Cranial Nerves (GSE/LMN) Flashcards
describe the major divisions of the brain rostral to caudal
prosencephalon, midbrain, pons, medulla oblongata
define prosencephalon and diencephalon and the common names these terms refer to
prosencephalon/forebrain: cerebrum (telencephalon), thalamus (diencephalon)
diencephalon: between brain; contains epithalamus, hypothalamus, and thalamus
know what structures contribute CLINICALLY to the brainstem (3)
midbrain, pons, medulla
in terms of GSE/LMN function, list the 5 groups of cranial nerves
- 3, 4, 6
- 5
- 7
- 9, 10, 11
- 12
list where in the brain the cranial nerves enter and exit
CN2: prosencephalon
CN3 and 4: midbrain
CN5: pons
CN 6-12: medulla oblongata
describe the basic course the cranial nerves take as they course through the cranial cavity along the ventral aspect of the brain and how this can help you localize
3, 4, 5 ophthalmic, 6: via orbital fissure
5, 7, 8: pons/medulla junction
7, 8 and horner: tympanic cavity, middle ear
describe how postural reactions, evaluation of other cranial nerves, and mentation allow you to determine if a lesion is in one of the major divisions of the brain (CNS) or in the PNS (cranial nerve)
mentation: abnormal = central lesion
postural reactions: abnormal = central lesion
other cranial nerve neighbors: affected = central
what do lesions at or caudal to the midbrain result in?
gait abnormalities like GP proprioceptive ataxia/UMN paresis, vestibular ataxia, or cerebellar ataxia, as well as ipsilateral deficits in cranial nerves and ipsilateral postural reaction deficits (CN 3-12, behaves like spinal cord because ipsilateral because no crossover yet/after crossover)
what divisions of the brain contain the GSE/LMN for CN 3, 4, and 6?
pons: 3 and 4
medulla: 6
list the extraocular muscles innervated by CN 3 4 and 6
rectus muscle, oblique muscles, retractor bulbi muscle
LR 6, SO4, rest by 3
6: lateral rectus
4: dorsal oblique
3: medial, dorsal, ventral rectus, ventral oblique
what muscle of the superior eyelid is innervated by CN 3?
levator palpebrae suprioris (elevates upper eyelide)
what are the 2 types of functions of CN3?
GSE/LMN and parasympathetic
what is the foramen where CN 3, 4, and 6 exit the cranial cavity?
emerge from ventral brainstem, course ventrally along cranial cavity, and exit at the orbital fissure
which way will the eye move with stimulation of CN3?
medial, dorsa, ventral, extorsion
which way will the eye move with stimulation of CN 4?
intorsion
which way will the eye move with stimulation of CN 6?
lateral
what position will the eye have with a lesion affecting CN 3, CN 4, OR CN 6?
3: will move ventral and lateral
4: will extorsion
5: will move medial
describe the eye position relative to the orbit if CN3, CN4 AND CN6 are affected/abnormal
eye will look “normal” because everyone dropped their rope; so instead try to get the patient to follow an object with just eyes or move head side to side and should see nistagmus via CN 8 telling 3 4 and 6 to move eyes
what major division of the brain contains the GSE/LMN nuclei for the trigeminal nerve?
pons
what major division of the brain does the trigeminal nerve exit/enter?
ophthalmic exits at orbital fissure
maxillary exits at round foramen of alar canal
mandibular exits at oval foramen
name the 3 major branches of the trigeminal nerve; which has sensory funciton? which has motor function?
ophthalmic: sensory
maxillary: sensory
mandibular: sensory AND motor
what foramina do the branches do the trigeminal nerve use to exit the cranial cavity?
ophthalmic: orbital fissue
maxillary: round foramen of alar canal
mandibular: oval foramen
list the muscles of mastication (4)
- temporalis
- masseter
- pterygoid muscles: support eye in rostral postion
- rostral belly digastricus
describe the location of the temporalis and masseter muscles
temporalis: top of head
masseter: big cheek boy
what muscles of mastication open and which close the mouth?
digastricus is only opener of mouth, so temporalis, masseter, and pterygoids all close
name the cranial nerves that innervate the digastricus; name the cranial nerve that innervates the rostral belly and the caudal belly
rostral belly: mandibular of trigeminal
caudal belly: facial
describe the findings of a unilateral lesion affecting the mandibular branch of the trigeminal nerve
ipsilateral atrophy but no loss of function of muscles of mastication because the other side can still chew
describe the findings of a bilateral lesion affecting the mandibular branches of the trigeminal nerve
inability to close the mouth (dropped jaw)
broadly describe where each of the main branches of the trigeminal nerve provides cutaneous (sensory) innervation to the skin of the head/fave
ophthalmic: eye, medial canthus, nasal mucosa
maxillary: lateral canthus/lip over maxilla, skin on lateral rostral side of face
mandibular: skin over mandible, tongue, skin on lateral caudal side of face
specifically, describe where you would test/stimulate the skin that would assess the autonomous zone for each of the main branches of the trigeminal nerve
ophthalmic: medial canthus
maxillary: lateral canthus
mandibuular: skin over mandible or tongue
name the cranial nerve reflex that is the main means of assessing the ophthalmic and maxillary branches of the trigeminal nerve; describe how this is performed and the reaction (motor/efferent) that is observed
palpebral reflex; touch medial and lateral canthi and look for blinking or pulling back
name the main branch of the trigeminal nerve assessed when the mucosa of the nasal septum is stimulated; is this a response or a reflex? what does that imply?
ophthalmic! this is a response, which implies involvement of the contralateral prosencephalon
what major division of the brain contains the GSE/LMN nuclei of the facial nerve?
exits from rostral medulla with CN 8
what major division of the brain does the facial nerve exit and enter?
exit via internal acoustic meatus, through the facial canal, out through the stylomastoid foramen
what other cranial nerve does the facial nerve (CN7) course alongside as it exits the cranial cavity?
CN8 vestibulocochlear
what canal does the facial nerve use to exit the skull and in what bone? what foramen? what is it exposed to along the course of its canal and how does this affect the nerve?
facial canal in petrosal bone then out through the stylomastoid foramen; along the course of the canal, the facial nerve is exposed to the tympanic cavity (middle ear), making it vulnerable to injury/disease with middle ear issues
name 2 other nervous system structures involving the tympanic cavity and inner ear
- vestibulocochlear nerve (CN8)
- sympathetic nerves involved with horner syndrome
what does observing deficits involving the facial nerve, vestibulocochlear nerve, and horner syndrome localize to?
disease/lesion of middle/inner ear
within the canal in the petrosal bone, what 2 branches does the facial nerve give off? function?
- major petrosal nerve: provides preganglionic parasympathetics
- stapedius nerve: innervates the stapedius muscle that protects the ear from loud noises
what is the name of the group of muscles that the facial nerve innervates? broadly describe their function
the muscles of facial expression; facial expressions
once outside of the skull, name the 2 major branches of the facial nerve
- buccal branches: involves movement of lips and nose
- auricular palpebral branch: involves eyelid and ear movements
describe the findings of a lesion of the facial nerve
- drooping snoot
- drooling bc lips can’t keep saliva in mouth
- ears not moving
- lips drooping
- not blinking
name the cranial reflex and cranial nerve response that are the main means of testing the function of the facial nerve
pelpebral and menace: if both abnormal = lesion in 7
auricular reflex; poke in the ears and see if they feel/move it
what does the facial nerve provide to the head?
preganglionic parasympathetic innervation to the glands of the head
lacrimal gland: provides tears
what are 2 other glandular tissues innervated by the facial nerve? give function and consequence of loss of function
- salivary glands: produce saliva; loss of function results in xerostomia (dry mouth)
- lateral nasal glands: moisture to the nasal cavity and nasal planum; loss of function results in build up of nasal crust
what cranial nerves provide preganglionic parasympathetic innervation to the head?
3, 7, 9, 10
from the ganglion, what cranial nerve branches do postganglionic parasympathetic axons course with? what does this mean?
course with branches of CN 5 (hop on the trigeminal bus because it goes everywhere), meaning that in addition to dysfunction of one of the CN nerves that has preganglionic parasympathetic function, diseases affecting CN V can also result in loss of parasympathetic functions
what neurotransmitter is released from postganglionic parasympathetic axons?
acetylcholine
what cranial nerve provides for the preganglionic parasympathetic neurons to 2 salivary glands, lateral nasal glands, and lacrimal glands? what branch carries these preganglionic axons?
facial nerve; major petrosal branch
broadly define KCS
stands for keratoconjunctivitis sicca; is essentially dry eye due to decreased tear production
what method is use in clinical practice to measure tear duct production
Schirmer tear test
what are the 3 ways of decreasing tear production?
- glandular: immune-mediated destruction of the lacrimal gland
- neurological: cranial nerve 5
- neurological: cranial nerve 7
describe why one would see KCS with lesions involving the facial nerve (neurogenic) and trigeminal nerve (neurotropic)
CN 5 tells CN 7 to make tears; so need both working for proper tear production
state the anticipated measurement of tear production with a lesion affecting the parasympathetic fibers of CN 7
decreased
state the anticipated measurement of tear production with a lesion affecting CV 5 (sensory function, not postganglionic axons)
decreased
name the major division of the brain that contains the GSE/LMN nuclei of CN 9 10 and 11 and the nucleus that gives rise to them
a large nucleus that spans the caudal medulla; exit via jugular foramen to tympano-occipital fissure
describe the relationship of CN 9 10 and 11 to the guttural pouch in the horse
name the branch of CN 10 that provides innervation that OPENS the rima glottidis of the larynx; name the muscle that accomplishes this
vagus nerve has a branch called recurrent laryngeal nerve that provides GSE function to cricoarytenoideus dorsalis, which opens the rima glottidis
name the time/phase of respiration when the rima glottidis is actively opened
opened to open the larynx during inspiration; deficits in the recurrent larygneal branch of the vagus nerve will result in laryngeal paralysis
name the cranial nerve reflex that is used to assess CN 9 and 10
gag reflex
describe the clinical consequence anticipated with dysfunction of CN 9 and 10
dysphagia
how else might you assess the function of CN 9 and 10 other than a reflex test?
??
name the muscle of the shoulder that is innervated by the spinal branch of CN 11
trapezius
name the major division of the brain that contains the GSE/LMN nuclei for CN 12
in the caudal medulla
describe the function of CN 12
provides GSA to extrinsic and intrinsic muscle of the tongue
describe the clinical finding in the tongue with unilateral deficits in CN 12 (2 key features)
atrophy and ??
describe how you would figure out if there was bilateral CN 12 dysfunction
??
