Lect 8 CN palsies 1

Question 1

Match the following fascicular CN III lesions to their characteristics:

1) Benedikt syndrome
2) Weber syndrome

a) ipsilateral CN III palsy
b) red nucleus lesion
c) cerebral peduncle lesion
d) contralateral hemiplegia
e) contralateral hemitremor/involuntary movements

Answer 1

1) Benedikt syndrome
a) ipsilateral CN III palsy
b) red nucleus lesion
e) contralateral hemitremor/involuntary movements

2) Weber syndrome
a) ipsilateral CN III palsy
c) cerebral peduncle lesion
d) contralateral hemiplegia

Question 2

(T/F) CN III enters orbit through SOF and annulus of Zinn

Answer 2

true

Question 3

Match the following divisions of CN III and where they innervate:

1) superior division
2) inferior division

a) SR
b) MR
c) ciliary ganglion
d) IR
e) LPS
f) IO

Answer 3

1) SUPERIOR division
a) SR
e) LPS (levator palpebrae superioris)

2) INFERIOR division
b) MR
c) ciliary ganglion
d) IR
f) IO

Question 4

Which one of the following is NOT true in regards to Aberrant regeneration?

a) It is ALWAYS due to a compresion lesion or trauma
b) the hallmark sign of primary aberrant regeneration is a slow growing compression lesion of CN III (meningioma)
c) It is NEVER caused by ischemic CN III palsy
d) Secondary aberrant regeration NEVER follows an acute CN III palsy

Answer 4

d) Secondary aberrant regeration NEVER follows an acute CN III palsy (FALSE, it does)

Question 5

Which one of the following is NOT abnormal in a pt with CN III palsy?

a) ADduction
b) ABduction
c) Supraduction
d) Infraduction

Answer 5

b) ABduction (because ABduction is controlled by CN 6)

Question 6

Which one of the following is NOT a sign of CN III palsy?

a) ptosis due to LPS weakness
b) eye ABducted in primary gaze
c) constricted pupil
d) intorsion intact

Answer 6

c) constricted pupil (dilated pupil is the correct sign of a CN III palsy)

**NOTE: eye will be abducted in primary gaze due to the unopposed action of LR

Question 7

Which one of the following is the #1 cause of CN III palsy in children?

a) traumatic
b) congenital
c) neoplasm
d) aneurysm

Answer 7

b) congenital=45%

• traumatic=20%
• neoplasm=10%
• aneurysm=5%

Question 8

Which one of the following is the #1 cause of CN III palsy in adults?

a) ischemic
b) neoplastic
c) trauma
d) idiopathic
e) aneurysm of PCA

Answer 8

d) idiopathic=25%

• ischemic=20%
• aneurysm of PCA=20%
• neoplastic=15%
• trauma=15%

Question 9

Which one of the following statements are NOT true?

a) In regards to CN III palsy management, we assume PCA aneurysm until proven otherwise
b) The trochlear nerve (CN IV) is the only nerve to leave from the dorsal midbrain
c) CN IV is very thick and short making it least susceptible to trauma
d) CN IV innervates the contralateral SO muscle

Answer 9

c) CN IV is very thick and least susceptible to trauma (FALSE, it is very thin and long making is vulnerable to trauma)

Question 10

Which one of the following is NOT correct?

a) Nuclear CN IV will cause ipsilateral Horner’s syndrome due to adjacent descending sympathetic fibers
b) a symptom of CN IV palsy is a head tilt away from the paretic (paralyzed) side
c) A symptom of CN IV palsy is a V-pattern tropic posture due to overaction of both IO muscles
d) The most common cause of CN IV palsy is traumatic

Answer 10

d) The most common cause of CN IV palsy is traumatic (FALSE, it is undetermined)

• undetermined=32%
• traumatic=29%
• vascular=18%
• neoplastic=5%

Question 11

Which one of the following is NOT true regarding skew deviation vs. CN IV palsy?

a) Skew deviation can mimic CN IV palsy
b) The hypertropic eye is intorted in skew deviation
c) Skew deviation presents vertical or oblique deviation due to cerebeller lesion
d) The hypertopic eye is extorted in CN IV palsy
e) pts with congenital CN IV palsy have increased vertical fusional ranges (normal :2, congenital: 8+)

Answer 11

c) Skew deviation presents vertical or oblique deviation due to cerebeller lesion (FALSE, skew deviation presents vertical or oblique deviation due to midbrain lesion)

Question 12

T/F: a CN 3 palsy you cannot close the eye and CN 7 palsy, you cannot open the eye

Answer 12

False (CN 3 palsy means you cannot open the eye and CN 7 means you cannot close the eyes)

Question 13

Which one of the following does not describe Horner’s syndrome?

a) intracavernous sinus CN 3 palsy
b) contralateral
c) sympathetic
d) runs along ICA plexus

Answer 13

b) contralateral (false, its ipsilateral)

Question 14

In a CN3 palsy, if the pupil is blown, this is indicative of:

A) compressive
B) ischemic
C) inflammatory
D) infectious

Answer 14

A) compressive (pupils sparring CN3 palsy is ischemia due to DM and HTN)

Question 15

What goes through the wall and the body of the cavernous sinus?

Answer 15

wall: CN III, IV, V1, V2
body: CN VI, ICA

Question 16

What goes through the orbital apex?

Answer 16

CN III, IV, V1, VI (causes of orbital apex lesions are tumor, infection, and inflammation)

Question 17

What do you want to rule out in 65+ year old patient who present with CN3 palsy?

Answer 17

GCA (giant cell arteritis)

Question 18

When would you use MRA (magnetic resonance angiography) and CTA (computed tomography angiography)?

Answer 18

If an ischemic CN3 is unresolved after 90 days

Question 19

T/F: in a CN6 palsy a patient would turn their head in the direction of the lesion

Answer 19

True

Question 20

You perform an alternating cover test on your patient and when you cover the right eye, the left eye comes down and when you cover the left eye, the right eye goes up. Which type of deviation is this?

A) Left hyper
B) Right hyper
C) Ortho
D) Left hypo

Answer 20

A) Left hyper