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MM Test 3 > B6.054 Steroid Myopathies > Flashcards

B6.054 Steroid Myopathies Flashcards

1
Q

symptoms of myopathy

A 
difficulty climbing stairs. standing
falls
trouble combing hair, brushing teeth
dysphagia / dysarthria
fatigue, myalgia, tenderness
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2
Q

signs of myopathy

A

proximal weakness: neck, shoulder, hip
normal tendon reflexes
normal sensory exam
facial or bulbar weakness

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3
Q

Ddx for myopathy

A 
myositis
MD
toxic exposure: SANAM
metabolic enzyme defect
mitochondrial muscle disease
endocrinopathy
critical illness myopathy
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4
Q

Ddx for proximal muscle weakness

A 
myopathy
NMJ defect (lambert eaton, MG)
CIDP (inflammation of peripheral nerves)
motor neuron diseases: SMA, ALS
myelopathy
sarcopenia
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5
Q

when does muscle aging start?

A

age 40

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6
Q

lab evaluation of myopathic disorders

A 
serum CK
electrolytes, thyroid
serum Abs
needle EMG
nerve conduction study
biopsy
non-ischemic forearm test
urine for myoglobin
muscle imaging
molecular/genetic studies
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7
Q

how might you get an excess of endogenous steroids

A

Cushings > bilateral adrenalectomy > excessive pituitary ACTH secretion > proximal myopathy (Nelson Syndrome)

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8
Q

which steroids are particularly likely to cause drug induced steroid myopathy

A

9-a-fluorinated corticosteroids
triamcinolone, betamethasone, dexamethasone
(long duration)

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9
Q

which steroids rarely cause myopathy

A

prednisone dose equivalent < 30 mg qd

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10
Q

complications of critical illness

A

CIM: critical illness myopathy
CIN: critical illness neuropathy
PNMB: prolonged neuromuscular blockade

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11
Q

mechanisms of steroid myopathy

A

not fully understood

likely due to impaired protein synthesis and muscle catabolism

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12
Q

which muscle fibers are more susceptible to steroid myopathy

A

type 2 fibers (fast, glycolytic)

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13
Q

cellular transcription changes caused by steroids that can induce myopathy

A

induced ubiquitin ligases: atrogin 1, muscle RING finger 1
suppress mammalian/ mechanistic target of rapamycin (mTOR)
these changes lead to an imbalance between anabolism and catabolism of muscle proteins, resulting in atrophy

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14
Q

growth factor changes contributing to steroid myopathy

A

negative changes in IGF-1 and myostatin

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15
Q

muscle weakness pattern associated with Cushings

A

insidious onset

proximal muscle weakness and wasting without involvement of distal or cranial muscles

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16
Q

fat redistribution in Cushings

A

supraclavicular and temporal fossa
facial rounding
central obesity
buffalo hump

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17
Q

skin findings in Cushings

A

wide (>1 cm) purple striae
bruising
hirsutism
poor wound healing

18
Q

pediatric findings in Cushings

A

decreased linear growth with continued weight gain

19
Q

behavioral / psych effects of Cushings

A

decreased libido
lethargy
depression

20
Q

other endocrine changes in Cushings

A

impaired glucose tolerance / diabetes

menstrual changes

21
Q

muscle weakness seen in exogenous steroid myopathy

A

proximal, symmetric weakness
legs > arms
wasting and myalgias

22
Q

systemic effects of exogenous steroids

A 
weight gain
HTN
hyperlipidemia
glucose intolerance
diabetes
osteopenia
menstrual changes
impotence
23
Q

purpose of EMG

A

measure integrity of nerves, muscles, and their junction

24
Q

what makes up a normal motor unit action potential

A

1 axon with its constituent muscle fibers

25
Q

appearance of nerve injury on EMG

A

more fiber recruitment
extra amplification
polyphasic shape rather than triphasic

26
Q

appearance of muscle injury on EMG

A

action potential amplitude decreased, but shape is the same

27
Q

lab results seen in steroid myopathy

A

normal CK

normal or mild myopathy on EMG

28
Q

muscle pathology of steroid myopathy

A

type 2 fiber atrophy

myosin loss

29
Q

treatment of endogenous steroid myopathy

A

pituitary tumor removal in Cushings

ketoconazole

30
Q

treatment of exogenous steroid myopathy

A

reduce dose of steroids

supportive care / physical therapy

31
Q

mnemonic for generalized weakness in the ICU

A 
MUCESS
Medication (steroids, NMBA)
Undiagnosed neuromuscular disorders (ALS, MG)
Critical illness myopathy / neuropathy
Electrolyte disorders
Systemic illness
Spinal cord damage
32
Q

what is Guillain-Barre

A

ascending paralysis, often post infectious (GI or resp)

peripheral neuropathy and weakness that eventually progresses to resp failure

33
Q

what is an example of a trigger of Guillain-Barre

A

vaccines (flu shots)

1/100,000

34
Q

causes of muscle weakness after ICU admit

A 
CIM
CIP
prolonged NM blockage
acute necrotizing myopathy
cachectic myopathy
not GBS
35
Q

medical conditions associated with CIM

A 
sepsis
renal/liver failure
asthma
organ transplant
use of IV steroids and/or NMBAs
36
Q

challenges associated with NM evaluation in the ICU

A

history and exam may be unobtainable or unreliable due to sedation, intubation, or encephalopathy
reflexes may be preserved even in patients with severe myopathies/neuropathies
muscle atrophy may be difficult to detect due to generalized edema

37
Q

useful investigations in evaluating ICU weakness

A 
MRI cervical spine, and possibly brain
nerve conduction
repetitive nerve stimulation studies for PNMB
needle electromyography
serum CK, ANA, RF, TSH, aldolase
CSF if suspecting GBS
38
Q

how many pts get CIM?

A

up to 46% of patients evaluated for ICU weakness

39
Q

clinical features of CIM

A

severe resp weakness requiring ventilator
generalized or proximal flaccid paralysis
muscle atrophy
cranial nerves usually spared
normal sensory exam
reflexes may be normal, reduced, or absent

40
Q

lab features of CIM

A

CK often mildly elevated within 9 days after exposure to steroids, but can remain normal or very low
aldolase may be elevated

41
Q

which types of sensory nerves are tested by nerve conduction studies

A

a-alpha
a-beta
larger and faster conduction velocity
proprioception and touch sensing

42
Q

which types of sensory nerves are ignored by nerve conduction studies

A

a-delta
C
smaller and slower conducting
pain and temperature sensing

MM Test 3 (31 decks)

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