Using specialized magnetic resonance imaging technology, a study from Taiwan found that patients with fibromyalgia have decreased brain connectivity in specific regions, including the insula and the default mode network.
The insula is part of the cerebral cortex and has been proposed to act as a switching core that relays sensory information. The default mode network (DMN) is a network of interacting brain regions that is normally active when a person is in a “restful” state and not focused on a particular task.
Patients with fibromyalgia are hypersensitive to pain, and studies have shown increased pain responses in the pain network in the brain, including the insula and DMN regions.
Technical limitations have prevented the study of in-depth changes in brain connectivity.
The study, “Altered insula–default mode network connectivity in fibromyalgia: a resting-state magneto encephalographic study,” was recently published in the Journal of Headache and Pain.
A research team used a specialized type of magnetic resonance imaging (MRI) technique called magnetoencephalography (MEG). This technique maps brain activity by recording magnetic fields produced by electrical currents occurring naturally in the brain by using very sensitive magnetometers.
Twenty-eight patients with fibromyalgia were enrolled in the study, along with 28 age- and sex-matched controls. All study participants were from 20 to 60 years old.
All patients with fibromyalgia completed a questionnaire on the distribution, intensity, and duration of their pain, along with related symptoms, including fatigue, headaches, lower abdominal pain, and depression.
For each participant, the researchers determined the number of tender points as well as the total tenderness score.
At resting state, MEG activities of the study participants were analyzed at 1–40 Hz for functional brain connectivity between the insula and the DMN. The lower the number of Hz, the slower the brain activity or the slower the frequency of the activity.
Results showed patients with fibromyalgia reported more tender points and higher total tenderness score.
These patients also had a decreased resting-state insula–DMN connectivity in all frequencies examined, but this was only significantly different from healthy controls at a specific frequency, the theta band (4–8 Hz; theta brainwaves occur most often in sleep but are also dominant in deep meditation).
“Our results demonstrate that the insula–DMN connectivity in [fibromyalgia] was significantly decreased at the theta band. A recent review identified the theta oscillation as the main change that occurs in brain rhythm during chronic pain,” the researchers wrote.
“The present findings of decreased theta connectivity between the insula and the DMN may reflect persistent pain encoding associated with the chronic pain state of [fibromyalgia].”
Additionally, in patients with fibromyalgia, the right insula–DMN connectivity at the beta band (13–25 Hz; beta brainwaves dominate the state of consciousness when a person is in an alert state) was negatively correlated with the number of tender points and the total tenderness score; while at the delta band (1–4 Hz; brainwaves during sleep) it was negatively correlated with Fibromyalgia Symptom Severity and functional disability.
“Our present findings highlight the complex role of neural synchrony between the insula and the DMN in pain, emotional, and cognitive processing,” researchers wrote.
“We confirmed the frequency-specific reorganization of the insula–DMN connectivity in [fibromyalgia]. The clinical relevance of this connectivity change may warrant future studies to elucidate its causal relationship and potential as a neurological signature for [fibromyalgia,” they added.
Additionally, the team suggests that MEG may serve as an objective measure of clinical pain in patients with fibromyalgia.