CN Palsies Part I

Question 1

Components of the _____ nerve include the nucleus, whose cell bodies are in the midbrain, at the level of the SC. Fascicles, which are axons that are portions of the nerve still traveling through brain tissue, basilar components, intracavernous, and infraorbital. You can have a lesion at any one of these points.

Answer 1

oculomotor

Question 2

The ____ nucleus is responsible for maintaining stability in limbs. It coordinates muscle tone, body position, and gait. Not same as ataxia, where its uncoordinated movement. Tremor is at rest.

Answer 2

red

Question 3

superior Cerebellar_____ are responsible for coordination of movement. Cerebral peduncles are descending _____ and sensory tracts

Answer 3

peduncles; motor

Question 4

Fascicular lesions include _____ CN III palsy, and ataxia, _____ tremor and motor weakness

Answer 4

ipsilateral; contralateral

Question 5

whatever affects your cerebellum is always on the ___ side

Answer 5

same

Question 6

____ Syndrome is a red nucleus lesion which causes ipsilateral CN III palsy and contralateral _____/involuntary movements

Answer 6

Benedikt; hemitremor; localized to midbrain

Question 7

______ Syndrome is cerebral peduncle lesion which causes ipsilateral CN III palsy and contralateral ______/motor weakness

Answer 7

Weber; hemiplegia

Question 8

_____ CN III palsy starts as a series of rootlets that leave the midbrain _____ and pass between posterior cerebral and superior cerebellar arteries. It runs laterally to the _____ ____ arteries. Causes of this type of palsy is due to an aneurysm of the _____ or head trauma.

Answer 8

Basilar; ventrally; posterior communicating, PCA

Question 9

Which nerves are located in the wall of the cavernous sinus?

Answer 9

V1, V2, CN III, and CN IV

Question 10

Which nerves are located in the body of the cavernous sinus

Answer 10

CN VI

Question 11

any compressive disease, NOT ischemic, affects the ____ first. A single lesion that affects CN III and IV is probably in the _____ ____

Answer 11

pupil; cavernous sinus

Question 12

What can an intracavernous CN III palsy include?

Answer 12

1. CN III
2. CN IV
3. CN VI
4. Horners syndrome
5. Facial pain, numbness

Question 13

Why would you get Horners syndrome with an intracavernous CN III palsy?

Answer 13

Horner’s is part of your sympathetic chain, which is wrapped around your ICA. If its an isolated Horner’s, the lesion won’t be in the cavernous sinus, but if its a complicated Horner’s (III, IV, VI) we can localize it to the cavernous sinus

Question 14

cavernous sinus is a _____ sinus which drains blood.

Answer 14

venous; drains through the jugular veins. All the venous blood that the cavernous sinus is collecting from the front part of your eye is trying to drain back, but it gets stuck and stays in the front part of your eye. This will be seen as engorgement of blood vessels in the conj. Pts can also develop glaucoma bc of elevated episcleral venous pressure.

Question 15

what are causes of intracavernous CN III palsy

Answer 15

1. DM (pupil will be spared)
2. pituitary apoplexy
3. aneurysm
4. meningioma
5. carotid cavernous fistula
6. inflammation (tolosa hunt syndrome) –>idiopathic, very painful

Question 16

vortex veins drain into _____ veins which drain into cavernous sinus

Answer 16

ophthalmic (superior and inferior)

Question 17

Intra orbital CN III palsy deals with superior division of CN III which includes _____ and _____. Inferior division includes IR, IO, MR, and _____ ganglion. Etiologies include it being traumatic, vascular or compressive.

Answer 17

SR; LPS; ciliary;

Question 18

_____ apex is where everything leaves the orbit. Orbital apex syndrome is a compressive disorder affecting CN _____, ____, _____or _____. Common causes include tumor, infection or inflammation

Answer 18

orbital; III; IV, V1, VI

Question 19

what are signs of mechanical compression that involve the Pupillary motor fibers

Answer 19

1. Aneurysm
2. Trauma
3. Tumor
4. Uncal herniation

Question 20

what are signs of CN III palsy

Answer 20

1. LPS weakness: ptosis
2. eye abducted in primary gaze due to unopposed action of LR
3. abnormal adduction
4. abnormal subraduction
5. abnormal infraction
6. dilated pupil
7. normal abduction
8. intorsion due to intact SO innervation by CN IV

Question 21

_____ regeneration is caused by a misdirection of regenerating axons which re-inervate the wrong EOM’s, and it is ALWAYS _______

Answer 21

Aberrant; compressive

Primary: no preceding history of acute CN III palsy
-hallmark of slow-growing compressive lesion of CN III (meningioma)

Secondary: follows an acute CN III palsy
-trauma, aneurysm, congenital

Question 22

what are signs of aberrant regeneration

Answer 22

1. eyelid retraction on downgaze
2. eyelid retraction on adduction
3. pupil constriction on adduction with poor light response
4. globe retraction on upgaze

Question 23

what are causes of CN III palsy in adults

Answer 23

1. idiopathic
2. ischemic - if pupil is spared resolves in 3 months
3. compressive: aneurysm of PCA, trauma, or neoplastic

Question 24

what are causes of CN III palsy in children

Answer 24

1. congenital
2. traumatic
3. neoplasm
4. aneurysm

Question 25

How do you manage a CN III palsy if there is incomplete palsy and pupil is involved. what if its an complete palsy without pupil involvement?

Answer 25

Think PCA aneurysm, STAT ER referall for neuroimaging;

Think ischemic; monitor carefully for pupil involvement, monitor for aberrant regeneration, MRI/MRI/CTA if unresolved after 90 days.
In 65+ year olds: rule out GCA

Question 26

whats GCA

Answer 26

Giant cell arteritis; pain, hurts when they chew, scalp hurts when they brush hair, weight loss, appetitie decreased, fevers, cold chills at night

Question 27

CN IV is the only CN to leave from dorsal midbrain.Its very long and slender, and vulnerable to trauma. It is is the midbrain at the level of the ____ colliculus

Answer 27

inferior

Question 28

what are symptoms of CN IV palsy

Answer 28

1. acute onset of vertical diplopia
2. head tilt away from paretic side
3. overreaction of ipsilateral IO muscle (upshoot in adduction and abduction of eye in elevation)
4. bilateral involvement:
   - >10 degrees of cyclodeviation on double Maddox rod test.
   - V- pattern due to overreaction of both IO muscles

Question 29

a nuclear CN IV palsy will cause ____ SO palsy and _____ horners syndrome due to adjacent descending sympathetic fibers

Answer 29

contralateral; ipsilateral

Question 30

a dorsal midbrain disease in CN IV will cause ____ CN IV palsy, LND (light near dissociation) pupil, loss of vertical gaze, papilledema, and convergence retraction nystagmus

Answer 30

ipsilateral

Question 31

A CN IV palsy due to cavernous sinus will present with ____ CN IV palsy, ipsilateral CN III palsy, V1, V2, and ipsilateral ______ syndrome

Answer 31

ipsilateral; horners

Question 32

what are causes of CN IV palsy

Answer 32

1. undetermined
2. traumatic; usually bilateral
3. vasculopathic; must be isolated (no horner’s or orbital signs)
4. neoplastic

young adults: trauma, idiopathic, congenital
elderly: idiopathic, congenital (head tilt + vertical vergence ranges (>2)) or vasculopathic

Question 33

how do you manage an isolated CN IV palsy

Answer 33

1. congenital: manage with prism: BD prism in front of hypertropic eye
2. vasculopathic: blood work to rule out DM, HTN, GCA
3. young patients without vasculopathic: MRI