In a recent study entitled “Fibromyalgia patients have reduced hippocampal volume compared with healthy controls,” researchers report reduced volume in fibromyalgia patients’ hippocampus and suggest this phenotype may underline the symptoms of both memory and cognitive abnormalities. The study was published in the Journal of Pain Research. 

Fibromyalgia (FM) is a disorder estimated to affect 5.8 million Americans and is characterized by widespread musculoskeletal pain, which often is accompanied by other symptoms, including fatigue, sleep, memory and mood problems. Notably, FM is currently thought of as a disease that also affects the central nervous system, with FM patients exhibiting cognitive abnormalities. Previous reports observed changes in size and function in brain regions, such as the cingulate, amygdala, thalamus, and the parahippocampal gyrus.

Here, the authors determined if FM patients have differences in hippocampus volume due to its pivotal role in memory and spatial navigation. To accomplish this, the research team acquired magnetic resonance imaging (MRI) scans from fibromyalgia patients (40 women patients) and healthy controls (20 women). All control individuals were screened and excluded if presenting a history of disease, including cancer, diabetes, neurological disorders or severe cognitive impairment, or drug usage, such as antidepressants, antihistamines and analgesics.

The authors found that FM patients’ brains had significantly smaller hippocampi (both left and right hippocampi, the two units that compose the hippocampus). Additionally, the team excluded a potential role for depression in this phenotype (FM patients have higher incidence of depression), since it had no impact on hippocampi volume, either in the left or right brain hemisphere. Although FM patients also exhibited higher Beck Depression Inventory (BDI) and Pain Disability Index (PDI) scores, the team observed no relationship between these parameters and hippocampal volume.

The authors hypothesize a mechanism for hippocampal atrophy in FM patients, including a chemical imbalance between excitatory and inhibitory neurotransmitters, as glutamate and amma-aminobutyric acid (GABA), respectively. This hypothesis needs to be addressed in future studies to further understand the role of hippocampal structure and function in fibromyalgia.

More information about fibromyalgia can be found here at the National Institute of Arthritis and Musculoskeletal and Skin Diseases.