Abstracts

Regions of seizure onset and propagation in human generalized tonic-clonic seizures are not well understood. Electroconvulsive therapy (ECT)-induced seizures can be used as a model system to study human seizures under controlled conditions. We performed cerebral blood flow (CBF) measurements with single photon emission computed tomography (SPECT) during ECT-induced seizures to study seizure onset and propagation., ECT stimulation induces a typical generalized tonic-clonic seizure, resembling spontaneous generalized seizures in both clinical and electroencephalogram (EEG) manifestations. We imaged CBF during ECT-induced seizures and divided the patient pool into two groups based on timing of ictal (during seizure) SPECT tracer injections: 0s after ECT stimulation (early group), and 30s after ECT (late group). Statistical parametric mapping (SPM) was used to determine regions of significant CBF changes between ictal and interictal scans on a voxel-by-voxel basis., In the early injection group, we saw CBF increases near the regions of the bitemporal stimulating electrodes as well as in the basal ganglia and thalamus. With late injections, we observed increases mainly in the parietal and occipital lobes; these same regions showed no changes at earlier times. Significant CBF decreases occurred only at the later injection time, and these were localized to the bilateral cingulate gyrus and left dorsolateral frontal cortex., Activations in distinct regions in the early and late groups, as well as sparing of intervening brain structures, suggest that ECT-induced seizures propagate from the site of initiation to other specific brain regions. Further work will be needed to determine if this propagation occurs through cortical-cortical or cortico-thalamo-cortical networks. Elucidating the mechanisms of seizure spread can have profound impact on developing treatments to prevent abnormal neuronal firing, and block seizure generalization. Propagation between focal higher order circuits may also have implications for the profound impairment of consciousness seen in generalized tonic-clonic seizures., (Supported by the Dana Foundation and by the Betsy and Jonathan Blattmachr Family.)