neuromuscular (myasthenia)

Question 1

myasthenia crisis

Answer 1

decreased function of the muscles that control breathing

2. 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

Question 2

prednisone

Answer 2

reduces the production of harmful antibodies

Question 3

how does removing the thymus help with myasthenia gravis

Answer 3

help T helps make antibodies and they are found in the thalmus

Question 4

sxs other than fatigue associated

Answer 4

b. Occ difficulty swallowing or slurring of speech
c. Ptosis
d. Diplopia
e. Gait instability
g. Limb weakness proximal, often asymmetric with DTRs preserve

Question 5

gender distribution

Answer 5

M:F 2:3

Question 6

in order to produce symptoms Ach receptors must be reduced what %

Answer 6

iii. Ach receptors must be reduced to 30% for symptoms

Question 7

what cells are effected in myasthenia gravis

Answer 7

iv. Smooth, cardiac muscle cells and sensory cells are unaffected

Question 8

what are the theories behind the thymus and it’s involvement with myasthenia gravis

Answer 8

iii. Hyperplastic in 65% (possible differences in age of onset)
iv. Thymic tumors (thymomas) 10%

or T cell theory

Question 9

stressors associated with myasthenia gravis

Answer 9

1. Surgery is a big physical stressor - their symptoms will get worse
2. Menstruation í physical stressor

Question 10

MCC of myasthenia crisis

Answer 10

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.

Question 11

unofficial in office tests

Answer 11

ice pack test or upward eye gaze

cool affected area for 2 minutes, ptosis resolves

Question 12

diagnostic tests for myasthenia gravis

Answer 12

i. Antibodies in blood 85%
ii. Electromyographic testing
iii. Edrophonium testing:
iv. Neostigmine longer acting - can be used to verify

Question 13

what do we use when antibody test is negative but you still suspect myasthenia gravis

how does this work

Answer 13

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.

Question 14

why do you have to titrate the dose of neostigmine

Answer 14

2. If you overmedicate with neostigmine, you will get very twitchy so have to titrate the dosing

Question 15

Tx for myastheia gravis

Answer 15

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)

Question 16

why do you see muscle atrophy with MG

Answer 16

1. 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

Question 17

other other therapy for mg

Answer 17

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

Question 18

Possible transmission of MG

Answer 18

i. Mothers can transmit MG to their newborns (can pass antibodies) but it can usually be cleared

Question 19

how common is this

Answer 19

1-7/10,000

1. 3-5 less common than cystic fibrosis

Question 20

what muscles are mainly effected

Answer 20

1. Eyes, eyelids, facial expression, chewing, swallowing

Question 21

fundamental defect in myasthenia gravis

Answer 21

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

Question 22

compare ALS and MG

Answer 22

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)

Question 23

tx for ALS

Answer 23

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)