Reprinted with the kind permission of Cort Johnson and Health Rising.
“If we lose sight of pleasures … that intoxicate the senses in the most sensuous and beautiful and simplest of ways, then we’ve lost a lot.” – Savannah Page
Researchers have used heat, electricity, chemicals, and pressure to evoke pain in FM patients and controls, and in every study people with FM have felt pain at lower levels of stimulation than healthy controls.
We know, though, that FM is about more than pain. People with Fibromyalgia report they have problems with sensitivity to stimuli in general. They tend to become more fatigued in stimuli-saturated environments, and they tend to retreat to less stimulating environments such as their bedroom. Research studies have borne out FM patients’ experiences, confirming that they are more sensitive to stimuli like heat, sound and touch.
This suggests FM is not just a pain condition, but that the FM patient’s entire sensory apparatus is a bit out of kilter. Just how and why that’s happening is another question. One study finding reduced electrical responses in the sensory cortices of the brain to sounds in FM suggested that this part of the brain was, oddly enough, under-responding to stimuli, not over-responding.
This is a different pattern than has normally been seen with pain. Studies suggest that the nervous system in the brain and spinal cord is amplifying or over-responding, not under-responding, to pain signals in FM.
Other studies show that the insula – the part of the brain that integrates sensory inputs from around the body and determines how much attention should be paid to them – is activated in Fibromyalgia patients more than expected. One of the sensations the insula evokes is the sensation of “unpleasantness”.
The findings suggest that a slow initial processing of stimuli in the lower brain regions is followed by a greatly accelerated one in the higher brain regions.
In this study Spanish and Colorado researchers dug more deeply into this intriguing slow-fast sensory cortex-insula effect in FM. Would the slow-fast pattern of processing non-painful stimuli hold? And are the sensory problems in FM connected with the pain people with FM experience, or are they separate?
These researchers used functional MRI to assess the brain functioning of FM patients when they were presented with non-painful sensory stimuli such as sound, light, and touch. Pain levels and levels of sensory unpleasantness were assessed.
They found significantly reduced responses to the sensory signals when they first hit the brain (sensory/auditory cortices, hippocampi, basal ganglia) and increased activity in the higher parts of the brain – the insula – that integrate both pain and sensory signals together.
[Reduced activation of the basal ganglia was recently found in Chronic Fatigue Syndrome, and similar hypersensitivity to sensory stimuli has also been observed by many ME/CFS patients.]
Distressingly Slowed Processing
The study also found that the levels of unpleasantness associated with non-painful stimuli – the sensory overload effect – was associated with and appeared to be coming from slowed initial brain response at the auditory and visual cortices. Somehow the brain’s inability to process normal sensory signals at a normal rate was causing distress.
The fact that the more pain the FM patients were experiencing the more bothered they were with the stimuli suggested that the pain and sensory problems are connected in FM.
If the brain is being under-stimulated by sensory stimuli why are highly stimulating environments (lots of lights, sounds, and people) so bothersome? The paper doesn’t explain why, but it could result from many different kinds of stimuli–none of which the brain is processing particularly well–hitting the central nervous system at the same time.
That could be causing the insula – to prevent itself from burning out – to down regulate the sensory processing regions of the brain. It’s to the insula we go next.
Other studies have fingered a hyperactive insula as a key player in the pain problems people with FM face, but this is the first study to suggest the insula plays a role in problems with non-painful stimulation in FM as well. It simply took exposure to ordinary and non-painful stimuli for the insula to flare up in the Fibromyalgia patients.
The insula is believed to be a center of “interoception” and an important regulator of homeostasis in the body. One of the evolutionarily older structures in the brain, the insula is also referred to as a “paralimbic cortex”. As such it regulates basic bodily functions such as the autonomic nervous system, oxygen levels. The insula also controls blood pressure before and after exercise, suggesting that the altered blood pressure variability Dr. Newton found in ME/CFS patients upon standing could relate to insular cortex problems.
In humans, the insula participates in higher brain functions such as the conscious awareness and assessment of how one’s body is functioning. Activity of the insula, for instance, appears to determine how aware one is of one’s heartbeat. In my experience increasing fatigue generally associated with increased awareness of my heartbeat.
Subscribe to the World's Most Popular Newsletter (it's free!)
Overactivation of this little slice of the brain, then, could effect symptoms ranging from sensory overload, to blood pressure problems to mood.
The study suggests that the problems with over-stimulation in FM are, ironically, caused by reduced, not heightened sensory processing. Why the brains of people with Fibromyalgia are slower at processing sensory signals is unclear, but three ideas stick out:
- Reduced cerebral blood flow in some parts of the brain could play a role.
- The areas of the brain in question could be so depleted of resources (perhaps because of reduced blood flows) that they’re simply not functioning well.
- The higher regions of the brain could also be having so much trouble integrating the various sensory inputs that they’re shutting down the pipelines to them in order to save themselves.
Migraine, Fibromyalgia, and Chronic Fatigue Syndrome
Several factors suggest (at least to me, a laymen) that migraine may present a model for what’s going on in FM and possibly ME/CFS. (Rates of migraine appear to be greatly increased in ME/CFS.) Both sensory dysregulation and problems with blood flows may be occurring in all three disorders.
A similar under/over-activation pattern (in a different part of the brain) occurs in migraine. Decreased pre-activation of the cerebral cortex in migraine is associated with increased hyper-responsiveness of the visual cortex. [Interestingly, this pattern is present in between migraine attacks and normalizes just before they occur and during the attack; i.e. the visual cortex in migraine sufferers is highly activated when migraine sufferers are not suffering from migraines. Is an over-activated visual cortex protective in some way?]
Using transcranial direct current stimulation (tDS) to increase the pre-activation of the visual cortex reduced the hyperesponsiveness in the visual cortex itself, and, more importantly, migraine frequency, and the length of migraine attacks in one study. It also reduced the need for medication. This suggests that “simply” stimulating one part of the brain can cause other parts of the brain to calm down.
Reduced brain blood flows appear to play a significant role in migraine and ME/CFS as well . Migraines appear to occur when nerves constrict the blood vessels at the base of the brain reducing blood flows. As arteries in other parts of the brain open up in an attempt to increase blood flow, they impact the surrounding nerves causing inflammation, pain, and the migraine.
Baraniuk found the increased rates of migraine in ME/CFS and GWS, and he pulls together both dysregulated sensory pathways and blood vessel problems to try to explain them. He proposes dysregulation of the sensory relays in the brain are causing excessive pain (hyperalgesia, allodynia), fearful memories (similar to PTSD), and brain fog, while vascular problems are causing gray matter thinning as well as white matter problems.
Could sensory relay and blood flow problems characterize many so-called functional disorders?
If under-activation of the sensory cortex is contributing to the pain in FM, the authors suggested that activating it more by increasing sensory stimulation could reduce pain levels. In fact, studies have shown that increasing the right kind of stimuli can reduce pain.
One Fibromyalgia study found that simply adding warmth to a painful area reduced pain by about 20% for an hour or so in about 30% of patients. Massage therapy actually gets the highest effectiveness rating of any treatment on PatientsLikeMe for Fibromyalgia.
A recent study finding that a TENS (transcutaneous electrical nerve stimulation) unit applied to the spine in FM reduced leg pain, but only when the TENS unit was active. TENS does not always work with pain; it has not proven particularly effective in treating neck and back pain. TENS, or something like it, however, may be more effective in treating neuropathic pain.
A review of electroacpuncture found it was helpful in blocking neuropathic pain in several disorders including diabetic neuropathy. A recent study found TENS, remarkably, was as effective in reducing pain as was local anesthesia in children undergoing dental work, and more effective in reducing their heart rates.
The effectiveness of the TENS unit while it’s active indicates that neurostimulation even in the periphery can be helpful. Ultimately, though, neurostimulation of the central nervous system using tDS and other methods may be more effective.
More study is needed, but this study suggests it may be possible, at some point, to reduce the pain in FM as well by increasing the activity of the sensory cortices that first process sensory stimuli. Whether doing so would reduce insular activity as well is not clear.
This isn’t the first FM study to find problems with processing sensory information.
Slowed processing of sensory signals and increased activity of the insular cortex in the brain contributes both to the pain and stimuli issues found in Fibromyalgia. The cause of the slowed sensory stimuli processing is not clear, but could result from reduced blood flows, exhaustion of the areas processing the signals, or a deliberate down-regulation of these areas by higher brain regions that are having trouble integrating sensory inputs from across the body.
Increasing the activity of an under-active part of the brain to reduce over-activity of another part of the brain appears to be helpful in migraine, which shares several characteristics with both FM and ME/CFS. More research is needed but a similar approach could potentially be helpful in both disorders.
About the Author: Cort Johnson has had ME/CFS for over 30 years. The founder of Phoenix Rising and Health Rising, Cort has contributed hundreds of blogs on chronic fatigue syndrome, fibromyalgia and their allied disorders over the past 10 years. Find more of Cort’s and other bloggers’ work at Health Rising.