Pain and cognition in multiple sclerosis

Objective. The goal of the present study was to examine the relationship between pain and cognition in patients with multiple sclerosis. Design. Cross-sectional. Setting. Nursing home and personal environment of the investigators. Subjects. Two groups of participants were included: 91 patients with multiple sclerosis and 80 matched control participants. Methods. The level of pain was measured by the following pain scales: Number of Words Chosen- Affective, Colored Analogue Scale for pain intensity and suffering from pain, and the Faces Pain Scale. Mood was tested by administering the Beck Depression Inventory and the Symptom Check List- 90 anxiety and depression subscale. Global cognitive functioning was assessed by the Mini Mental State Examination. Memory and executive functions were assessed by several neuropsychological tests. Results. Multiple sclerosis (MS) patients scored significantly lower than control participants on themajority of the neuropsychological tests. The MS patients experienced more pain compared with control participants, despite the fact that they were taking significantlymore painmedication.No significant correlation was observed between cognition and pain in MS patients. Verbal working memory explained 10% of pain intensity (trend). Mood appeared to be a significant predictorof pain in patientswithmultiple sclerosis. Conclusion. The lack of a relationship between cognition and pain might be explained by the fact that, compared with control participants, patients with multiple sclerosis activate other non-pain-related areas to perform executive functions and memory tasks.