myasthenia gravis Flashcards
(61 cards)
1
Q
mg definition
A
a chronic auto-immunye neuromuscular disease causing weakness in the voluntary (skeletal) muscles
2
Q
mg caused by a reduced availability of ? at the NMJ
A
acetylcholine
3
Q
which dysarthria would you expect with mg
A
flaccid only (failed muscle contractions, never spastic)
4
Q
mg hallmark feature
A
- skeletal (voluntary) muscle weakness following periods of activity
- weakness rapidly improves after a period of rest
5
Q
chronic or gradual onset in mg?
A
both
6
Q
how does the neuromuscular junction work
A
- axons release neurotransmitter (acetylcholine)
- neurotransmitter travels across the synapse and attaches to receptors on the post-synaptic membrane
- receptors are stimulated which causes muscle contraction
7
Q
mg pathophysiology
A
body makes antibodies to cockblock the acetylcholine from the receptors :(
- the immune system produces antibodies that interfere with the NMJ
- antibodies block, alter, or destroy receptors for acetylcholine at the NMJ
- prevents muscular contraction from occurring
8
Q
2 prevalence peak decades in mg
A
- women: 20/30 years
- men: 70/80 years
9
Q
gender ratio in mg
A
3:1, f:m
10
Q
typical clinical features of mg
A
- fatigueable ptosis
- extraocular muscle weakness: diplopia, limitation of eye movements
- facial weakness
- weakness of eye closure
11
Q
ptosis
A
eyelid drooping
12
Q
what is the first symptom in 2/3 of mg patients
A
ptosis
13
Q
diplopia
A
double vision
14
Q
does mg have fasciculations?
A
no, only mnd
15
Q
mg ocular muscle weakness features
A
fluctuating ptosis, diplopia
16
Q
mg bulbar muscle weakness features
A
- dysarthria
- painless dysphagia
- dysphonia
- masticatory weakness
17
Q
mg facial muscle weakness features
A
- facial weakness
- inability to close eye firmly
- drooling of saliva
18
Q
mg axial muscle weakness features
A
flexion or extension of the neck
19
Q
mg limb muscle weakness features
A
weakness involving the arms more than legs
20
Q
mg respiratory muscle weakness features
A
- labor breathing
- orthopnea
- dyspnea
- respiratory failure
21
Q
orthopnea
A
shortness of breath that occurs while lying flat and is relieved by sitting or standing
22
Q
dyspnea
A
feeling short of breath
23
Q
initial bulbar symptom in ?%
A
15%
24
Q
bulbar signs in mg
A
- nasal regurgitation
- hypernasality
- difficulty masticating solids
- weak breathy voice quality
25
external contributing factors (that can trigger mg symptoms)
- emotional upset
- hypo-/hyperthyroidism
- menstrual cycle
- systemic illness
- pregnancy
- increased body temperature (hot baths, fireplace)
- meds affecting neuromuscular transmission
26
mg rating scale
- Osserman Classification System
27
Osserman Classification System
- Class 1 (any eye muscle weakness, possible ptosis, all other strength is normal)
to
- Class 5 (intubation needed to maintain airway)
28
6 subtypes of mg
- ocular
- early onset
- late onset
- thymoma MG
- seronegative MG x 2
29
role of the thymus gland in risk factors for mg
- 10-20% of people with mg have a thymoma
- 20-40% of people with a thymoma will develop mg
30
full clinical evaluation
- elicit fatigue
- repeatedly blink (ptosis)
- upward gaze (double vision)
- count 1-100 (dysarthria)
- abduct arm (unilateral weakness)
- forced vital capacity
- hx thymoma
31
mg diagnostic tests
- tensilon (edrophonium) test
- ice-pack test
- electrophysiological tests (EMG, nerve conduction)
- auto-antibody test (blood test)
32
tensilon (edrophonium) test
- prolongs the duration of action of acetylcholine
- increases the amplitude and duration of the contractions
33
edrophonium chloride function
short-acting acetylcholinesterase inhibitor
34
tensilon (edrophonium) test sensitivity
71.5-95%
35
the tensilon (edrophonium) test is most reliable in people with ?
ptosis, nasal speech, or strabismus
36
important requirement before administering the tensilon (edrophonium) test
need to fatigue before administering it to see changes
37
MG prognosis
- relatively normal, not degenerative
- may go into remission temporarily and muscle weakness can disappear (discontinue meds)
38
MG management
- cholinesterase inhibitors
- corticosteroids
- plasma exchange
- immuno-suppression
- IVIG
- thymectomy
39
(MG management) cholinesterase inhibitors
- mimic neurotransmitters and prevent the breakdown of neurotransmitters
- manage fatigue
40
(MG management) corticosteroids
- complete relief of symptoms in most patients
- managing acute relapses
- reduce inflammation in the CNS
41
(MG management) plasma exchange
- 2nd line of therapy (after corticosteroids)
- blood filter to take out antibodies
- often 4-5 treatments over 2 weeks in hospital
42
(MG management) immuno-suppression
- stop the immune system from cockblocking the neurotransmitters
- prednisone
43
(MG management) IVIG
- intraveneous immunoglobulin
- injected with normal antibodies to change immune system responses
44
(MG management) thymectomy
remove enlarged or tumorous thymus
45
2 potential MG crises
- myasthenic crisis
- cholinergic crisis
46
myasthenic crisis
- severe weakness from MG
- need intubation for ventilatory support or airway protection
47
intubation for a myasthenic crisis is indicated if ?
- evidence of respiratory muscle fatigue
- increasing tachypnea
- declining tidal volumes, hypoxemia, hypercapnea, and difficulty handling secretions
48
favored treatment for myasthenic crisis
plasma exchange
49
cholinergic crisis
- overdose of cholinesterase inhibitors
- sweating, constricted pupils, excessive salivation, muscle fasciculations
50
thymectomy goal
stable, long-lasting remissions
51
MG SLT-related assessments
- MG-ADL
- MG-QOL15
52
SLT assessment in MG
- observe muscle fatigue at rest and during OMA
- check low tone/flaccidity in OMA
- evaluate over time
- stress/fatigue tests (count 1-100, include solids in swallow eval)
53
MG dysarthria
- hypernasality
- weak, breathy voice
- low volume
- misarticulation
- fatigability
54
dysarthria management
- observe the effects of medical intervention
- educate causes and factors affecting speech
- energy conservation (rest before conversation, short sentences, take breaks, calls early in day, non-verbal options, quiet environment)
55
NB for dysarthria management
- muscle strengthening exercises and speech drilling are contra-indicated
- can't reverse neurotransmitter blocking
- will only worsen the dysarthria
56
possible prostheses
- ptosis props
- palatal lift prosthesis
57
prosis props
- hold eyelids up
- useful for reading books and watching movies
58
palatal lift prosthesis
- help hold up soft palate
- good for correcting hypernasality (not misarticulation)
- removed when eating and drinking
59
dysphagia in MG
- difficulty masticating solid foods (fatigue)
- nasal regurgitation of fluids
- weak tongue movements
- reduced hyolaryngeal excursion
- poor airway protection
- impaired UES tone
- weak cough
60
dysphagia management in MG
- observe effects of medicine
- education
- compensatory (small meals, small bolus, avoid chewy solids, multiple swallows)
61
NB for dysphagia management
direct rehab contra-indicated
