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Neurology > NMJ and muscle pathologies > Flashcards

NMJ and muscle pathologies Flashcards

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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?

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A

Visible, fast, fine, spontaneous twitch

22
Q

Why do fasciculations occur?

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A

Healthy muscle; stress, caffeine, fatigue

Denervated muscle which becomes hyperexcitable

23
Q

What are fasciculations a sign of?

24
Q

What is myotonia?

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A

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-

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