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Disease Processes > Neuromuscular Disease > Flashcards

Neuromuscular Disease Flashcards

1
Q

How is skeletal muscle structured?

A 
Skeletal muscle (organ)- consists of epimysium, muscle fascicles, perimysium, nerves and blood vessels.
Muscle Fascicle (tissue)- contains muscle fibres and endomysium.
Muscle Fibre (cell)- consists of sarcolemma, sarcoplasm, nucleus, mitochondria, myofibril
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2
Q

How does skeletal muscle contract?

A

1) Ca2+ irons bind to troponin molecule
2) binding weakens troponin-tropomyosin complex and actin
3) troponin molecule changes position, rolling away from active sites on actin
4) allowing them to interact with energised myosin heads
5) myosin heads form cross-bridges with actin sites.
6) ATP in myosin head used as energy
7) as ATP used ADP + Pi is released, causing “power stroke”
8) another ATP molecule binds to head, breaking the cross bridge

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3
Q

What are the types of idiopathic Destructive/inflammatory myopathies?

A

Polymyositis
Dermatomyositis (also juvenile DM)
Inclusion body myositis

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4
Q

What’s autoimmune Disease?

A

Immune system mistakenly attacked self-components including cells leading to chronic progressive dysfunction.
Mediated by B & T cells

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5
Q

What are the sub types of IIM?

A

Adult dermatomyositis (DM)- neck, should, arms and top of legs.
Adult polymyositis (PM)- “ “
Juvenile myositis (DM»PM)
Cancer- associated myositis (CAM)
Connective tissue disease associated myositis
Inclusion body myositis (IBM)- legs and forearm muscles

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6
Q

What’s IIM?

A

An acquired inflammatory cell infiltration in skeletal muscle causing myalgia, fatigue and weakness and thus disability.
Infiltration with variable numbers of CD8+ & CD4+ T cells some B cells and macrophages
Groups of acquired, heterogenous systemic connective tissue diseases characterised by chronic muscle weakness due to striated muscle inflammation of unknown cause.

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7
Q

What is the rate of progression for IIMs?

A

IBM = very slow over years

Other forms = weeks to months

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8
Q

What’s the patten of muscle weakness for Myositis?

A

Proximal > distal (except IBM)

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9
Q

What’s proximal weakness?

A

Difficulty riding from chair or combing hair
Difficulty standing on toes
Hands grip

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10
Q

Which myositis is symmetric?

A

PM & DM are almost always symmetric where as IBM mostly asymmetric

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11
Q

What are the extra-muscular manifestations of myositis?

A

Dysphagia (all except IBM)- pharyngeal dysphagia, order esophagogram, difficult to treat.
Cardiomyopathy- asymptomatic, pulmonary artery hypertension, ECHO in suspected cases.
Lung- respiratory muscle weakness, PFTs and HRCT chest in suspected
Arthritis
Rathaus phenomenon- spasms of arteries= reduced blood flow

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12
Q

How do you evaluate myositis?

A 
Manual muscle testing (MMT)
Skin involvement (DM rash, heliotrope (purple), periorbital oedema (puffy eyes))
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13
Q

How to diagnose myositis?

A

1) symmetrical proximal weakness of limb-girdle muscles and anterior neck flexors/extensors
2) muscle biopsy for evidence
3) elevation of serum skeletal muscle enzymes (CK- creative kinase, marker of muscle damage present in circulation)
4) typical EMG features of myopathy
5) typical DM rash

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14
Q

How is skeletal muscle structured?

A 
Skeletal muscle (organ)- consists of epimysium, muscle fascicles, perimysium, nerves and blood vessels.
Muscle Fascicle (tissue)- contains muscle fibres and endomysium.
Muscle Fibre (cell)- consists of sarcolemma, sarcoplasm, nucleus, mitochondria, myofibril
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How does skeletal muscle contract?

A

1) Ca2+ irons bind to troponin molecule
2) binding weakens troponin-tropomyosin complex and actin
3) troponin molecule changes position, rolling away from active sites on actin
4) allowing them to interact with energised myosin heads
5) myosin heads form cross-bridges with actin sites.
6) ATP in myosin head used as energy
7) as ATP used ADP + Pi is released, causing “power stroke”
8) another ATP molecule binds to head, breaking the cross bridge

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What are the types of idiopathic Destructive/inflammatory myopathies?

A

Polymyositis
Dermatomyositis (also juvenile DM)
Inclusion body myositis

17
Q

What’s autoimmune Disease?

A

Immune system mistakenly attacked self-components including cells leading to chronic progressive dysfunction.
Mediated by B & T cells

18
Q

What are the sub types of IIM?

A

Adult dermatomyositis (DM)- neck, should, arms and top of legs.
Adult polymyositis (PM)- “ “
Juvenile myositis (DM»PM)
Cancer- associated myositis (CAM)
Connective tissue disease associated myositis
Inclusion body myositis (IBM)- legs and forearm muscles

19
Q

What’s IIM?

A

An acquired inflammatory cell infiltration in skeletal muscle causing myalgia, fatigue and weakness and thus disability.
Infiltration with variable numbers of CD8+ & CD4+ T cells some B cells and macrophages
Groups of acquired, heterogenous systemic connective tissue diseases characterised by chronic muscle weakness due to striated muscle inflammation of unknown cause.

20
Q

What is the rate of progression for IIMs?

A

IBM = very slow over years

Other forms = weeks to months

21
Q

What’s the patten of muscle weakness for Myositis?

A

Proximal > distal (except IBM)

22
Q

What’s proximal weakness?

A

Difficulty riding from chair or combing hair
Difficulty standing on toes
Hands grip

23
Q

Which myositis is symmetric?

A

PM & DM are almost always symmetric where as IBM mostly asymmetric

24
Q

What are the extra-muscular manifestations of myositis?

A

Dysphagia (all except IBM)- pharyngeal dysphagia, order esophagogram, difficult to treat.
Cardiomyopathy- asymptomatic, pulmonary artery hypertension, ECHO in suspected cases.
Lung- respiratory muscle weakness, PFTs and HRCT chest in suspected
Arthritis
Rathaus phenomenon- spasms of arteries= reduced blood flow

25
Q

How do you evaluate myositis?

A 
Manual muscle testing (MMT)
Skin involvement (DM rash, heliotrope (purple), periorbital oedema (puffy eyes))
26
Q

How to diagnose myositis?

A

1) symmetrical proximal weakness of limb-girdle muscles and anterior neck flexors/extensors
2) muscle biopsy for evidence
3) elevation of serum skeletal muscle enzymes (CK- creative kinase, marker of muscle damage present in circulation)
4) typical EMG features of myopathy
5) typical DM rash

27
Q

How to analyse the pathology of a muscle biopsy?

A

Routine histology
Electron microscopy for IBM
Biochemical analysis for metabolic myopathies
Special staining for muscle dystrophies

28
Q

What to look for in a muscle biopsy?

A

Major Histocompatibility Complex l (MHC I)
Human Leukocyte Antigen (HLA)
Present intracellular antigens on the Cells surface
Marker of myositis
Membrane bound receptors
Synthesised with ER
Pick up and present, digest protein fragments
Recognised as “self” in normal conditions

29
Q

What’s the histopathology DM?

A

Inflammatory infiltrate
Perifascular infiltrate
Perifascular atrophy
MHC-L overexpressed- predominantly localised to fibres

30
Q

What’s the histopathology of PM?

A

Cellular infiltrate predominantly within fascicle with inflammatory cells (cytotoxic CD8+ T cells) invading individual muscle fibres

31
Q

What’s is Inclusion Body Myositis? (IBM)

A

Male predominance
Inflammatory muscle disease characterised by slow progression of weakness and wasting of both distal and proximal muscles.
Dysphagia
Tendency to distal and asymmetric muscle involvement

32
Q

What are the hallmarks for IBM?

A

Normal or low level CK elevation compared to PM and DM

Distinctive histology

33
Q

How is myositis treated?

A

Immunosuppressant drugs eg.
Corticosteroids- strongest drug available for reducing inflammation, have serious side effects.
Methotrexate
Cyclophosphamide

34
Q

How can ER stress induce cytokines release?

A

Can release in absence of immune cells
Myokines may be chemotactic- recruiting immune cells to muscle
Myokines may act directly on muscle contributing to contractile and bioenergetic dysfunction.

Disease Processes (14 decks)

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