A comparative study of electroencephalography and computed axial tomography in recent cerebral infarction.

In order to re-assess the present role of electroencephalography in the investigation of cerebral infarct, we prospectively studied 50 adults with recent supratentorial cerebral infarction over a ten-month period. All 50 patients had EEG's and CT scans within the first two weeks of the apoplectic event. The time span between the two procedures was one week or less in all patients. We monitored the following EEG parameters: characteristics of alpha rhythm (depressed, unchanged, or enhanced); prevalence, type, rhythmicity, and topography of focal slowing; and presence or absence of FIRDA. We grouped the patients on the basis of CT findings as follows: depth of the infarct (cortical-subcortical, deep white matter, or lacunar); size of the infarct (large, medium, or small); and presence or absence of mass effect. Statistical analysis revealed no differences with regard to the EEG parameters between the groups. However, when patients were categorized according to topography of the infarct, the group with parietal infarct showed a significantly higher incidence of depressed alpha rhythm compared with the groups with frontal or occipital infarct. Of the 50 patients, four patients whose history and clinical presentation suggested infarct had normal CT scans despite the presence of EEG abnormality. On the contrary, in two patients, the EEG was normal, whereas the CT confirmed the infarct. Our data suggested that physiological factors may play a major role in the pathogenesis of EEG abnormalities in cerebral infarct, thus accounting for the discrepancies between the EEG parameters and CT findings observed in our population. It was also suggested that EEG's be included routinely in the investigation of cerebral infarct.