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Flashcards in NMJ and muscle pathologies Deck (51):
1

Symptoms of LMN disorders?

Weak
Low tone
Fasciculations

2

What innervated skeletal muscle fibres?

Motor neurones whose cell bodies arise in the ventral horn of the spinal cord

3

What is the motor end plate?

Synapses formed between motor neurons and the muscle

4

What is a motor unit?

A single motor neurone and all of the muscle fibres it innervates

5

What occurs when an action potential reaches the nerve?

Ca 2+ channels open
Vesicles of ACh are released into the synaptic cleft
ACh receptor opens and renders the membrane permeable to Na/K+ ions
Depolarisation starts an action potential at the motor end plate

6

What is the action of acetylcholinesterase?

Breaks up ACh into acetate and choline

7

What happens to choline in the synaptic cleft?

Sequestered into presynaptic vesicles

8

How does botulism affect the presynaptic membrane?

Cleaves presynaptic proteins involved in vesicle formation and blocks vesicle docking with the presynaptic membrane

9

What are the symptoms of botulism toxin?

Rapid onset weakness WITHOUT sensory loss

10

What is the pathogenesis of Lambert Eaton Myasthenic Syndrome?

Antibodies to presynaptic calcium channels leading to vesicle release
Strong assoc with small cell lung carcinoma

11

What is the treatment for LEMS?

3-4 diaminopyridine

12

What is the pathogenesis of myasthenia gravis?

Autoimmune antibodies to AChR resulting a reduced number of functioning receptors leading to muscle weakness and fatigability
Flattening of endplate folds
Even with normal ACh; transmission becomes inefficient

13

What is the role of the thymus in myasthenia?

75% have hyperplasia or thymoma

14

What is the epidemiology of myasthenia gravis?

Occurs at any age; 2 peaks of incidence
Females in 3rd decade
Males in 6/7th decade
Female:male ration 3:2

15

What are the clinical features of myasthenia?

Fluctuating weakness throughout the day; tends to be best in the morning
Extraocular weakness
Facial and bulbar weakness
Limb weakness is proximal

16

What is the treatment for myasthenia?

Acetylcholinesterase inhibitor; pyridostigmine
IVIg in acute emergencies
Thymectomy

17

What immune modulating drugs are used in myasthenia?

Steroids
Azathioprine
Mycophenolate
Emergency; plasma exchange or immunoglobulin

18

What drug should be avoided in myasthenia?

GENTAMICIN
Lots of antibiotics CI, lots of anaesthetic drugs are CI

19

What do most people with myasthenia die from?

Resp failure
Aspiration pneumonia
Immunosuppression SE in the elderly
Co-morbid

20

What are the different types of muscle fibres?

Type 1; slow oxidative; resist fatigue, myoglobin, RED
Type 2a; fast oxidative; aerobic metabolism
Type 2b; fast glycolytic, easily fatigued

21

What is a fasciculation?

Visible, fast, fine, spontaneous twitch

22

Why do fasciculations occur?

Healthy muscle; stress, caffeine, fatigue
Denervated muscle which becomes hyperexcitable

23

What are fasciculations a sign of?

MND

24

What is myotonia?

Failure of muscle relaxation after use
Chloride channel issues

25

What are the Si/Sy of muscle disease?

Myalgia
Muscle weakness
Wasting
Hyporeflexia

26

What can cause a head drop?

Myopathy
Myositis
MND

27

What muscles are commonly weak in muscle disease?

Proximal leg
Shoulder girdle
Neck weakness

28

What are immune mediated muscle weaknesses?

Dermatomyositis
Polymyoisitis

29

What are inherited muscle disorders?

Muscular dystrophies
Limb girdle muscular dystrophies
Myotonic dystrophy

30

What are congenital muscle disorders?

Congenital myasthenic syndromes
Congenital myopathies

31

What is the pattern of muscle disease in polymyositis?

Symmetrical
Progressive proximal weakness developing over weeks to months

32

What test will help in the diagnosis of polymyositis?

Raised CK
Muscle biopsy
EMG

33

Difference between polymyositis and dermatomyositis?

Dermatomyositis will show cutaneous features such as heliotrope rash and shawl sign
Also has a 50% recurrence with an underlying malignancy

34

What is the presentation of inclusion body myositis?

Slowly progressive weakness in the 6th decade with characteristic thumb sparing

35

What is the inheritance of myotonic dystrophy?

AD of trinucleotide repeat disorder with anticipation

36

What is the presentation of myotonic dystrophy?

Myotonic
Weakness
Cataracts
Ptosis
Frontal balding
Cardiac defects

37

What are the inherited muscular dystrophies?

Duchenne and Becker

38

What infective causes can result in muscle disease?

Viral; coxsackie
Trypanosomiasis
Cisticercosis
Borrelia

39

What are some common drugs that cause myopathy?

Necrotising myopathies; stating, fibrates
Corticosteroid myopathy
Lysosomal storage myopathy; hydroxychloroquine, amiodarone
Hypokalemic myopathy; diuretics, OCP

40

What is rhabdomyolysis?

Damage to skeletal muscle causes leakage of large quantities of toxic intracellular contents into the plasma such as myoglobin

41

What can cause rhabdomyolysis?

Crush injuries
Toxins
Post-convulsions
Extreme exercise

42

What is the triad of rhabdo?

Myalgia
Muscle weakness
Myoglobinuria

43

What are common complications of rhabdo?

AKI
DIC

44

What should be tested in examination of muscles?

Inspection; thin, wasted, fasciculations
Palpation
Strenth
Neck strength
Core strength
Fatiguability

45

What does 0 on the MRC muscle power grading mean?

No movement at all

46

What does 1 on the MRC muscle power grading mean?

Flicker of movement when attempting to contract the muscle

47

What does 2 on the MRC muscle power grading mean?

Some muscle movement if gravity removed but none against gravity

48

What does 3 on the MRC muscle power grading mean?

Movement against gravity but not against resistance

49

What does 4 on the MRC muscle power grading mean?

Movement against resistance but not full strength

50

What does 5on the MRC muscle power grading mean?

Normal strength

51

Is 4 on the MRC muscle power grading split up?

Yes; can be 4+ or 4-