NMJ and Muscle Diseases

Question 1

presentation of lmn

Answer 1

fasciculations (spontaneous discharges)

fibrillations (1 single muscle discharge, unsynchronized)

Question 2

most common type of childhood disease

Answer 2

duchenne muscular dysthrophy

Question 3

disease progression of duchenne muscular dystrophy

Answer 3

ascending pattern
3-5: difficulty running, jumping, hopping, gower maneuver
6-8: toe walking
8-10: need braches, joint contractures
12-16: wheelchair-dependent or bed bound, contractures, scoliosis
16-18: systemic manifestations, dec pulmo fn

Question 4

lab findings in dmd

Answer 4

increased ck 20-100x
muscle biopsy is standard of diagnosis
immunoperoxidase stain: absent dystrophic in sarcolemma (absent stain)

Question 5

treatment for dmd

Answer 5

supportive
prednisone
eteplirsen

Question 6

presentation of beckers muscular dystrophy

Answer 6

ambulatory beyond 15 yo
cardiomyopathy
myalgias
myoglobinuria

Question 7

lab findings in beckers muscular dystrophy

Answer 7

similar to dmd but less severe

REDUCED amount of dystrophin (not absent)

Question 8

presentation of central core myopathy

Answer 8

generalized weakness or hypotonia
delayed motor milestones
affects proximal muscles (legs > arms)
minimal facial/neck flexor/ bulbar symtptoms

Question 9

lab findings in central core myopathy

Answer 9

normal cks
myopathic pattern in emg
muscle biopsy with structural alteration within the center of the muscle fiber

Question 10

forms of nemaline myopathy

Answer 10

mutation in tropomyosin, nebulin, troponin t, and actin

severe infantile form, static/slowly progressive form, adult onset form

Question 11

lab findings in nemaline myopathy

Answer 11

type 1 fiber predominance and hypotrophy

nemaline rods on sarcomela

Question 12

clinical features of myotonic dystrophy 1

Answer 12

distal limb weakness
progressing proximally
neck flexor involvement sometimes bulbar muscle
dysarthria
myotonia

Question 13

specific features in myotonic dystrophy 1

Answer 13

cataracts
frontal balding
testicular atrophy
impotence
hyperinsulinemia

Question 14

lab tests for myotonic dystrophy 1

Answer 14

normal ck
muscle biopsy: pyknotic nuclear clumps, agulated fibers
emg: fibrillating, pws, myopathic mups, myotonic discharges

Question 15

types of myotonia

Answer 15

percussion myotonia: thenar muscle delayed relaxation
grip release myotonia: delayed release of grip
tongue myotonia

Question 16

hypokalemic vs hyperkalemic periodic paralysis

Answer 16

table 6

Question 17

largest group of aceuqired and treatable cause of skeletal muscle weakness

Answer 17

inflammatory myopathies

Question 18

types of inflammatory myopathies

Answer 18

polymyositis, dermatomyositis, inclusion body myositis

Question 19

pathogenesis of inflammatory myopathies

Answer 19

triggering events causing autoimmune or t-cell mediated reaction

complement mediated microangiopathy and muscle ischemia –> necrosis, degeneration, phagocytosis of muscle fibers

Question 20

pathogenesis of dm vs pm

Answer 20

table 7

derma: perifascicular atrophy
poly: cd8 or mhc-1 lesion

Question 21

clinical presenation of inflammatory myopathies

Answer 21

progressive, symmetric proximal muscle weakness
skin manifestations in dm
systemic symptoms
associated malignancies

Question 22

inflammatory myopathy with poor outcome

Answer 22

inclusion body myositis

Question 23

skin manifestations of dm

Answer 23

heliotrope rash (eyes)
v sign and shawl sign
gottron's papules
mechanic hands
periungual telangiectasia

Question 24

treatment for inflammatroy myopathies

Answer 24

glucocorticoids
methotrexate, azathioprine, mycophenolate
immunomodulation (IV Ig)

Question 25

acquired myopathies with endocrine or systemic disease

Answer 25

thyrotoxic myopathy (proximal muscle weakness, myalgia, bulbar and respi muscles hypothyroid myopathy: proximal arm/leg weakness, fatigue, cramps, pain, stiffness, 10x ck hyperparathyroid myopathy: muscle weakness in osteomalacia

Question 26

often performed to diagnose a myopathy

Answer 26

``` ck levels thyrotropin, electrolytes, renal and liver function, cbc, esr, serum protein electrophoresis/immunofixation genetic testing ncs/emg muscle biopsy = GOLD STANDARD ```

Question 27

presenatations in nmj diseases

Answer 27

weakness | no sensory loss

Question 28

first thing to do when evaluating nmj diseases

Answer 28

rule out umn lesion first rule out sensory problems fluctuating pain in ocular or proximal muscles = nmj

Question 29

autoimmune disease of postsynaptic ach receptors

Answer 29

myasthenia gravis

Question 30

treatment of mg

Answer 30

acetylcholinesterase inhibitors | immunosuppressors

Question 31

clinical features of mg

Answer 31

fluctuating weakenss, diurnal pattern eye muscles are involved first (weakness, diplopia, ptosis) progression to other areas

Question 32

PE of mg

Answer 32

ocular weakness/ptosis with no pupillary dysfunction bifacial weakness poor gag, palatal elevation, dysarthria, dysphonia elicited by upward gaze or forward arm abduction

Question 33

simpson's test (upward gaze test)

Answer 33

fatigued eyelid when looking upwards (asymmetrical)

Question 34

gorelick's test

Answer 34

passive opening of the left eyelid leads to a decrease in the right eyes

Question 35

ice pack test

Answer 35

slows down the enzyme breakdown of ach = improved nmj transmission

Question 36

clinical features of lambert-eaton myasthenic syndrome

Answer 36

weakness, fatigability of proximal limb muscles, eom and bulbar sparing facilitation in sustained contraction autonomic symptoms, myalgias

Question 37

treatment for mg

Answer 37

mestinon, prednisone, azathioprine, plasma exchange or ivig | thymectomy

Question 38

treatment for l-e ms

Answer 38

mestinon, plasma exchange or ivig or steroids, tumor treatment

Question 39

clinical findings in botulism

Answer 39

``` descending paralysis (eye head, neck, trunk, limbs) 12-72 hrs after ingestion and progresses for several days no sensory or tendon reflex abnormalities ```

Question 40

pathogenesis of botulism

Answer 40

c. botulinum toxin prevents release of ach at nmj and autonomic synapses inhibit synaptobrevin

Question 41

treatment for botulism

Answer 41

ventilator assistance supportive care trivalent antitoxin guanidine hcl

Question 42

rns response in mg

Answer 42

slow rns, not enough ach, epp does not reach threshold normal at first then reduced amplitude

Question 43

rns response in mg

Answer 43

rapid rns epp above threshold incremental response, gradual increase in amplitude

Question 44

edrophonium test

Answer 44

block ach degradation = more free ach

Question 45

serologic tests for nmj diseases

Answer 45

achr modulating antibodies achr blocking antibodies strational antibodies anti-muscle specific receptor tk antibodies

Question 46

treatments for nmj disorders

Answer 46

``` cholinesterase inhibitors (pyridostigmine) plasma exchange or ivig or steroids thymectomy (gold standard) ```

Question 47

moa of cholinesterase inhibitors

Answer 47

prevents ache in degrading ach

Question 48

indications for plasma exchange ivig steroids

Answer 48

accutely ill patient (myasthenic crisis) improve symptoms prior to elective surgery non-response to other forms of therapy