Quantitative EEG in hospital encephalopathy: review and microstate analysis

Hospital-acquired encephalopathy is a widely prevalent disorder. The quantitative changes in EEG associated with this condition have long been noted, including slowing of the background frequency and changes in the frequency band power. EEG has had limited clinical use, despite its ability to continuously track clinical severity. We review the development of the use of EEG and particularly quantitative EEG in the assessment of hospital-acquired encephalopathy. Recent advances in EEG technology have included network and microstate analyses, and continuous EEG monitoring, leading to renewed interest in the use of quantitative EEG. We describe the development of microstate analysis that has allowed novel quantitative analysis of the resting state background. We examined the microstates of 16 inpatients with encephalopathy and 20 control patients. The global variance explained by the four standard resting microstates was smaller in patients with encephalopathy. This suggests a decrease in microstate stability, indicating a breakdown in the resting state network dynamics. Modern analysis and acquisition techniques hold the promise of renewed interest in quantitative EEG techniques in the assessment of hospital-acquired encephalopathy.