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Pain may explain memory issues in patients with fibromyalgia
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Pain and accompanying depression and anxiety might be reasons for the lack of working memory in patients with fibromyalgia, according to a recent study.
Forty-one women were enrolled in the study — 19 with fibromyalgia (FM) and 22 healthy participants. The mean ages of the patients were 38.73 years and 38.27 years, respectively. The control group included volunteers who were screened for chronic widespread pain, generalized weakness, sleep disturbance and specific tender points. The FM patients were recruited from outpatient rheumatic clinics at five hospitals in South Korea. The mean disease duration for FM was 39.41 months, and those patients showed average tender points of 13.37.
Seven FM patients reported taking antidepressants: six on 75 mg pregabalin once daily, and one on 75 mg pregabalin and 25 mg milnacipran once daily.
The patients with FM displayed inferior mean performance compared with controls based on n-back tasks for accuracy and response time. These differences were statistically significant (P<.05), except in the 0-back accuracy task.
During n-back tasks, researchers utilized functional MRI to study activated and deactivated brain regions. The researchers also found significant relationships between the FM group and the controls when using the Beck depression inventory and Beck anxiety inventory as covariates (P<.01 for both).
Between-group analyses showed that within the working memory network, the inferior parietal cortex was associated with pain ratings that were mild (r=0.309, P=.049) and moderate (r=0.331, P=.034). Two-sample between-group analysis showed significantly higher activation in the controls than the FM group in the ventrolateral prefrontal cortex (VLPFC), the thalamus, middle temporal cortex and inferior parietal cortex (P<.05, FDR-corrected for multiple comparisons at the voxel level). The comparison also showed the left dorsolateral prefrontal cortex, right VLPFC and right inferior parietal cortex were related to depression and anxiety ratings.
“During the n-back memory task, FM patients showed reduced activation in several brain regions which may be associated with impairments in maintenance and manipulation of working memory,” the researchers said. “The working memory deficit found in FM patients may be attributable to differences in neural activation of the frontoparietal memory network and may result from both pain itself and depression and anxiety associated with pain.”
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