Closed Loop Vagal Nerve Stimulation for Patients With Posttraumatic Stress Disorder

Vasal nerve stimulation (VNS) is self-administered using the electroCore non-invasive VNS device. The intensity of the stimulus (the current amplitude) is adjusted by the user, to the maximum tolerable level to ensure VNS without causing excessive pain (typically 10-30 V), the burst frequency to 5 kilohertz (kHz), and the envelope frequency to 25 Hz. These are the standard frequency settings that electroCore has demonstrated to be most effective in capturing the vagus nerve based on evoked potential studies. The duration of delivery is 2 minutes, one minute into which the high-resolution positron emission tomography (HR-PET) scan is conducted; following an additional 8 minutes, a second VNS delivery is administered, after which another scan is obtained.

Sham vasal nerve stimulation (VNS) is self-administered using the electroCore non-invasive VNS device. The device is programmed such that no actual stimulation is given to the vagus nerve. The duration of delivery is 2 minutes, one minute into which the HR-PET scan is conducted; following an additional 8 minutes, a second sham VNS delivery is administered, after which another scan is obtained.

Oxygen-15 labelled water is a radioactive variation of regular water, in which the oxygen atom has been replaced by oxygen-15 (15O), a positron-emitting isotope. 15O-water is used as a radioactive tracer for measuring and quantifying blood flow using positron emission tomography (PET) . H2\[15O\] will be prepared on-site in the Emory PET Center cyclotron. During the hours of the test, an intravenous infusion of normal saline will be started to permit the bolus injection of H2\[15O\]. Subjects will receive a 20 mCi intravenous bolus of H2\[15O\] for each of the 14 scans during exposure to neutral and traumatic scripts.