Researchers and the University of California San Diego have shown that stimulation of the vagus nerve could serve as a possible treatment for patients diagnosed with post-traumatic stress disorder (PTSD) to decrease both emotional and physical pain.
PTSD is condition triggered by a traumatic event and is a common mental condition suffered after military service. The condition can cause anxiety, chronic pain, and involves negative thoughts and intrusive memories and can be extremely debilitating. There are treatments for PTSD such as anti-anxiety medications and anti-depressants, which are often used alongside psychotherapy.
Imanuel Lerman, MD, associate professor at University of California San Diego School of Medicine and a pain management specialist at UC San Diego Health and Veterans Affairs San Diego Healthcare System, was interested in the connection between pain and mental health and conducted a study to investigate the role the vagus nerve plays in emotional and physical pain.
The vagus nerve helps to regulate breathing rate, digestive tract movement, heart rate, and other bodily functions and carries sensory information from internal organs to the brain. Stimulation of the vagus nerve has already been approved by the FDA as a treatment for acute migraines and chronic cluster headaches. The technique is a form of neuromodulation pain management and involves stimulation of the spinal cord and dorsal root ganglion.
“It’s thought that people with certain differences in how their bodies — their autonomic and sympathetic nervous systems — process pain may be more susceptible to PTSD,” said Lerman. “And so we wanted to know if we might be able to re-write this ‘mis-firing’ as a means to manage pain, especially for people with PTSD.
For their study the researchers applied a painful heat stimulus to the legs of 30 patients and monitored the patients’ brains using fMRI scans. Half of the patients had the vagus nerve simulated via electrodes placed on the neck and the other half received mock stimulation of the vagus nerve. In addition, sweat measurements were taken from the skin before and during the heat stimulus to determine how the sympathetic nervous system was responding to pain.
Patients who received vagus nerve stimulation had a lower peak response to the heat stimulus in several regions of the brain known to be involved in sensory and discriminative pain processing, as well as in areas known to be emotional pain centers. In addition, the pain response in those regions was delayed by an average of 10 seconds following vagus nerve stimulation compared to the control group.
Compared to the control group, the sweat response decreased over time and the brainstem centers involved in the fight-or-flight response were also dampened following vagus nerve stimulation.
The level of stimulation required to achieve the same outcomes is likely to differ from patient to patient and the level of stimulation may need to be increased over time, so a personalized approach to treatment would be required, noted Lerman.
The results of the study are promising and Lerman and his team are hoping to use the technique in a clinical trial.
The study is detailed in the paper – Noninvasive vagus nerve stimulation alters neural response and physiological autonomic tone to noxious thermal challenge – which was recently published in the journal PLOS ONE. DOI: 10.1371/journal.pone.0201212