Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Neuro-ophthalmic Disease Final > CN IV Palsy > Flashcards

CN IV Palsy Flashcards

1
Q

What are the primary, secondary and tertiary actions of the superior oblique muscle?

Innervated by CN IV

A
  • primary: intorsion
  • Secondary: depression
  • Tertiary: abduction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

3 unique characteristics of CN IV

A
  1. longest intracranial course
  2. thinnest nerve (in terms of number of fibers)
  3. Only CN that decussates and exits at the dorsal aspect of the brainstem
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Normally, when the head tilt, the eye on top extorts/intorts and the eye on the bottom extorts/intorts

A

top eye extorts; bottom eye intorts

extort: IO and IR laterally rotate away from note

intort: SO and SR laterally rotate toward nose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In a LEFT CN IV palsy, there will a be a RIGHT hyper/hypo tropia and extorsion/intorsion in primary gaze

A

hypertropia; extorsion

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Vertical diplopia with a CN IV palsy is greater at near/distance

A

near

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Because objects will appear tilted to someone with a CN IV palsy, they will develop a compensatory head tilt toward/ away from the affected side

A

away

Right CN IV palsy develops head tilt to the left

CN IV: TILT AWAY to relieve torsional diplopia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Park’s 3-Step test is useful to detect what?

A

A single paretic vertical muscle

SO

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How is Park’s 3-Step done?

A

Perform ACT is primary gaze, right and left gaze, and with head tilted right and left

detects small deviations, tests for comitancy and quantifies devation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

A patient with a RIGHT CN IV palsy will have hypertropia worse in which gaze/ head tilt?

A

Left gaze; right head tilt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is a subjective measurement of the angle of excyclotorsion?

A

Bilateral Maddox Rod

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is an objective way to measure the angle of excyclotorsion?

A

Fundus photos

Normal Fundus: fovea slightly lower than optic disc; excyclotorsion: fovea will present as markedly lower

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What does it mean if the objective measurement of the angle of excyclotorsion equals the subjective measurement?

A

Recent onset SO palsy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What does it mean if the objective measurement of the angle of excyclotorsion is greater than subjective?

A

Longstanding SO palsy

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What will subjective and objective testing look like when the SO palsy is congenital?

A

Will only notice the objective measurement; patient will not report anything for subjective

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

3 most common etiologies of CN IV palsy?

A

congenital, traumatic, ischemic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

3 causes of congenital CN IV Palsy?

A
  1. hypoplasia of trochlear nucleus
  2. anaomalies of the SO muscle
  3. Birth Trauma
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What physical characteristics might someone with congenital CN IV palsy present with?

A

mild facial symmetry; long-standing head tilt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Vertical vergence ranges are small/ large in congenital CN IV Palsy

A

Large

10-15 PD

19
Q

Why is CN IV vulnerable to trauma?

A

long course and surrounding structures

20
Q

What can happen to CN IV at the free tentorial edge

A

compression

21
Q

What can happen to CN IV at the ambient cistern?

A

Subarachnoid hemorrhage

22
Q

What is the laterality of traumatic CN IV palsy?

A

unilateral or bilateral

23
Q

What is the prognosis for traumatic CN IV palsy?

A

partial or complete resolution

24
Q

What systemic diseases are often see with ischemic CN IV Palsy?

A

microvascular disease

HTN, DM, atherosclerosis, smoking

25
Q

What is the onset of diplopia associated with ischemic CN IV Palsy?

A

Acute

no other CN involvement, neurologic signs or symptoms

26
Q

What are the fusional ranges associated with ischemic CN IV Palsy?

A

Normal

27
Q

How long does it take for ischemic CN IV Palsy to resolve?

A

3-4 months

28
Q

What are the 5 syndromes of CN IV Palsies?

A
  1. Nuclear-fascicle syndrome
  2. subarachnoid space
  3. cavernous sinus syndrome
  4. orbital syndrome
  5. isolated CN IV palsy: acquired and congenital
29
Q

What neurologic signs are associated with Nuclear-Fascicular CN IV palsy?

A

there are none

30
Q

Is the CN IV palsy ipsilateral or contralateral to the lesion in nuclear-fascicular CN IV Palsy?

A

contralateral

fasicicles from nucleus decussate to innervate contralateral SO

31
Q

Does Horner’s syndrome occur ipsilateral or contralateral to the lesion in nuclear-fascicular CN IV Palsy?

A

Ipsilateral

oculosympathetic pathways descend through the dorsolateral tegmentum of the midbrain adjacent to the trochlear fascicles

32
Q

What is the most common cause for the bilateral CN IV palsy that occurs within the subarachnoid space?

A

Trauma

contracoup forces by the tentorial edge injur the nerves at this site

less frequent causes: subarachnoid hemorrhage, tumor and meningitis
Trauma is the most common cause of CN IV palsy in adults

33
Q

If someone presents with bilateral CN IV Palsy, what else should we look for?

A

Dorsal Midbrain syndrome

34
Q

What is the clinical picture of subarachnoid CN IV palsy?

A
  • LND pupils
  • Collier’s lid tuck in upgaze (lid retraction with limited upgaze)
  • LHyper greater in left head tiltand right gaze
  • RHyper greater in right head tilt and left gaze
  • > 10 degrees of excyclotorsion
35
Q

When is observation only acceptable in CN IV palsy?

A

unilateral cases: with established history of trauma or with increased vertical vergences

36
Q

When does isolated, unilateral palsy withOUT trauma need to be worked up?

A

When there are no obvious microvascular ischemic or other risk factors

Work up: BP, Glucose tolerance test, CBC with diff, ESR/ CRP, RPR, FTA-Ab, ANA

37
Q

When is neuroimaging ordered in CN IV Palsy in adults?

A
  • bilateral
  • evidence of dorsal midbrain syndrome
  • involvement of other crainial nerves
  • ischemic palsy suspected, but not resolving in 3-4 months
38
Q

What is the most common cause of CN IV Palsy in Children?

A

Congenital

39
Q

When are children with CN IV palsy observed only?

No workup ordered

A
  • Unilateral with established history of trauma
  • Unilateral with increased vertical vergences
40
Q

When is neuroimaging ordered for children with CN IV palsy?

A
  • bilateral
  • evidence of dorsal midbrain syndrome
  • other cranial nerves involved
41
Q

When should caution be used with monocular occlusion as a management option for CN IV Palsy?

A

Children- may develop amblyopia

42
Q

How can prism be used to manage CN IV palsy?

A

BD over the hyper (paretic) eye; can split prism between the two eyes

BD over hyper eye; BU over fellow eye

43
Q

Which type of CN IV Palsy would benefit the most from surgery?

A

traumatic

Wait at least 6 months for spontaneous improvement

allow time to see if blood/ edema will clear; relieve symptoms with occlusion therapy or prism in meantime

43
Q
A

Neuro-ophthalmic Disease Final (2 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions