By Elizabeth Akincilar
Understanding and effectively treating chronic pain continues to challenge the medical community. Now more than ever, there is a sense of urgency to treat this disease. With the astounding reports of opiate addiction and opiate related deaths in this country, we now know that throwing drugs at chronic pain is not the answer. So what is the answer? Thankfully there is a lot of ongoing research trying to figure that out. At the 3rd World Congress of Abdominal and Pelvic Pain in October 2017, some exciting research about chronic pelvic pain was presented which we will share here in the 3rd post of our blog series covering the conference.
Dr. Thomas Chelimsky, a neurologist from the Medical College of Wisconsin, presented his research about the autonomic features of chronic pelvic pain.
To effectively treat pelvic pain, we first must better understand pelvic pain itself. People suffering with pelvic pain often have comorbidities, which are other chronic diseases or conditions that are simultaneously present. Dr. Chelimsky examined some of the comorbidities that are often present with chronic pelvic pain. He presented research suggesting that many of the psychological comorbidities that we see with chronic pelvic pain, such as depression and anxiety, seem to be driven by the pain disorder, not the psychological disorder. Additionally, he suggested that certain comorbidities seemed to coincide with particular types of pelvic pain syndromes. I found these bits of research particularly interesting:
- Interstitial Cystitis/Painful Bladder Syndrome (IC/PBS) was more associated with dyspepsia and chronic idiopathic nausea
- Myofascial pelvic pain (MPP) was more associated with dysmenorrhea, migraine, Post-Traumatic Stress Disorder (PTSD), and Chronic Regional Pain Syndrome (CRPS)
- Having both MPP and IC/BPS resulted in an increased chance of also having fibromyalgia and panic disorder
- Having two pelvic pain disorders and PTSD was associated with having more comorbidities
- Age of onset of comorbidities was earlier for PTSD, dysmenorrhea, migraine, depression, and panic attacks and later for fibromyalgia and chronic fatigue syndrome
He posed the question, does this information tell us something about the role our autonomic nervous system (ANS) plays in chronic pain?
To review, the autonomic nervous system is the part of the nervous system that acts largely unconsciously and regulates bodily functions such as heart rate, digestion, urination, and sexual arousal. It is the primary mechanism in control of the fight-or-flight response. There are two parts that make up the ANS, the sympathetic and the parasympathetic nervous system. The sympathetic nervous system is often considered the “fight or flight” system, whereas the parasympathetic nervous system is considered the “rest and digest” or “feed and breed” system.
Dr. Chelimsky presented one study that found a difference in the sweat response between MPP and IC/PBS. Sweat response is controlled by the sympathetic nervous system. This study found an increase in sweat response in the group with MPP versus the IC/PBS group, suggesting that the sympathetic nervous system may be more involved with MPP versus IC/PBS. Additionally, the parasympathetic nervous system was more affected in the IC/PBS group versus the MPP group.
How does this information help us treat pelvic pain? Here’s a summary of the New Pelvic Pain Model he suggested.
IC/PBS seems to cause visceral hypersensitivity via an autonomic mechanism that impairs vagal functioning. The vagus nerve is the 10th cranial nerve and works with the parasympathetic nervous system. Therefore, a proposed treatment strategy for people with IC/PBS could be to stimulate the vagal system.
MPP seems to cause vascular hypersensitivity via sympathetic autonomic neuropathy. Therefore, a proposed treatment strategy would involve improving vascular flow via manipulation or reducing sympathetic outflow.
For people suffering from both MPP and IC/PBS, the proposed treatment strategy would be to combine both treatments for MPP and IC/PBS.
Interestingly, this may partially explain why physical therapy is particularly helpful for patients with MPP. Much of manual therapy is focused on improving vascular flow.
This is suggesting that the brain may be the driver in chronic pain; therefore, management needs to be directed at the brain rather than the end organ.
The periaqueductal gray (PAG) is a part of our midbrain that may play a pivotal role in treating chronic pain. The major functions of the PAG include control of pain and analgesia, fear and anxiety, vocalization, lordosis and cardiovascular control.
The PAG is a dynamic structure. In order for the PAG to do its job, which in part is to control pain, it has to grow. Research has found that in people with chronic pain, it doesn’t grow. One study showed that in patients with endometriosis and no pelvic pain the PAG was larger than in patients with endometriosis and pelvic pain. Jandra wrote more about this last week in the second post of our #WCAPP17 blog series, Endometriosis: Beyond the Lesions.
So, how do we stimulate the PAG so it can grow and reduce pain? Dr. Chelimsky suggests that we improve vagal function. He suggests three methods to improve vagal function:
- Cognitive Behavioral Therapy (CBT)
- Direct stimulation of the vagus nerve with auricular stimulation
- Interval exercise training
We still have much to learn about chronic pelvic pain, but it is research such as this that is bringing us one step closer to more effective treatments.
We thank Dr. Chelimsky for a fantastic presentation! The entire lecture is available here, starting on page 100.