neuromuscular (myasthenia) Flashcards
myasthenia crisis
decreased function of the muscles that control breathing
- Diaphragm is a skeletal muscle. In some pt’s, you can have a life threatening emergency where they need to be ventilated b/c they can’t breathe
prednisone
reduces the production of harmful antibodies
how does removing the thymus help with myasthenia gravis
help T helps make antibodies and they are found in the thalmus
sxs other than fatigue associated
b. Occ difficulty swallowing or slurring of speech
c. Ptosis
d. Diplopia
e. Gait instability
g. Limb weakness proximal, often asymmetric with DTRs preserve
gender distribution
M:F 2:3
in order to produce symptoms Ach receptors must be reduced what %
iii. Ach receptors must be reduced to 30% for symptoms
what cells are effected in myasthenia gravis
iv. Smooth, cardiac muscle cells and sensory cells are unaffected
what are the theories behind the thymus and it’s involvement with myasthenia gravis
iii. Hyperplastic in 65% (possible differences in age of onset)
iv. Thymic tumors (thymomas) 10%
or T cell theory
stressors associated with myasthenia gravis
- Surgery is a big physical stressor - their symptoms will get worse
- Menstruation í physical stressor
MCC of myasthenia crisis
e. MCC = infection
can also be triggered by adverse reaction to medication
f. Drugs with cholinergic or anti-cholinergic potential should be used carefully or not at all.
unofficial in office tests
ice pack test or upward eye gaze
cool affected area for 2 minutes, ptosis resolves
diagnostic tests for myasthenia gravis
i. Antibodies in blood 85%
ii. Electromyographic testing
iii. Edrophonium testing:
iv. Neostigmine longer acting - can be used to verify
what do we use when antibody test is negative but you still suspect myasthenia gravis
how does this work
iii. Edrophonium
Rapid onset (30s), short duration/half life (5 min) acetylcholinesterase inhibition increases pool of available ACh. Improvement of symptoms immediate (also in ALS which is degeneration of motor cells). Now used when antibody testing is negative.
why do you have to titrate the dose of neostigmine
- If you overmedicate with neostigmine, you will get very twitchy so have to titrate the dosing
Tx for myastheia gravis
1/3 resolve spontaneously
ii. Pharmacologic tx with cholinesterase inhibition and steroids
iii. Non-pharmacologic therapy with PT
iv. - Acetylcholinesterase inhibition
v. - Thymectomy
vi. - Immunosuppression w/ steroids
vii. - PlasmapheresisIntravenous Immunoglobulin (IVIG)
why do you see muscle atrophy with MG
- As these muscles deteriorate, the Ach is normally in us at rest being released at low levels which is maintaining our muscle tone and supporting the growth of that tissue
a. When you take that influence away, the muscle atrophies
b. PT is really important to help keep the muscle contracting so they don’t atrophy quickly
other other therapy for mg
iii. Electroacupuncture warming therapy demonstrated a 93% effective rate when paired with pharmacologic treatment (pyridostigmins and prednisone) compared to 70% for meds alone in 1 study of 60 patients
iv. IL-4 levels were lower in observation group
NO REAL EVIDENCE FOR vIT k
Possible transmission of MG
i. Mothers can transmit MG to their newborns (can pass antibodies) but it can usually be cleared
how common is this
1-7/10,000
1. 3-5 less common than cystic fibrosis
what muscles are mainly effected
- Eyes, eyelids, facial expression, chewing, swallowing
fundamental defect in myasthenia gravis
Fundamental defect = Loss of acetylcholine receptors by binding of autoantibodies to receptor or muscle cell proteins (muscle-specific kinase) with flattening of post-synaptic folds.
iii. Release of Ach normal
compare ALS and MG
MG and ALS both function at the end of the neuron.
ALS cells die, MG, blocked transmission of the signal. impacts are initially the same, but the ALS pt gets much worse to the point where they are no longer functional (wheelchair bound, die of respiration complications)
tx for ALS
blocking Achesterase may help ALS initially, but eventually they’re going to lose so many neurons that it wont help (bc all their neurons are gone)
