NMJ and Muscle Diseases Flashcards
presentation of lmn
fasciculations (spontaneous discharges)
fibrillations (1 single muscle discharge, unsynchronized)
most common type of childhood disease
duchenne muscular dysthrophy
disease progression of duchenne muscular dystrophy
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
lab findings in dmd
increased ck 20-100x
muscle biopsy is standard of diagnosis
immunoperoxidase stain: absent dystrophic in sarcolemma (absent stain)
treatment for dmd
supportive
prednisone
eteplirsen
presentation of beckers muscular dystrophy
ambulatory beyond 15 yo
cardiomyopathy
myalgias
myoglobinuria
lab findings in beckers muscular dystrophy
similar to dmd but less severe
REDUCED amount of dystrophin (not absent)
presentation of central core myopathy
generalized weakness or hypotonia
delayed motor milestones
affects proximal muscles (legs > arms)
minimal facial/neck flexor/ bulbar symtptoms
lab findings in central core myopathy
normal cks
myopathic pattern in emg
muscle biopsy with structural alteration within the center of the muscle fiber
forms of nemaline myopathy
mutation in tropomyosin, nebulin, troponin t, and actin
severe infantile form, static/slowly progressive form, adult onset form
lab findings in nemaline myopathy
type 1 fiber predominance and hypotrophy
nemaline rods on sarcomela
clinical features of myotonic dystrophy 1
distal limb weakness progressing proximally neck flexor involvement sometimes bulbar muscle dysarthria myotonia
specific features in myotonic dystrophy 1
cataracts frontal balding testicular atrophy impotence hyperinsulinemia
lab tests for myotonic dystrophy 1
normal ck
muscle biopsy: pyknotic nuclear clumps, agulated fibers
emg: fibrillating, pws, myopathic mups, myotonic discharges
types of myotonia
percussion myotonia: thenar muscle delayed relaxation
grip release myotonia: delayed release of grip
tongue myotonia
hypokalemic vs hyperkalemic periodic paralysis
table 6
largest group of aceuqired and treatable cause of skeletal muscle weakness
inflammatory myopathies
types of inflammatory myopathies
polymyositis, dermatomyositis, inclusion body myositis
pathogenesis of inflammatory myopathies
triggering events causing autoimmune or t-cell mediated reaction
complement mediated microangiopathy and muscle ischemia –> necrosis, degeneration, phagocytosis of muscle fibers
pathogenesis of dm vs pm
table 7
derma: perifascicular atrophy
poly: cd8 or mhc-1 lesion
clinical presenation of inflammatory myopathies
progressive, symmetric proximal muscle weakness
skin manifestations in dm
systemic symptoms
associated malignancies
inflammatory myopathy with poor outcome
inclusion body myositis
skin manifestations of dm
heliotrope rash (eyes) v sign and shawl sign gottron's papules mechanic hands periungual telangiectasia
treatment for inflammatroy myopathies
glucocorticoids
methotrexate, azathioprine, mycophenolate
immunomodulation (IV Ig)
acquired myopathies with endocrine or systemic disease
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
often performed to diagnose a myopathy
ck levels thyrotropin, electrolytes, renal and liver function, cbc, esr, serum protein electrophoresis/immunofixation genetic testing ncs/emg muscle biopsy = GOLD STANDARD
presenatations in nmj diseases
weakness
no sensory loss
first thing to do when evaluating nmj diseases
rule out umn lesion first
rule out sensory problems
fluctuating pain in ocular or proximal muscles = nmj
autoimmune disease of postsynaptic ach receptors
myasthenia gravis
treatment of mg
acetylcholinesterase inhibitors
immunosuppressors
clinical features of mg
fluctuating weakenss, diurnal pattern
eye muscles are involved first (weakness, diplopia, ptosis)
progression to other areas
PE of mg
ocular weakness/ptosis with no pupillary dysfunction
bifacial weakness
poor gag, palatal elevation, dysarthria, dysphonia
elicited by upward gaze or forward arm abduction
simpson’s test (upward gaze test)
fatigued eyelid when looking upwards (asymmetrical)
gorelick’s test
passive opening of the left eyelid leads to a decrease in the right eyes
ice pack test
slows down the enzyme breakdown of ach = improved nmj transmission
clinical features of lambert-eaton myasthenic syndrome
weakness, fatigability of proximal limb muscles, eom and bulbar sparing
facilitation in sustained contraction
autonomic symptoms, myalgias
treatment for mg
mestinon, prednisone, azathioprine, plasma exchange or ivig
thymectomy
treatment for l-e ms
mestinon, plasma exchange or ivig or steroids, tumor treatment
clinical findings in botulism
descending paralysis (eye head, neck, trunk, limbs) 12-72 hrs after ingestion and progresses for several days no sensory or tendon reflex abnormalities
pathogenesis of botulism
c. botulinum toxin prevents release of ach at nmj and autonomic synapses
inhibit synaptobrevin
treatment for botulism
ventilator assistance
supportive care
trivalent antitoxin
guanidine hcl
rns response in mg
slow rns, not enough ach, epp does not reach threshold
normal at first then reduced amplitude
rns response in mg
rapid rns
epp above threshold
incremental response, gradual increase in amplitude
edrophonium test
block ach degradation = more free ach
serologic tests for nmj diseases
achr modulating antibodies
achr blocking antibodies
strational antibodies
anti-muscle specific receptor tk antibodies
treatments for nmj disorders
cholinesterase inhibitors (pyridostigmine) plasma exchange or ivig or steroids thymectomy (gold standard)
moa of cholinesterase inhibitors
prevents ache in degrading ach
indications for plasma exchange ivig steroids
accutely ill patient (myasthenic crisis)
improve symptoms prior to elective surgery
non-response to other forms of therapy
