Structural determinants of electroencephalographic findings in acute hemispheric lesions

We studied electroencephalograms and computed tomographic scans of 54 patients with acute hemispheric strokes. Electrographic parameters evaluated included field, amplitude, frequency, persistence, and reactivity of focal or lateralized slow-wave activity. Ipsilateral and contralateral background activity were also assessed. Structural and clinical features studied were lesion size, density, mass effect, location, tissue involvement, deep structure involvement, level of consciousness, and outcome. The data were analyzed using computer sorting and the χ² test. The field, amplitude, and frequency of focal slow-wave abnormalities generally failed to show a specific association with structural details. Continuous focal abnormalities correlated with large lesions (p < 0.05), mass effect (p < 0.05), and altered state of consciousness (p < 0.05). Reactive focal abnormalities were associated with small lesions (p < 0.05) and the absence of mass effect (p < 0.02). Ipsilateral background activity abnormalities correlated with lesion size (p < 0.001) and mass effect (p < 0.01). Attenuation of ipsilateral background activity was more important than irregularity. Abnormal background activity contralateral to the lesion side was associated with alteration of consciousness (p < 0.05).