Table 2.
EEG characteristics in various locations and subtypes of ischemic stroke.
| Stroke Subtypes | Summary | Time Frame of EEG Detection Relative to Stroke Onset | EEG/qEEG Characteristics |
|---|---|---|---|
| Large (Cortical, including ACA, MCA, PCA territories) | EEG abnormalities following cortical infarction depended on infarct location | <2 weeks (<24 h (34%), <1 week (50%)) | Lateralized EEG abnormalities 80% in MCA territory, 86% in cortical watershed zone, but 50% in PCA territory [177] |
| Strong association between EEG mapping of δ power and lesion locations by CT | <24 h | Close correlation between EEG abnormalities (increased δ power) except striatocapsular in 85% patients [182] | |
| EEG monitoring is useful in all ischemic strokes regardless of locations. Also, pdBSI predicted radiologically (CT, MRI) confirmed stroke with an accuracy higher than the National Institute of Health stroke score (NIHSS) score at admission |
<7 days (<72 h (81%)) | Increased pdBSI, DTABR, even in PCS and LACS [184] | |
| Small (subcortical, lacunar) | EEG has relatively low sensitivity in patients with subcortical infarcts | <2 weeks (<24 h (34%), <1 week (50%)) | 82% normal or non-lateralized EEG changes in subcortical lesions [177] |
| EEG has relatively low sensitivity in patients with first lacunar infarcts | <7 days | Abnormal EEG in 43% patients with first lacunar stroke [183] | |
| EEG abnormalities depend on affected lesions in subcortical regions | <24 h | Normal EEG in striatocapsular regions 70% abnormal EEG in other subcortical regions [182] | |
| TIA | EEG has low sensitivity in patients with TIA | <24 h | Non-significant difference between TIA and control by using pdBSI and DTABR [185] |
| DCI in SAH | ADRs may allow earlier detection of DCI in patients with severe SAH | Post-operative day two to post-SAH day 14 | ADR decrease in patients with DCI [186] |
| EEG changes preceded detection of vasospasm/DCI in standard procedures by 2.3 days | 2–12 days (median 5.2 days) | Decrease in α or θ power few days before vasospasm/DCI [187] | |
| Malignant MCA infarction | Emergence of high-voltage contralateral hemisphere δ activity might represent midline shift due to substantial edema in ipsilateral hemisphere and increased intracranial pressure | <25 h | Increasing δ power in contralateral hemisphere in malignant course [188] |
| EEG and brain stem auditory evoked potentials have prognostic value for patients who develop malignant edema | <24 h | Diffuse generalized slowing and slow δ activity in the ischemic hemisphere pointed to a malignant course [190] |
Abbreviations: CT: computed tomography; MRI: magnetic resonance imaging; qEEG: quantitative electroencephalography; ACA: anterior cerebral artery; MCA: middle cerebral artery; PCA: posterior cerebral artery; ACS: anterior circulation syndrome; POCS: posterior circulation syndrome; LACS: lacunar syndrome; DCI: delayed cerebral ischemia; SAH: subarachnoid hemorrhage; ADR: α/δ ratio; DTABR: (δ + θ)/(α + β) power ratio; pdBSI: pairwise derived brain symmetry index; TIA: transient ischemic attack; CT: computed tomography; MRI: magnetic resonance imaging.