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neurology > Myopathies > Flashcards

Myopathies Flashcards

1
Q

Pt has isolated raised ALT and AST, what should also be tested?

A

CK
- AST and ALT are also in muscle

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2
Q

Feature of glucose problem (eg glycogen storage disease) myopathy?
Feature of lipid problem myopathy?

A

Cant sprint - need glucose
Cant run a marathon - needs longer active energy ie lipids metabolism

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3
Q

Main clinical feature of inclusion body myositis (IBM)?

A

IBM is the commonest myositis in 50-60yr pts, commonest aquired muscle disease in 50-60yrs

Will have long arm flexor weakness and knee extensor weakness
- Trouble getting up off floor or going up stairs
- Cant peel fruits, can pull out draws

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4
Q

Classification of myopathy?

A

Inflamatory (idiopathic inflamatory myopathies)
- Polymyositis
- dermatomyositis
- inclusion body myositis
- necrotising autoimmune myositis

Mitochronidial

Inherited
- structure
- metabolic

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5
Q

Features of dermatomyositis?

A

Cutaneous features
- Gotrons papules
- Malar rash
- Shalls sign

Muscle features:
- Porgressive symetrical muscle weakness
- promximal upper and lower limb weakness ie cant climb stairs

Labs:
- Raised CK

Note skin features usually preceed muscle findings

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6
Q

Dermatomyositis is associated with?

A

Malignancy (ovarian, lung, breast)

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7
Q

Autoantibodies in dermatomyositis? associated conditions and clinical features?

A
  • Anti Mi2 (high risk of high CK and severe weakness but good response to Rx. Low risk cancer)
  • Anti MDA5 - Low risk cancer. high risk lung disease and get skin ulcerations
  • Anti Jo1 (associated with ILD)
  • Anti SRP (associated with cardiomyopathy and rapidly progressive myositis)
  • NXP 2 - calcinosis . Associated with malignancy
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8
Q

Antibodies in immune mediated necrotising myopathy?

A

anti HMG CoA reductase
- Statin exposure
- Idiopathic

Anti SRP
- F>M, myocarditis and ILD

Seronegative
- cancer, drugs/toxins

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9
Q

Can pt have HMG CoA reductase antibodies without statin exposure?

A

Yes

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10
Q

How does the treatment of statin myopathy differ from treatment of immune mediated necrotising myopathy?

A

Many pts get raised CK and cramps on statin
Treat statin myopathy with cease drug, most will resolve

If pts get statin related immune mediated necrotising myopathy then needs aggresive treatment with imunosupression (steroids, IVIG, steroid sparing agents)

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11
Q

What is statin myopathy?

A

Dose dependant myotoxic effect of statin
Clinically can have mild myalgia to rhadbo

Usualy reversible with cease drug, if CK continues to rise and there is progressive myopathy post cease drug then be concerned for immune mediated necrotising myopathy related to statin

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12
Q

What is inclusion body myositis? clinical features? basic labs?
Treatement?

A

This is the most common muscle disease in pt aged >50yrs (many prieviously Dx as steroid unresponsive poilymyositis)

Characterised by weakness of long finger flexors and knee extensors (quads)
- often cant peel veg or open draw
- cant stand up off floor or chair
Proximal leg weakness causes hypertrophy of calves to compensate

CK often elevated

IVIG if have dysphagia, otherwise nil treatment

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13
Q

What is limb girdle muscle dystrophy (LGMD)?

A

LGMD is a term for a group of disease that cause wasting and weaknes of the muscles of the proximal arm and leg
- weakness is typically slow and progressive

Examples include duschenes and beckers muscular dystrophy

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14
Q

What are some characteristic features of LGMD on clinical examination?

A

Popeye arms
Calf hypertrophy

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15
Q

Treatment for LGMD?

A

None
- exception is spinal muscle atrophy

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16
Q

What are glycogen storage diseases? what are some common examples?

A

GLycogen storage disease is an unbrella term for a large group of inherited or environmental (mostly inherited) metabolic conditions in an enzyme involved in glycogen synthesis, breakdown, or glucose breakdown is affected.
Usually affects the muscle of liver

Some examples:
- McArdles disease
- Pompe disease (including late onset Pompe disease)
-> onsets in infancy or late onset
-> Limb girdle weakness and resp weakness think pompes

17
Q

What are mitochondrial cytopathies? what are some common examples?

A

This is an umbrella term for a group of diseases caused by mitochondrial dysfunction
- can be an isolated muscle disease or a systemic disease (more common)

Examples:
- MERRF - mitochondrial epilepsy with ragged red fibres
- MELAS - mitochondrial myopathy, encephalopathy, lactic acidosis, stroke like episodes
- MNGIE- mitochondrial neurogastrointestinal encephalomyopathyies

18
Q

What is malignant hyperthermia? What causes it?

A

Malignant hyperthermia is an inheritable predsposition for a severe GA related reaction that typically involved muscle rigidity, fever, tachycardia.
Complications include rhabdo and hyperkalaemia

Gene is the RYR1 gene

19
Q

What is the hallmark feature of myesthinia gravis? What are some other examination features?

A

Fatiguability
- often pts with say they are worse in the late day
Often occular or at least with prominent occular involvement (neck and limb girdle can be affect, resp muscles can be affected)

Nil smooth muscle or cardio inv
Nil muscle wasting, preserved reflexes

20
Q

Explain the time course of MG?

A

Progressive
Relapsing remitting

21
Q

How can you test the weakness of the resp muscle without directly assessing respiration in MG pts?

A

Head flexion and extension
- flexion is a measure of resp success weakness

22
Q

Drugs that can worsen MG?

A

STEROIDS
- can give low dose but if start at high dose then will cause myesthinic crisis

Aminoglycosides
Tetracyclines
BB
CaC blockers
Muscle relaxants (beware GA)

23
Q

MG is strongly associated with…?

A

Thymoma (10%)
- pts require open thymectomy (oplder males more likely to get)

Thymic lymphoid hyperplasia (70%)

24
Q

Antibodies in MG? Which is teh associated prognosis?

A

Antibody to Ach receptor (most common)
- easiest to treat with good prognosis
Anti Musk
- Usually generalized weakness
- severe weakness, hard to treat, slower to recover
Anti LRP4
- mild to moderate disease

25
Q

MCS and EMG in MG. WHat do they show?

A

Routine MCS and EMG are normal

Repetitive stimulation EMG shows decremental compound muscle action potention (fatiguability)

26
Q

MG treatment?

A

Anticholinesterase drugs (symptomatic managment)
- pyridostigmine
- neostigmine

Thymectomy
Steroids (start cautiously, low dose)
Rituxumab (esp anti Musk)
Eculizumab (MAB C5 inhibitor)
Efgartigimod - FCRn blocker / inhibitor. Not availible in Aus)

27
Q

Difference between LEMS and MG?

A

LE demonstrates improvement with reapeated contraction
MG demonstrates fatiguability

LE is a presynaptic problem (release of Ach)
MG is post synaptic problem (Ach receptors)

28
Q

What is LEMS usually associated with?

A

SCLC, breast cancer
- often prodromal to cancer

29
Q

Antibodies in LEMS?

A

antibody to presynaptic voltage gated Ca channels (VGCC)

30
Q

What is periodic paralysis? what are the two most common forms and the typical presentation?

A

THis is a rarte group of genetic conditions characterised by episodic and elf limiting weakness to common triggers such as cold, heat, high carbohydrate meals, not eating, stress or excitement and physical activity of any kind

Underlying mechanism is defects with various ion channels on muscles that mediation contraction and relaxtion

Hypokalaemia and hyperkalaemia are most common
- Typical presentation is large high salt and carb meal leading to paralysis

31
Q

When to suspect neurological paraneuoplastic syndrome?

A

Rapidly progressive
Bizzare or unusual presentation
Associated with encephalopathy

neurology (6 decks)

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