Objective: To review the electroencephalographic changes in conventional tracings made in patients with an acute attack of delirium described in the literature.
Patients and methods: These alterations are considered in a sub-sample of 60 patients randomly selected from a sample of 223 persons admitted to hospital for different medical and surgical conditions and seen in psychiatric consultation for delirium during the years 1996 and 1997 in the Hospital General Yagüe in Burgos, Spain. The methods used included a conventional EEG tracing, following the usual clinical technique, in the context of a prospective, observational study. The changes were classified according to the trace seen and overall criterion of the neurophysiologist. The results were compared with simple statistical tests (frequency and percentage counts, chi squared and residual contingency tables, average comparisons and unidirectional Anova variance analysis and Bonferroni post hoc test).
Results: Marked alterations of tracings were seen in 83.3% of cases (78.7% 'slight', 'moderate' and 'excessive' slowing and 6.6% 'rapid' anomalies. Statistically, 'multi-factorial' and 'on dementia' types of delirium (characterized on the electroencephalogram by different degrees of slowing of the recording) could be clearly differentiated from delirium due to abstinence from alcohol which was mainly seen with 'fast' recordings.
Conclusion: It was confirmed that there are two distinct types of delirium which are very different from the electroencephalographic point of view.