Vagus nerve stimulation (VNS Therapy®) is designed to prevent seizures by sending regular, mild pulses of electrical energy to the brain via the vagus nerve. These pulses are supplied by a device something like a pacemaker. 1  The VNS device is sometimes referred to as a pacemaker for the brain..  The vagus nerve is part of the autonomic nervous system, which controls functions of the body that are not under voluntary control, such as the heart rate.