THE START-STOP-START PHENOMENON IN SCALP-SPHENOIDAL ICTAL RECORDINGS

The start-stop-start (SSS) phenomenon is an apparent abortive ictal on set separated from the main seizure discharge. It was previously descr ibed in seizures recorded with subdural electrodes. We have observed t his phenomenon in scalp-sphenoidal ictal recordings as well. We retros pectively reviewed 435 seizures recorded with scalp-sphenoidal electro des from 61 patients with temporal lobe epilepsy. We found SSS onset i n 15 seizures of 8 patients, representing 26% of these patients' seizu res. The first ''start'' usually had a narrow field, typically in the sphenoidal electrode. The mean duration of the first ''start'' was 11 sec and that of the stop 8 sec. The restart had a different morphology and frequency in 87% and had a wider field in 67% of seizures. The cl inical onset followed the first start and preceded the restart in most of the seizures. In 1 patient, 1 seizure with SSS was correctly local ized and lateralized, whereas 5 of 7 without SSS were falsely laterali zed. The recognition of the SSS phenomenon may improve the accuracy of seizure localization in scalp-sphenoidal recordings.