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Binocular vision 2 > Myogenic palsies > Flashcards

Myogenic palsies Flashcards

1
Q

what is meant by myogenic

A

it is something to do with the muscle itself and the nerves are not affected

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2
Q

list 4 myogenic conditions

A
  • Myasthenia Gravis
  • Chronic Progressive External Ophthalmoplegia (CPEO)
  • Orbital myositis
  • Rhabdomyosarcoma
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3
Q

what type of condition is myasthenia gravis
what does it affect
what is the prevalence
how serious is this condition

A
  • autoimmune condition
  • affects the striated muscles in the body e.g. respiratory system
  • 1 / 10,000 in the UK
  • Life threatening disease
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4
Q

what is myasthenia gravis classified into

A
  • paediatric:
    neonatal
    congenital
    juvenile
  • adult
    ocular
    generalised
  • drug related
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5
Q

how is ocular myasthenia gravis a variable condition and what what age can it come about

A
  • one day the eye can be turning in and he next day it can be turning out etc
  • ocular can start at any age, so theres no specific age group
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6
Q

what is meant by neonatal myasthenia gravis

what is the outcome for these patients

A
  • Born to myasthenia mother

- Disease self limiting (in 6 weeks approx.)

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7
Q

what is meant by congenital myasthenia gravis

A

Infants born to non myasthenic mothers

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8
Q

what is meant by juvenile myasthenia gravis

what is different between this and adult type

A
  • Develop in infancy

- More spontaneous remissions than adults

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9
Q

what is ocular myasthenia limited to in adults

and what sign shows that it is unlikely to become generalised

A
  • Limited to eye muscles

- If still limited to eye muscles after 2 years unlikely to become generalised

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10
Q

what is affected in generalised myasthenia gravis in adults

A

Excessive fatigability of striated muscle including respiratory muscles

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11
Q

how many % of ocular myasthenia patients go on to become generalised

A

10%

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12
Q

what happens in the muscles to cause myasthenia gravis

A
  • Myasthenic patients develop antibodies to the receptor sites at the muscle end plate
  • Antibodies prevent the acetylcholine from binding
  • Reducing the take-up of the neurotransmitter
  • Acetylcholine continues to be released until the supply exhausted and the muscle fatigues
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13
Q

what are the 5 systemic signs and symptoms of general myasthenia gravis and explain each one

A
  • General
    Fatigue
    Lack of energy
  • Limb girdle
    Difficulty getting out of a chair
    Difficulty climbing stairs
  • Facial
    Lack of facial expression
  • Bulbar
    Problems with speech
  • Respiratory
    Problems breathing
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14
Q

list the 3 ocular signs of myasthenia gravis

A
  • Ptosis
  • Diplopia
  • Orbicularis weakness
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15
Q

how will you test if a patient is suffering from general fatigue due to general myasthenia gravis in practice
and how may a patient describe their symptoms of fatigue which may give clues to myasthenia gravis

A
  • ask px to put their arms out, you push down on them and see how much the px can take
  • px will say they don’t have the strength to push them selves up off the chair
  • if a px says they get breathless but don’t have any asthma or respiratory disorders
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16
Q

when does the symptoms of myasthenia gravis tend to occur which gives clues to the condition

A
  • their symptoms of fatigue occur after exercise or a hot shower
  • their symptoms will get worse e.g. their ptosis at the end of the day, they can’t keep their eyes open
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17
Q

what is a ddx of ocular myasthenia gravis

A

IR palsy

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18
Q

explain how you test is a patient is suffering from ocular myasthenia in practice

A

by testing their orbiculares weakness

the px with the frontal muscle to try and keep their eyes open
if you want to establish that a px has a ptosis due to myasthenia gravis
in clinic, first thing to do is suspend all over actions of the frontalis muscle but getting your thumb and pressing it onto their forehead, this immediately takes the frontal out of play
the px is to look straight ahead and you want them to elevate their eyes as your looking for the Ach receptors to build up
so you can see when the px is looking up that their lids will start to come down and when looking straight ahead, they will have ptosis

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19
Q

describe 5 signs about the ptosis that describes ocular myasthenia gravis

A
  • Often the initial sign
  • Usually bilateral often asymmetrical
  • Increases with fatigue
  • Frontalis over-action is often seen in attempt to elevate eye
  • Lid retraction occasionally in an attempt to elevate the more ptotic eye
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20
Q

what should you ask the px if you detect ptosis

A

ask about the diurnal variation of the ptosis e.g. what time of day does it get worse

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21
Q

how is cogan’s lid twitch test carried out in patients with ocular myasthenia gravis

A
  • Request patient to depress their eyes for 15 seconds
  • Lid movement follows eyes movement on depression
  • Return eyes to primary position
  • The lid initially moves above its previous level
  • Returns to its original ptotic position
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22
Q

describe the type of diplopia symptoms a px with ocular myasthenia gravis will have

A
  • Variable diplopia changes from horizontal to vertical
  • Patient report images become seperated further as muscles fatigue
  • May mimic any type of muscle palsy
  • May initially present as L-R palsy and come back as IR palsy
  • May mimic internuclear ophthalmoplegia (INO)
  • May mimic gaze palsy
23
Q

list 4 types of conditions the diplopia seen in ocular myasthenia can mimic

A
  • May mimic any type of muscle palsy
  • May initially present as L-R palsy and come back as IR palsy
  • May mimic internuclear ophthalmoplegia (INO)
  • May mimic gaze palsy
24
Q

what orbiculares weakness shows sign of ocular myasthenia gravis and how can you test this in practice

A
  • Can usually close eyes
  • May not be able to bury eye lashes
  • Unable to stop examiner opening eyes with gentle pressure
25
Q

what 7 ocular findings that vary over the course of the examination will indicate/make you suspect ocular myasthenia gravis
what will you do and why

A
  • Ptosis
  • Ocular motility
  • Prism cover test
  • Convergence
  • Prism fusion range
  • Hess chart
  • Saccades

If see variations in these then refer in suspicion of myasthenia gravis to avoid the 10% that go on to have general MG

26
Q

what is seen when investigating a patient’s saccades that is indicative of ocular myasthenia gravis

A

there are more fatigues on gliding saccades i.e. the catch up phase will get slower the more they fatigue

27
Q

what can be done to detect myasthenia gravis, and how much % in patients with generalised myasthenia gravis is it detected in and how much % of patients with ocular myasthenia gravis is it detected in

A

Receptor antibodies detected in the blood

  • of 80 to 90% of patients with generalised myasthenia
  • of 50 to 60% of patients with ocular myasthenia
28
Q

what is the prognosis of myasthenia gravis like

list 4 systemic drugs/treatment for myasthenia gravis and why each one is given/done

A
  • The prognosis of myasthenia gravis is good
  • Longer acting anticholinesterases (mestonin):
    give artificial Ach receptor to reduce the Ach build up
  • Immunosuppressive agents such as systemic steroids:
    e. g. prednisalone is severe cases, to reduce the auto immune response
  • Plasmaphoresis to reduce level of circulating antibody
  • Thymectomy: removal of thymus (rare)
29
Q

what are the 3 treatment/management options for ocular myasthenia gravis

A
  • Ptosis props
    Contact lens
  • Occlusion
    Blenderm on glasses
    Frosted lens
    Occlusive contact lens
  • Surgery
    Contraindicated unless stable for a long time
30
Q

why is the patient not surgically treated for their ptosis and diplopia with ocular myasthenia gravis

A

because of the variability

31
Q

why is surgery to treat ocular myasthenia gravis contraindicated

A

because of the variability
a patient must be stable for 2-3 years
however at the end they usually change again

32
Q

name another myogenic condition other than myasthenia gravis that involves ptosis

A

Chronic progressive external ophthalmoplegia (CPEO)

33
Q

list the 8 characteristics of Chronic progressive external ophthalmoplegia (CPEO)

A
  • Progressive symmetrical loss of ocular motility
  • Progressive symmetrical bilateral ptosis
  • Loss of Bell’s reflex (i.e. eyes don’t roll upwards when lids are closed)
  • If loss symmetrical may not complain of diplopia
  • If during the early stages of the disease the restriction is not exactly equal then the patient may complain of diplopia
  • Orbicularis weakness
  • Pupillary responses are normal as smooth muscle is not affected by the disease
  • In the end stages of the disease the eyes become severely mechanically restricted eyes “FROZEN EYE”
34
Q

how do the symptoms of Chronic progressive external ophthalmoplegia (CPEO) occur

A

very gradually but there is no variety like there is with myasthenia gravis

35
Q

when may a px with Chronic progressive external ophthalmoplegia (CPEO) complain of diplopia and when may they not complain of diplopia

A
  • diplopia: in early stages of disease when the restrictionists not exactly equal
  • no diplopia: if loss is symmetrical
36
Q

which response is not affected in Chronic progressive external ophthalmoplegia (CPEO) and why

A

pupillary response not affected/are normal

as smooth muscle is not affected by the disease

37
Q

what happens in the end stages of Chronic progressive external ophthalmoplegia (CPEO)

A

the eyes become severely mechanically restricted eyes “FROZEN EYE” in a straight ahead position in primary position and left slightly esot or exot

38
Q

what is not seen with Chronic progressive external ophthalmoplegia (CPEO) that is seen with myasthenia gravis and what age do these people tend to develop this condition

A
  • no fatigue is seen with this

- presents at a younger age

39
Q

explain the aetiology of Chronic progressive external ophthalmoplegia (CPEO)

A
  • It is the commonest of the mitochondrial myopathies.
  • CPEO is often associated with Kearne-Sayre-Daroff syndrome
  • Kearne-Sayre-Daroff syndrome (Features):
    Onset before 20 years old with a strong family history
    Fine pigmentary retinopathy
    Heart conduction block
40
Q

what are the 3 features of Kearne-Sayre-Daroff syndrome, which is associated with Chronic progressive external ophthalmoplegia (CPEO)

A
  • Onset before 20 years old
  • Fine pigmentary retinopathy
  • Heart conduction block
41
Q

what is the 2 management options of Chronic progressive external ophthalmoplegia (CPEO), if the patient complains of diplopia
and what management option is of not much use

A 
- Occlusion 
Occlusive contact lens
Blenderm
Frosted glasses
as want to make px unilaterally comfortable
  • Surgery if eye is grossly eccentrically fixated
  • Prisms – not much use
42
Q

what is Orbital Myositis also known as

A

idiopathic pseudo orbital tumour

43
Q

what are sometimes associated with Orbital Myositis

A

autoimmune disorders

44
Q

what happens in Orbital Myositis

A

get restrictions of the muscles and develop a squint

45
Q

list 5 differential diagnosis of Orbital Myositis

A
  • orbital cellulitis
  • orbital abscess
  • hematoma
  • Grave’s disease (thyroid eye disease)
  • real tumours
46
Q

what sign is seen in Orbital Myositis, what is used to measure this sign and what condition does it mimic

A
  • proptosis
  • measured using an exophthalmometer
  • mimics TED
47
Q

how can you investigate Orbital Myositis and what will be seen in this

A
  • CT scan

- enlarged extra ocular muscles - causes an anterior displacement of the globe

48
Q

what is the management of Orbital Myositis

A
  • Condition self-limiting
  • Usually resolves in 8 weeks itself
  • Very high dose of systemic steroids speed recovery
49
Q

what can be taken with Orbital Myositis to speed up its recovery

A

very high dose of systemic steroids

50
Q

what is Rhabdomyosarcoma
when does it usually present
what may it present with

A
  • Highly malignant tumour striated muscle
  • Usually presents in childhood
  • May present with a subtle tropia
51
Q

what signs is seen with a Rhabdomyosarcoma

A

limited eye movements with a squint from a fast growing tumour
Rapid tumour growth will lead to proptosis

52
Q

what is the progression of Rhabdomyosarcoma and what can this lead to

A

Rapid tumour growth will lead to proptosis

53
Q

what does someone with Rhabdomyosarcoma require and what are the 3 possible treatment options

A
  • Rapid diagnosis and treatment required
  • Radiotherapy
  • Chemotherapy
  • Enucleation of eye for no further progression

Binocular vision 2 (20 decks)

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