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Neurology > NMJ and muscle disorders > Flashcards

NMJ and muscle disorders Flashcards

1
Q

What is Lambert Eaton Myasthenic syndrome LEMS

A

Autoimmune condition with Ab forming against presynaptic Ca channels

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2
Q

Characteristics of LEMS

A

Proximal muscle weakness
autonomic features
absent deep tendon reflexes

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3
Q

Diagnosis and treatment of LEMS

A

Anti-VGCC Ab - Dx

diaminopyridien - Mx

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4
Q

What is myasthenia gravis MG

A

Autoimmune condition affecting the postsynaptic ACh receptors

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5
Q

Features of MG

A

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

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6
Q

Drugs that can exacerbate MG

A 
Gentamicin
B blockers 
Verapamil 
Phenytoin 
Lithium 
Penicillamine 
chloroquine
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7
Q

Investigations and management of MG

A

Ix - anti-AChR, anti-MUSK, TFT, CT thymus

Mx - Pyridostigmine, thymectomy

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8
Q

Management of myasthenic crisis

A

plasmapharesis and IVIG

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9
Q

Features of myotonic dystrophy

A 
Myotonia = impaired muscle relaxation following use 
Distal muscle weakness 
Ptosis 
Cataracts
Cardiac defects 
Frontal balding
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10
Q

features of LMN disorders

A

weakness
hypotonia
fasciculations

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11
Q

features of UMN disorders

A

hypertonia
spasticity
stiffness

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12
Q

what is a motor unit

A

aMN and all the skeletal muscle fibres it innervates

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13
Q

what is a motor end plate

A

synapse formed between the motor neuron and muscle

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14
Q

describe the presynaptic part of neurotransmission

A

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

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15
Q

describe the postsynaptic part of neurotransmission

A

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

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16
Q

which enzyme breaks down ACh at the synaptic cleft

A

acetylcholinesterase

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17
Q

why is curare dangerous

A

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

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18
Q

curare is only toxic when administered PO, true or false

A

FALSE

toxic when IV/IM

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19
Q

list PRE synaptic disorders

A

botulism

LEMS

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20
Q

which microorganism causes botulism and where is it found

A

clostridium botulinum

soil

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21
Q

how does botulinum toxin work molecularly

A

cleaves presynaptic proteins involved in vesicle formation

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22
Q

features of botulism

A

rapid onset weakness with no sensory loss

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23
Q

what is LEMS associated with

A

SCLC

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24
Q

Myasthenia gravis MG is a pre/post synaptic disorder

A

POST synaptic disorder

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25
Q

what is the most common NMJ disorder

A

MG

26
Q

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

A

true

27
Q

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

A

false, because there are not enough AChR

28
Q

when do symptoms of MG start

A

when AChR reduce by 30%

29
Q

which antibodies are associated with MG

A

ACh antibodies

30
Q

what else is important to look for in patient with MG

A

thymoma

31
Q

which cranial nerves are affected in bulbar palsy

A

CN IX, X, XI, XII LMN

32
Q

what is pyridostigmine

A

acetylcholinesterase inhibitor

allows persistence of ACh in synaptic cleft

33
Q

which antibiotic must be avoided in those with MG and why

A

gentamicin

causes myasthenic crisis and respiratory failure

34
Q

sarcomeres are present in smooth muscle, true or false

A

false
NO sarcomeres
only in skeletal and cardiac muscle

35
Q

describe type 1 muscle fibres

A

slow oxidative

high resistance to fatigue

36
Q

describe type 2a muscle fibres

A

fast oxidative

37
Q

describe type 2b muscle fibres

A

fast glycolytic

low resistance to fatigue

38
Q

what are fasciculations and why do they occur

A

visible fast fine spontaneous twitch

occur in denervated muscle which becomes hyperexcitable

39
Q

what are fasciculations a sign of

A

disease of motor neuron

40
Q

what is myotonia

A

failure of muscle relaxation after use

41
Q

what is myotonia a disorder of

A

Cl- channel disorder

usually hereditary

42
Q

what is dystonia

A

uncontrolled muscle cramps and spasms

43
Q

list autoimmune muscle diseases

A

polymyositis

dermatomyositis

44
Q

what is polymyositis and its treatment

A

symmetrical progressive proximal weakness developing over weeks-months
steroids

45
Q

how high in CK in polymyositis

A

very high

>1000

46
Q

how does dermatomyositis differ from polymyositis

A

heliotrope rash

underlying malignancy

47
Q

what is inclusion body myositis

A

slowly progressive weakness in 60s

48
Q

what is characteristic about inclusion body myositis

A

thumb sparing

49
Q

inclusion body myositis is responsive to steroids, true or false

A

FALSE

no steroid response

50
Q

what is the commonest muscular dystrophy

A

myotonic dystrophy

51
Q

inheritance pattern of myotonic dystrophy and what the genetic defect is

A

AD

trinucleotide repeat disorder with anticipation

52
Q

infective causes of muscle disease

A

coxsackie
trypansomiasis
cistercercosis
borrelia

53
Q

toxic causes of muscle disease

A

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

54
Q

what is rhabdomyolysis

A

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

55
Q

causes of rhabdomyolysis

A

crush / trauma
seizures
statins
extreme exercise

56
Q

triad of rhabdomyolysis

A

myalgia
muscle weakness
myoglobinuria

57
Q

which scale is used to test muscle power

A

MRC muscle power grading

58
Q

describe the MRC scale

A

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
Q

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

A

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

60
Q

appearance of Charcot Marie Tooth on histology

A

onion bulb appearance

Neurology (25 decks)

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