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Neuro-ophthalmic Disease Final > CN VI Palsy > Flashcards

CN VI Palsy Flashcards

1
Q

In order to be considered comitant, what is the tolerance in different fields of gaze?

A

5 PD

decompensating phorias and congenital phorias tent to be comitant

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2
Q

what kind of problem is associated with noncomitant deviation?

A

muscle or nerve

“n”oncomitant= “n”erve

devation is largest in direction of action of the affected muscle

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3
Q

What are 2 ways to test for comitance?

A

ACT 9-Diagnostic Action Fields; Maddox Rod

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4
Q

when quantifying versions

What is the +/- scale?

A

(+)= overacting muscle
(-)= underacting muscle

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5
Q

When quantifying versions

What is the 1-4 scale?

A

1= minimal OA/ UA
4= gross/ marked OA/ UA

UA: does not cross midline; OA: iris buried under eyelid

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6
Q

What are the potential causes of an underacting EOM?

(-)UA

A

Mechanical, Paresis secondary to trauma, Innervational

Mechanical: tendon/ligament abnormality; faulty EOM insertion; scar formation s/p EOM Sx; Paresis: neurologic/ cranial nerve damage; direct trauma to muscle; innervational: impairments to CN III, IV, VI

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7
Q

What are the potential causes of an overacting EOM?

(+) OA

A

Mechanical; Idiopathic, Hering’s Law

Mechanical: faulty EOM insertion

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8
Q

If palsy improves when affected eye is fixating (normal eye is covered) is it paretic or mechanical?

A

Paretic

ductions>versions

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9
Q

If Palsy does not improve when affected eye is fixating (normal eye covered), is it paretic or mechanical?

A

Mechanical

ductions = versions

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10
Q

What does forced duction testing determine?

A

If limitation is mechanically restrictive

(-) FDT = no resistance: paretic
(+) FDT = resistance: mechanical

mechanical: tumor, graves disease, muscle entrapment

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11
Q

What does Force Generation Testing assess?

A

Active movement of the globe

determines potential force of the muscle

(+) FGT: can’t break resistance: paretic
(-) FGT: can break resistance: mechanical
inversely related to FDT

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12
Q

FGT/FDT testing has the patient look toward the restricted gaze

A

FDT

FGT has patient loook in opposite direction of restriction

FGT is testing strength while FDT is passive

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13
Q

What EOM does CN VI innervate? What is its action?

A

Lateral rectus; abduction

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14
Q

Where is the abducens nucleus?

A

Pons on the floor of the fourth ventricle

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15
Q

CN VI arises at the pontomedullary junction medial to CN VII

What 2 structures does CN VI pass between?

A

anterior inferior cerebellar artery and internaly auditory artery

trigeminal nerve also close

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16
Q

What opening does CN VI travel through to innervate the lateral rectus?

A

superior orbital fissure

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17
Q

What 4 structures are involved in abduction and horizontal gaze?

A

CN VI nucleus, PPRF, MLF, CN VI fascicles

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18
Q

What is it called when there is an inability to move both eyes in the SAME direction?

A

Gaze palsy

19
Q

What is the signature motility of CN VI palsy?

A

Eso deviation at distance

D>N

worse in gaze direction of affected eye; head turns toward direction of paretic muscle to compensate

20
Q

What are the 6 syndromes of CN VI?

A
  1. brainstem syndrome
  2. subarachnoid space syndrome
  3. petrous apex syndrome
  4. cavernous sinus syndrome
  5. orbital apex syndrome
  6. isolated CN VI palsy
21
Q

In Brainstem syndrome, there is a(n) ipsilateral/ contralateral gaze palsy with ipsilateral/ contralateral facial weakness

A

ipsilateral; ipsilateral

22
Q

Brainstem Syndrome

A lesion to the abducens nucleus causes a ipsilateral/ contralateral gaze palsy due to its proximity to what structure?

A

ipsilateral/ paramedian pontine reticular formation

23
Q

What 3 neurologic signs is fascicular sixth nerve palsy associated with?

A

Foville’s syndrome; Raymond syndrome; Millard-Gubler syndrome

24
Q

What are the three causes of Foville’s syndrome?

Foville’s: CN V, VI, VII and VIII palsies; oculosympathetic denervation and contralateral hemiparesis

A
  • Stroke (older adults)
  • Demyelination/ MS (younger patients)
  • Tumor (any age)
25
Q

What are the 3 causes of Subarachnoid space syndrome?

A
  • anterior inferior cerebellar artery aneurysm
  • Trauma
  • Elevated ICP

elevated ICP: subarachnoid hemorrhage; hydrocephalus, IIH; Post-LP or Post epidural

26
Q

CN VI courses across the bony clivus as it enteres the cavernous sinus

If trauma occurs or ICP increases, what happens to CN VI?

A

It can become compressed and lead to 6th nerve palsy

Once ICP reduces, palsy improves

27
Q

(subarachnoid syndrome)

What is the most common neurological structural condition?

A

Chiari malformation

brainstem shifts forward w/ cerebellar tonsils at foramen magnum entranc

Flow and reabsorption of CSF blocked: HA and papilledema

28
Q

What can happen at the Petrous apex that can cause CN VI palsy?

A

Gradenigo’s syndrome; petrous bone fracture; inferior petrosal sinus infection/ thrombosis; tumors (nasopharyngeal carcinoma)

29
Q

What causes Gradenigo’s syndrome?

A

Otitis Media: middle ear infection

30
Q

What are the symptoms of Gradenigo’s syndrome?

A
  • Recent onset CN VI palsy with earache and facial pain; ipsilateral facial palsy, fever, headache, vomiting, vertigo
  • Ipsilateral CN VI palsy
  • V1, V2: ipsilateral facial pain or numbness, decreased corneal sensation
  • +/- facial nerve: ipsilateral facial palsy
31
Q

What is the management of Gradenigo’s Syndrome?

A
  • MRI imaging (T2 weighted)
  • Culture ear drainage
  • CBC with diff
  • CRP

Tx: high-dose Ab treatment

cases of high-risk inflammation: mastoidectomies and petrosectomies

32
Q

When a tumor erodes through the petrous bone and affects CN VI and the SPG, what else is affected?

A

parasympathetic fibers of CN VII

innervation of lacrimal gland

cause decreased tearing on ipsilateral side

33
Q

If Cavernous Sinus syndrome is caused by Aneurysm of the ICA, what nerve is affected first?

A

CN VI

34
Q

What are ocular signs of Orbital Apex Syndrome?

seen in assocation with other CN palsies and vision loss due to CN II

A

ptosis, proptosis, conjunctival chemosis/ injection

35
Q

What is the typical patient profile of an isolated CN VI Palsy?

A

Patient over 50 years old with history of DM or HTN

36
Q

What is the onset and prognosis of Isolated CN VI Palsy?

A

Sudden onset; resolves within 3 months

37
Q

What is the management of isolated CN VI Palsy?

A
  • Manage systemic risk factors
  • GCA more common than CN Palsy over 50 years old: Run ESR/ CRP
  • No Improvement/ worsening: MRI of brain and orbits; MRA/ CTA if vascular process suspected
  • Under 50: post-viral infection most common
  • R/o mass lesions or MS: MRI

CN VI most common cranial nerve affected by MS

38
Q

What is the agenesis of CN VI known as?

A

Duane’s retraction syndrome

congenital: familial motility disorder of horizontal gaze; F>M

Aberrant regeneration d/t CN VI not developing properly; LR innervation by CN III: co-contraction of MR and LR

39
Q

Is Duane’s Retraction Syndrome unilateral or bilateral?

A

Unilateral (80%)

left eye predominance

associated with other congenital anomalies: Moebius syndrome; Morning Glory Syndrome and Goldenhar syndrome

40
Q

Which Duane’s type is most common?

A

Type I

abduction defecit; ET common

Type II: adduction defecit; XT common; Type III: abduction and adduction; XT common

41
Q

In all 3 types of Duane’s retraction syndrome, there is a narrowing/ widening of the palpebral fissure

A

Narrowing

42
Q

Why does the globe retract with Duane’s Retraction Syndrome?

A

Co-contraction of MR and LR

eye “sucks back” into the globe

Right Duane’s Type I: right globe retraction when patient looks to the LEFT (Abduction defecit)

43
Q

What is the management for Duane’s Retraction Syndrome?

A
  • No cure: provide education and reassurance
  • Surgery: reduce angle of strabismus to reduce/ stop compensatory head posture

Neuro-ophthalmic Disease Final (2 decks)

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