Continuous EEG monitoring during thrombolysis in acute hemispheric stroke patients using the brain symmetry index

Continuous EEG monitoring could benefit stroke patients as it may detect changes in brain function in a possible reversible state, allowing early intervention. The Brain Symmetry Index (BSI) was introduced previously as a measure to quantify ischemia in acute hemispheric stroke patients, and a positive correlation was found between the BSI and the National Institutes of Health Stroke Scale. Here, we explore the feasibility and potential clinical relevance of continuous EEG monitoring in acute hemispheric stroke, with the BSI as an indicator of the effect of thrombolysis with recombinant tissue plasminogen activator (r-tPA). Patients with acute hemispheric stroke treated with r-tPA were monitored using a bipolar eight channel EEG. The BSI is defined as the mean of the absolute value of the difference in the mean hemispheric amplitude spectrum; values range from 0 (no asymmetry) to 1 (maximal asymmetry). The clinical condition of the patients was assessed with the National Institutes of Health Stroke Scale. In this pilot study 16 patients were included. In all patients, the BSI remained constant or showed improvement during and after treatment with r-tPA. The correlation between the BSI and National Institutes of Health Stroke Scale in this study is significant, and confirms previous results. The correlation between the change in BSI and the change in National Institutes of Health Stroke Scale during treatment with r-tPA is significant, as well. No clinical significant complications occurred during r-tPA treatment. Our results show that continuous EEG monitoring using the BSI is technically feasible and provides real-time information about the effect of thrombolysis in acute hemispheric stroke patients.