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BV simon > Ocular Palsies > Flashcards

Ocular Palsies Flashcards

1
Q

When do you get triad of symptoms?

A

lesions of ocular motor nuclei
nerves weaken
paralyse of the EOM

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2
Q

What is strabismus?

A

Deviation of the eye from the primary gaze position in the opposite directions of the muscle’s normal action

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3
Q

What is diplopia?

A

Double vision

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4
Q

What is external Ophthalmoplegia?

A

Limitation of eye movements in the muscles normal directions of action

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5
Q

How do you get classical nerve palsies?

A

Complete (all nerves function effected)
Isolated ( no other brain or nerve involvement)
Unilateral (1 nerve and one eye only )

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6
Q

Who gets 3rd nerve palsies?

A

Adult more

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7
Q

Who gets 4th nerve palsies

A

Children more

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8
Q

Who gets 5th Nerve palsies ?

A

Adult more

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9
Q

Who gets mixed nerve palsies?

A

Equal in children and adults

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10
Q

What are the potential acquired causes?

A

Nuclei in the brainstem

Intra cranial nerve (classical cause)

Intra cranial nerve (mixed multiple involvement)

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11
Q

How does nuclei in the brainstem cause problems?

A

Other brainstems structures are involved

vascular infarct, tumors, inflammation

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12
Q

How does classical intra cranial cause problems?

A 
trauma, 
tumours, 
arterial aneurysms, 
subarachnoid space 
ischemic micro - vascular neuropathy
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13
Q

How does mixed intra cranial nerve cause problems?

A

In or near cavernous sinus,

inflammation

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14
Q

How is acquired classical adult palsies caused?

A

Vascular - common in type 2 diabetes in older px

25% idiopathic

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15
Q

Why does each muscle have an action ?

A

contributions of their anatomy to this

Origins, orbital paths and scleral insertions

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16
Q

What are the medial walls of orbits ?

A

Medial walls formed by ethmoid bones and are parallel to visual axis

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17
Q

What is the angle of medial walls and lateral walls?

A

45 degrees

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18
Q

What is the angle between the visual axis and orbital axis of each eye?

A

22.5 degrees

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19
Q

Where does the 4 rectus and the superior oblique originate?

A

common tendon (the annulus of zinn) attached to the bone at the orbital apex, and encircling the optic canal and adjoining part of the superior orbital fissure

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20
Q

Where do the 4 rectus insert?

A

insert near the limbus anterior to the equator

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21
Q

What do SR and IR do?

A

SR & IR run parallel to the orbital axis 23 degrees to the visual axis in primary gaze and have a convex insertion

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22
Q

Where does the SO pass?

A

The SO passes backwards through the trochlear pulley at 45 degrees to the visual axis and insert posterior to the equator

23
Q

Where does the IO originate from ?

A

From a short tendon attached to the anterior medial wall of the orbit just inferior to the rim of lacrimal fossa

24
Q

Where does the IO run?

A

Runs parallel backwards at 51 degrees to the visual axis under the IR and inserts posterior to the equator

25
Q

What are the three paths of the rectus muscles?

A

Equator of the globe
Mid orbital region
common annular tendon

26
Q

What does the scleral to limbus distance of rectus muscles show?

A

How strong or weak the muscle is

The closer to limbus the stronger the muscle

27
Q

Which rectus is the strongest?

A

Medial rectus - 5.5mm insertion distance sclera to limbus

28
Q

What type of insertion does the superior oblique have?

A

Wide insertion by long tendon 20mm posterior and lateral to the equator under the SR muscle

29
Q

What type of insertion does the inferior oblique have?

A

Wide insertion by short tendon

30
Q

What are the key features of classical 3rd nerve palsy?

A

Ocular deviation
external ophthalmoplegia
Internal ophthalmoplegia
Complete or partial ptosis

31
Q

What does complete deviation show in 3rd nerve palsy?

A

complete exotropia (abduction) and some depression (hypotropia)

32
Q

What does external ophthalmoplegia show in 3rd nerve palsy?

A

limited no adduction or elevation eye movement

33
Q

What does internal ophthalmoplegia show in 3rd nerve palsy?

A

dilated unreactive pupil and loss of accommodation

34
Q

What does complete or partial potosis show in 3rd nereve palsy?

A

so no or little diplopia

35
Q

Why do you get these features in 3rd nerve palsy?

A

All adductors (MR, IR, SR) and elevators (SR, IO) are paralysed with 2 abductors (LR, SO) and depressors(SO) unopposed

36
Q

Why do you get undilated and unresponsive pupil?

A

Constriction sphincter muscle paralysed, dilator muscle unopposed

37
Q

Why do you get ptosis?

A

levator palpebrae superioris muscle paralysed, orbicularis oculi unopposed

38
Q

What is common cause of 3rd nerve palsy?

A

Posterior Communicating artery aneurysm

39
Q

What does the 3rd nerve contain?

A

parasympathetic, nerve fibres cause pupil to constrict and run from superior to inferior

40
Q

What does the 3rd nerve axons occupy?>

A

Superficial edge supplied by larger blood vessels

41
Q

What problems do you get with spared pupillomotor axons in diabetic retinopathy?

A

PCoA aneurysm somewhere else non directly on the axons and spares the pupil

42
Q

What is effected in diabetic retinopathy?

A

The deep micro vascular capillaries in the nerve

43
Q

What are clinical key features of 6th nerve palsy?

A

External ophthalmoplegia - limited no abduction eye movements

ocular deviation - complete adduction

Horizontal diplopia - worsening with gaze towards the affected side and at far

44
Q

What does the 6th nerve palsy have compared to 3rd nerve palsy?

A

No ptosis

45
Q

What do you have to do for 6th nerve palsy and esotropia?

A

Compensatory strategy= abnormal head posture,

reduce diplopia

46
Q

What are some causes of 6th nerve palsy?

A

Lateral head trauma to temporal bone

Arterial pathology

Non classical brainstem tumours

47
Q

What is meant by lateral head trauma to temporal bone

A

inward movement of petrous portion crushes nerve against the clivus at the petro-sphenoidal ligament

48
Q

What is meant by arterial pathology?

A

Hardening or aneurysm of the basilar artery or AICA near nerve exit from the brainstem

49
Q

What is meant by non classical brainstem tumours?

A

Downwards pressure ruptures nerve in the same region

50
Q

What are the clinical features of 4th nerve palsy?

A

Ocular deviations - exotorsion, hypetropia and exotropia

External ophthalmoplegia - limited no adduction especially on near gaze

Torsional and vertical diplopia- worse when looking down or near

51
Q

When do patients complain of SO palsy?

A

Read , walk or down the stairs

52
Q

What are the causes of 4th nerve palsy?

A

> Frontal head trauma- whiplash
Brainstem tumours that pushes brain back and forwards
Rupture nerve by displacement as long thin and unprotected by dura as it curves around the midbrain and into subarachnoid space

53
Q

What do you do in 4th nerve palsy?

A

Compensation - head tilt away from affected eye to reduce vertical and torsional components of diplopia

54
Q

What happens if you get a lesion in 6th nerve ?

A

Lesion in pons on abducens nerve - would be subarachnoid space - right eye esotropia
Cause: aneurysm in artery

BV simon (5 decks)

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