Monitoring of Cortical Activity Postreperfusion. A Powerful Tool for Predicting Clinical Response Immediately After Recanalization

ABSTRACT BACKGROUND In acute ischemic stroke, although early recanalization predicts rapid neurological recovery, in some cases early reperfusion does not immediately correlate to clinical improvement as “stunned brain” patients. The cortical activity monitoring in stroke patients is usually performed to evaluate epileptic activity through electroencephalogram. Bispectral index (BIS) monitor the cortical activity by fronto‐temporal electrodes and is currently used for monitoring level of conscious on sedo‐analgesia patients. Some studies have shown certain sensibility to detect cerebrovascular events during carotid revascularization. We aimed to evaluate the impact of BIS monitoring before and shortly after reperfusion on early and delayed clinical improvement on stroke patients. METHODS Consecutive patients with acute anterior circulation ischemic stroke who received reperfusion therapies were monitored with bicortical BIS during the first 6 hours of admission. We registered initial and final BIS value on the affected and contralateral side and determined asymmetry and changes in relation to recanalization and other clinical variables as sedation and perprocedure complications. We defined major clinical improvement decrease ≥8 points at discharge or 5 day at admission. Infarct volume was measure on 24‐hour CT scan. Modified Rankin score at 3 months was evaluated. RESULTS A total of 53 patients were monitored with BIS. Median age was 73 years, median baseline National Institutes of Health Stroke Scale (NIHSS) 16. We observed an inverse correlation between final BIS score and NIHSS at discharge ( P < .001; r = −.538) and infarct volume at 24 hours ( P = .031; r = −.430). A receiver–operator characteristic curve identified a final BIS score of >81 as the value that better predicted further clinical improvement. After adjusting for recanalization, posttreatment NIHSS and age, final BIS emerged as the only independent predictor of clinical improvement(OR 1.21; CI 95%:1.01–1.28; P = .024). Among patients without improvement at 24 hours, after adjusting for recanalization, posttreatment NIHSS and age, final BIS value >81 emerged as the only independent predictor of clinical improvement(OR 11.6; CI 95%:1.112–122.3; P = .04). CONCLUSION BIS value is associated with clinical and radiological variables in acute stroke patients. The final BIS value is a powerful independent predictor of further clinical improvement. Larger studies are needed to assess the value of post reperfusion cortical activity measured by BIS.