damaged nerve (vagus)
- Hoarseness
How does an accessory nerve palsy present
weakness turning head to contralateral side
Give 3 ways a hypoglossal nerve palsy may present
- Tongue fasciculations
- Deviation to side of lesion when tongue is protruded
- Ipsilateral tongue wasting
What is bell’s palsy
unilateral, idiopathic, LMN facial nerve palsy
Describe the epidemiology of bell’s palsy
- peak incidence 20-40 years
- more common in pregnant women
Describe the features of Bell’s palsy
- LMN facial nerve palsy -> forehead affected
- altered taste
- dry eyes
- post-auricular pain
How is Bell’s palsy managed
- eye care: drops, lubricants and night time taping
- oral prednisolone within 72 hours of onset
- if the paralysis shows no sign of improvement after 3 weeks, refer urgently to ENT
