Session 5 - cranial nerves Flashcards
where do cranial nerves arise from
brainstem
what does the brain stem regulate
cardio-respiratory functions
maintains consiousness
what does the brain stem continue as when it passes though the foramen magnum
spinal cord
what is nuclei
collection of cell bodies of nerve fibres that make up the whole cranial nerve
which cranial nerves arise from the forebrain
olfactory
optic
which cranial nerves arise from the midbrain
occulomotor
trochlear
which cranial nerves arise from the pons
trigeminal
abducens
facial
vestibulocochlear
which cranial nerves arise from the medulla
glossopharyngeal
vagus
accesory
hypoglossal
what axons does cranial nerve I olfactory carry
and what is its function
what is its route
special sensory
smell
olfactory region of nasal cavity- cribriform foramina- olfactory bulb- olfactory tracts- forebrain
how can the olfactory nerve be tested
test one nostril at a time
use smelling salts
what is anosmia
what is the most common cause of anosmia
loss of sense of smell
common cold
what axons does cranial nerve II optic carry
and what is its function
what is its route
special sensory
vision
takes signals from the retina, passes through the optic canal. the optic fibres from the left and cross over at the chiasma. from the optic chiasma they go along the optic tracts to the primary visual cortex in the occipital lobe
originate from the forebrain
how can the optic nerve be tested
visual test (snellen chart and visual fields) testing pupils responses and reflexes using pen torches
why does the optic nerve swell when there is raised intracranial pressure
and what clinical sign does this present as
the optic nerve carries extensions of meninges
presents as papillodema
why might you get bitemporal hemianopia
pituitary tumors compress the optic chiasm
what axons does cranial nerve III occulomotor carry
and what is its function
what is its route
motor
and carries some autonomic parasympathetic fibres
motor function - innervates most of the extra occular muscles and levator palpibrae superioris (muscle thag keeps eyelid open)
autonomic- sphincter pupillae, whcih constrcits to make the pupil smaller
and ciliary muscle, which changes the shape of the lens
orginates in the mid brain and travels in the cavernous sinus and through the superior orbital fissure to the orbit
why might the occulomotor nerve get compressed
increased intracranial pressure can cause the uncus of the temporal bone to slip over the edge of the tentorium cerebelli, as the occulomotor nerve runs just at the edge of the tentorium cerebelli this squashes the occulomotor nerve
of the occulomotor nerve undergoes compression which function is first to go and why
how would a patient present
the parasympathetic functions
the parasympathetic fibres sit around the periphery of the occulomotor nerve
so the innervation to the pupil is lost and this is shown as blown or fixed dilated pupil
how can you test the occulomotor nerve
inspection of eyelids and pupils and eye movements
test the pupillary light reflexes
how does the pupil look in severe ptosis
down and out position
what axons does cranial nerve IV trochlear carry
and what is its function
what is its route
motor
supplies the extra orbital muscles superior oblique
midbrain, then through the cavernous sinus and out the superior orbital fissure into the orbit (runs along with the occulomotor nerve)
which cranial nerve is the only nerve to emerge through the dorsal aspect of the brainstem
trochlear nerve IV
has the longest intracranial course
how do you test the trochlear nerve
eye movements (also tests III,VI)
How might patient correct damage to the trochlear nerve
they get diplopia which worse on downward gaze
corrected by tilting their hear
what axons does cranial nerve V trigeminal carry
and what is its function
what is its route
sensory and motor
main sensory nerve supplying the face
innervates the muscles of mastication
originate from the pons
there are three divisions, opthalmic, maxillary and mandibular
opthalmic goes through superior orbital fissure and into the orbit to provide sensation to cornea and conjunctiva in the eye
maxillary travels through foramen rotundum
mandibular travels through foramen ovalis
how do you test the trigeminal nerve
check the dermatomal areas relation to CV Va, Vb and Vc
test the muscles of mastication
test corneal reflex
which nerve has the afferent limb of the corneal reflex
CN V trigeminal
what is trigeminal neuralgia
it is a sudden attack of severe sharp shooting facial pain that can last from a few seconds to two minutes
it usually affects one side of the face
usually cause by compression of the trigeminal nerve
what is shingles also knows as and which nerve does it affect
Orofacial acute herpes zoster (shingles) is an acute viral disease affecting the trigeminal nerve (CN V). It is the result of reactivation of the varicella zoster virus (VZV) that remained dormant in the trigeminal nerve root ganglion following exposure or clinical manifestation of chickenpox. Reactivation could be due to immunosuppression, or it could be age-related
what is the infraorbital nerve a branch of
and where does it provide sensation to
CNVb maxillary division
provides sensation to the skin on the cheek and below the eyelid
what is a blowout fracture
which nerve does it injure
it is fracture of the orbit
the contents of the orbit are forced back
causing an increase in pressure in the orbit cavity
the floor of the orbit gives way
causing damage to the infraorbital nerve
causes decreased sensation to the area under the eye
what are two branches of the CN Vc madibular division
inferior alveolar which runs through the base of the mandible and then becomes the mental nerve as it comes through the mental foramen- provides sensation to lip and chin
lingual nerve- goes to tongue and general sensory innervation to the anterior 2/3 of the tongue
which nerve will be damaged in a fracture to the mandible
and how does this present
the inferior alveolar nerve
presents with numbness over lip, chin and along lower gum and teeth
which nerve is numbed in tooth extraction
the inferior alveolar nerve
but it also affects the lingual nerve as they are so close to each other
what axons does cranial nerve VI abducens carry
and what is its function
what is its route
motor
innervates lateral rectus muscle of the eye
originates from the pons, along cavernous sinus, through superior orbital fissure and out of the orbit
how do we test cranial nerve VI abducens
eye movements
patients present with diplopia
what axons does cranial nerve VII facial carry
and what is its function
what is its route
motor, special sensory and autonomic (parasympathetic)
motor- muscles of facial expression
special sensory- taste to anterior 2/3 of the tongue
parasympathetics- lacrimal and salivary glands
originates from pons and travels through internal auditory meatus and along the petrous part of the temporal bone and exits through the base of the skull giving off five branches extracranially and 2 branches intracranially
which branch of the facial nerve VII provides tastes to the anterior 2/3 of the tongue
chorda tympani nerve
which branch of the facial nerve VII provides parasympathetics to lacrimal and salivary glands
greater petrosal nerve
why might an acousitc neuroma affect the facial nerve
acoustic neuromas are usually found on the vestibulocochlear VIII nerve
it runs through the internal auditory meatus with the facial nerve
so an acoustic neruoma can compress the facial nerve
which nerves senses eye closure (sensory)
and which nerves causes the closure of the eyelid (motor)
trigeminal nerve
facial nerve
how do you test the facial nerve VII
test muscles of facial expression
test the corneal reflex (efferent limb)
test taste on the anterior 2/3 of the tongue
what axons does cranial nerve VIII vestibulocochlear carry
and what is its function
what is its route
special sensory
hearing and balance
originates from the pons and goes through the internal auditory meatus. In the distal aspect of the IAM, the vestibulocochlear nerve splits, forming the vestibular nerve and the cochlear nerve.
what does the vestibular part of the vestibulocochlear nerve do?
The vestibular nerve innervates the vestibular system of the inner ear, which is responsible for detecting balance
what does the cochlear part of the vestibulocochlear nerve do?
The cochlear nerve travels to cochlea of the inner ear, forming the spiral ganglia which serve the sense of hearing.
where is the primary auditory cortex located
in the temporal lobe
how do you test the vestibulocochlear nerve
test hearing and enquire about balance
rinnes and webers tests (tuning fork)
what is presbyacusis
it is a progressive, usually bilateral, sensorineural hearing loss that occurs in older people as they age
what is nystagamus
which nerve is damaged
a condition of involuntary eye movement
may result in reduced or limited vision
vestibulocochlear CNVIII
damage to which nerve can cause vertigo
viestibulocochlear
what is an acoustic neuroma
and which nerves does it affect
symptoms
it is a benign tumours of the shwann cells surrounding the vestibulocochlear nerve, and thus compressing it
can also effect the facial and trigeminal nerve
sensorineural unilateral hearing loss
tinnitus
vertigo
numbness, pain or weakness down one half of face
what axons does cranial nerve IX glossopharyngeal nerve carry
and what is its function
what is its route
general sensory, special sensory, autonomic and motor
general sensation of soft palete, tonsils and phraynx
special sensory to middle ear and tympanic membrane (hearing) and sensory from carotid body and sinus (senses increases in pressure)
taste and genera sensation to posterior 1/3 on tongue
autonomic innervation to parotid gland
motor innervation to stylopharyngeus which helps you swallow
from medulla it runs through the jugular foramen and descends down the neck
how do you test the glossopharyngeal IX nerve
gag reflex
usually tested along with crainal nerve X vagus
what axons does cranial nerve X vagus carry
and what is its function
what is its route
general sensory, motor, and parasympathetic autonomic fibres
sensory to lower pharynx and larynx
muscles of soft palette, pharynx(swallow) and larynx(vocal cords)
parasympathetic to thoracic and abdominal viscera
arises from the medulla, goes through the jugular foramen to enter the neck in the carotid sheath
which vessels do the left and right recurrent laryngeal (branches of vagus) nerves go under
and what do they innervate
left- left recurrent laryngeal nerve turns under arch of aorta
right- right recurrent laryngeal nerve turns under right subclavian
they innervate the vocal cords
how do you test the vagus nerve X
noting speech- look out for hoarseness of voice
swallow and cough
ahhh to observe any deviations of the uvula- as muscles above uvular contract to maintain it in the midline
gag reflex (efferent limb)
what axons does cranial nerve XI (spinal) accessory carry
and what is its function
what is its route
motor
spinal root innervates sternocleidomastoid and trapezius
comes off the spinal cord runs through the foramen magnum and then through jugular foramen to supply muscles in the neck
how do we test the spinal accessory nerve
shrug shoulders against resistance
turn head against resistance (both sides)
which nerve runs down through the neck in the posterior triangle
spinal accessory
what axons does cranial nerve XII hypoglossal carry
and what is its function
what is its route
motor
innervates muscles of the tongue
from medulla it goes through the hypoglossal cabal and heads towards the tongue
it runs medial to angle of mandible and crosses internal and external carotid arteries in neck
how do you test the hypoglossal nerve XII
inspection for weakness and atrophy of tongue muscles on the ipsilateral side
movement of tongue
describe how a carotid sinus message works
CN IX (glossopharyngeal) detects afferent signals from carotid sinus relaying any increased pressure to brainstem (medulla) eff efferent response in this reflex is increased autonomic output via vagus to AV node in heart to slow heart rate
