Neurology Book

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MyopathyAka: Myositis

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  1. See Also
    1. Myopathy Causes
    2. Acute Motor Weakness Causes
    3. Muscular Dystrophy
  2. Findings
    1. Suggestive of Myopathy
      1. Gradual onset of symmetric weakness
      2. Proximal weakness
        1. Difficulty combing hair
        2. Difficulty walking up stairs
      3. Neck Flexion weaker than neck extension
      4. Deep Tendon Reflexes preserved
    2. Suggestive of alternative diagnosis (i.e. Neuropathy)
      1. Sudden onset of asymmetric weakness
      2. Paresthesias in extremities
      3. Bowel dysfunction (e.g. stool Incontinence)
      4. Bladder dysfunction (e.g. Urinary Incontinence)
      5. Distal weakness suggests Neuropathy
        1. Except in Guillain-Barre, Myotonic Dystrophy
      6. Deep Tendon Reflexes lost
  3. History: Direct to specific Myopathy
    1. Family History of Myopathy: Muscular Dystrophy
    2. Difficult swallowing: Polymyositis
    3. Weakness varies and includes eyes: Myasthenia Gravis
    4. Age of onset
      1. Age <30: Muscular Dystrophy
  4. Labs
    1. Creatine Phosphokinase (CPK) increased
    2. Aspartate Aminotransferase (AST) may be increased
    3. Aldolase may be increased
    4. Lactate Dehydrogenase (LDH) may be increased
  5. Diagnostics
    1. Electromyogram (EMG)
    2. Nerve Conduction Studies (NCS)
    3. Muscle biopsy
  6. Causes
    1. See Myopathy Causes
    2. See Medication Causes of Myositis
    3. See Muscular Dystrophy
    4. See Acute Motor Weakness Causes
      1. Critical to rule-out emergent causes
    5. List of some treatable myopathies
      1. Thyroid Myopathy (Hypothyroidism, Hyperthyroidism)
      2. Steroid Myopathy
      3. Polymyositis
      4. Alcoholic Myopathy
      5. Periodic paralysis
      6. Polymyalgia Rheumatica
      7. Myasthenia Gravis
      8. Eaton-Lambert Syndrome

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