The cardioinhibitory responses of the right posterior insular cortex in an epileptic patient

Abstract

Background: The insular cortex (IC) has long been implicated in the central regulation of the autonomic nervous system but its precise role remains to be determined. We studied the role of IC in cardiovascular control using a multimodality approach consisting of isometric handgrip exercises, functional magnetic resonance imaging (fMRI) activation during handgrip exercises, and direct electrical stimulations of the posterior right IC in a single patient.

Method: A 24-year-old patient had medically intractable epilepsy secondary to a small ganglioglioma in the right posterior IC. His cardiovascular responses to 30 and 70% maximum voluntary contraction (MVC) handgrip exercises were recorded in the lab and during fMRI and compared to those of 10 healthy control subjects. He subsequently underwent stereo-electroencephalography with depth electrodes in the right posterior IC and further study of the cardiovascular responses to electrical stimulation at rest and during MVC handgrip exercises.

Result: fMRI data showed nearly absent activation in the right IC relative to healthy subjects. At rest, electrical stimulation of the right posterior inferior IC but not the superior IC suppressed heart rate (HR) by 3 beats per minute. During exercise, the HR response to isometric handgrip contraction was weakened when the right posterior inferior IC was simultaneously stimulated.

Conclusion: This study shows that, in this patient, the right posterior inferior IC is an important cardioinhibitory center and interference with this region alters the cardiac response to handgrip exercise. Further investigations are required to examine the cardiovascular control of the IC.