Cranial Nerves Flashcards
Cranial nerves are form what part of the NS?
peripheral
What are the 12 cranial nerves? pneumonic
OOOTTAFVGVAH
What is cranial nerve I?
olfactory
What is cranial nerve II?
optic
What is cranial nerve III?
oculomotor
What is cranial nerve IV?
trochlear
What is cranial nerve V?
trigeminal
What is cranial nerve VII?
facial
What is cranial nerve VIII?
vestibulocochlear
What is cranial nerve IX?
glossopharyngeal
What is cranial nerve X?
vagus
What is cranial nerve XI?
accessory
What is cranial nerve XII?
hypoglossal
What are cranial nerves I & II, and where are they located?
olfactory and optic
in cerebrum
What are cranial nerves III & IV, and where are they located?
oculomotor and trochlear
in midbrain
What is cranial nerve V and where is it located?
trigeminal
in pons
What are cranial nerves VI, VII & VIII, and where are they located?
abducens, facial and vestibulocochlear
pontomedullary junction
What are cranial nerves IX, X, XI, XII and where are they located?
glossopharyngeal, vagus, accessory, hypoglossal,
medulla
What are the 3 sensory-only cranial nerves?
olfactory (I)
optic (II)
vestibulocochlear (VIII)
What are the 5 motor-only cranial nerves?
oculomotor (III)
trochlear (IV)
abducens (VI)
accessory (XI)
hypoglossal (XII)
What cranial nerves are both sensory and motor?
trigeminal (V/5)
facial (VII/7)
glossopharyngeal (IX/9)
vagus (X/10)
olfactory epithelium located where?
roof of nose
What type of neuron is the olfactory nerve (I)? What sets it apart from other CNS?
bipolar, axon makes it the shortest CN
Where is the olfactory bulb?
bulb over cribriform plate of ethmoid bone
How is smell transmitted to the brain?
olfactory tract takes smell to olfactory cortex
What are the different problems relating to smell?
anosmia
dysosmia
hyposmia
hyperosmia
phantosmia
What is anosmia?
loss of smell
What is dysosmia?
distorted sense of smell
What is hyposmia?
reduced ability to smell
What is hyperosmia?
increased ability to smell
What is phantosmia?
olfactory hallucinations
What drug classes can cause smell disorders/chemosensory effects?
topical decongestants
antibiotics
antihypertensives
antihistamines
antilipidemics
What are examples of decongestants that have a chemosensory effect?
decongestants containing zinc
What are examples of antibiotics that have a chemosensory effect?
amoxicillin
azithromycin
ciprofloxacin
What are examples of antihypertensives that have a chemosensory effect?
amlodipine
diltiazem
enalapril
What is an example of an antihistamine that has a chemosensory effect?
fluticasone
What is optic neuropathy?
damage to the optic nerve
What drugs can induce optic neuropathy?
ethambutol
amiodarone
vigabatrin
What is ethambutol optic neuropathy dependent on?
dose and duration
What dose and duration does optic neuropathy occur with ethambutol occur?
around 6% of px at a daily dose of 25mg/kg/day within 3-6 months of starting
How does amiodarone cause neuropathy?
irreversible demyelination
How do you monitor for neuropathy with ethambutol?
screen every weeks when dose >15mg/kg, every 3-6 mths for lower doses
How often is optic neuropathy for vigabatrin monitored for?
screening prior to starting treatment, then every 6 months, then 3 yrs and annually
What is the cause of vigabatrin-induced optic neuropathy?
idiosyncratic - nasal visual field loss
What is maculopathy?
damage to retina so px cannot focus on one thing but still has peripheral vision
What drugs can cause maculopathy?
chloroquine, hydroxychloroquine
thioridazine
canthaxanthin
tamoxifen, nicotinic acid
How does thioridazine cause maculopathy?
deposits drug in retinal pigment epithelium RPE
dose exceeds >800mg/day for a few weeks
How do chloroquine and hydroxychloroquine cause maculopathy?
deposit drug in retinal pigment epithelium RPE
occurs in 7.5% of pts if used for >5 yrs
How does canthaxanthin cause maculopathy?
deposits of tiny crystals, and foveolar cyst formation (duration dependent)
How do tamoxifen and nicotinic acid cause maculopathy?
deposits of tiny crystals & foveolar cyst formation, (dose dependent)
What is the function of the optic nerve?
vision:
- visual acuity
- colour
- contrast
- visual field
Pneumonic for remembering innervation of extraocular muscles
LR6SO4
lateral rectus innervated by CN 6, abducens
superior oblique innervated by CN 4, trochlear
all rest innervated by CN 3, oculomotor
What muscles are involved in eye movement?
4 recti muscles:
- superior, inferior, medial and lateral
2 obliques:
- superior and inferior oblique
levator palpebral superioris
Which eye movement muscles does the oculomotor nerve (3) innervate?
superior, inferior and medial rectus
inferior oblique
levator palpebral superioris
(up down and inwards)
Which eye movement muscle does the abducent nerve (6) innervate?
lateral rectus (move eye to outer side)
Which eye movement muscles does the trochlear nerve (4) innervate?
superior oblique
in and down
What should you remember in terms of where the eye muscles move the eye?
recti muscles are predictable and move according to their name
(sup up and inf down)
oblique muscles do the opposite - O for opposite
Where do each rectus muscle move the eye?
lateral moves to lateral side out
medial moves medially in to nose
superior moves eye up and out
inferior moves eye down and out
Where do the oblique muscles move the eye?
superior oblique moves eye down and in
inferior oblique moves eye up and in
Based on the nerve that innervates the MR, SR, IR, IO, LPS: what type of innervation supplies these muscles?
motor
What branch of the nervous system supplies the sphincter pupillae and ciliary muscle?
the parasympathetic
What can damage to the oculomotor nerve (3) result in?
right third nerve palsy
What are signs of right nerve palsy?
ptosis (drooping of upper lid)
mydriasis (pupil dilation)
cycloplegia (paralysis of eye)
normal abduction
limited elevation and depression
What does damage of the trochlear nerve result in?
right fourth nerve palsy
Based on what the trochlear nerve innervates, what are the signs of 4th right nerve palsy?
innervates superior oblique muscle which moves eye down and in
What affects the trochlear nerve and why?
raised intracranial pressure ICP due to it being the only nerve to come out of dorsal side of brainstem, and its long course
What can damage to the abducent nerve (VI) result in?
right 6th nerve palsy (improper innervation of lateral rectus muscle)
one eye facing closer into nose
What can affect the abducent nerve and why?
longest nerves, so can be compressed by downward herniation due to raised ICP
What drugs can cause myopathy of the extraocular muscle?
(antitumour therapies targeting immune checkpoints)
tremelimumab
durvalumab
What are the symptoms of drug-induced myopathy?
diplopia (double vision)
ptosis
fatigue
weakness
How do you examine the signs of myopathy of extraocular muscles?
electromyography (EMG) and muscle biopsy
would see multiple muscle weakness to varying extent
How do you treat drug-induced myopathy?
withdraw drug and oral steroid therapy
What are the 3 divisions of the trigeminal nerve?
ophthalmic
maxillary
mandibular
What is the ophthalmic division of the trigeminal nerve?
sensory: including dura mater and forehead
What is the maxillary division of the trigeminal nerve?
sensory: lower lid, cheek and maxillary sinus
What is the mandibular division of the trigeminal nerve?
mix of sensory and motor:
- sensory: lower jaw, angle and temple
- motor: muscles of mastication
What is trigeminal neuralgia?
chronic pain disorder characterised by sudden unilateral severe facial pain
What are the 2 types of trigeminal neuralgia?
classic
atypical
What is classic trigeminal neuralgia?
intermittent sudden burning/shock of pain lasting from a few seconds to 2 mins per episode
What is atypical trigeminal neuralgia?
constant aching, burning, stabbing that stays for weeks and months
What parts innervated by the facial nerve are sensory?
anterior 2/3 of tongue
external ear
What parts innervated by the facial nerve are motor?
muscles of facial expression
stapedius muscle
posterior belly digastric
stylohyoid
What parts of the facial nerve are innervated by parasympathetic input?
nasal, lacrimal glands
sublingual
submandibular
What is bells palsy?
Inflammation or viral infection of the facial nerve that causes one sided weakness or the entire face
What are some signs of bells palsy?
lower motor neuron lesion of facial nerve
ipsilateral facial muscle weakness (same side)
drooping of mouth
loss of forehead wrinkle
unable to close eyelids
loss of taste
What are the functions of the branches of the vestibulocochlear nerve (branches are in the name)?
vestibular - balance
cochlear - hearing
What can be used to diagnose deafness due to CN 8?
tuning fork tests (Weber’s and Rinne’s)
What is a cerebellopontine angle tumor and what CNs does it affect?
acoustic neuroma affecting 7,8 and later 10,11
What is drug-induced ototoxicity?
irreversible destruction of outer hair cells in organ of Corti, at cochlea and type I hair cells in vestibular apparatus
What drug class can cause ototoxicity?
aminoglycosides (dose and duration dependent)
What aminoglycosides are vestibulotoxic?
streptomycin and gentamicin
What aminoglycosides are cochleotoxic?
neomycin and kanamycin
Which of the aminoglycosides are safer (in terms of ototoxicity)?
amikacin and tobramycin
What are signs of ototoxicty?
hearing loss
tinnitus
disequilibrium
dizziness and vertigo
How can ototoxicity be screened for?
audiograms
serum drug levels
renal functions
How long does it take drug-ototoxicity to resolve?
6 months
What parts innervated by the glossopharyngeal nerve (IX) are sensory?
posterior 1/3 of tongue (remember anterior 2/3 is facial, VI)
palate
oropharynx
middle ear
What parts innervated by the glossopharyngeal nerve (IX) are motor?
stylopharyngeus
What parts innervated by the glossopharyngeal nerve (IX) are parasympathetic?
parotid gland
What parts innervated by the vagus nerve (IX) are sensory?
pharynx
larynx
external ear
dura mater
aortic body chemoreceptors
aortic arc baroreceptors
What parts innervated by the vagus nerve (IX) are motor?
palatoglossus
palate
pharynx
larynx
What parts innervated by the vagus nerve (IX) are parasympathetic?
heart
bronchi
GI tract
What 2 roots does the accessory nerve arise from?
nucleus ambiguous and spinal C1-5
What muscles does the accessory nerve innervate?
sternocleidomastoid
trapezius
How do you test the accessory nerve function?
ask patient to raise shoulder or
turn face against resistance applied by hand of examiner
What is the function of the hypoglossal nerve (12)?
facilitating tongue movement
What muscles does the hypoglossal nerve innervate?
intrinsic muscles of tongue:
hypoglossus
genioglossus
styloglossus
How do you test hypoglossal nerve function?
protrude tongue straight and move from side to side
How does the tongue behave with an upper motor neuron lesion in the hypoglossal nerve?
tongue is spastic, protrusion away
How does the tongue behave with an lower motor neuron lesion in the hypoglossal nerve?
tongue shows wasting and fasciculations
