Cognition and Perception Deficits in Fibromyalgia and Rheumatoid Arthritis

Performance on the CVLT-2 during induced pain

Objective: Chronic pain patients frequently report cognitive problems including learning and memory. However, recent research involving induced pain has demonstrated an absence of reliably detectable decrements on several standard cognitive measures, suggesting that factors other than pain likely explain perceived cognitive deficits in chronic pain patients. This study examined potential effects of induced pain on verbal learning and memory as measured by the California Verbal Learning Test (CVLT-2). Potential effects of self-reported pain intensity were also evaluated. Method: Participants (111 non-clinical undergraduate students in the Southwestern United States) completed one version (Standard or Alternate) of the CVLT-2 under normal conditions, and then were administered the other version (Alternate or Standard) either while experiencing cold pressor-induced pain (Pain condition) or non-painful warm water immersion (Control condition). Results: For the Pain condition decrements in performance across most CVLT-2 variables were observed, including a mean T-score decrease of 10.98 (SD = 10.99) for Trials 1-5, whereas the comparable decrease in the Control condition was an average of 1.5 words (SD = 8.27). Self-reported pain intensity was significantly correlated with the degree of Time 1 to Time 2 performance decrement for Short-Delay Free Recall (r = -.51, p < .050), but not for Trials 1-5 (r = -.37, p = .160). Conclusion: Induced pain produces detectable decrements in performance on a standard clinical measure of verbal learning and memory performance, suggesting that pain in clinical populations may contribute to learning and memory deficits apart from potential neurological conditions.

Effects of COMT Genotypes on Working Memory Performance in Fibromyalgia Patients

Growing research has reported the presence of a clear impairment of working memory functioning in fibromyalgia. Although different genetic factors involving dopamine availability (i.e, the COMT gene) have been associated with the more severe presentation of key symptoms in fibromyalgia, scientific evidence regarding the influence of COMT genotypes on cognitive impairment in these patients is still lacking. To this end, 167 participants took part in the present investigation. Working memory performance was assessed by the application of the SST (Spatial Span Test) and LNST (Letter and Number Sequence Test) belonging to the Weschler Memory Scale III. Significant working memory impairment was shown by the fibromyalgia patients. Remarkably, our results suggest that performance according to different working memory measures might be influenced by different genotypes of the COMT gene. Specifically, fibromyalgia patients carrying the Val/Val genotype exhibited significantly worse outcomes for the span of SST backward, SST backward score, SST total score and the Working Memory Index (WMI) than the Val/Val healthy carriers. Furthermore, the Val/Val patients performed worse on the SST backward and SST score than heterozygotes. Our findings are the first to show a link between the COMT gene and working memory dysfunction in fibromyalgia, supporting the idea that higher COMT enzyme activity would contribute to more severe working memory impairment in fibromyalgia.

Neuropsychological Changes in Complex Regional Pain Syndrome (CRPS)

Complex Regional Pain Syndrome (CRPS) is a poorly understood chronic pain condition of multifactorial origin. CRPS involves sensory, motor, and autonomic symptoms primarily affecting one extremity. Patients can also present with neuropsychological changes such as reduced attention to the CRPS-affected extremity, reminiscent of hemispatial neglect, yet in the absence of any brain lesions. However, this "neglect-like" framework is not sufficient to characterise the range of higher cognitive functions that can be altered in CRPS. This comprehensive literature review synthesises evidence of neuropsychological changes in CRPS in the context of potential central mechanisms of the disorder. The affected neuropsychological functions constitute three distinct but not independent groups: distorted body representation, deficits in lateralised spatial cognition, and impairment of non-spatially-lateralised higher cognitive functions. We suggest that many of these symptoms appear to be consistent with a broader disruption to parietal function beyond merely what could be considered "neglect-like." Moreover, the extent of neuropsychological symptoms might be related to the clinical signs of CRPS, and rehabilitation methods that target the neuropsychological changes can improve clinical outcomes in CRPS and other chronic pain conditions. Based on the limitations and gaps in the reviewed literature, we provide several suggestions to improve further research on neuropsychological changes in chronic pain.