Muscle Weakness Eval

Question 1

Fatigue

Asthenia

Muscle Weakness

Answer 1

• Fatigue – unable to cont performing specific task after mult repetitions
• Asthenia – exhaustion w/o specific complaint of muscle weakness; associated depression
• Muscle weakness – cannot perform single repetition

Question 2

What to ask in Hx

Answer 2

• Timing - rapid onset (can remember) v insidious onset
• Proximal (lower problems w/ standing from chair or upper problems brushing hair) v. distal muscles (difficulty standing on toes or fine motor activities of hands)
• If focal or asymmetric - most likely near etiology (ex - only 1 foot)
• Associated symptoms -
  
  • Arthritis, rash, swallowing problems (rheum)
  • Wt gain or wt loss - endocrine (thyroid)
• Family hx (genetic myopathies or rheum/autoimmune)
• Med use - including statins and fibric acid derivatives (gemfibrozil)

Question 3

What labs to order

Answer 3

• CK - enzyme leak in muscle injury
• Inflammatory and autoimmune tests
  
  • ESR - sedimentation rate
  • ANA + other auto-antibodies
• Lumbar puncture - if worried about MS and other near conditions

Question 4

EMG

Answer 4

(done if myopathy is suspected and CK is elevated)

• Detect electrical activity of muscle
• If normal EMG then not electrical problem so not a true myopathy
• Sensitive but does not give specific cause

Question 5

Muscle Biopsy Findings by Etiology

Answer 5

• inflammatory cells (autoimmune)
• fiber necrosis
• ragged red fibers (mitochondrial myopathy)
• atrophy or degeneration of fibers (drug-induced)

Question 6

Tx by Etiology

Answer 6

• If drug induced… stop offending drug
• If autoimmune… glucocorticoids + other immunosuppressants
• If endocrine … thyroid hormone replacement
• If genetic … often just supportive