Myopathy Flashcards

1
Q

what is the most common neuropathic complication of DM?

A

distal symmetric polyneuropathy

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2
Q

what characterizes symmetric PROXIMAL neuropathy?

A

insidious, progressive (weeks-months) weakness affecting hip and thigh muscles

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3
Q

what are the findings in asymmetric proximal motor neuropathy?

A
  • prominent anterior thigh pain with weakness of quadriceps / iliopsoas with loss of patellar reflex
  • initial recovery may be rapid but incomplete
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4
Q

which is more common in diabetic peripheral neuropathy:

  • pain and paresthesias, or
  • sensory weakness and sensory loss?
A

pain and paresthesias

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5
Q

what is the polyol pathway theory with respect to diabetic peripheral neuropathy?

A
  • elevated blood glucose levels lead to high nerve glucose concentration
  • glucose gets converted to sorbitol via polyol pathway catalyzed by aldose reductase which leads to decreased myoinosotol
  • decreased myoinosotol interferes with Na pump
  • decreased aldose reductase leads to decreased levels of NO and glutathione buffer against oxidative injury
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6
Q

what are the clinical features of diabetic peripheral neuropathy?

A
  • insidious combination of sensory, motor, and autonomic features
  • length-related or stocking glove pattern
  • usually worse at night
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7
Q

what are the treatment options for peripheral neuropathy that target underlying conditions and palliative options?

A
  • treat underlying condition: blood sugar, offending toxin, B12 / thyroid deficiency
  • IVIG, plasmapheresis
  • palliative / preventative: foot care, weight reduction. orthotics
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8
Q

what are the treatment options for peripheral neuropathy that target symptoms?

A
  • antidepressants
  • antiepileptic
  • analgesics
  • topical agents
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9
Q

what are the age of onset characteristics in myasthenia gravis?

A

bimodal: 15-30 (women) and 60-75 (men)

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10
Q

what is the clinical history for myasthenia gravis?

A
  • hallmark: fluctuating weakness, increased with exertion and improved with rest
  • ptosis, diplopia on presentation
  • bulbar symptoms: facial weakness, dysarthria, dysphagia, neck flexor more than neck extensor
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11
Q

what is the provocative test for myasthenia gravis?

A

upgaze for 30’-60’

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12
Q

what are the muscular manifestations of myasthenia gravis?

A
  • ocular: failure of upgaze, asymmetric ptosis
  • facial muscle: unable to bury lashes, horizontal smile
  • oropharyngeal: flaccid dysarthria with nasal regurgitation, jaw weakness
  • limbs: upper extremities more common than lower
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13
Q

which upper limb muscles are primarily affected in myasthenia gravis?

A

deltoid and wrist

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14
Q

what is the pathophysiology of myasthenia gravis?

A
  • structure and function of NMJ is altered
  • anti-Ach Abs block post synaptic receptors
  • blockade starts an immunological cascade damaging postsynaptic membrane
  • leads to decreased ability of muscle to depolarize, and therefore, weakness
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15
Q

what are the diagnostic tests for myasthenia gravis?

A
  • edrophonium
  • electrodiagnostic testing, single fiber EMG
  • imaging: CT
  • labs: Ach receptor antibodies, anti-striated muscle Ab
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16
Q

what is the MOA of edrophonium?

A

AchE inhibitor - increases Ach at NMJ

17
Q

what is the symptomatic treatment for myasthenia gravis? what are the side effects?

A
  • cholinesterase inhibitors - inhibit breakdown of Ach at NMJ
  • Gi hyperactivity, increased secretions
18
Q

what is the disease modifying therapy for myasthenia gravis? who is it for and what does it do?

A
  • thymectomy - for generalized disease under age 60

- reduces immune response

19
Q

what are the immunosuppressive drugs for myasthenia gravis?

A
  • corticosteroids
  • azathioprine
  • mycophenolate mofetil
  • cyclosporin
20
Q

what therapies are used for myasthenic crisis?

A
  • plasmapheresis

- IVIG

21
Q

what are the features of myopathies?

A
  • weakness: symmetric, proximal, neck flexor, waddling gait
  • preserved sensation / reflexes
  • creatine kinase
22
Q

what marker is elevated in the majority of myopathies?

A

CK

23
Q

what are the broad categories of myopathies?

A
  • inflammatory
  • endocrine
  • toxic
  • muscular dystrophies
  • metabolic
24
Q

what are the clinical features of polymyositis?

A
  • subacute proximal weakness
  • painless
  • spares eyes, face
  • neck weakness, dysphagia
25
Q

what are the diagnostic criteria for polymyositis? what is the definitive test?

A
  • elevated CK
  • EMG with “myopathic” and “inflammatory” changes
  • biopsy: antigen specific cytotoxic T cells, direct muscle fiber damage (DEFINITIVE TEST)
26
Q

what is seen on biopsy in dermatomyositis / polymyositis?

A
  • fiber splitting
  • necrosis
  • vacuolization
  • perivascular inflammation
27
Q

what are the clinical features of steroid myopathy?

A
  • subacute to chronic proximal weakness
  • CK NORMAL
  • biopsy: type II atrophy
  • EMG NORMAL
28
Q

what are the CK findings in steroid myopathy?

A

normal

29
Q

what are the EMG findings in steroid myopathy?

A

normal

30
Q

what are the biopsy findings in steroid myopathy?

A

type II atrophy

31
Q

what are the sequalae of statin myopathy?

A
  • myalgia: muscle complaints w/o CK elevation
  • myositis: muscle symptoms WITH CK elevation
  • rhabdomyolysis: CK elevation 10x normal with increased creatinine
32
Q

what are the AHA guidelines for statin myopathy?

A

discontinue agent if rhabdomyolysis occurs

33
Q

what are the summaries of MOTOR symptoms for:

  • motor neuron disease
  • neuropathy
  • NMJ
  • myopathy
A
  • motor neuron disease: asymmetric, variable location, atrophy, fasciculations
  • neuropathy: symmetric, distal over proximal
  • NMJ: diplopia, ptosis, easy fatiguability
  • myopathy: symmetric, proximal over distal
34
Q

what are the summaries of SENSORY symptoms for:

  • motor neuron disease
  • neuropathy
  • NMJ
  • myopathy
A
  • motor neuron disease: absent
  • neuropathy: distal over proximal, paresthesias, dysesthesias, autonomic symptoms
  • NMJ: absent
  • myopathy: absent
35
Q

what are the summaries of REFLEXES for:

  • motor neuron disease
  • neuropathy
  • NMJ / myopathy
A
  • motor neuron disease: hyperactive
  • neuropathy: diminished
  • NMJ / myopathy: normal