PING-PONG SEIZURES

We explored the frequency with which EEG ictal events shifted laterali ty during a complex partial seizure (CPS), a phenomenon termed ping-po ng seizures. Coded and shuffled 5-s segments from records of 38 scalp EEG monitored patients and 2 patients with implanted depth electrodes were categorized as left, right, or unclear laterality. Thirteen patie nts (33%) showed a ping-pong effect. Mean duration of time to switch l aterality was 10.3 +/- 7.2 s. Two patients with depth wires also demon strated ping-pong seizures. No patient reversed laterality twice. If t he beginning of a seizure is obscure or missed, the apparent lateraliz ation may be incorrect.