CN IV Palsy Flashcards

1
Q

What is the most common CN palsy?

A

CN IV palsy

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2
Q

When the the superior oblique a pure depressor?

A

In 37 degrees of adduction

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3
Q

When is the superior oblique an intorter and abductor?

A

In 53 degrees abducted

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4
Q

What is the tertiary action of the SO?

A

abduction

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5
Q

What are the 2 circumstances where the hypertropia will be worse? (signature findings)

A
  1. across from vertically limited eye

2. ipsilateral head tilty

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6
Q

What are the 3 steps in Parks 3-step testing?

A
  1. Check hyper in Primary Gaze
  2. Check hyper in right/left gaze
  3. Check higher in right/left head tilt
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7
Q

Anything greater than 10 degres of torsion for one eye is suggestive of?

A

Bilateral CN IV palsy

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8
Q

A unilateral CN IV palsy usually has how many degrees of torsion?

A

2-5 degrees

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9
Q

What are the 3 ways we can test excyclotorsion subjectively?

A
  1. Bilateral Maddox Rod
  2. Subjective drawing
  3. Bagolini Lenses
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10
Q

In a CN IV palsy, the eye will be intorted or extorted?

A

Extorted

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11
Q

When measuring excyclotorsion, if the objective and subjective measurement are the same this means?

A

Recently acquired and acute onset (possibly trauma)

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12
Q

When measuring excyclotorsion, if the objective finding is greater than the subjective findings this means?

A

Chronic palsy, longstanding

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13
Q

When measuring excyclotorsion, if there is no subjective finding but an objective finding this means?

A

Congenital/acquired in childhood

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14
Q

What type of lesion will cause someone to get a bilateral CN IV palsy?

A

Lesion at anterior medullary velum (where both nerves cross)

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15
Q

What is the main finding in a bilateral CN IV palsy?

A

Reversing hyper in right and left gaze

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16
Q

How long must you wait before surgery is considered for a bilateral 4th palsy?

A

must wait 1 year

17
Q

What is the most common cause of a 4th palsy in adults and kids?

A

Trauma

18
Q

What is the workup for a 4th nerve palsy in a 20-50 year old?

A
  1. Neuroimaging: MRI

2. Follow the patient

19
Q

What is the workup for a 4th nerve palsy in a 50+ year old?

A
  1. Neuroimagin: MRI

2. Vasculopathic workup

20
Q

What are the 3 ways to manage a 4th nerve palsy?

A
  1. Fresnel prisms + Patch for 9-12 months
  2. Monitor for 2’ contracture
  3. Sx = must wait 1 year