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Neuroanatomy 2 > Optic neuropathies > Flashcards

Optic neuropathies Flashcards

1
Q

how long is the intraocular portion of the optic nerve?

  1. The intraorbital
  2. Intracannalicular
  3. Intracranial
A
  1. 1mm in length
  2. 25 mm
  3. 9mm
  4. 16mm
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2
Q

what are the 3 clinical pearls about the optic nerve?

A
  1. Longer than orbital length (stretch)
  2. Attached to dura in optic canal (site of injury)
  3. 2 nerves form the chiasm - pathology there is chiasmopathy, optic neuropathy or both
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3
Q

What is a disorder that preferentially affects ganglion cells?

A

Glaucoma - will respect horizontal midline

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4
Q

What is the cup of the optic nerve composed of?

A

Dead tissue

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5
Q

What part of the eye is mostly responsible for central visual acuity?

A

The maccula/fovea

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6
Q

If you have a lesion of the right optic tract what defects do you expect?

A
  1. RAPD in the left eye

2. Heminiopia

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7
Q

Vast majority of optic neuropathies are…

A

Asymmetric

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8
Q

What is the function of the RAPD?

A

Compares the amount of light perceived by each optic nerve

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9
Q

What disease is RAPD present in?

A
  1. Most optic neuropathies
    ALWAYS IN OPTIC NEURITIS
  2. Diseases producing diffuse retinal dysfunction
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10
Q

A lesion in the optic tract is enough to produce a RAPD why?

A

There is a 6% difference in the proportion of fibers that cross behind the chiasm

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11
Q

Will patient with cataracts have a RAPD?

A

Never!

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12
Q

How do you evaluate an optic nerve clinically?

A

Borders (are they sharp)
color (pink is normal, pallor is pathologic)
cup (yellow hole in the middle)
are there hemorrhages?

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13
Q

What are Drusen

A

Small calcium deposits in the nerve

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14
Q

What is Pepilledema?

A

Swelling of the optic nerve due to increased ICP, and swelling is BILATERAL

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15
Q

What is the general flow chart from increased ICP to optic nerve swelling?

A

–> narrower spaces for CSF circulation, CSF excess around the optic nerve

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16
Q

Papilledema is swelling of which portion of the optic nerve?

A

VISIBLE portion - secondary to increased ICP

17
Q

In papilledema is swelling often uni or bilateral?

A

bilateral

18
Q

When might papilledema appear unilateral?

A

If one of the nerves is atrophic

19
Q

What is the mechanism for papilledema?

A

Axoplasmic stasis - slowing axoplasmic flow at lamina cribrosa - transmitted along meningeal sheaths IN SUBARACHNOID SPACE

20
Q

What is the difference between papilledema and other optic neuropathies?

A

Central vision is NORMAL

21
Q

When does central vision fail?

A

when nerve swells and fluid accummulates around the nerve seeps into the maccula

22
Q

If disc swelling is chronic how will the disc appear?

A

Axons die, whitish color, cup disappears

23
Q

What is the first step in diagnosing papilledema?

A

MRI

24
Q

If MRI for suspected papilledema is normal what do you do?

A

Do a lumbar puncture and assess opening pressure and measure CSF composition -

25
Q

what is the most common inflammatory - infectious cause of optic neuropathy?

A

Syphillis, TB, viruses, fungi

26
Q

what is the most common inflammatory - non- infectious cause of optic neuropathy?

A

Demyelinating optic neuritis, sarcoid,

27
Q

Most common causes of optic neuropathies for patients under 50

A

Demyelinating neuropathies - usually UNIlateral visual loss, RAPD and pain on eye movement

28
Q

Most common causes of optic neuropathies for patients OVER 50

A

Ischemic - non arteritic (more common) and arteritic (rarer can lead to bilateral blindness)

29
Q

In patients under 50 with demyelinating neuropathies what proportion have optic nerve head swelling?

A

1/3 with variable swelling,

2/3 with normal appearing nerve

30
Q

describe the visual loss in non-arteritic ischemic optic neuropathies

A

Altitudinal - respects horizontal midline due to hypo-perfusion of the optic nerve head

31
Q

What age group does giant cell arteritis affect?

A

Older patients over 70

32
Q

What are common systemic symptoms of giant cell arteritis ?

A
  1. Jaw claudications
  2. Headache
  3. scalp tenderness
  4. wt loss
  5. shoulder pain and fatigue
33
Q

Which two inflammatory markers are high in giant cell arteritis?

A

ESR and CRP

Neuroanatomy 2 (25 decks)

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