The incidence of muscle weakness was determined in 830 children (3 months to 17 years of age) admitted for >24 hours to the intensive care unit over a 1-year period at the Hospital for Sick Children, Toronto, Canada. Generalized weakness developed in 14 (1.7%), and 4 failed repeated attempts to extubate. The age distribution was bimodal, with 3 under age 3 years and 11 age 10 or older. Eleven had multiple organ dysfunction and 9 had sepsis. Most received corticosteroids, neuromuscular blocking agents, or aminoglycoside antibiotics. Eight of the 14 were organ or bone marrow transplant recipients. EMG findings in 5 were abnormal and myopathic in 4, with short-duration, low-amplitude motor unit potentials and small polyphasic potentials. Nerve conduction studies done in 7 patients showed decreased compound muscle action potentials in 4, normal findings in 2, a compressive neuropathy in 1, and a demyelinating polyneuropathy in 1. Serum creatine kinase was elevated to 2 to 100 times the upper limit of normal in 3. A histological diagnosis of acute quadriplegic myopathy was made in all 3 patients with muscle biopsy. Three died; and in survivors, weakness persisted for 3 to 12 months after discharge. 
COMMENT. The incidence of neuromuscular weakness in critically ill children in an ICU is infrequent and develops mainly in older children, over 10 years of age, and especially in transplant recipients.