Quantitative EEG indices of sub-acute ischaemic stroke correlate with clinical outcomes

Objective: We investigated the ability of quantitative electroencephalography (QEEG) measures in sub-acute stroke to assist monitoring or prognostication of stroke evolution. QEEG indices and National Institutes of Health Stroke Scale (NIHSS) scores were compared. Methods: Ischaemic cortical stroke patients were studied. Resting, 62-channel EEG and NIHSS score were acquired at 49 +/- 3 h post-symptom onset, and NIHSS administered at 30 +/- 2 days post-stroke. Mean power was calculated for delta (1-4 Hz), theta (4.1-8 Hz), alpha (8.1-12.5 Hz) and beta (12.6-30 Hz) frequency bands, using a 62-channel electrode array and a 19-channel subset. Results: Thirteen patients (6 male, median age 66, range 54-86 years) were studied. Sub-acute delta:alpha power ratio (DAR; r = 0.91, P < 0.001), relative alpha power (r = -0.82, P < 0.01), and NIHSS score (r = 0.92, P < 0.001) each were significantly correlated with 30-day NIHSS score. The former two significant correlations were upheld in 19-channel EEG data. QEEG measures involving theta or beta power were not significantly correlated with NIHSS scores. Conclusions: QEEG measures such as DAR demonstrate potential to augment bedside assessment of cerebral pathophysiology and prognostication of stroke evolution. A standard, 19-channel array seems adequate for these purposes. Future studies in larger samples should investigate the potential effects on these measures of sleep state and possible causes of artefacts. Significance: QEEG measures from a standard number of electrodes, if available rapidly and robust to potential artefacts, may inform future management of stroke patients. (c) 2007 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.