Hemispheric influence on autonomic modulation and baroreflex sensitivity

Several studies suggest hemispheric lateralization of autonomic cardiovascu lar control. There is controversy regarding which hemisphere dominates symp athetic or parasympathetic activity. Hemispheric influences on baroreflex s ensitivity (BRS) have not yet been evaluated. To determine hemispheric auto nomic control in epilepsy patients, we assessed cardiovascular and barorefl ex modulation before and during hemispheric inactivation. For 15 patients w ith drug-refractory epilepsy, we analyzed autonomic heart rate (HR) and blo od pressure (BP) modulation and BRS before and during left and right intrac arotid amobarbital procedure (IAP). After Blackman-Tukey spectral analysis, we calculated the low-frequency (LF: 0.04-0.15 Hz) and high-frequency (HF: 0.15-0.5 Hz) power of HR and BP as well as BRS as the LF transfer function gain between BP and HR. Right hemispheric inactivation induced a significa nt decrease of BP and an increase of HF power of HR and BP (p < 0.05). Left inactivation increased HR BP, and LF power of both signals and decreased B RS by nearly 30% (p < 0.05). The results confirm previous IAP studies showi ng sympathetic lateralization in the right hemisphere and, moreover, demons trate parasympathetic predominance and up-regulation of BRS in the left hem isphere. In epilepsy patients, unilateral electrical activity might derange autonomic balance between both hemispheres and contribute to cardiovascula r dysregulation and sudden fatalities.