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Flashcards in NMJ and muscle disorders Deck (60):
1

What is Lambert Eaton Myasthenic syndrome LEMS

Autoimmune condition with Ab forming against presynaptic Ca channels

2

Characteristics of LEMS

Proximal muscle weakness
autonomic features
absent deep tendon reflexes

3

Diagnosis and treatment of LEMS

Anti-VGCC Ab - Dx
diaminopyridien - Mx

4

What is myasthenia gravis MG

Autoimmune condition affecting the postsynaptic ACh receptors

5

Features of MG

Thymoma
Ptosis, diplopia, internuclear ophthalmoplegia
Fatiguability - especially after exercise
jaw, facial, phayngeal and respiratory muscles affected
Myasthenia crisis = weakness of respiratory muscles
bulbar palsy
proximal limb muscle weakness

6

Drugs that can exacerbate MG

Gentamicin
B blockers
Verapamil
Phenytoin
Lithium
Penicillamine
chloroquine

7

Investigations and management of MG

Ix - anti-AChR, anti-MUSK, TFT, CT thymus
Mx - Pyridostigmine, thymectomy

8

Management of myasthenic crisis

plasmapharesis and IVIG

9

Features of myotonic dystrophy

Myotonia = impaired muscle relaxation following use
Distal muscle weakness
Ptosis
Cataracts
Cardiac defects
Frontal balding

10

features of LMN disorders

weakness
hypotonia
fasciculations

11

features of UMN disorders

hypertonia
spasticity
stiffness

12

what is a motor unit

aMN and all the skeletal muscle fibres it innervates

13

what is a motor end plate

synapse formed between the motor neuron and muscle

14

describe the presynaptic part of neurotransmission

AP moves along the nerve causing depolarisation
voltage gated Ca channels open causing Ca influx
ACh released from vesicles into synaptic cleft

15

describe the postsynaptic part of neurotransmission

ACh diffuses across synaptic cleft
AChR open meaning membrane is permeable to Na and K ions
this causes depolarisation at the motor end plate

16

which enzyme breaks down ACh at the synaptic cleft

acetylcholinesterase

17

why is curare dangerous

occupies same position on AChR but does not open ion channel therefore no muscle contraction --> respiratory muscle paralysis and failure

18

curare is only toxic when administered PO, true or false

FALSE
toxic when IV/IM

19

list PRE synaptic disorders

botulism
LEMS

20

which microorganism causes botulism and where is it found

clostridium botulinum
soil

21

how does botulinum toxin work molecularly

cleaves presynaptic proteins involved in vesicle formation

22

features of botulism

rapid onset weakness with no sensory loss

23

what is LEMS associated with

SCLC

24

Myasthenia gravis MG is a pre/post synaptic disorder

POST synaptic disorder

25

what is the most common NMJ disorder

MG

26

there is flattening of endplate folds in MG, true or false

true

27

in MG, even with normal amount of ACh, transmission is effective, true or false

false, because there are not enough AChR

28

when do symptoms of MG start

when AChR reduce by 30%

29

which antibodies are associated with MG

ACh antibodies

30

what else is important to look for in patient with MG

thymoma

31

which cranial nerves are affected in bulbar palsy

CN IX, X, XI, XII LMN

32

what is pyridostigmine

acetylcholinesterase inhibitor
allows persistence of ACh in synaptic cleft

33

which antibiotic must be avoided in those with MG and why

gentamicin
causes myasthenic crisis and respiratory failure

34

sarcomeres are present in smooth muscle, true or false

false
NO sarcomeres
only in skeletal and cardiac muscle

35

describe type 1 muscle fibres

slow oxidative
high resistance to fatigue

36

describe type 2a muscle fibres

fast oxidative

37

describe type 2b muscle fibres

fast glycolytic
low resistance to fatigue

38

what are fasciculations and why do they occur

visible fast fine spontaneous twitch
occur in denervated muscle which becomes hyperexcitable

39

what are fasciculations a sign of

disease of motor neuron

40

what is myotonia

failure of muscle relaxation after use

41

what is myotonia a disorder of

Cl- channel disorder
usually hereditary

42

what is dystonia

uncontrolled muscle cramps and spasms

43

list autoimmune muscle diseases

polymyositis
dermatomyositis

44

what is polymyositis and its treatment

symmetrical progressive proximal weakness developing over weeks-months
steroids

45

how high in CK in polymyositis

very high
>1000

46

how does dermatomyositis differ from polymyositis

heliotrope rash
underlying malignancy

47

what is inclusion body myositis

slowly progressive weakness in 60s

48

what is characteristic about inclusion body myositis

thumb sparing

49

inclusion body myositis is responsive to steroids, true or false

FALSE
no steroid response

50

what is the commonest muscular dystrophy

myotonic dystrophy

51

inheritance pattern of myotonic dystrophy and what the genetic defect is

AD
trinucleotide repeat disorder with anticipation

52

infective causes of muscle disease

coxsackie
trypansomiasis
cistercercosis
borrelia

53

toxic causes of muscle disease

drugs - statins, steroids, hydroxychloroquine, amiodarone, OCP, diuretics, IFNa
venom

54

what is rhabdomyolysis

skeletal msucle damage resulting in leaking of large quantities of toxic intracellular contents into plasma

55

causes of rhabdomyolysis

crush / trauma
seizures
statins
extreme exercise

56

triad of rhabdomyolysis

myalgia
muscle weakness
myoglobinuria

57

which scale is used to test muscle power

MRC muscle power grading

58

describe the MRC scale

0 - no movement at all
1 - flicker of movement when attempting to contract muscle
2 - some muscle movement with gravity removed
3 - movement against gravity but not resistance
4 - movement against resistance but not full strength
5 - normal strength

59

What is McArdles disease and what condition are patients at risk of

autosomal recessive condition with myophosphorylase deficiency resulting in impaired glucose release from glycogen in muscles
Rhabdomyolysis

60

appearance of Charcot Marie Tooth on histology

onion bulb appearance