Insular Role in Blood Pressure and Systemic Vascular Resistance Regulation

The insula is a brain area involved in the modulation of autonomic responses. Previous studies have focused mainly on its heart rate regulatory function, but its role in vascular control is not well defined. Ictal/postictal blood pressure (BP) fluctuations may have a role in the pathogenesis of sudden unexpected death in epilepsy. This study aims to characterize the insular influence on vascular regulation through direct high-frequency electrical stimulation (E-stim) of different insular regions during stereo-electroencephalographic studies.

An observational, prospective study was conducted, involving people with epilepsy who underwent E-stim of depth electrodes implanted in the insular cortex. Patients with anatomical or electrophysiological insular abnormalities, E-stim producing after discharges, or any elicited symptoms were excluded. Variations of BP and systemic vascular resistance (SVR) during the insular stimuli were analyzed, comparing them with those observed during E-stim of control contacts implanted in cortical noneloquent regions and sham stimulations.

Fourteen patients were included, five implanted in the right insula and nine in the left. We analyzed 14 stimulations in the right insula, 18 in the left insula, 18 in control electrodes, and 13 sham stimulations. Most right insular responses were hypertensive, whereas most left ones were hypotensive. E-stim of the right insula produced a significant BP and SVR increase, whereas the left insula induced a significant BP decrease without SVR changes. The most remarkable changes were elicited in both posterior insulas, although the magnitude of BP changes was generally low. Control and sham stimulations did not induce BP or SVR changes.

Our findings on insular stimulation suggest an interhemispheric difference in its vascular regulatory function, with a vasopressor effect of the right insula and a vasodilator effect of the left one.