Neurochemical Correlates of Brain Atrophy in Fibromyalgia Syndrome: A Magnetic Resonance Spectroscopy and Cortical Thickness Study

Repetitive Transcranial Magnetic Stimulation in Fibromyalgia: Exploring the Necessity of Neuronavigation for Targeting New Brain Regions

Fibromyalgia and osteoarthritis are among the most prevalent rheumatic conditions worldwide. Nonpharmacological interventions have gained scientific endorsements as the preferred initial treatments before resorting to pharmacological modalities. Repetitive transcranial magnetic stimulation (rTMS) is among the most widely researched neuromodulation techniques, though it has not yet been officially recommended for fibromyalgia. This review aims to summarize the current evidence supporting rTMS for treating various fibromyalgia symptoms. Recent findings: High-frequency rTMS directed at the primary motor cortex (M1) has the strongest support in the literature for reducing pain intensity, with new research examining its long-term effectiveness. Nonetheless, some individuals may not respond to M1-targeted rTMS, and symptoms beyond pain can be prominent. Ongoing research aims to improve the efficacy of rTMS by exploring new brain targets, using innovative stimulation parameters, incorporating neuronavigation, and better identifying patients likely to benefit from this treatment. Summary: Noninvasive brain stimulation with rTMS over M1 is a well-tolerated treatment that can improve chronic pain and overall quality of life in fibromyalgia patients. However, the data are highly heterogeneous, with a limited level of evidence, posing a significant challenge to the inclusion of rTMS in official treatment guidelines. Research is ongoing to enhance its effectiveness, with future perspectives exploring its impact by targeting additional areas of the brain such as the medial prefrontal cortex, anterior cingulate cortex, and inferior parietal lobe, as well as selecting the right patients who could benefit from this treatment.

Assessment of neurotransmitter imbalances within the anterior cingulate cortex in women with primary dysmenorrhea: An initial proton magnetic resonance spectroscopy study

PURPOSE

The neural pathophysiology underlying primary dysmenorrhea (PDM), which leads to poor mode and changes in central pain modulatory systems, remains largely unknown. The objective of this study was to investigate the changes in glutamate/glutamine (Glx) and gamma-aminobutyric acid (GABA+) levels within anterior cingulate cortex (ACC), and their associations with clinical indicators in PDM women.

METHODS

Using 3 T proton magnetic resonance spectroscopy (1H-MRS), we acquired and compared ACC-Glx and ACC-GABA+ levels in PDMs (N = 41) and age- and education-matched healthy controls (HCs) (N = 39) during both the menstrual and periovulatory phases, and between menstrual and periovulatory phases within each group. Total creatine (Cr referencing) level was used as an endogenous reference. The correlations of ACC-neurotransmitter levels with clinical characteristics and the correlations of ACC-Glx with ACC-GABA+ levels in the two groups were analyzed.

RESULTS

Compared to HCs or the periovulatory phase, PDMs exhibited significantly increased ACC-Glx levels (p < 0.05) during the menstrual phase. Positive correlations between GABA+ and Glx levels (r = 0.385, p = 0.025) were found in PDMs during the menstrual phase. ACC-GABA+ levels were associated with self-rating distress scale (SDS) scores (GABA+/Cr: r = 0.369, p = 0.045) and pain catastrophizing scale (PCS) scores (GABA+/Cr: r = 0.373, p = 0.042) in PDM group in only the menstrual phase.

CONCLUSION

Our study represents the first report of ACC-GABA+/Glx imbalances in PDMs during the menstrual phase, which may underlie the mechanisms mediating depression and painful catastrophic symptoms.

Pain Biomarkers in Fibromyalgia Syndrome: Current Understanding and Future Directions

Fibromyalgia is a complex and heterogeneous clinical syndrome, mainly characterized by the presence of widespread pain, possibly associated with a variety of other symptoms. Fibromyalgia can have an extremely negative impact on the psychological, physical and social lives of people affected, sometimes causing patients to experience dramatically impaired quality of life. Nowadays, the diagnosis of fibromyalgia is still clinical, thus favoring diagnostic uncertainties and making its clear identification challenging to establish, especially in primary care centers. These difficulties lead patients to undergo innumerable clinical visits, investigations and specialist consultations, thus increasing their stress, frustration and even dissatisfaction. Unfortunately, research over the last 25 years regarding a specific biomarker for the diagnosis of fibromyalgia has been fruitless. The discovery of a reliable biomarker for fibromyalgia syndrome would be a critical step towards the early identification of this condition, not only reducing patient healthcare utilization and diagnostic test execution but also providing early intervention with guideline-based treatments. This narrative article reviews different metabolite alterations proposed as possible biomarkers for fibromyalgia, focusing on their associations with clinical evidence of pain, and highlights some new, promising areas of research in this context. Nevertheless, none of the analyzed metabolites emerge as sufficiently reliable to be validated as a diagnostic biomarker. Given the complexity of this syndrome, in the future, a panel of biomarkers, including subtype-specific biomarkers, could be considered as an interesting alternative research area.

The puzzle of fibromyalgia between central sensitization syndrome and small fiber neuropathy: a narrative review on neurophysiological and morphological evidence

Fibromyalgia (FM) is a condition characterized by chronic widespread pain whose pathogenesis is still not fully defined. Evidence based on structural and functional neuroimaging methods, electrophysiological, and morphological - skin biopsy - features demonstrated a central and peripheral nervous system involvement. A dysfunction in nociceptive inputs processing at the central level was highlighted as the primary cause of FM, but other data coming from different laboratories contributed to emphasize again the peripheral origin of FM. In fact, small fibers neuropathy (SFN) was observed in a large number of patients submitted to skin biopsy. The complex interaction between central and peripheral factors is opening a new scenario about the management of this neurological disorder. Whether proximal SFN is an initiating event leading to FM or is the consequence of stress-related insular hyper excitability remains unclear. Mild sufferance of peripheral afferents could function as a trigger for an exaggerated response of the so-called "salience matrix" in predisposed individuals. On the other side, the intriguing hypothesis rising from animal models could indicate that the cortical hyper function could cause peripheral small afferent damage. The research should go on the genetic origin of such peripheral and central abnormalities, the acquired facilitating factors, and the presence of different phenotypes in order to search for efficacious treatments, which are still lacking.

Fibromyalgia Detection Based on EEG Connectivity Patterns

Objective: The identification of a complementary test to confirm the diagnosis of FM. The diagnosis of fibromyalgia (FM) is based on clinical features, but there is still no consensus, so patients and clinicians might benefit from such a test. Recent findings showed that pain lies in neuronal bases (pain matrices) and, in the long term, chronic pain modifies the activity and dynamics of brain structures. Our hypothesis is that patients with FM present lower levels of brain activity and therefore less connectivity than controls. Methods: We registered the resting state EEG of 23 patients with FM and compared them with 23 control subjects’ resting state recordings from the PhysioBank database. We measured frequency, amplitude, and functional connectivity, and conducted source localization (sLORETA). ROC analysis was performed on the resulting data. Results: We found significant differences in brain bioelectrical activity at rest in all analyzed bands between patients and controls, except for Delta. Subsequent source analysis provided connectivity values that depicted a distinct profile, with high discriminative capacity (between 91.3–100%) between the two groups. Conclusions: Patients with FM show a distinct neurophysiological pattern that fits with the clinical features of the disease.

Altered central pain processing in fibromyalgia-A multimodal neuroimaging case-control study using arterial spin labelling

Fibromyalgia is characterized by chronic pain and a striking discrepancy between objective signs of tissue damage and severity of pain. Function and structural alterations in brain areas involved in pain processing may explain this feature. Previous case-control studies in fibromyalgia focused on acute pain processing using experimentally-evoked pain paradigms. Yet, these studies do not allow conclusions about chronic, stimulus-independent pain. Resting-state cerebral blood flow (rsCBF) acquired by arterial spin labelling (ASL) may be a more accurate marker for chronic pain. The objective was to integrate four different functional and structural neuroimaging markers to evaluate the neural correlate of chronic, stimulus-independent pain using a resting-state paradigm. In line with the pathophysiological concept of enhanced central pain processing we hypothesized that rsCBF is increased in fibromyalgia in areas involved in processing of acute pain. We performed an age matched case-control study of 32 female fibromyalgia patients and 32 pain-free controls and calculated group differences in rsCBF, resting state functional connectivity, grey matter volume and cortical thickness using whole-brain and region of interest analyses. We adjusted all analyses for depression and anxiety. As centrally acting drugs are likely to interfere with neuroimaging markers, we performed a subgroup analysis limited to patients not taking such drugs. We found no differences between cases and controls in rsCBF of the thalamus, the basal ganglia, the insula, the somatosensory cortex, the prefrontal cortex, the anterior cingulum and supplementary motor area as brain areas previously identified to be involved in acute processing in fibromyalgia. The results remained robust across all neuroimaging markers and when limiting the study population to patients not taking centrally acting drugs and matched controls. In conclusion, we found no evidence for functional or structural alterations in brain areas involved in acute pain processing in fibromyalgia that could reflect neural correlates of chronic stimulus-independent pain.