At present, delirium represents the most frequent form of acute disturbance of mental state and behaviour that could be encountered in all medical specialties and in all types of hospitals, especially those with a higher percentage of older patients (geriatrics) or critically ill patients (intensive care units). Increased incidence of delirium (associated with the population ageing and increased proportion of seriously or critically ill patients) may be expected in the near future. Most frequent precipitating (in general every serious somatic disease, surgery, trauma, drug or withdrawal effects, primary brain lesion) and predisposing factors (older age, pre-existing dementia) are now well known. However, detailed etiopathogenesis of cerebral dysfunction, specific risk factors of the so-called septic encephalopathy in the critically ill and the importance of localisation in primary cerebral affections remains to be elucidated. Nowadays, this syndrome has been under-diagnosed, about 2/3 cases of delirium, particularly the so-called hypoactive type have remained unrecognized. The use of validated screening tests augments significantly the detection of delirium. Diagnosis of delirium in intensive care unit patients, mostly sedated and unable to communicate, requires special tests. Multimodal preventive and curative measures have probably positive effects on the occurrence and severity of delirium. However, elucidating the delirium etiopathogenesis may bring more effective methods resulting in minimizing the delirium consequences such as increased mortality deteriorated cognitive and functional repair, institutionalization of patients, and higher economical costs at the care of them. Delirium is an important multidisciplinary neurological and psychiatric problem representing challenge for the two specialties comparable with the importance of the dementia problem.

        Key words: delirium, septic encephalopathy, risk factors, critically ill patients