Fibromyalgia (FM), of course, is much more than about pain. Called the “prototypical functional pain syndrome,” people with fibromyalgia often experience problems thinking (fibro-fog), sleep and autonomic nervous system problems, depression and catastrophizing. The multidimensional aspects of fibromyalgia suggest that more than one part of the brain must be involved.
There’s also more to pain that just pain. Pain can be accompanied by catastrophizing thoughts and feelings of unpleasantness that are separate from the pain itself. These “pain plus” symptoms are common in fibromyalgia, and they imply different areas of the brain are affected as well.
This study sought to understand both where the pain problems and pain plus symptoms that can make pain so much worse come from in fibromyalgia.
The somatosensory link: S1 functional connectivity is altered by sustained pain and associated with clinical/autonomic dysfunction in fibromyalgia. Jieun Kim, PhD1,5*, Marco L. Loggia, PhD1,2, Christine M. Cahalan, BS2, Richard E. Harris, PhD3, Florian Beissner, Dr. phil. nat.1,4, Ronald G. Garcia, MD, PhD1,8,Hyungjun, Kim, PhD1,5, Ajay D. Wasan, MD, MSc6, Robert R. Edwards, PhD2,7,#, and VitalyNapadow, PhD1,2,9,#, Arthritis & Rheumatology DOI 10.1002/art.39043
A multi-center effort from researchers from Harvard, Michigan, Korea, Colombia, and Germany examined how the pain and other symptoms of FM are linked in the brain. First they used brain imaging to examine the status of the somatosensory cortex – a part of the brain that processes “somatic” or sensory signals – in relation to other parts of the brain at rest.
Then they wrapped a pressure cuff around their lower leg and inflated it enough to cause the pain receptors in their deep muscle tissues to flare up for six minutes. As they did so they repeated the brain scans.
First they examined how active the connections between the somatosensory regions of the brain that process sensory signals in the leg, back, face, finger and hand were. Then they examined how active the connections between the somatosensory region and parts of the brain involved in pain catastrophizing and autonomic nervous system functioning were.
As expected the FM patients experienced pain at a much lower cuff pressure than did the healthy controls.
The widespread pain the FM patients came in with suggested that the activity between the different regions of the somatosensory cortex would be increased. After all, the experience of pain in different areas of the body should show up as increased activity in different areas of the somatosensory cortex. Oddly enough, though, reduced activity was found.
The opposite pattern occurs in healthy people. Being exposed to the same pain stimulus over time, causes the strength of the connections between the different sub-regions of their somatosensory cortex to increase. As that happens their sensitivity to the pain decreases.
The opposite is happening in fibromyalgia.
Insula – A Key Brain Region in Fibromyalgia
Evoking pain with the pressure cuff indicated that a strong communication stream opened between somatosensory cortex and a part of the brain called the insula in the FM patients – but not the healthy controls. For some reason, the heretofore underactive somatosensory cortex appeared to be pounding the insula with information.
In the healthy controls, however, the pain opened up a connection to a part of the brain called the SPL associated with “attention processing”. That suggested that the healthy controls were noticing the pain more but they weren’t emotionally rocked by it. Their brains were simply keeping an eye on it.
Just six months ago a similar pattern involving sensory distress in fibromyalgia appeared. Exposing FM patients to light, sound and noise produced a slowed somatosensory activation followed by activation of the insula – and the production of unpleasant sensations.
In 2013 evidence suggested the “gates” in the brainstem that filter out sensory signals are broken in fibromyalgia. Bansai, interestingly enough, believes the same process is at work in ME/CFS patients, in particular, very severely ill patients who are unable to tolerate stimuli.
- Sensory Overload: Study Suggests Brains in Fibromyalgia Are Being Pummeled With Too Much Information
It’s at the insula or the connections to the insula that a host of problems kick in worsening everything. The emotional toll that pain can bring such as catastrophizing, anxiety and worry appear to be associated with the somatosensory cortex- insula connection in FM.
Autonomic Nervous System – Again…
“Thus, anterior insula connectivity to S1 appears to play a crucial modulatory role in not only hyperalgesia and temporal summation, but also autonomic responsivity to evoked pain, which may reflect elevated levels of clinical pain severity and pain catastrophizing.” Authors
Researchers usually stop at the psychological ramifications of pain when discussing the insula, but it is also one of the two main autonomic nervous system (ANS) regulators in the brain.
As the pain stimulus continued the connectivity to the right anterior part of the insula continued to build. (This part of the insula is responsible for regulating the autonomic response to external sensory signals). As that happened, the FM patients experienced further reductions in their ANS stability and increased emotional distress. That suggested that activation of this one part of the insula is responsible for both the autonomic nervous system dysregulation and emotional distress found in FM.
It’s possible that the emotional hit experienced and the autonomic nervous system dysregulation found in FM are all of a piece; when you get one – you get the other. That’s simply the consequence of activating this one part of the brain.
Since the connection to the insula was also associated with ever increasing pain as the pain stimulus continued, the insula is also implicated in episodes that increase pain sensitivity in FM.
Interestingly, the connection between the pain catastrophizing and insular activation was not seen during rest. It only occurred when the pain response was being evoked – and the autonomic nervous system was being triggered.
Speculation From a Layman
We could be seeing breakdowns all along the sensory processing circuits in both fibromyalgia and chronic fatigue syndrome. It may start at damaged neurons (small fiber neuropathy) or over-active receptors in the muscles (the Lights work) that send sensory signals zinging to the brainstem – breaking it down. The somatosensory cortex reacts to the subsequent information overload by down-regulating itself – allowing the insula to get hard. In another pathway from the brainstem the prefrontal cortex buckles results in amygdala activation.
Blasting the insula and amygdala – the two main autonomic nervous regulators in the brain – kicks off or exacerbates the autonomic nervous system problems, interferes with sleep and cognition, and increases the emotional burden of the disorder. The fight-flight system is turned on leaving FM and ME/CFS patients unable to fully rest and heal.
This study and others suggest that the distressing wired and tired aspect of ME/CFS and FM that leaves one on edge, feeling emotionally fragile and exhausted, could be a function of autonomic nervous system dysfunction.