• Disuse of muscles
  • Anemia
  • Malnutrition
  • Electrolyte abnormality, eg, hypercalcemia, hypokalemia, hyponatremia
  • Endocrine disease, eg, hypothyroidism, diabetes mellitus, Cushing’s syndrome, Addison’s disease, hyperaldosteronism
  • Chronic lung or heart disease
  • Malingering
Upper motor neuron disease
  • Stroke
  • Space-occupying lesion, eg, brain tumor
  • Spinal cord lesion
  • Multiple sclerosis
Lower motor neuron disease
  • Anterior horn cell, eg, poliomyelitis, amyotrophic lateral sclerosis (ALS), West Nile virus
  • Motor nerve root, eg, disk protrusion
  • Nerve plexus, eg, brachial plexus neuropathy
  • Peripheral nerve, eg, diabetes mellitus, alcoholism, heavy metals, Guillain-Barré syndrome
  • Neuromuscular junction, eg, myasthenia gravis, Eaton-Lambert syndrome, botulism, organophosphate poisoning, tick paralysis, drug-induced, eg, aminoglycoside
  • Myopathy, eg, polymyositis, corticosteroids, hypothyroidism, alcohol
  • Other: aortic dissection, periodic paralysis, eg, hypokalemic, hyperkalemic, thyrotoxic

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Last updated: December 1, 2014