Neuro - Cranial nerves

how many paired cranial nerves are there and what do they carry?

12 pairs, carry sensory, motor and autonomic information

your patients left pupil does not constrict when light is shown into the right eye. The right eye constricts when light is shown into the left eye and the right eye. what CN is impaired?

CN III

your patient presents with left side facial weakness, you notice bilateral forehead wrinkling when you asks them to open they eyes. where is the lesion

right CN VII

what kind of nerves are cranial nerves

peripheral nerves

if a peripheral nerve is damaged, what kind of impairment is it (site of lesion)

ipsilateral

axons from the sensory nerves travel via ----, through the ---, and synapse on the -----

olfactory nerves, cribiform plate, olfactory bulbs

where is the intrarhinal cortex located

temporal lobe

what is one sense that does NOT travel through the thalamus

smell

list out the pathway for cranial nerve I

olfactory nerve -> cribriform plate -> olfactory bulbs -> olfactory tracts -> temporal lobe

loss of sense of smell

anosmiaa

what's the most common type of impairment for anosmia

bilateral

s/s of CN I damage

head trauma, Parkinson, Alzheimers, covid

unilateral anosmia (ipsilateral)

rarely noticeable clinically as the contralateral nostril compensates for losss

bilateral anosmia (bilateral involvement )

first complaint is often the LOSS OF TASTE due to contribution of spell to detect flavor

this nerve receives visual information and is located in the retina

CN II- Optic nerve

pathway for the optic nerve

optice nerve -> optic chiasm -> optic tract -> lateral geniculate -> primary visual cortex

optic neuritis

inflammatory demyelinating condition of optic nerve

what is the primary sign of MS

temporary blindness

where is CN III (oculomotor) located

upper midbrain

how many extra ocular muscles make up CN III

6: 4 rectus muscles , 2 oblique muscles

what motor nerve helps lift the eyelid

levator palpebrae

pupil contraction is a form of what kind of response

autonomic

ptosis

droopy eyelid, loss of innervation to levator palpebrae muscle

what is lost when a pupil dilates/ becomes enlarged

loss of function to ciliary muscles that constrict pupil; loss of autonomic function

what is the most common presentation for damage to CN III

double vision (diplopia)

this is the smallest cranial nerve but has the longest path and is located in the midbrain

CN IV- Trochlear nerve

if there is damage to the CN IV after it has left the brainstem, what kind of issues will it cause?

ipsilateral palsy

this nerve is located in the pons and exits the brainstem at the pontomedullary junction

CN VI- Abducens nerve

CN VI controls what muscle?

lateral rectus muscle; abduction of the eye

what are the 3 branches to CN V- Trigeminal

ophthalmic (V1)

maxillary (V2)

Mandibular (V3)

what is the largest cranial nerve

Trigeminal CN V

CN V bring ---- to the face/ anterior 2/3 of tongue and --- to muscles of mastication

sensory (touch, pain, temp, joint position and vibration ) and motor

if someone has a lesion on CN V where is the impairment going to be

ipsilateral side of face for sensation and motor

what nerves are tested with corneal reflex

CN V and CN VII

categorizes by brief episodes of severe pain

common in V2,V3

present in MS

trigeminal neuralgia

this nerve sits in the pons and breaks

into 5 major segements :

CN VII - facial nerve

temporal, zygomatic, buccal, mandibular, cervical

CN VII sends what to the anterior 2/3 of tongue?

sensory

when CN VII uses motor it does what ?

causes muscles of facial expression to work

stapedius

works to dampen movements of inner ear

CN VII UMN lesion

loss of motor to contralateral lower face

CN VII LMN lesion

ipsilateral loss of motor to whole face (bell's palsy)

usually a viral cause, impairment to all divisions of facial nerve. s/s = unilateral facial weakness, inability to close eyelid, dry eye

bell's palsy

this nerve exits the brainstem at the pontomedullary junction lateral to the facial nerve

CN VIII- vestibulocochlear

originates in the medulla oblongata of brain stem

CN IX- glossopharyngeal nerve

where does CN IX send sensory and motor info to?

sensory: posterior 1/3 of tongue and pharynx

motor: supplies stylopharyngess msucle, elevates pharynx when talking and swallowing

the parasympathetic function of CN IX does what

assist with parotid gland function, (secretes saliva to help with chewing)

if theres a lesion on CN IX, what is impaired

posterior 1/3 of tongue, pharynx, and palate / taste

this is the wandering nerve and travels all throughout the thoracic cavity

CN X- vagus

parasympathetic function of CN X

function to heart, lungs, rest and digest

brachial motor function

pharyngeal muscles (swallowing) and laryngeal muscles (voice box)

sensory function for CN X

special sense of taste from pharynx and epiglottis, chemo and baroreceptors of the aortic arch

what is a disorder of CN X

Postural Orthostatic Tachycardia Syndrome (POTS): low BP and HR in response to activity, syncope

spinal accessory nerve is what CN

CN XI

function of CN XI

send motor info to the sternocleidomastoid and traps

Sternocleidomastoid muscle does what

tilts head to ipsilateral side and rotates to contralateral side

trapezius muscle does what

elevates shoulder

if theres a lesion to the CN XI, what kind of neurons are affected?

LMN

impairment of the CN XI is commonly from?

trauma, surgical procedure

CN XII

hypoglossal nerve

what is the function of CN XII

send motor nerves to the muscles of the tongue

if theres a UMN lesion on CN XII what happens

causes a contralateral tongue weakness

if theres a LMN lesion on CN XII then...

lesions will cause ipsilateral tongue weakness

where will the tongue deviate to when there is a lesion

toward the side of weakness

dysarthria

tongue weakness