Abstracts

RATIONALE: Based on EEG-video documentation of pentylenetetrazole-induced seizures in epileptic patients, Ajmone Marsan and Ralston (1957) postulated that occipitally originating seizures could propagate either in a supra-Sylvian or infra-Sylvian direction, determined largely by origin above or below the calcarine fissure. We thus analysed occipital seizure propagation patterns. As clinical manifestations of occipitally originating seizures may reflect the propagated site, such documentation may have significant clinical implications.
METHODS: We visually analysed subdurally recorded occipitally originating seizure propagation characteristics among 16 patients undergoing bilateral subdural electrode coverage of the occipital, temporal and parietal lobes.
RESULTS: All seizures propagated. Propagation direction did not correlate with seizure origin within the occipital lobe (mesial vs. lateral; supra-calcarine vs. infra-calcarine). Seizures propagated to both supra-Sylvian and infra-Sylvian regions in 10 patients, to infra-Sylvian only (temporal lobe) in 6 patients; exclusively supra-Sylvian spread never occurred. Seizures spread bilaterally in 10 patients, ipsilaterally in only 6 but never only contralaterally. Seizures propagated within 5 seconds of origin in 12 patients and over 5 seconds in 4.
CONCLUSIONS: Propagation to other lobes was a consistent feature of occipitally originating seizures. However, direction of propagation did not reflect the intra-occipital origin. Early propagation and contralateral propagation were common features.
[Supported by: Research Office, Faculty of Medicine and Dentistry, The University of Western Ontario, London, Ontario]