cranial nerves: clinical Flashcards by a m

what would a fracture to the cribiform plate result in?

anosmia - loss of sense of smell

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most common cause of anosmia?

URTI

head injuries e.g. shearing forces / basilar skull fracture

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how will you fracture the cribiform plate?

from anterior cranial fossa trauma

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what can fracture to the cribiform plate also result in?

leakage of CSF through the nose (rhinorrhoea)

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what can rhinorrhoea lead to?

brain infections, including meningitis

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what is common with viral / allergic rhinitis?

transient olfactory impaiment

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what can fracture to the optic canal damage?

the optic nerve

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what does damage to the optic nerve result in?

loss to papillary constriction

complex pathway from retina to visual cortex - occipital lobe

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Different lesions to optic nerve give rise to?

different patterns of visual loss:

e.g. optic neuritis, pituitary tumour, stroke

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pressures on the optic pathway result from?

raised intracranial pressure / loss of blood from the central artery of the retina

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what can pressures on the optic pathway result in

blurring of the margins of the optic disc and subsequent visual field defects

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what is swelling of the optic disc? result from?

papilloedema

from pressures on the optic pathway

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causes of compression on the optic pathway? leading to?

pituitary adenomas / carotid aneurysm

cause visual field defects

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lesions to oculomotor nerve results in?

diplopia (double vision)
ptosis (drooping eyelid)
pupillary dilation (absent papillary light reflex)

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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)

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is trochlear nerve (CN IV) usually damaged?

rarely paralysed alone

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how can you usually correct damage to trochlear nerve?

slight tilt of the head

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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

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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)

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what is a cause of trochlear nerve (IV) damage in children?

congenital nerve palsy

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what can result in damage to the trigeminal nerve (V)?

trauma, tumour, aneurysms, meningeal infections, shingles, trigeminal neuralgia

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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)