The trial was led by Imanuel Lerman, MD, associate professor at University of California San Diego School of Medicine, Jacobs School of Engineering and Qualcomm Institute, and a pain management specialist at UC San Diego Health and Veterans Affairs San Diego Healthcare System and the findings of the study appear in the journal
The vagus nerve runs a long course from the brain stem down the neck on both sides into the abdomen. It is involved in several vital body functions such as regulation of heart rate, digestion and bowel movements, breathing, and many others.
Being a critical nerve involved in several vital functions, the study team hoped to analyze if the vagus nerve is able to influence how the brain centers process physical pain and emotional pain (in conditions such as PTSD) and whether stimulation of the vagus nerve can reduce the chronic physical pain present in PTSD
patients. "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,"
Lerman said. "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."
Analyzing Effect of Vagal Stimulation in Pain/Heat Perception
- The study team employed functional magnetic resonance imaging (fMRI) to visualize the brain of 30 normal and healthy volunteers when a painful heat stimulus was given over their legs
- Scientists measured the sweat response on the skin of participants before the heat was applied, and at several points as the heat increased to determine how the body's sympathetic nervous system reacts to pain
- Half the volunteers were given non-invasive vagus nerve stimulation for two minutes - via electrodes placed on the neck, about 10 minutes before the painful heat stimulus. The other half received a mock stimulation where the vagus nerve was not stimulated
- The team found that stimulation of vagus reduced peak response to heat stimulus in several areas of the brain that function in perception of pain sensation as well as areas that process emotional pain
- Additionally, the pain response was delayed in these brain centers. In participants pre-treated with vagus nerve stimulation, the pain response was activated 10 seconds later than mock stimulated participants
- Participants pre-treated with vagus nerve stimulation showed decreased sweat response over time in comparison to the mock group suggesting that vagal stimulation influenced autonomic response (eg sweating) in response to heat or painful stimulus
- Vagal nerve stimulation blunted the normal response of brainstem centers critical for the fight-or-flight-type responses, which also regulates the sweat response
The findings of the study suggest that vagal stimulation may be beneficial in blunting pain response and this can be used to treat PTSD patients
suffering from chronic pain.
The study team plans to start a new trial with military veterans, with and without PTSD to determine if vagus nerve stimulation at home can decrease emotional pain and chronic pain associated with PTSD. The study is funded by the Veterans Affairs Healthcare System. "Not everyone is the same - some people may need more vagus nerve stimulation than others to achieve the same outcomes and the necessary frequencies might change over time -- so we'll need to personalize this approach,"
Lerman said. "But we are hopeful and looking forward to the next steps in moving this approach toward the clinic."
Vagal nerve stimulation can help to reduce chronic physical pain in patients with PTSD. Side effects of vagal stimulation include nausea, coughing, breathlessness and hoarseness. Reference :
- Noninvasive vagus nerve stimulation alters neural response and physiological autonomic tone to noxious thermal challenge - (https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0201212)