Delta Power Is Higher and More Symmetrical in Ischemic Stroke Patients with Cortical Involvement

Abstract

A brain injury resulting from unilateral stroke critically alters brain functionality and the complex balance within the cortical activity. Such modifications may critically depend on lesion location and cortical involvement. Indeed, recent findings pointed out the necessity of applying a stratification based on lesion location when investigating inter-hemispheric balance in stroke. Here, we tested whether cortical involvement could imply differences in band-specific activity and brain symmetry in post stroke patients with cortico-subcortical and subcortical strokes. We explored brain activity related to lesion location through EEG power analysis and quantitative Electroencephalography (qEEG) measures. Thirty stroke patients in the subacute phase and 10 neurologically intact age-matched right-handed subjects were enrolled. Stroke patients were equally subdivided in two groups based on lesion location: cortico-subcortical (CS, mean age ± SD: 72.21 ± 10.97 years; time since stroke ± SD: 31.14 ± 11.73 days) and subcortical (S, mean age ± SD: 68.92 ± 10.001 years; time since stroke ± SD: 26.93 ± 13.08 days) group. We assessed patients’ neurological status by means of National Institutes of Health Stroke Scale (NIHSS). High density EEG at rest was recorded and power spectral analysis in Delta (1–4 Hz) and Alpha (8–14 Hz) bands was performed. qEEG metrics as pairwise derived Brain Symmetry Index (pdBSI) and Delta/Alpha Ratio (DAR) were computed and correlated with NIHSS score. S showed a lower Delta power in the Unaffected Hemisphere (UH) compared to Affected Hemisphere (AH; z = −1.98, p < 0.05) and a higher Alpha power compared to CS (z = −2.18, p < 0.05). pdBSI was negatively correlated with NIHSS (R = −0.59, p < 0.05). CS showed a higher value and symmetrical distribution of Delta band activity (z = −2.37, p < 0.05), confirmed also by a higher DAR value compared to S (z = −2.48, p < 0.05). Patients with cortico-subcortical and subcortical lesions show different brain symmetry in the subacute phase. Interestingly, in subcortical stroke patient brain activity is related with the clinical function. qEEG measures can be explicative of brain activity related to lesion location and they could allow precise definition of diagnostic-therapeutic algorithms in stroke patients.

Predicting stroke severity with a 3-min recording from the Muse portable EEG system for rapid diagnosis of stroke

“…Therefore, our follow up study will validate these findings using a much larger sample size so that subgroup analyses will be adequately powered. Third, scalp measures of EEG measure cortical activity, and the effects of stroke on cortical activity likely vary depending on stroke location 12 . In this sample, only three stroke patients had subcortical stroke, leaving us underpowered to detect effects of stroke location on EEG.…”

“…The power spectrum begins to return to normal in the first 3 months after stroke, but quantitative EEG (qEEG) can still show abnormalities, such as impaired symmetry, that persist past the point of good motor recovery 11 . Past studies have shown that qEEG indices such as DAR can be used for both diagnosis of ischemic stroke 6 , 8 , 12 , 13 and prediction of clinical outcomes 7 , 14 – 18 .…”

“…The majority of strokes are unilateral, and thus deficits (e.g., motor impairments) are lateralized as well 19 . Therefore, brain symmetry is another qEEG measure that has been used to distinguish stroke from control populations 7 , 8 , 12 – 14 , 18 . The brain symmetry index was first used during carotid surgery as a reliable method to detect early brain ischemia 20 .…”

“…Higher pdBSI is often associated with worse outcome 7 , 10 , 21 . However, it has also been shown that pdBSI may vary based on stroke location, with cortical strokes having more symmetrical activity compared to subcortical strokes 12 .…”

Sleep-like bistability, loss of causality and complexity in the brain of Unresponsive Wakefulness Syndrome patients

“…In physiological conditions, active inhibition (especially GABAB) plays an important role in inducing cortical OFF--periods (18,21). This is known to occur locally after a stroke (50), but may involve the whole remaining cortex following severe, multifocal injury (42).…”