ObjectiveTo establish the prevalence, clinical characteristics, and electrophysiologic features of residual neuromuscular dysfunction after prolonged critical illness.DesignProspective follow-up study of survivors of prolonged critical illness.SettingA university hospital and two district general hospitals in the UK.PatientsThe study occurred for a period of 5 yrs. All patients during that time who were in the intensive care unit for >28 days were entered in the study.Measurements and Main ResultsAt follow-up, length of intensive care unit and hospital stay, duration of mechanical ventilation and admission Acute Physiology and Chronic Health Evaluation II score were recorded from the case notes. A clinical history was obtained, a Barthel Index disability score was calculated, and a full neurologic examination was performed. Nerve conduction studies, needle electromyography, single-fiber electromyography and thermal thresholds were performed. A total of 195 patients were identified. There were 86 survivors, of whom 47 could be contacted and 22 consented to be studied. The median time from intensive care unit discharge to follow-up was 43 months (range, 12–57 months). All gave a clear history of severe weakness and functional impairment after hospital discharge and, in all, recovery was prolonged. Motor or sensory deficits were present on clinical examination in 59% of the patients studied. Common peroneal nerve palsy was present in two patients. A total of 21 of 22 (95%) patients had electromyographic evidence of chronic partial denervation at follow-up, findings indicative of a preceding axonal neuropathy. The single-fiber electromyographic studies were also consistent with a preceding motor neuropathy.ConclusionSevere weakness requiring prolonged rehabilitation and abnormal clinical neurologic findings are extremely common in survivors of protracted critical illness. Neurophysiologic evidence of chronic partial denervation of muscle consistent with previous critical illness polyneuropathy is almost invariable and can be found up to 5 yrs after intensive care unit discharge in >90% of these long-stay patients. Evidence of myopathy is unusual. These findings have important implications for the management and rehabilitation of intensive care survivors.