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Neurology > NMJ and muscle pathologies > Flashcards

NMJ and muscle pathologies Flashcards

1
Q

Symptoms of LMN disorders?

A

Weak
Low tone
Fasciculations

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2
Q

What innervated skeletal muscle fibres?

A

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

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3
Q

What is the motor end plate?

A

Synapses formed between motor neurons and the muscle

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4
Q

What is a motor unit?

A

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

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5
Q

What occurs when an action potential reaches the nerve?

A

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

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6
Q

What is the action of acetylcholinesterase?

A

Breaks up ACh into acetate and choline

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7
Q

What happens to choline in the synaptic cleft?

A

Sequestered into presynaptic vesicles

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8
Q

How does botulism affect the presynaptic membrane?

A

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

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9
Q

What are the symptoms of botulism toxin?

A

Rapid onset weakness WITHOUT sensory loss

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10
Q

What is the pathogenesis of Lambert Eaton Myasthenic Syndrome?

A

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

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11
Q

What is the treatment for LEMS?

A

3-4 diaminopyridine

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12
Q

What is the pathogenesis of myasthenia gravis?

A

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

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13
Q

What is the role of the thymus in myasthenia?

A

75% have hyperplasia or thymoma

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14
Q

What is the epidemiology of myasthenia gravis?

A

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

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15
Q

What are the clinical features of myasthenia?

A

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

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16
Q

What is the treatment for myasthenia?

A

Acetylcholinesterase inhibitor; pyridostigmine
IVIg in acute emergencies
Thymectomy

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17
Q

What immune modulating drugs are used in myasthenia?

A

Steroids
Azathioprine
Mycophenolate
Emergency; plasma exchange or immunoglobulin

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18
Q

What drug should be avoided in myasthenia?

A

GENTAMICIN

Lots of antibiotics CI, lots of anaesthetic drugs are CI

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19
Q

What do most people with myasthenia die from?

A

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

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20
Q

What are the different types of muscle fibres?

A

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

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21
Q

What is a fasciculation?

A

Visible, fast, fine, spontaneous twitch

22
Q

Why do fasciculations occur?

A

Healthy muscle; stress, caffeine, fatigue

Denervated muscle which becomes hyperexcitable

23
Q

What are fasciculations a sign of?

A

MND

24
Q

What is myotonia?

A

Failure of muscle relaxation after use

Chloride channel issues

25
Q

What are the Si/Sy of muscle disease?

A

Myalgia
Muscle weakness
Wasting
Hyporeflexia

26
Q

What can cause a head drop?

A

Myopathy
Myositis
MND

27
Q

What muscles are commonly weak in muscle disease?

A

Proximal leg
Shoulder girdle
Neck weakness

28
Q

What are immune mediated muscle weaknesses?

A

Dermatomyositis

Polymyoisitis

29
Q

What are inherited muscle disorders?

A

Muscular dystrophies
Limb girdle muscular dystrophies
Myotonic dystrophy

30
Q

What are congenital muscle disorders?

A

Congenital myasthenic syndromes

Congenital myopathies

31
Q

What is the pattern of muscle disease in polymyositis?

A

Symmetrical

Progressive proximal weakness developing over weeks to months

32
Q

What test will help in the diagnosis of polymyositis?

A

Raised CK
Muscle biopsy
EMG

33
Q

Difference between polymyositis and dermatomyositis?

A

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

34
Q

What is the presentation of inclusion body myositis?

A

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

35
Q

What is the inheritance of myotonic dystrophy?

A

AD of trinucleotide repeat disorder with anticipation

36
Q

What is the presentation of myotonic dystrophy?

A 
Myotonic
Weakness
Cataracts
Ptosis
Frontal balding
Cardiac defects
37
Q

What are the inherited muscular dystrophies?

A

Duchenne and Becker

38
Q

What infective causes can result in muscle disease?

A

Viral; coxsackie
Trypanosomiasis
Cisticercosis
Borrelia

39
Q

What are some common drugs that cause myopathy?

A

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

40
Q

What is rhabdomyolysis?

A

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

41
Q

What can cause rhabdomyolysis?

A

Crush injuries
Toxins
Post-convulsions
Extreme exercise

42
Q

What is the triad of rhabdo?

A

Myalgia
Muscle weakness
Myoglobinuria

43
Q

What are common complications of rhabdo?

A

AKI

DIC

44
Q

What should be tested in examination of muscles?

A 
Inspection; thin, wasted, fasciculations 
Palpation
Strenth
Neck strength
Core strength
Fatiguability
45
Q

What does 0 on the MRC muscle power grading mean?

A

No movement at all

46
Q

What does 1 on the MRC muscle power grading mean?

A

Flicker of movement when attempting to contract the muscle

47
Q

What does 2 on the MRC muscle power grading mean?

A

Some muscle movement if gravity removed but none against gravity

48
Q

What does 3 on the MRC muscle power grading mean?

A

Movement against gravity but not against resistance

49
Q

What does 4 on the MRC muscle power grading mean?

A

Movement against resistance but not full strength

50
Q

What does 5on the MRC muscle power grading mean?

A

Normal strength

51
Q

Is 4 on the MRC muscle power grading split up?

A

Yes; can be 4+ or 4-

Neurology (48 decks)

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