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 the majority of the neuropsychological tests. The MS patients experienced more pain compared with control participants, despite the fact that they were taking significantly more pain medication. 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 predictor of pain in patients with multiple 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.