Neuromuscular Disease Flashcards
(34 cards)
How is skeletal muscle structured?
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 does skeletal muscle contract?
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
What are the types of idiopathic Destructive/inflammatory myopathies?
Polymyositis
Dermatomyositis (also juvenile DM)
Inclusion body myositis
What’s autoimmune Disease?
Immune system mistakenly attacked self-components including cells leading to chronic progressive dysfunction.
Mediated by B & T cells
What are the sub types of IIM?
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
What’s IIM?
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.
What is the rate of progression for IIMs?
IBM = very slow over years
Other forms = weeks to months
What’s the patten of muscle weakness for Myositis?
Proximal > distal (except IBM)
What’s proximal weakness?
Difficulty riding from chair or combing hair
Difficulty standing on toes
Hands grip
Which myositis is symmetric?
PM & DM are almost always symmetric where as IBM mostly asymmetric
What are the extra-muscular manifestations of myositis?
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
How do you evaluate myositis?
Manual muscle testing (MMT) Skin involvement (DM rash, heliotrope (purple), periorbital oedema (puffy eyes))
How to diagnose myositis?
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
How is skeletal muscle structured?
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 does skeletal muscle contract?
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
What are the types of idiopathic Destructive/inflammatory myopathies?
Polymyositis
Dermatomyositis (also juvenile DM)
Inclusion body myositis
What’s autoimmune Disease?
Immune system mistakenly attacked self-components including cells leading to chronic progressive dysfunction.
Mediated by B & T cells
What are the sub types of IIM?
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
What’s IIM?
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.
What is the rate of progression for IIMs?
IBM = very slow over years
Other forms = weeks to months
What’s the patten of muscle weakness for Myositis?
Proximal > distal (except IBM)
What’s proximal weakness?
Difficulty riding from chair or combing hair
Difficulty standing on toes
Hands grip
Which myositis is symmetric?
PM & DM are almost always symmetric where as IBM mostly asymmetric
What are the extra-muscular manifestations of myositis?
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
