In our continuing series on “Pain and the Great Brain Robbery!” we have previously written about research describing brain changes in IBS and FMS, and these two latest studies add to that knowledge. However, it should be recognized that, while the specific brain structures involved might be of most interest only to neuroscientists and somewhat confusing to others, an appreciation of the underlying principle that structural and functional brain changes strongly affect patients with chronic pain disorders and influence their care should be of importance for all healthcare providers.
In the first study, writing in the July 2010 edition of the journal Gastroenterology investigators reported using magnetic resonance imaging (MRI) to examine brain anatomy differences in a relatively large sample of patients with IBS (n=55) compared with healthy control subjects (n=48) [Seminowicz et al. 2010]. They found that IBS was associated with decreased gray matter density in widespread areas of the brain, including portions of the prefrontal cortex, parietal cortex, ventral striatum, and thalamus. Whereas, compared with controls, there was significantly increased gray matter density in patients with IBS in the anterior cingulate cortex and the orbitofrontal cortex. Differences accounting for increased anxiety and depression in patients with IBS were primarily found in the prefrontal and parietal cortices.
COMMENT: Interestingly, we had previously noted research by a Canadian team [Blankenstein et al. 2010, blogpost here] that found increased gray matter in the thalamus region and thinning of the cingulate cortex in patients with IBS; which is the complete opposite of that reported by Seminowicz and colleagues [2010, above]. Also in the Canadian research, subjects with IBS of shorter duration had thinning of the insular cortex and those with less pain catastrophizing (exaggerated emotional reaction) had prefrontal cortex thickening; again, these changes were contrary to those reported by Seminowicz et al. Therefore, cortical structure changes are apparent and important in IBS but may be variably influenced by the duration of IBS and a patient’s affective response to the condition. Hopefully, further research will clarify the relationships.A second new study, this one addressing fibromyalgia syndrome, reveals evidence that patients with FMS have greater connectivity between multiple brain networks and the insular cortex, which affects the sensation of pain. Writing in the August 2010 edition of Arthritis and Rheumatism, researchers at Massachusetts General Hospital and the University of Michigan report on 18 women with FMS who underwent 6-minute function magnetic resonance imaging (fMRI) brain scans and compared their results with 18 healthy control subjects [Napadow et al. 2010]. On average, all women were in their mid-to-late 30s. Patients with FMS had the condition for at least one year, had pain for more than half of each day, and limited the introduction of new medications or treatment strategies to control their symptoms prior to the experiment. Participants rated their FMS pain intensity at the time of their brain scans, while at rest, with some reporting little pain while others reported feeling more intense pain.
Brain scans showed that connectivity, or neural activity, between certain brain networks and the insular cortex — a region of the brain involved in pain processing — was heightened in women with FMS compared with those without the condition. Such connectivity to the insular cortex was even stronger in participants reporting more intense pain. The brain networks involved included the default mode network (DMN) and the right executive attention network (EAN). The DMN plays a role in "self-referential thinking," such as when you think about yourself or what's happening to you. The EAN is involved in working memory and attention, so if that particular brain network is distracted by pain it may explain the cognitive “fog” that some patients with FMS experience.
FURTHER COMMENT: For years FMS was a highly misunderstood syndrome, with some practitioners doubting it even existed or attributing the pain to depression or other psychological issues. This research helps to confirm that FMS is a neurobiological condition affecting sensory pain processing centers and some of the emotional and evaluative parts of the brain. The greater connectivity between brain networks and regions of the brain involved in pain processing may help explain why FMS sufferers feel pain even when there is no obvious cause. Despite this increased connectivity, we previously reported research showing that the brains of patients with fibromyalgia exhibit 3.3 times greater decreases in gray matter than healthy age-matched controls; in effect, each year that a patient has fibromyalgia is equivalent to 9.5 times greater loss of gray matter than they would expectedly have due to normal aging [Kuchinad et al. 2007, blogpost here].REFERENCES:
> Napadow V, LaCount L, Park K, et al. Intrinsic Brain Connectivity in Fibromyalgia Is Associated With Chronic Pain Intensity. Arthritis & Rheumatism. 2010(Aug) 62(8):2545-2555 [abstract here].
> Seminowicz DA, Labus JS, Bueller JA, et al. Regional Gray Matter Density Changes in Brains of Patients With Irritable Bowel Syndrome. Gastroenterology. 2010(Jul);139(1):48-57 [abstract here].