Neuromuscular Disorders Flashcards
skeletal muscle fibres are innervated by __ neurons whose cell bodies arise in the __ horn of the spinal cord
motor
ventral/anterior
define the motor end plate
synapses formed between terminal motor neurons and skeletal muscle
this enzyme breaks down Ach into ___ and ____
acetylcholinesterase
acetone
choline
is acetate or choline sequestered into presynaptic vesicles?
choline
clostridium botulinum exists where?
soil
MoA of botox?
cleaves presynaptic proteins involved in vesicle formation
lambert eaton myaesthenic syndrome involves an inflammatory response against what structure?
presynaptic Ca channels
Tx of lambert eaton myeasthenic syndrome?
3,4- diaminopyridine
LEMS is associated with what condition?
small cell carcinoma
myaesthenia gravis is a __-synaptic disorder
post
most common disorder of the NMJ
myaesthenia gravis
myaesthenia gravis is an autoimmune condition T or F
T
pathophysiology of myaesthenia gravis
antibodies made against ACh receptors causing muscle weakness and fatigue
symptoms of MG begin when ACh receptors are reduced to __% of normal
30
what gland plays a particular role in myaesthenia gravis?
thymus
name the 2 peaks of incidence of MG and the genders they appear in
females in 30s
men in 60s/70s
clinical presentation of MG
fluctuating weakness worse during day
extraocular, facial, bulbar weakness
mainly proximal limb weakness
limb weakness is worst __lly
proximally
Tx of MG acutely?
acetylcholinesterase inhibitor eg pyridostignmine
IV Ig’s and/or plasma exchange
thymectomy if thymus involved
mainstay Tx of MG?
immunomodulators
steroids
azathioprine (immunosuppressant)
what antibiotic should be avoided in MG?
gentamicin
smallest contractile unit in skeletal muscle
muscle fibre
which type of muscle has no sarcomeres?
smooth muscle
actin myosin ratio of smooth muscle?
10:1
fasciculations can be triggered by what?
stress
caffeine
fatigue
fasciculations are indicative of disease where?
motor neurone (NOT muscle)
where is the problem in myotonia?
chloride channels
define myotonia
failure of muscle relaxation after use
symptoms and signs of muscle disease?
myalgia
muscle weakness
wasting
hyporeflexia
immune mediated muscle disorders?
dermatomyositis
polymyositis
inherited muscle disorders?
muscular dystrophies
dystrophinopathies
myotonic dystrophies
congenital muscle disorders?
myaesthenic syndromes
congenital myopathies
describe the pattern of muscle weakness in polymyositis
symmetrical progressive proximal weakness that has a chronic onset
best marker for polymyositis?
CK
slowly progressive weakness in a patient in their 60s with sparing of their thumb…
inclusion body myositis
commonest MD
myotonic MD
how is myotonic MD inherited?
AD
clinical presentation of myotonic MD
myotonia weakness cataract ptosis frontal badling cardiac defects
muscular dystrophies are non inflammatory T or F
T
central and peripheral nerve dysfunction is a symptom of muscular dystrophy T or F
F, central and peripheral nerves not affected
infective causes of MD?
coxsackie
trpanosomiasis
cistercercosis
borrelia
patient with new onset myotonia after eating uncooked pork….
cistercercosis
what electrolyte imbalance can cause a myopathy?
hypokalemia
describe rhabdomyolysis?
skeletal muscle causes leakage of large quantities of toxic intracellular contents into plasma
triad of symptoms of rhabdomyolysis?
myalgia
muscle weakness
myoglobinuria
scoring a 4 on muscle grading means what?
movement against resistance but not full strength
scoring a 3 on muscle grading means what?
movement against gravity but not against resistance
scoring a 1 in muscle grading means what?
flicker of movement when attempting to contract muscle