cranial nerves: clinical Flashcards
what would a fracture to the cribiform plate result in?
anosmia - loss of sense of smell
most common cause of anosmia?
URTI
head injuries e.g. shearing forces / basilar skull fracture
how will you fracture the cribiform plate?
from anterior cranial fossa trauma
what can fracture to the cribiform plate also result in?
leakage of CSF through the nose (rhinorrhoea)
what can rhinorrhoea lead to?
brain infections, including meningitis
what is common with viral / allergic rhinitis?
transient olfactory impaiment
what can fracture to the optic canal damage?
the optic nerve
what does damage to the optic nerve result in?
loss to papillary constriction
complex pathway from retina to visual cortex - occipital lobe
Different lesions to optic nerve give rise to?
different patterns of visual loss:
e.g. optic neuritis, pituitary tumour, stroke
pressures on the optic pathway result from?
raised intracranial pressure / loss of blood from the central artery of the retina
what can pressures on the optic pathway result in
blurring of the margins of the optic disc and subsequent visual field defects
what is swelling of the optic disc? result from?
papilloedema
from pressures on the optic pathway
causes of compression on the optic pathway? leading to?
pituitary adenomas / carotid aneurysm
cause visual field defects
lesions to oculomotor nerve results in?
diplopia (double vision) ptosis (drooping eyelid) pupillary dilation (absent papillary light reflex)
what can damage to oculomotor nerve be a result of?
cavernous sinus thrombosis
aneurysm (of the posterior cerebral / superior cerebellar artery)
raised intracranial pressures
diabetes / hypertension (pupil sparing)
is trochlear nerve (CN IV) usually damaged?
rarely paralysed alone
how can you usually correct damage to trochlear nerve?
slight tilt of the head
what is the most common cause of trochlear nerve (IV) damage?
head injury - most common cause of acute injury
OR
raised ICP can stretch nerve
what can damage to trochlear nerve (IV) result in?
diplopia (double vision) - worse on downward gaze e.g. reading / walking downstairs
(eyeball can become slightly adducted and superiorly rotated)
what is a cause of trochlear nerve (IV) damage in children?
congenital nerve palsy
what can result in damage to the trigeminal nerve (V)?
trauma, tumour, aneurysms, meningeal infections, shingles, trigeminal neuralgia
what is trigeminal neuralgia?
intense pain from very light touch to certain divisions of trigeminal nerve on the face
what does trigeminal neuralgia affect?
affects the sensory root of CN V and produces excruciating and episodic pain to the maxillary or mandibular divisions of the nerve
what does damage to trigeminal nerve result in?
paralysis to muscles of mastication, loss of sensation to face, loss of corneal and sneezing reflex
(afferent limb of corneal reflex)
which infection can affect CN V?
herpes zoster infection
commonly affects opthalmic division (CN V1)
what can result in damage to abducens nerve (CN VI)?
any raised intracranial pressure e.g. bleed / tumour
what can damage to abducens result in (CN VI)? why?
abducens has long intradural course
result in diplopia (double vision) + adduction of eye
how else can abducens be damaged aside from raised intracranial pressure? (CN VI)
aneurysm to the cerebral arterial ring at the base of the brain
increase in pressure in the cavernous sinus from atherosclerotic changes in ICA
septic thrombus in the cavernous sinus secondary to infection in the paranasal sinuses
what is the most common presenting condition for facial nerve (CN VII)?
facial nerve palsy - entire drooping of 1 side of face
e.g. Bell’s palsy
how can damage to facial nerve occur? why?
branches of CN VII are superficial, subkect to knife wounds, cuts, birth injury
what else can cause damage to facial nerve?
fracture to the temporal bone - usually presents immediately
what can a central lesion of CN VII (lesion of CNS) result in?
paralysis of muscles in the inferior face on contralateral side
why is forehead wrinkling not visibly impaired in facial nerve injury?
innervated bilaterally
which type of tumour can result in facial nerve (CN VII) injury?
parotid tumous
which nerve has a close relationship with the facial nerve (CN VII)?
vestibulocochlear nerve (CN VIII)
what does damage to the vestibular + cochlear nerves (close anatomical relationship) normally caused by?
skull fractures, ear infections, central lesions
what does damage to vestibulocochlear nerve result in?
tinnitus / vertigo
hearing loss
which type of tumour can develop from vestibulocochlear nerve?
acoustic neuroma can develop from the neurolemma cells of vestibular nerve
what can acoustic neuroma result in?
compression of the facial nerve
what can lesions to glossopharyngeal nerve (CN IX) result in?
uncommon
dysphagia, BP problems, parotid gland secretions
what is recurrent laryngeal nerve a branch of?
vagus nerve (CN X)
what can damage to recurrent laryngeal nerve result in?
hoarseness and dysphonia
+ weak cough
why is left RLN damaged more commonly compared to right?
longer course
how are recurrent laryngeal nerves normally damaged?
by aneurysms of arch of aorta
cancer of thyroid / larynx
enlarged mediastinal lymph nodes
what does damage to both L + R recurrent laryngeal nerve result in?
dysphagia, aphonia, inspiratory stridor
when does external branch of superior laryngeal nerve become damaged? why?
external branch of the superior laryngeal nerve runs close to the superior thyroid artery and so can be damaged during thyroid surgery
damage to external branch of superior laryngeal nerve result in? why?
weakness in phonation due to the loss of the cricothyroid muscle
what can produce a left recurrent laryngeal nerve palsy?
enlarged left atrium can produce a left recurrent laryngeal nerve palsy
how does enlarged atrium produce a left recurrent laryngeal nerve palsy?
by pushing the pulmonary artery up to compress the nerve against the aortic arch
if lesion of CN X is present, what will be a presenting symptom?
deviation of the uvula when soft palate elevated ‘Aaah’
when is spinal accessory nerve (CN XI) damaged?
in surgery e.g. lymph node biopsy / cannulation of UJV
stab wounds
what does damage in spinal accessory nerve (CN XI) result in?
loss of innervation to the SCM / trapezius
what can damage to hypoglossal nerve (CN XII) result in?
weakness and atrophy of tongue muscles on ipsilateral side (same side)
