Abstracts

Rationale: Epilepsy is one of the most common neurological disorders, affecting 1% of the population. Loss of consciousness is a major morbidity associated with epileptic seizures. Recognizing the mechanisms behind loss of consciousness could have a major impact on improving treatments for patients with epilepsy as well as improving quality of life. Our lab has used SPECT imaging and intracranial EEG analysis to develop a proposed mechanism for loss of consciousness in patients with focal temporal seizures. This hypothesis, the network inhibition hypothesis, states that seizure activity localized to the temporal lobe leads to inhibition of thalamic and brainstem arousal regions. This in turn causes slow wave activity in the association cortex. There is limited research on the mechanisms of loss of consciousness in frontal lobe seizures. Methods: We looked at 6 patients and 9 seizures from a cohort of patients from the Yale Epilepsy Surgery Database. We included patients that were undergoing intracranial EEG monitoring for surgical evaluation. We focused on patients that had focal frontal lobe seizures and who were unresponsive during their seizures. Results: We observed that all 9 seizures had widespread low voltage fast activity. Initial analysis of seizures without impaired responsiveness suggests that this pattern is not consistently expressed in other frontal lobe seizures. Conclusions: While temporal lobe seizures seem to cause loss of consciousness through subcortical inhibition leading to depressed activity in the frontal and parietal lobes, our findings suggest that frontal lobe seizures may lead to loss of consciousness through a different mechanism. An investigation of a larger cohort with and without impaired responsiveness is needed to confirm and improve our understanding of this mechanism. An improved understanding of impaired consciousness during seizures may help guide treatment to prevent this important epilepsy comorbidity. Funding: James G. Hirsch M.D., Endowed Medical Student Research Fellowship Yale University School of Medicine Medical Student Research Fellowship National Institutes of Health-NHLBI Medical Student Research Fellowship