Background and aims: Existing studies on cognitive impairment in chronic pain do not describe peripheral neuropathic pain (PNP) in a satisfactory manner, nor do they allow for head-to-head comparisons between pain conditions. To inform future treatments we aimed to rigorously compare cognitive impairments between fibromyalgia (FM) and PNP. 

Methods: Potential participants were seen at a tertiary pain center by a pain specialist, who performed a structured diagnostic assessment. Sixty-five patients met diagnostic criteria and completed a survey, IQ tests and computerized neuropsychological testing. Four outcomes sensitive to differences in executive functioning was pre-selected. Substantial differences between the participants in the two diagnostic groups were analyzed through t-tests or chi square statistics. Multivariate analysis was performed using linear regression models. 

Results: Linear regression models showed that when controlling for age, gender, years lived with pain, a diagnosis of PNP was significantly associated with more errors on the most demanding stage of visual encoding and retrieval (PAL 8 shapes, p=0.04).

Conclusion: Worse performance within the cognitive component of new learning and memory was here associated with a diagnosis of PNP. This translates into severe problems with retaining and using information in a fast pace, a staple of modern work life. Moreover, a reduced capacity to encode and retrieve patterns when compared to FM could have significant implications for treatment in these pain conditions, such as developing diagnose-specific cognitive training programs.

DIFFERENT PAIN - DIFFERENT BRAIN? A COMPARISON OF COGNITIVE IMPAIRMENTS IN PATIENTS WITH PERIPHERAL NEUROPATHIC PAIN AND FIBROMYALGIA