Seventy elderly patients meeting the DSM-III criteria for delirium were examined during the acute stage and followed up to one year. The mean age of the patients was 75 years (range 60-88), their delirium lasted on average 20 days (range 3-81) and the psychiatric hospitalization on average 30 days (range 8-365). The most common etiologies for delirium were stroke, infections and metabolic disorders. For 57 cases (81%) a predisposing structural brain disease was found. During the index admission, the cognitive dysfunction associated with delirium ameliorated significantly (the mean +/- SD Mini-Mental State Examination score 9.7 +/- 6.6 at admission and 13.9 +/- 7.2 at discharge; P less than 0.001), but during the one-year follow-up progression of the basic central nervous system disease was seen together with declining cognition and deterioration of functions of daily living.

SUMMARY Spectral analysis of EEG was conducted for 51 elderly delirious patients meeting the Diagnostic and Statistical Manual of Mental Disorders III (DSM-III) criteria and for 19 controls. As a whole group, and also when subdivided according to the type of delirium, severity of cognitive decline or the type ofcentral nervous system disease, delirious patients showed significant reductions of alpha percentage, increased theta and delta activity and slowing of the peak and mean frequencies and these changes were also obvious in individual recordings. The alpha percentage and various ratio parameters correlated significantly with Mini Mental State score, and delta percentage and mean frequency with the lengths of delirium and hospitalisation. The results indicate an association between spectral EEG changes and severity of cognitive deterioration in delirium.Delirium is an organic mental disorder characterised by disorganisation of mental functioning due to widespread, temporary derangement of cerebral metabolism appearing symptomatically during the course of an underlying physical illness."-3 It features concurrent disorders of attention, perception, thinking, memory, psychomotor behaviour, and the sleepwaking cycle with fluctuations in depth, and often with delusions or hallucinations.4 The aetiology of delirium is almost invariably multifactorial, often including a predisposing central nervous system (CNS) disease and one or more possible causative factors.56In demented patients, a number of studies with routine and quantitative EEG have shown slowing of the mean occipital frequency and increased activity in the lower frequency bands with correlation to the degree of dementia, especially in Alzheimer's disease.7'2 In delirious patients, previous studies using routine EEG have also shown an increase ofslow wave activity and slowing and disruption of the normal alpha rhythm.5"3'4 As information concerning the possible correlations between the clinical symptoms (such as severity ofcognitive deterioration and type of delirium) and EEG changes in delirious patients is limited, we decided to study the spectral EEG changes in delirious elderly patients meeting the DSM-III Address for reprint requests: Hannu Koponen, MD,

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SynopsisCerebrospinal fluid somatostatin-like immunoreactivity (CSF SLI) was determined for 67 elderly patients who met the DSM-III criteria for delirium and for 19 age-matched controls. As a group, and also when subdivided according to the type of delirium, severity of cognitive decline or the type of central nervous system disease, the delirious patients showed significant reductions of SLI compared with the controls, together with a declining trend associated with increasing cognitive dysfunction. These findings are in accordance with previous observations that reduced CSF SLI is associated with diseases in which cognitive function is disturbed and they extend this finding to delirium.