EEG Monitoring in Carotid Endarterectomy

To the Editor.—We agree with many of the conclusions and observations made by Elmore and colleagues¹ in the June 1990 issue of the Archives regarding monitoring for carotid endarterectomy with computerized electroencephalographic (EEG) brain mapping. However, in their discussion of our previous reports on this topic, they incorrectly cited the criteria we used. They said we used only new asymmetry as a criterion for EEG "change." However, we actually reported^2,3 on any significant EEG "change" on carotid cross-clamping, whether it was a new asymmetry or a generalized change from intraoperative preclamp baseline EEG. We only required that the change be substantially greater than the ordinary fluctuations seen during the routine baseline portion of the operation, prior to clamping. Many of the changes reported in our study were indeed generalized changes of the EEG background, including generalized loss of fast activity, increase in slow activity, or, occasionally, a