Abstracts

The importance of the insular cortex and adjacent temporal lobe in cardiovascular regulation has been demonstrated. Some studies have suggested that cortical cardiac autonomic influences may be lateralized, with sympathetic representation lateralized to the right insula and parasympathetic to the left. Ictal bradycardia, although rare, offers an opportunity to study the functional anatomy of cardiac rate control. A query was performed on all electronic reports of prolonged EEG monitoring studies performed at Mayo Clinic Rochester from January 1990 to December 2004. Ictal bradycardia was defined as an R-R interval of greater than 2.0 seconds or activation of cardiac pacing during a recorded seizure. All clinical and electrophysiological data in identified patients were reviewed to determine localization and lateralization of EEG activity at seizure onset and at the onset of bradycardia in these patients. A literature review of previously reported cases was also conducted. Thirteen patients were identified out of 6,168 patients who underwent video-EEG monitoring at our institution during the study period. Ictal bradycardia was present in 29 of 60 recorded seizures in these patients. Seizure onset was localized to the temporal lobe in all patients. EEG activity at seizure onset did not consistently lateralize to either hemisphere. Seven patients had ictal bradycardia with right temporal seizure onset, five with left temporal seizures and one with bitemporal seizure onset. Seizure activity was bilateral at bradycardia onset in 9 of 13 patients. One patient had seizure activity confined to the right hemisphere, and 3 had only left hemisphere activity at bradycardia onset.
One hundred six cases of ictal bradycardia were found in the literature, with 80 of these patients having simultaneous EEG and ECG monitoring. Of these, seizure onset was localized to the temporal lobe in 35 patients, to the frontotemporal region in 15, the frontal lobe in 13 and the occipital lobe in one. Information regarding the EEG lateralization at seizure onset was available in 55 cases, but only 21 of these cases had information on EEG lateralization at the onset of bradycardia. While 34 of 55 patients had seizure onset lateralized to the left hemisphere at seizure onset, 11 of 21 had bilateral activity at bradycardia onset. Both our series and a review of the ictal bradycardia literature support the association of ictal bradycardia with temporal lobe onset seizures. However, ictal bradycardia does not appear to be a consistent lateralizing finding. The distribution of seizure activity at the onset of bradycardia was bilateral in our series, suggesting that bradycardia is more likely to occur in the setting of bilateral hemispheric seizure activity. These data do not support the presence of a lateralized cortical zone associated with parasympathetic cardiovascular activity in humans. (Supported by NINDS P01 NS32352-P2.)