Cranial nerves Flashcards
3 parts of brainstem?
midbrain, pons, medulla
example of disease in which lesion is in the brainstem?
MS- may also affect optic tract
example of disease in which lesion at NMJ?
myasthenia gravis: AI destruction of end-plate ACh receptors by autoantibodies
what can be given to treat myasthenia gravis?
AChesterase inhibitors e.g. neostigmine- more ACh around to bind to end-plate receptors so less likely that autoantibodies will bind so less receptors destroyed
how is 1st cranial nerve tested for?
ask patient if they have noticed any changes in their sense of smell, can test ability of each nostril to distinguish smells e.g. peppermint- left nostril supplied by L olfactory nerve, R by R nerve, but patient may think that they can smell fine if sense of smell only lost from inside 1 nostril
how is 2nd cranial nerve tested for?
visual acuity: snellen chart, test each eye separately
visual fields: movement of finger from side
pupils: size, shape, symmetry, pupillary response to light- sensory limb= optic nerve, motor limb= oculomotor, and accomodation reflex
opthalmoscopy- view optic disc- pale or swollen- papilloedema?
remember to check if patient normally wears glasses, can ask to put these on if so.
how are 3rd, 4th and 6th cranial nerve tested for?
eye movements- H shape with finger
characteristics of oculomotor nerve palsy?
down and out eye, dilated pupil (mydriasis), ptosis (full), loss of accomodation reflex, loss of pupillary reflex
common infection of the trigeminal nerve and how does this occur?
Shingles- herpes-zoster infection
Reactivation of the latent varicella-zoster virus in dorsal root ganglia, possible as a result of a compromised IS e.g. on corticosteroids. Virus causes chickenpox, and then remains latent in the body located in the dorsal root ganglion= location of cell body of 1st order afferent neurones in acsedning tracts of somatosensory system.
causes of space occupying lesions (SOLs)?
tumour abscess aneurysm cyst chronic SD haematoma granuloma
signs of SOLs?
headaches- worse on walking and lying down vomiting seizures irritability papilloedema
functions of frontal lobe?
memory
voluntary movements
functions of parietal lobe?
speech
functions of temporal lobe?
sound awareness
functions of occipital lobe?
interpretation of visual stimuli
clinical presentation of SOL in frontal lobe?
hemiparesis
dysphasia
personality change
what is guillain barre syndrome?
IS attack on part of peripheral nervous system
pathophysiology of Parkinson’s?
degeneration of dopaminergic neurones in substantia nigra pars compacta
3 cardinal signs of Parkinson’s disease?
resting tremor
bradykinesis
muscular rigidity
causes of bilateral hemianopia?
optic chiasm compression e.g. pituitary adenoma and ICA aneurysm
what is a homonymous hemianopia and what are its causes?
1/2 of visual field lost in each eye which is contralateral to the side of lesion. Lesions lie beyond chiasm in tracts, radiation, or occipital cortex e.g. stoke, tumour, abscess
causes of nystagmus?
involuntary eye oscillations, often jerky.
vestibular lesion- acute- nystagmus away from lesion, chronic=towards
cerebellar lesion- if unilateral, nystagmus is towards affected side
MS
up and down nystagmus- maybe midbrain lesion
causes of optic neuritis?
pain on movement of eye, loss of central vision
demyelination e.g. MS
syphilis- can also cause poster column degenerative changes, leading to loss of fine touch and conscious proprioception- causes +ve Romberg sign and sensory ataxia.
causes of papilloedema (swollen optic disc)
tumour
abscess
hydrocephalus
idiopathic IC hypertension
how might the oculomotor nerve be compressed alone?
uncal herniation (part of parahippocampal gyrus) also tumour, and aneurysm of posterior communicating artery along with other nerves e.g. abducens and trochlear- could be cavernous sinus thrombosis and superior orbital fissure lesion.
which side of the brain is dominant in most people?
left, * write with right hand
so Broca’s area and Wernicke’s area for speech usually on L side of brain. visual fields affected?
how can mild ptosis in horner’s syndrome be overcome by patient?
if patient looks up
what ptosis generally occurs with myasthenia gravis?
bilateral partial ptosis
* contrast to unilateral full ptosis with oculomotor nerve lesion, and unilateral partial ptosis with Horner’s syndrome.
causes of conductive hearing loss?
otitis externa acute otitis media chronic otitis media with effusion foreign body ruptured TM otosclerosis cholesteatoma
causes of sensori-neural hearing loss?
meniere’s disease
vestibular schwanoma
damage to hair cells by loud noises
hair cell death by ototoxic drugs e.g. gentamicin and furosemide
what am I looking for on general inspection of pateint?
pain/discomfort
facial asymmetry
loss of expression
muscle wasting
what might patient with trochlear nerve palsy complain of?
diplopia (double vision) on looking down and in, often noticed on descending stairs, head tilting compensates for this- head tilted away from side where superior oblique affected.
resting gaze of someone with trochlear nerve palsy?
eye slightly elevated
SO normally causes depression when the eye is adducted
patient has +ve weber’s test in right ear, and +ve rinne’s tests in both ears, what type of hearing loss?
left ear sensorineural hearing loss
a patient has right ear conductive hearing loss, what would their results be with weber’s and rinne’s?
weber's= sound heard loudest in right ear rinne's= rinne +ve in left ear, and rinne -ve in right ear= sound heard loudest when tuning fork placed on mastoid process compared to when placed just in front of the EAM.
resting gaze of someone with abducens nerve palsy?
slightly adducted
functions of superior oblique muscle?
intorsion of eye when abducted, depression of eye when adducted
functions of inferior oblique muscle?
extorsion of eye when abducted, elevation of eye when adducted
functions of superior rectus muscle?
elevation of eye when abducted, intorsion of eye when adducted
functions of inferior rectus muscle?
depression of eye when abducted, extorsion of eye when adducted
problem patient may complain of if abducens nerve palsy?
horizontal double vision (diplopia) when looking outwards
if damage to trigeminal nerve, what would happen when patient asked to open their mouth?
jaw would deviate towards side of lesion
on asking ptnt to say ‘aaahh’ what would happen to the uvula if lesion of the left vagus nerve?
palate pulled to normal side, so the right.
causes of olfactory nerve lesions?
frontal love tumour
meningitis
respiratory tract infection, common cold
trauma e.g. fracture of cribiform plate of ethmoid bone- would also expect CSF rhinorrhoea
smell loss= anosmia
causes of monocular blindness?
lesion of 1 eye or optic nerve e.g. MS, giant cell arteritis
causes of bilateral blindness?
neurosyphillis
causes of optic atrophy (pale optic discs and reduced acuity)?
MS
frontal tumours
cause of oculomotor nerve palsy without dilated pupil?
diabetes mellitus
hypertension
cause of oculomotor nerve palsy with down+out eye, ptosis AND dilated pupil?
tumour
posterior communicating artery from ICA (anterior circulation to brain) aneurysm
causes of damage to just trochlear or abducens nerve alone?
trochlear= trauma to orbit abducens= MS, pontine stroke
what may cause sensory loss in face?
herpes zoster
nasopharyngeal cancer
cause of LMN lesion of facial nerve?
bell’s palsy
skull fracture
infection e.g. herpes zoster
acoustic neuroma
causes of UMN lesion of facial nerve?
stroke
tumour
causes of glossopharyngeal, vagus and hypoglossal nerve individual damage?
neck tumours
trauma
brainstem lesions
causes of accessory nerve damage?
trauma
tumour
stroke
polio
cause of damage to both IX,X and XI cranial nerves?
jugular foramen lesion
what features of parkinson’s disease might you see on a patient when doing a cranial nerve examination?
lack of facial expression
as muscles in face become rigid*
causes of optic neuritis?
multiple sclerosis
drugs e.g. isoniazid
motor component of glossopharyngeal nerve?
supplies stylopharyngeus muscle= elevates pharynx during swallowing and speech
skeletal muscles innervated by vagus nerve?
cricothyroid intrinsic laryngeal muscles palatopharyngeus salpingopharyngeus 3 constrictors of the pharynx
