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NEUROLOGICAL DISEASE > MYOPATHIES > Flashcards

MYOPATHIES Flashcards

1
Q

What characterises a myopathy?

A

Weakness most often proximal

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2
Q

What are the clinical features of myopathies?

A 
Weakness
Loss of tone (often hard to distinguish)
Wasting
Preserved reflexes
Myotonia
Pain (rarely)
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3
Q

What is myotonia?

A

Persistence of contraction during attempted relaxation, often for several seconds.

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4
Q

How might you distinguish a lower motor neuron lesion from a myopathy?

A

Preservation of reflexes

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5
Q

Which of the myopathies display myotonia?

A

Myotonic distrophy
Paramyotonia congenita
Hyperkalaemic periodic paralysis
Congenital myotonia.

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6
Q

What are the X-linked myopathies?

A

Duchenne’s muscular dystrophy
Becker’s muscular dystrophy
Emery-Dreifuss dystrophy

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7
Q

What are the autosomal dominant myopathies?

A

Fascio-scapulo-humeral dystrophy
Scapulo-peroneal dystrophy
Myotonic dystrophy

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8
Q

What are the mitochondrial inherited myopathies?

A

Chronic progressive external opthalmoplegia

Kearns-Sayre syndrome

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9
Q

What is the underlying pathology of Duchenne muscular dystrophy?

A

Absence of dystrophin, a protein vital for connecting cytoskeleton of muscle to extracellular matrix.

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10
Q

By what age does Duchenne muscular dystrophy become apparent?

A

3-4

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11
Q

By what age is a child with Duchenne muscular dystrophy usually wheelchair bound?

A

10

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12
Q

What is the mean life expectancy of someone with Duchenne muscular dystrophy?

A

20

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13
Q

What complication will most patients with Duchenne muscular dystrophy die of?

A

Respiratory failure
Cardiomyopathy
Usually die in the third decade

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14
Q

What are the clinical features of Duchenne muscular dystrophy?

A 
Initial proximal muscle weakness
Pseudohypertrophy of calves due to accumulation of fat and connective tissue
Gower's sign
Waddling gait
Difficulty standing up
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15
Q

What is Gower’s sign with reference to muscular dystrophy?

A

Patient attempts to climb their own legs when rising to an erect position.

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16
Q

What will blood tests of someone with Duchenne muscular dystrophy show?

A

Grossly elevated creatinine kinase.

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17
Q

What are the managements option for Duchenne muscular dystrophy?

A

Management is supportive

Steroids may provide short term improvement

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18
Q

What is the underlying pathology of Becker’s muscular dystrophy?

A

Altered dystrophin (as opposed to absent dystrophin in Duchenne)

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19
Q

When do the symptoms of Becker’s muscular dystrophy begin?

A

Around the age of 10

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20
Q

What are the clinical features of Becker’s muscular dystrophy?

A

Cramps associated with exercise
Cardiomyopathy often ends being worse than the skeletal weakness and patients often die before the skeletal problems overwhelm them.

21
Q

What are the complications that might arise when someone with a muscular dystrophy undergoes surgery and has a general anaesthetic?

A

Malignant hyperthermia-type reaction with life threatening rhabdomyolysis.

22
Q

What is rhabdomyolysis?

A

Damaged skeletal muscle breaks down rapidly, releasing proteins such as myoglobin into the bloodstream. This is toxic to the kidneys.

23
Q

What is the most common adult myopathy?

A

Myotonic dystrophy with a prevalence of 1 in 7000

24
Q

What is the underlying pathology of myotonic dystrophy?

A

Defects in the myotonin protein kinase gene.

25
Q

How is the genetic transmission of myotonic dystrophy unusual relative to other disorders that exhibit anticipation?

A

Female transmission results in more severely affected offspring. In other disorders with anticipation (whereby successive generations are more severely affected), paternal transmission leads to more severely affected offspring.

26
Q

What are the clinical features of myotonic dystrophy?

A 
Progressive proximal and distal muscle weakness, especially in upper limbs
Myotonia
Myopathic faces
Ptosis
Cataracts
Frontal balding
Dysarthria and dysphagia
Mild intellectual impairment
Cardiomyopathy
Testicular atrophy
Glucose intollerance/diabetes
27
Q

Between what ages do the symptoms of myotonic dystrophy usually develop?

A

20-50

28
Q

What are the channelopathies?

A

Periodic paralyses - periods of sudden weakness with alterations in serum potassium levels. They are genetic mutations resulting in abnormalities of some ions chanels.

29
Q

What are the clinical features of hypokalaemic periodic paralysis?

A

Attacks of generalised weakness following heavy carbohydrate meal or after a period of rest following strenuous exercise.
Potassium levels drop to around 3.0 mmol/L

30
Q

What is the management for someone experiencing an acute attack of hypokalaemic periodic paralysis?

A

Potassium replacement

31
Q

What is the prophylactic management of someone diagnosed with hypokalaemic periodic paralysis?

A

Potassium supplements

Potassium sparing diuretics

32
Q

What are the clinical features of hyperkalaemic periodic paralysis?

A

Attacks of proximal weakness about 30 minutes after exercise or during fasting.
Potassium rises above 5.0 mmol/L

33
Q

What is the management for someone experiencing an acute attack of hyperkalaemic periodic paralysis?

A

IV calcium gluconate

Salbutamol

34
Q

What disease groups are polymyositis and dermatomyositis associated with?

A

Connective tissue disorders

Carcinomas

35
Q

What are the clinical features of polymyositis and dermatomyositis?

A 
30s-40s
More common in women
Proximal muscle weakness
Pain
Associated skin changes
36
Q

What are the skin changes associated with polymyositis and dermatomyositis?

A

Macular erythema on the face - blue violet rash in peri-orbital area
Erythematous plaques - dorsal aspect of fingers
Nail-fold haemorrhages
Skin sensitive to the light

37
Q

What are the complications associated with polymyositis and dermatomyositis?

A

Bulbar dysfunction
Respiratory muscle weakness
Interstitial fibrosing lung disease

38
Q

What would blood tests reveal in someone with polymyositis or dermatomyositis?

A

Raised ESR
Very high CK
Autoantibodies - anto-Jo, antinuclear antibodies, RF, ENAs

39
Q

What would EMG of someone with polymyositis or dermatomyositis reveal?

A

Myopathic picture, but may include fibrillations

40
Q

What would the muscle biopsy of someone with polymyositis or dermatomyositis reveal?

A

Muscle fibre necrosis with an inflammatory infiltrate

41
Q

What investigations should be ordered for someone with suspected polymyositis or dermatomyositis?

A

ESR
FBC
Autoantibodies - Anti-Jo

EMG

Biopsy

Investigation for underlying carcinoma (eg x-ray)

42
Q

What are the treatment options for someone with polymyositis or dermatomyositis?

A

Corticosteroids
Other immunosuppressive drugs - azathioprine and cyclophosphamide
Removal of associated tumour

43
Q

What is the most common cause of muscle disease in people aged over 50?

A

Inclusion body myositis

44
Q

What are the clinical features of inclusion body myositis?

A

Weakness and wasting of flexor muscles of the forearm and hand - causing weak grip and grasp.
Some proximal muscle involvement
Oesophageal involvement

45
Q

What common disease is inclusion body myositis associated with?

A

Diabetes

46
Q

What is the main investigation for patients with suspected inclusion body myositis?

A

Muscle biopsy

47
Q

What do people diagnosed with inclusion body myositis die of?

A

Respiratory compromise or aspiration pneumonia

48
Q

What are the drugs that are known to induce myopathies?

A 
Statins
Steroids
Chloroquine
Amiodarone
Doxorubicin
Zidovudine (AZT)
49
Q

What are the electrolyte and endocrine associated myopathies?

A

Thyrotoxicosis
Cushing’s syndrome
Hypokalaemia
Vitamin D deficiency

NEUROLOGICAL DISEASE (21 decks)

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