NEW YORK (Reuters Health) – A paper in the July issue of the Journal of Rheumatology suggests that hippocampus dysfunction may explain some symptoms of fibromyalgia syndrome.

Dr. Yasser Emad, of Cairo University, Egypt, and colleagues used proton magnetic resonance spectroscopy (1H-MRS) to examine hippocampal function in 15 patients with fibromyalgia syndrome and 10 healthy age-matched controls.

Using 1H-MRS, the researchers calculated hippocampal levels of N-acetyl aspartate (NAA), choline, creatine and their ratios and compared the findings between groups. All study participants also underwent assessments of sleep patterns, cognitive function, and symptoms of depression. The number of tender points was assessed in all patients, and a visual analog scale was used to measure pain.

Patient age averaged 35.7 years, and mean disease duration was 18.1 months. All patients had cognitive functional impairment on the Mini Mental State Examination, eight (35.5%) were depressed on the basis of the Hamilton Depression Scale, and nine (60%) had sleep disturbances. None of the control subjects had cognitive impairment, depression, or sleep disturbance.

“NAA levels of the right and left hippocampi were lower in the patients compared to controls (p = 0.05 and p < 0.003, respectively),” Dr. Emad’s team explains. “Another statistically significant difference was observed in choline levels in the right hippocampus, which were higher in the patient group.” Patients also had significantly lower NAA/choline and NAA/creatine ratios compared to controls.

There were no differences between groups in other measured metabolites or in the choline/creatine ratio.

In the patient group, language scores were significantly correlated with choline and creatine levels (p = 0.041 and p = 0.006, respectively), but there was no significant correlation between metabolites or their ratios and numbers of tender points, Fibromyalgia Impact Questionnaire score, or pain as assessed by the visual analog scores.

“The hippocampus was dysfunctional in patients with fibromyalgia, as shown by lower NAA levels…, representing neuronal or axonal metabolic dysfunction,” the investigators conclude. “As the hippocampus plays crucial roles in maintenance of cognitive functions, sleep regulation, and pain perception, we suggest that metabolic dysfunction of hippocampus may be implicated in the appearance of these symptoms associated with this puzzling syndrome.

J Rheumatol 2008;35:1371-1377.