Is Life Better After Motor Cortex Stimulation for Pain Control? Results at Long-Term and their Prediction by Preoperative rTMS

Background: A positive effect of motor cortex stimulation (MCS) (defined as subjective estimationsof pain relief ≥ 30%) has been reported in 55 – 64% of patients. Repetitive magnetic corticalstimulation (rTMS) is considered a predictor of MCS effect. These figures are, however, mostly basedon subjective reports of pain intensity, and have not been confirmed in the long-term.Objectives: This study assessed long-term pain relief (2 – 9 years) after epidural motor cortexstimulation and its pre-operative prediction by rTMS, using both intensity and Quality of Life (QoL)scales.Study Design: Analysis of the long-term evolution of pain patients treated by epidural motor cortexstimulation, and predictive value of preoperative response to rTMS.Setting: University Neurological Hospital Pain Center.Methods: Patients: Twenty patients suffering chronic pharmaco-resistant neuropathic pain.Intervention: All patients received first randomized sham vs. active 20Hz-rTMS, beforebeing submitted to MCS surgery. Measurement: Postoperative pain relief was evaluated at 6 monthsand then up to 9 years post-MCS (average 6.1 ± 2.6 y) using (i) pain numerical rating scores (NRS);(ii) a combined assessment (CPA) including NRS, drug intake, and subjective quality of life; and (iii) ashort questionnaire (HowRu) exploring discomfort, distress, disability, and dependence.Results: Pain scores were significantly reduced by active (but not sham) rTMS and by subsequentMCS. Ten out of 20 patients kept a long-term benefit from MCS, both on raw pain scores and onCPA. The CPA results were strictly comparable when obtained by the surgeon or by a third-partyon telephonic survey (r = 0.9). CPA scores following rTMS and long-term MCS were significantlyassociated (Fisher P = 0.02), with 90% positive predictive value and 67% negative predictive valueof preoperative rTMS over long-term MCS results. On the HowRu questionnaire, long-term MCSrelated improvement concerned “discomfort” (physical pain) and “dependence” (autonomy for dailyactivities), whereas “disability” (work, home, and leisure activities) and “distress” (anxiety, stress,depression) did not significantly improve.Limitations: Limited cohort of patients with inhomogeneous pain etiology. Subjectivity of thereported items by the patient after a variable and long delay after surgery. Predictive evaluation basedon a single rTMS session compared to chronic MCS.Conclusions: Half of the patients still retain a significant benefit after 2 – 9 years of continuousMCS, and this can be reasonably predicted by preoperative rTMS. Adding drug intake and QoLestimates to raw pain scores allows a more realistic assessment of long-term benefits and enhancethe rTMS predictive value.The aims of this study and its design were approved by the local ethics committee (University HospitalsSt Etienne and Lyon, France).Key words: Neuropathic pain, chronic refractory pain, repetitive transcranial magnetic stimulation,rTMS, epidural motor cortex stimulation, MCS, quality of life, predictive value