A systematic literature review of psychological characteristics as determinants of outcome for spinal cord stimulation therapy

Psychological factors are deemed important when considering patients for suitability for Spinal Cord Stimulation (SCS). However, there is to date no consensus on which psychological characteristics or tests to undertake. This review analyses the literature to determine findings concerning the psychological characteristics observed and their impact on SCS efficacy for chronic pain. A search in the databases Cochrane, EBSCOhost (CINAHL, MEDLINE, PsycINFO and PsycARTICLES) and a hand search of reference lists from selected articles were performed, resulting in nine relevant articles. The Minnesota Multiphasic Personality Inventory was the most commonly used tool for assessing psychological factors. Only one study used a semi-structured interview instead of questionnaires. Studies lacked long term followup. Depression was identified in six studies as a factor that reduces efficacy, also as a characteristic that can improve after successful SCS by two studies. One study did not include patients with depression, due to previous research indicating depression as a contra-indication. Hypochondriasis and hysteria had conflicting results for prediction of efficacy. Mania was predicted by only two studies as a positive indicator for success. Further long term studies of psychological factors on outcome from SCS are needed.