Relationship between regional pertechnetate cerebral circulation time and EEG in patients with cerebral infarction

The qualitative and regional correlations between the EEG and the cerebral circulation time (CCT), obtained by using intravenously injected pertechnetate and a multidetector device, were studied in 75 patients with supratentorial cerebral infarction. Because bolus dispersion and changes in systemic circulation may distort absolute CCT values when intravenous injection of the isotope is used, the inter- and intrahemispheric relative CCT values were used as indices of CCT. Overall good correlations could be demonstrated between both inter- and intrahemispheric CCT abnormalities and the EEG, though not in all patients. The number of patients with pathological CCT findings showed a tendency to increase with increasing severity of the EEG abnormality. The number of abnormal CCT areas per patient (indicating the size of the circulation disturbance) also increased significantly with increasing severity of the EEG disturbance. Interestingly, relative 'hypervelocity' areas occurred in fewer patients with normal or clearly disturbed EEGs than in patients with mildly disturbed EEGs, perhaps due to differences in autoregulatory capacity and collateral circulation. Within the EEG focus the relative number of CCT abnormalities was greater than outside it. In spite of this fairly good overall correlation between the EEG focus and the CCT abnormality, more than 10% of the patients with an EEG focus showed no CCT abnormalities, thus indicating the complementary roles of these methods. The present study on cerebral infarction, though using intravenously injected pertechnetate for the CCT measurement, showed a reasonable correspondence with earlier reports on the relationship between the EEG and either the CBF or the CCT (obtained by intra-arterially injected isotope). This would seem to suggest that the used non-invasive method for regional CCT measurement has potential for evaluation of cerebral haemodynamics.