Cerebral disorders detected by EEG and missed by CAT scan.

EEG recordings of the electrical seizure activity during unilateral non-dominant (right) hemisphere electroconvulsive therapy reveal three phases of activity: (1) Phase I initial 14-22 Hz rhythmic activity; (2) Phase II arhythmic polyspike activity; and (3) Phase III rhythmic 2 1/2-3 1/2 Hz. spike/polyspike-wave activity. The Phase II polyspike activity appears as an orderly march beginning in the right anterial temporal area. The Phase II activity is of higher voltage on the right side compared to the left side. The Phase III activity ends abruptly with a nearly isoelectric tracing (the "fit switch").