Critical illness neuropathy and myopathy.

S evere weakness with respiratory failure is a serious and common complication of critically ill patients in the intensive care unit setting. Recent studies have elucidated 2 entities characterized by severe weakness that occur as a result of these circumstances: critical illness neuropathy and critical illness myopathy. Both are the result of a serious illness, in contrast to weakness arising from a primary neurological disorder that results in admission to an intensive care unit (eg, myasthenic crisis, Guillain-Barré syndrome, rhabdomyolysis, or botulism). Critical illness neuropathy and myopathy are difficult to distinguish from each other on purely clinical grounds, although certain clues may make one more likely. Nerve conduction studies, needle electromyography, and muscle biopsy are often necessary to make a firm diagnosis.