Thinking about movement hurts: the effect of motor imagery on pain and swelling in people with chronic arm pain.

OBJECTIVE

Chronic painful disease is associated with pain on movement, which is presumed to be caused by noxious stimulation. We investigated whether motor imagery, in the absence of movement, increases symptoms in patients with chronic arm pain.

METHODS

Thirty-seven subjects performed a motor imagery task. Pain and swelling were measured before, after, and 60 minutes after the task. Electromyography findings verified no muscle activity. Patients with complex regional pain syndrome (CRPS) were compared with those with non-CRPS pain. Secondary variables from clinical, psychophysical, and cognitive domains were related to change in symptoms using linear regression.

RESULTS

Motor imagery increased pain and swelling. For CRPS patients, pain (measured on a 100-mm visual analog scale) increased by a mean +/- SD of 5.3 +/- 3.9 mm and swelling by 8% +/- 5%. For non-CRPS patients, pain increased by 1.4 +/- 4.1 mm and swelling by 3% +/- 4%. There were no differences between groups (P > 0.19 for both). Increased pain and swelling related positively to duration of symptoms and performance on a left/right judgment task that interrogated the body schema, autonomic response, catastrophic thoughts about pain, and fear of movement (r > 0.42, P < 0.03 for all).

CONCLUSION

Motor imagery increased pain and swelling in patients with chronic painful disease of the arm. The effect increased in line with the duration of symptoms and seems to be modulated by autonomic arousal and beliefs about pain and movement. The results highlight the contribution of cortical mechanisms to pain on movement, which has implications for treatment.