Pre-implantation psychological assessment and two-year outcomes of spinal cord stimulation for chronic pain: a retrospective observational study

Abstract Background Chronic pain may improve with spinal cord stimulation (SCS), but whether pre-implantation psychological assessment carries prognostic value is unclear. We describe outcomes over two years following SCS implantation and tested whether the baseline MCMI-III profile was associated with them, in a cohort in which no patient was excluded from implantation on psychological grounds. Methods In this retrospective, single-center study (2012–2022, 40 consecutively implanted patients), the Millon Clinical Multiaxial Inventory (MCMI-III) was administered before implantation, and pain (VAS at rest and with movement), quality of life (EQ-5D-5L), perceived health (health VAS), and sleep quality (PSQI) were assessed pre-implantation and at 1 month, 6 months, 1 year, and 2 years. Each of the 24 MCMI-III scales was tested against outcomes using linear mixed-effects models, with false-discovery-rate (FDR) correction and adjustment for the Desirability validity scale. Results Outcomes improved substantially and durably after implantation: resting-pain VAS fell from 8.56 to 4.22 and movement-related VAS from 9.39 to 5.24 (~51 and 44%), the EQ-5D-5L index rose from 0.18 to 0.60, the health VAS from 31.4–54.9, and the PSQI improved from 15.5–10.1 (all p < 0.001); more than half of patients maintained a ≥50% pain reduction at two years. In exploratory analyses, several MCMI-III scales showed nominal associations with outcomes—most consistently Schizoid with poorer quality of life and Dysthymia with poorer perceived health—but none survived FDR correction, and most attenuated after adjustment for social desirability, in a cohort showing no clinically relevant variation on the severe personality and psychotic-spectrum scales. Conclusions Pain, quality of life, perceived health, and sleep improved substantially after implantation, and the improvements were sustained over two years. Associations between the baseline psychological profile and outcomes were exploratory and hypothesis-generating: our data neither support nor exclude a prognostic role for pre-implantation psychological screening, which is best used to generate hypotheses for prospective research rather than to select implantation candidates.