Motor innervation Flashcards
what is affected in a CN 3 nucleus lesion
- ipsilateral MR, IR, IO
- ipsilateral sphincter (dilated pupil),
- cb muscle (lack of acc),
- contra/ipsi SR
- bilateral ptosis
what happens if lesion when follows of the superior+ posterior cerebral arteries around the cerebral peduncles
contralateral body weakness if lesion is close to the cerebral peduncles
what does cn4 follow
superior cerebellar and posterior cerebral arteries around the cerebral peduncle
inferior branch of cn3
io, ir, mr, parasympathetic, pupils-sphincter
lagopthalmos
obicularis cannot close eye properly –> dryness of cornea –> blindness usually with a cn 7 palsy
external ophthalmoplegia affected muscles
any or all eoms can be affected
cn6 fascicle location
within pons–> corticospinal tract (contra-weakness)
cn6 in cav sin
- within the cav sin near ica
- sympathetic fibers leave the ica + travel with the cn6 before splitting to cn3 or cn4
- first nerve involved with ica aneurysm
- horner’s usually occurs in the cav sin due to all the signs
where does the cn4 travel through (last step)
travels through the superior orbital fissure above the CTR outside the muscle cone
what is the CN3 most frequently affected by
posterior communicating artery aneurysm
what does the SR nuclei innervate
contralateral superior rectus
what does cn6 nucleus contain and what do they do
internuclear neurons that travel in the MLF to the contralateral MR nucleus
cn4 fascicle location
posterior
below the inferior colliculus
why are you relatively extorted in primary gaze
- head tilt will force intorsion
- head turn will force the bad eye to abduct so the rectus muscles control up and down movements
- head is tilted downwards is the objects are more in line with the hyper eye
CN3 fascicle pathway
- passes through ipsilateral superior cerebellar peduncle (ipsi ataxia)
- through red nucleus (contra tremor)
- through cerebral peduncle (CST- contra weakness)
- passes through posterior cerebral artery + superior cerebellar artery
- follows the posterior communicating artery
what curves around the cn6 nucleus
facial nucleus
CN3 fascicle pathway innervention
- ipsilateral involvement of everything (MR, IR, IO, SR, levator, sphincter, CB)
- contra eye is normal
procerus
(pulls eyebrows down + medially)
cn 6 clinical correlate- sharp bend over the petrous ridge
susceptible to compression and stretching injuries, particularly with increased ICP
superior branch of cn3
sr, levator
if lesion above sof and ctr
so palsy
numbness of forehead (cn5)
trochlear nerve nucleus location
midbrain at the level of the inferior colliculus
- anterior to cerebral aqueduct
- dorsal to MLF
- caudal to cn3 nucleus
orbicularis
closes eyelids
what cranial nerves are involved in sensory for EOMS
2,5
cn6 lesion
gaze palsy innervation to LR to contralateral MR
what does the edinger westphal nucleus innervate
iris, sphincter (miosis), cb (acc, cb contracts, parasympathetic)
where wall does the cn4 enter
wall of cav sin
cn 6 palsy - what deviation from primary position
esotropic deviation- greater at distance
levator innervates
bilaterally
the parasympathetic fibers are spared in
spared in ischemic lesion due to vasculature surrounding the nerve
first thing to go involved in compressive lesions, including an aneurysm or tumor
cn 7 facial nucleus
loops around cn6 nucleus in pons
what branches does the facial nerve divide int
temporal and zygomatic supplies the frontalis , procerus, corrugator, orbicularis
what happens in a complete cn3 palsy
- ptosis
- the eye is positioned down and out due to the unopposed actions of the SO and LR
- they cannot adduct (MR)
- in the abducted position, cannot move up or down (SR, IR)
- in the adducted position, they cannot move the eye up (IO)
- pupil dilation
- decreased acc
what is the so palsy compensation
head tilt to the opposite shoulder
- chin down
- head turn towards
- in lateral movements -abducts- turns head away from eye involved bc to abduct eye (rectus muscles to go up and down)-minimizes diplopia
cn6 nerve pathway
- fascicle
- exit the groove between the pons and medulla
- runs along the occipital bone and posterior slope of the petrous portion of the temporal bone
- -makes a sharp bend over the petrous ridge - enters the cav sin
- enters the orbit through the superior orbital fissure within the ctr
what does cn 6 (abducens) innervate
LR
CN 4 pathway
- fascicle -below of inferior colliculus
- decussates
- follows the superior cerebellar and posterior cerebral arteries around the cerebral peduncle
- enters wall of cav sin
- travels through the SOF above the CTR
cn6 palsy restriction
cannot abduct eye
CN6 nucleus location
- within in the pons
- contains the abducens motor neurons
what does the trochlear nerve innervate
cn4
cn 7 pathway
- fascicle travels around the abducens nucleus
- emerges from the brainstem at the lower border of the pons
- enters the internal acoustic foramen (w/ cn 8)
- exits the skull through the stylomastoid foramen
- divide into several branches
what fibers are superficial on the cn3 nerve
parasympathetic
when cn3 fascicle goes through ipsi superior cerebellar peduncle
ipsi ataxia
what is an incomplete cn3 palsy
external ophthalmoplegia
where is the oculomotor nerve located
midbrain @ superior colliculus
- ventral to cerebral aquaduct
- dorsal to MLF
when cn3 fascicle goes through cerebral peduncle what happens
contra weakness
what is within the lateral wall of the cav sin
cn 3,4,6
sympathetic fibers join after leaving the ICA (join to go to eyelids)
what is spared in an external ophthalmoplegia
internal muscles (pupil, acc)
what cranial nerves are involved in motor for EOMS
3,4,6
7-eyelids
corrugator
(pulls eyebrowns medially)
cn4 lesion
contralateral so palsy
what is the first nerve the cav sin affected in ica aneurysm
cn 6
cn 4 palsy
eye deviation in primary position
hyper deviation (bc SO normally pulls eye down)
where is the oculomotor nerve subnuclei located
IR, IO, MR nuclei
-innervate ipsilateral eye
when cn3 fascicle goes through red nucleus
contralateral tremor
what does the oculomotor nerve innervate
IO, MR, SR, IR, Levator, pupils (sphincter), mullers
cn 6 palsy compensation
turn head towards action of muscle to compensate (towards paralyzed side)
cn4 restrictions
when adducted, eye won’t depress
what is spared in internal ophthalmoplegia
eoms
frontalis
(raises eyebrows)
cn 7 functions
- motor root –> facial muscles
- sensory root –> taste
- parasympathetic –> glands of face, lacrimal gland
