Differential consequences of left- and right-sided chronic pain.

OBJECTIVE: To test the neuropsychological hypothesis that left-sided pain will have more adverse consequences than right-sided pain by virtue of activation of the "depressogenic" right hemisphere. DESIGN: A retrospective analysis comparing data of chronic pain patients with left-sided pain to patients with right-sided pain. PATIENTS: All of the right-handed patients (n = 85) presenting with unilateral shoulder, arm, and hand pain and suspected of having Thoracic Outlet syndrome (TOS) were assessed as potential candidates for surgery at the Toronto Western Hospital Pain Investigation Unit over a 5-year period. OUTCOME MEASURES: Minnesota Multiphasic Personality Inventory (MMPI), SIP (Sickness Impact Profile). RESULTS: Contrary to the intuitive expectation that right-sided pain would be more disruptive in right-handed subjects, patients with left-sided pain had higher MMPI scores for hysteria and hypochondriasis and also had higher scores on the physical dimension of the SIP. CONCLUSION: Differences between the groups could not be accounted for by different etiologies because the proportions and causes of left- and right-sided pain were comparable. The results are consistent with the hypothesis that unilateral stimulation activates the contralateral cerebral hemisphere and arouses the emotions associated with that hemisphere.