Mod 10 Cranial Nerves Flashcards
Where are sensory nuclei of CNs lie in the brain and where do motor nuclei lie?
sensory: lateral
motor: medial
What makes CN I (olfactory) special?
does not:
- synapse in thalamus before reaching cerebral cortex
- attach brainstem
- have DRG equivalent
is: part of CNS
What forms the olfactory bulb?
bipolar neurons
What type of neurons fill the olfactory tract?
secondary neurons
How do you evaluate CN I in clinic?
test each nostril separately with familiar scent
- can have affect on olfaction, emotion, and memory
What is anosmia?
the inability to smell that may occur from a common cold, COVID, trauma, or PD and Alzheimer’s
What type of cell axons form the optic nerve?
retinal ganglion cell axons
Which CNs are components of the CNS?
olfactory and optic
How does the fact that CN II is part of the CNS have affect when it comes to diseases of the CNS?
patients with MS typically experience visual deficits first which can indicate MS
What are the ways to evaluate CN II in clinic?
- snellin chart
- quadrant testing
- pupillary light reflex (afferent limb)
How does CN III have a visceral motor function?
edinger - westfall nucleus is parasympathetic pre-ganglionic nucleus that control the iris sphincter muscle and ciliary muscle
Which eye muscles does CN III innervate?
- levator palpebrae superioris
- medial rectus
- inferior oblique
- inferior rectus
What is the pupillary light reflex?
shine light in the eyes
- consensual response: pupil constriction in opposite eye (CN II)
- direct response: pupil constriction in same eye (CN III)
What is anisocoria?
denotes pupillary size inequality
How would damage to CN II affect the pupillary light reflex?
no relay to the lateral geniculate nucleus so opposite CN III cannot fire
How would damage to CN III affect the pupillary light reflex?
no ipsilateral contraction due to the nerve not being able to accept the relayed communication from CN II
What is a good way to remember which extra ocular muscles are innervated by a CN?
SO4, LR6, the rest are 3
Where does CN III emerge from?
midbrain
What is the role of CN IV?
innervates superior oblique muscle
What is unique about CN IV?
axons leaving the trochlear nucleus cross midline to innervate contralateral superior oblique muscles
only CN to exit dorsal brainstem
What function is CN III?
somatic motor and visceral motor
What is the function of CN IV?
somatic motor
What is the function of CN VI?
somatic motor
Where is the abducens nucleus located?
caudal pons
What does CN VI do?
innervates lateral rectus muscles
How do you evaluate CN III, IV, and VI function in clinic?
H test
- smoothness
- convergence/divergence
- pupillary light reflex
What is opthalmoplegia?
disorder of eye movement causing the paralysis of one or more of the extra ocular muscles
What is strabismus?
disorder of eye movement causing the inability to direct both eyes to the same object
What is the difference between lateral and medial strabismus?
lateral: CN III paralysis (stuck lateral)
medial: CN VI paralysis (stuck medial)
What is diplopia?
disorder if eye movement causing double vision
What is ptosis?
disorder of eye movement causing weakness of levator palpebrae superioris muscle
What is the function of CN V?
general sensory and branchial motor
What are the three divisions of the trigeminal nerve?
- ophthalmic (V1)
- maxillary (V2)
- mandibular (V3)
Where are the trigeminal nerve sensory nuclei located in the brain?
large and located in the midbrain, pons, medulla, and cervical spinal cord
Where are the trigeminal nerve motor nuclei located?
pons
What does CN V do?
sensory innervation of face and head, motor innervation to muscles of mastication, small branch to tensor tympani
What is the main sensory nucleus of CN V role?
fine touch, pressure, vibration
What is the spinal nucleus of CN V role?
nociception and temperature
What is the mesencephalic nucleus of CN V role?
jaw proprioception (jaw reflex efferent limb)
What is the motor nucleus of CN V role?
muscles of mastication and tensor tympani
What is the motor pathway and UMN/LMN of the face?
corticobulbar tract
UMN: primary cerebral cortex
LMN: motor nucleus CN V
What is the fine touch, pressure, and vibration pathway of the face?
trigeminal pathway
What is the proprioception pathway of the face?
trigeminal pathway
What is the nociception and temperature pathway of the face?
trigeminal pathway
Where do the primary afferents of the trigeminal system terminate?
main trigeminal sensory, spinal nucleus, and mesencephalic nucleus
How do you evaluate the trigeminal nerve in clinic?
sensory test for DCML and STT (light touch, sharp, dull)
palpate MoM and resist jaw opening
What is herpes zoster opthalmicus?
inflammatory and infectious disease that causes 2-3 days of severe pain along V1 distribution with rash soon after
could cause corneal damage
What is the function of the facial nerve?
general sensory
special sensory
branchial motor
parasympathetic motor
Where do CN VII nuclei lie?
pons and medulla
What does the facial nerve do?
innervate sensory of ext ear, anterior 2/3 tongue for taste, muscles of facial expression, stapedius, lacrimal, submandibular, and sublingual glands
How do we evaluate CN VII in clinic?
special sensory: ask about taste
branchial motor: muscles of facial expression
What is Bell’s palsy?
most common disease of CN VII caused by herpes simplex virus
paralysis of facial muscles, and impaired corneal blink reflex
What is important to remember about Bell’s palsy and how it affects facial muscles?
UMN weakness: more observable in lower facial muscles
LMN weakness: more observable in both upper and lower facial muscles
What is the function of CN VIII?
special sensory
What does CN VIII do?
conveys vestibular and cochlear info
Where is CN VIII nuclei located?
caudal pons and rostral medulla
How do we clinically evaluate CN VIII?
- finger rub or whisper test
- Romberg/sharpened romberg
Where does CN VIII enter the brainstem?
rostral medulla
What is the function of CN IX?
- general sensory
- special sensory
- visceral sensory
- branchial motor
- visceral motor
Where are the nuclei of CN IX?
rostral medulla
Where does CN IX attach to the brainstem?
causal medulla
What is the function of the vagus nerve?
- general sensory
- special sensory
- branchial motor
- visceral motor
Where are the nuclei of CN X located?
mid medulla
How do you clinically evaluate CN IX and X?
- soft palate movement (“ah”)
- observe swallow
- observation of vocal quality
What can lesions of CN IX and X cause?
hoarseness of speech and difficulty swallowing
What side does the uvula deflect if damage to CN IX?
deflect to unaffected side
What is the function of CN XI?
branchial motor
Where are the nuclei of CN XI located?
medulla and cervical spinal cord
What does CN XI do?
SCM and traps
How do we clinically evaluate CN XI?
shoulder shrug test and resisted head turning
What is the function of CN XII?
somatic motor
Where are the nuclei of CN XII located?
medulla
What does CN XII do?
intrinsic and extrinsic muscles of the tongue
How do we clinically evaluate CN XII?
- protrusion and speech articulation
- “late night downtown”
- lick the lesion (goes toward affected side
