Cranial Nerves examination Flashcards
Where is the most likely place of lesion for a RAPD (relative afferent pupillary defect)
lesion of the optic nerve (between the retina and the optic chiasm
Both pupils constrict to light regardless of which pupil is illuminated. In RADP however, the … is damaged meaning whatever light the dominant eye is exposed to determines both pupil size.
CN 2 Optic nerve
How does RAPD manifest itself?
inappropriate pupillary dilation with light shining on.
How would a CN 3 lesion manifest itself? (3)
Ptosis
Dilated pupil
Eye out and downwards pointing
The … muscle is responsible for ptosis and it is innervated by CN …
levator palpebrae superioris
3
CN3 (via Edinger-Westphal–>ciliary ganglion; parasympathetic) controls accomodation via … muscles and pupillary constriction via … muscle.
Ciliary muscles
Sphincter pupillae
how would a trochlear nerve lesion present
Diplopia on looking down and in.
How do you remember the muscles innervated by CN4 and CN6
SO4LR6
CN3 lesion presents how
Horizontal diplopia on looking outwards
Horizontal nystagmus indicates … lesion
vestibular
Nystagmus can be normal in which 2 circumstances
2 or less oscillations
at the extremes of gaze
Acute horizontal nystagmus is present when pointed towards or away from the lesion??
Away
Chronic vestibular horizontal nystagumus is present when the eyes point…
Towards the lesion
Cerebellar lesion nystagmus will present with uni or bilateral lesion
Unilateral lesion
Cerebellar lesions present with nystagmus towards/away from affected side
Towards
How would Foramen Magnum lesions present ocularly
Downbeat nystagmus
Upbeat nystagmus is indicative of lesions of (2)
Midbrain
Base of 4th ventricle
What may also be present if ocular problems are present with tinnitus or deafness
CN 8 lesion (a peripheral cause)
How would you check pterygoids (CN5)
Opening jaw against resistance (jaw deviates to weak side)
how would you check masseters
Clench (feel for mass)
CN7 UMN lesions are represents in which 3rds of the face
The lower 2/3s on the contralateral side
What is the result of the forehead having bilateral representation in the brain?
UMNL are only represented in the lower 2/3s of the face. (unless bilateral identical lesions - Low % chance!!)
IN CN7 LMN lesions what parts of the face will be affected
Ipsilateral full 3/3s of face.
Describe Bell’s Sign
upgaze on attempted eye closure
When would you see bell’s sign
Facial nerve palsy (e.g. Bells)
What 2 non-facial questions could you ask to elucidate any CN7 palsys
Troubled by loud noises
noticed any change in taste
Why might a patient with a CN7 palsy have noticed a change in taste.
The chorda tymapani (a branch of 7) supplies the anterior 2/3s of tongue
Why might a patient with a CN7 palsy be troubled by loud noises
Prevents excessive movement of stapes. Reduced amplitude, dampens noise.
What is the mneumonic to remember Rinnes test.
SNAC-RIP
In what circumstances would air conduction>bone conduction (2)
Normal
Sensorineural hearing loss (SNHL)
In severe sensorineural hearing loss bone conduction is … than air conduction. Outline the pathophysiology.
>
Other cochlea picks up sound via conduction
If sound is similar in both ears when performing Webers test what can this mean (2)
Normal
Bilateral SNHL
In conductive hearing loss on which side would the sound localise during Webers
Affected (because the ambient noise in the room is masked so it sounds louder)
In SNHL hearing loss on which side would the sound localise during Webers
Contralateral
Vagus nerve lesions cause the … to be pulled … from the side of the lesion
palate (look at uvula)
away
The tongue is innervated by CN… and deviates …. the side of the palsy
12
Towards
What are the 3 ∆∆ of bilateral ptsosis
Myasthenia gravis
Myotonic dystrophy
congenital
What are the 3 ∆∆of unilateral ptosis
Horners syndrome
Congenital
CN 3 palsy
What cranial nerves can Pagets disease of the bone affect (3)
V
VII
VIII
What is the most common CN to be affected in Pagets
8
50% get hearing loss
Which 4 cranial nerves pass along the lateral wall of the cavernous sinus
III
IV
V (V1 and V2 only)
Which CN runs with the internal carotid artery through the cavernous sinus centre
Abducens
What would be the motor nerves affected in a cavernous sinus thrombosis.
III
IV
VI*
*most common
How might a cavernous sinus thrombosis present in sensory terms?
V1 and V2 pain (most frequently ophthalmic)
Which reflex may be lost in a cavernous sinus thrombosis
Corneal reflex
A cavernous sinus thrombosis may a present with what general clinical signs on top of motor and sensory signs (3)
Proptosis
peri-orbital oedema
headache
Syringobulbia: what would be the signs/symptoms you’d expect in VIII affection
Vertigo/nystagmus
Syringobulbia: what would be the signs/symptoms you’d expect in V affection
pain or sensory loss
What CN a part of a ‘Bulbar Palsy’
9,10,11,12
In syringobulbia which CN nerve is specifically spared
7
