Abstracts

RATIONALE: Few clinical works in the past and more recent studies in animals have focused on the possible participation of subcortical structures in epilepsy. Considering its widespread connectivity with medial limbic structures and temporal neocortical areas, the medial pulvinar nucleus (PuM) could be involved in epileptic activities originating in such structures. This study aims at evaluating this possibility by recording PuM activity in patients suffering from pharmacoresistant temporal epilepsy.
METHODS: Using stereo-electro-encephalographic recordings performed for presurgical examination, PuM and suspected epileptogenic zones activities were recorded in eight patients. Localization of recording sites was verified by superimposing post implantation frontal X-ray on MRI images. Signals were studied using spectral and time-frequency analysis.
RESULTS: During interictal period, fully awake patients presented with a peak of delta-theta activity in PuM. Avering PuM activity time-locked on cortical spikes showed that the latter were consistently followed by a potential transient in PuM. During ictal period, a clear propagation of ictal activity to the PuM was observed in seven patients who developed seizures. This thalamic activity was characterized either by the generation of rhythmic (5-12 Hz) spikes or by a recruiting low voltage high (27-31 Hz) frequency discharge appearing 1 to 77 sec after seizure beginning. The recruiting mode was observed only in association with neocortical discharges. In three patients, the onset of ictal activity in PuM correlated with a large seizure cortical diffusion suggesting an active participation of PuM to the seizure spread.
CONCLUSIONS: These results demonstrate an involvement of PuM in epilepsy of temporal origin. The precise role of this thalamic nucleus in the maintenance and/or propagation of paroxysmal activities remains to be clarified.
[Supported by: Hospices Civils de Lyon]