Myogenic palsies Flashcards
what is meant by myogenic
it is something to do with the muscle itself and the nerves are not affected
list 4 myogenic conditions
- Myasthenia Gravis
- Chronic Progressive External Ophthalmoplegia (CPEO)
- Orbital myositis
- Rhabdomyosarcoma
what type of condition is myasthenia gravis
what does it affect
what is the prevalence
how serious is this condition
- autoimmune condition
- affects the striated muscles in the body e.g. respiratory system
- 1 / 10,000 in the UK
- Life threatening disease
what is myasthenia gravis classified into
- paediatric:
neonatal
congenital
juvenile - adult
ocular
generalised - drug related
how is ocular myasthenia gravis a variable condition and what what age can it come about
- 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
what is meant by neonatal myasthenia gravis
what is the outcome for these patients
- Born to myasthenia mother
- Disease self limiting (in 6 weeks approx.)
what is meant by congenital myasthenia gravis
Infants born to non myasthenic mothers
what is meant by juvenile myasthenia gravis
what is different between this and adult type
- Develop in infancy
- More spontaneous remissions than adults
what is ocular myasthenia limited to in adults
and what sign shows that it is unlikely to become generalised
- Limited to eye muscles
- If still limited to eye muscles after 2 years unlikely to become generalised
what is affected in generalised myasthenia gravis in adults
Excessive fatigability of striated muscle including respiratory muscles
how many % of ocular myasthenia patients go on to become generalised
10%
what happens in the muscles to cause myasthenia gravis
- 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
what are the 5 systemic signs and symptoms of general myasthenia gravis and explain each one
- 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
list the 3 ocular signs of myasthenia gravis
- Ptosis
- Diplopia
- Orbicularis weakness
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
- 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
when does the symptoms of myasthenia gravis tend to occur which gives clues to the condition
- 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
what is a ddx of ocular myasthenia gravis
IR palsy
explain how you test is a patient is suffering from ocular myasthenia in practice
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
describe 5 signs about the ptosis that describes ocular myasthenia gravis
- 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
what should you ask the px if you detect ptosis
ask about the diurnal variation of the ptosis e.g. what time of day does it get worse
how is cogan’s lid twitch test carried out in patients with ocular myasthenia gravis
- 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
describe the type of diplopia symptoms a px with ocular myasthenia gravis will have
- 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
list 4 types of conditions the diplopia seen in ocular myasthenia can mimic
- 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
what orbiculares weakness shows sign of ocular myasthenia gravis and how can you test this in practice
- Can usually close eyes
- May not be able to bury eye lashes
- Unable to stop examiner opening eyes with gentle pressure
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
- 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
what is seen when investigating a patient’s saccades that is indicative of ocular myasthenia gravis
there are more fatigues on gliding saccades i.e. the catch up phase will get slower the more they fatigue
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
Receptor antibodies detected in the blood
- of 80 to 90% of patients with generalised myasthenia
- of 50 to 60% of patients with ocular myasthenia
what is the prognosis of myasthenia gravis like
list 4 systemic drugs/treatment for myasthenia gravis and why each one is given/done
- 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)
what are the 3 treatment/management options for ocular myasthenia gravis
- Ptosis props
Contact lens - Occlusion
Blenderm on glasses
Frosted lens
Occlusive contact lens - Surgery
Contraindicated unless stable for a long time
why is the patient not surgically treated for their ptosis and diplopia with ocular myasthenia gravis
because of the variability
why is surgery to treat ocular myasthenia gravis contraindicated
because of the variability
a patient must be stable for 2-3 years
however at the end they usually change again
name another myogenic condition other than myasthenia gravis that involves ptosis
Chronic progressive external ophthalmoplegia (CPEO)
list the 8 characteristics of Chronic progressive external ophthalmoplegia (CPEO)
- 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”
how do the symptoms of Chronic progressive external ophthalmoplegia (CPEO) occur
very gradually but there is no variety like there is with myasthenia gravis
when may a px with Chronic progressive external ophthalmoplegia (CPEO) complain of diplopia and when may they not complain of diplopia
- diplopia: in early stages of disease when the restrictionists not exactly equal
- no diplopia: if loss is symmetrical
which response is not affected in Chronic progressive external ophthalmoplegia (CPEO) and why
pupillary response not affected/are normal
as smooth muscle is not affected by the disease
what happens in the end stages of Chronic progressive external ophthalmoplegia (CPEO)
the eyes become severely mechanically restricted eyes “FROZEN EYE” in a straight ahead position in primary position and left slightly esot or exot
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
- no fatigue is seen with this
- presents at a younger age
explain the aetiology of Chronic progressive external ophthalmoplegia (CPEO)
- 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
what are the 3 features of Kearne-Sayre-Daroff syndrome, which is associated with Chronic progressive external ophthalmoplegia (CPEO)
- Onset before 20 years old
- Fine pigmentary retinopathy
- Heart conduction block
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
- 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
what is Orbital Myositis also known as
idiopathic pseudo orbital tumour
what are sometimes associated with Orbital Myositis
autoimmune disorders
what happens in Orbital Myositis
get restrictions of the muscles and develop a squint
list 5 differential diagnosis of Orbital Myositis
- orbital cellulitis
- orbital abscess
- hematoma
- Grave’s disease (thyroid eye disease)
- real tumours
what sign is seen in Orbital Myositis, what is used to measure this sign and what condition does it mimic
- proptosis
- measured using an exophthalmometer
- mimics TED
how can you investigate Orbital Myositis and what will be seen in this
- CT scan
- enlarged extra ocular muscles - causes an anterior displacement of the globe
what is the management of Orbital Myositis
- Condition self-limiting
- Usually resolves in 8 weeks itself
- Very high dose of systemic steroids speed recovery
what can be taken with Orbital Myositis to speed up its recovery
very high dose of systemic steroids
what is Rhabdomyosarcoma
when does it usually present
what may it present with
- Highly malignant tumour striated muscle
- Usually presents in childhood
- May present with a subtle tropia
what signs is seen with a Rhabdomyosarcoma
limited eye movements with a squint from a fast growing tumour
Rapid tumour growth will lead to proptosis
what is the progression of Rhabdomyosarcoma and what can this lead to
Rapid tumour growth will lead to proptosis
what does someone with Rhabdomyosarcoma require and what are the 3 possible treatment options
- Rapid diagnosis and treatment required
- Radiotherapy
- Chemotherapy
- Enucleation of eye for no further progression
