Contralateral hemisphere delta EEG in acute stroke precedes worsening of symptoms and death

Abstract

A number of recent studies report that quantitative electroencephalography (QEEG) measures of cerebral pathophysiology in acute or sub-acute stroke might augment future prognoses regarding patient outcomes (e.g., Claassen et al., 2004; Cuspineda et al., 2003; Finnigan et al., 2004, 2006, 2007; Jordan, 2004; Tecchio et al., 2007; van Putten and Tavy, 2004; Zappasodi et al., 2007). For example we have reported that QEEG delta (~1 to 4 Hz) power measures in acute stroke (Finnigan et al., 2004, 2006) and delta/alpha power ratio (DAR) measures in sub-acute stroke (Finnigan et al., 2007) are both highly correlated with ischaemic stroke patients’ outcomes assessed via the National Institutes of Health Stroke Scale (NIHSS). QEEG measures were averaged over all scalp electrodes and further a significant correlation between subacute DAR and outcome measures was obtained when the former was computed from a standard, 19-electrode array.Some QEEG measures incorporate separate computations for each cerebral hemisphere (e.g. van Putten and Tavy, 2004); Tecchio et al. (2007) acquired hemisphere-specific magnetoencephalography (MEG) data from subacute ischaemic stroke patients and reported that delta measures from the contralateral hemisphere (CH) appear valuable in predicting clinical outcome assessed via NIHSS at followup (median 7.8 months post-stroke). Moreover, multinomial logistic regression analyses revealed that this QEEG measure per se enhanced the sensitivity and specificity of outcome prediction beyond that afforded by subacute lesion volume defined via perfusion-weighted magnetic resonance imaging (MRI). These outcomes are consistent with QEEG and other observations we have acquired from acute ischaemic stroke patients, including those who have deceased in the ensuing days. Here we report cross-temporal NIHSS, QEEG and MRI data from two such patients. Approval to carry out the study was obtained from the local University and Hospital Human Experimental Ethics committees, and informed consent was obtained from the patients’ spouses.If potential issues such as those outlined above can be accounted for and if the delta observations presented and cited herein can be replicated in larger patient samples, such QEEG measures may become more routinely utilised in future to inform clinical prognoses and stroke patient management. For example QEEG measures, and crosstemporal changes in same, computed promptly (perhaps automatically) might help guide future clinical decisions about administration or efficacy of an intervention such as local, intra-arterial thrombolysis therapy. Further, in MCA infarction in adults under 60 years, where decompression surgery is being contemplated, such QEEG observations may assist in more timely decisions to operate. In such circumstances QEEG indices should of course be considered in concert with other (e.g. clinical and MRI) concomitant observations.