Motor Cortex Stimulation for Neuropathic Pain: A Randomized Cross-over Trial

Abstract

Background: Chronic motor cortex stimulation (MCS) has been used to treat medically refractory neuropathic pain over the past 20 years. We investigated this procedure using a prospective multicentre randomized blinded crossover trial. Methods: Twelve subjects with three different neuropathic pain syndromes had placement of MCS systems after which they were randomized to receive low ("subtherapeutic") or high ("therapeutic") stimulation for 12 weeks, followed by a crossover to the other treatment group for 12 weeks. The primary outcome measure was the pain visual analogue scale (VAS). Secondary outcome measures included McGill Pain Questionnaire (MPQ), Beck Depression Inventory-II, medication log, work status, global impression of change, and SF-36 quality of life scale. Results: The trial was halted early due to lack of efficacy. One subject withdrew early due to protocol violation and five subjects withdrew early due to transient adverse events. Six subjects with upper extremity pain completed the study. There was no significant change in VAS with low or high stimulation and no significant improvement in any of the outcome measures from low to high stimulation. SF-36 role physical and mental health scores were worse with high compared to low stimulation (p = 0.024, p = 0.005). Conclusions: We failed to show that MCS is an effective treatment for refractory upper extremity neuropathic pain and suggest that previous studies may have been skewed by placebo effects, or ours by nocebo. We suggest that a healthy degree of skepticism is warranted when considering this invasive therapy for upper extremity pain syndromes.RÉSUMÉ: Stimulation du cortex moteur pour traiter la douleur neuropathique: une étude randomisée avec permutation. Contexte: La stimulation chronique du cortex moteur (SCM) a été utilisée pour traiter la douleur neuropathique réfractaire au traitement médical au cours des 20 dernières années. Nous avons étudié cette technique au moyen d'un essai prospectif multicentrique randomisé à double insu avec permutation. Méthode: Un système de SCM a été mis en place chez douze sujets atteints de trois syndromes différents de douleur neuropathique. Ils ont été assignés au hasard au groupe recevant une stimulation faible (« sous-thérapeutique ») ou élevée (« thérapeutique ») pendant 12 semaines avec permutation des groupes et traitement pendant 12 semaines additionnelles. Le critère d'évaluation primaire était le résultat obtenu à l'échelle visuelle analogue (EVA). Les critères d'évaluation secondaires comprenaient le questionnaire McGill sur la douleur, l'Inventaire de dépression de Beck II, un journal de la médication, la situation d'emploi, l'impression globale de changement et l'échelle SF-36 de qualité de vie. Résultats: L'étude a été interrompue précocement en raison du manque d'efficacité. Un sujet a été exclu tôt pour cause de non-respect du protocole et 5 sujets se sont retirés peu de temps après le début du traitement en raison d'effets indésirables passagers. Six sujets présentant de la douleu...

Motor Cortex Stimulation in Patients with Chronic Central Pain

“…Some researchers suggest that MCS is suitable in chronic, permanent pain but not in paroxysmal pain, when DREZotomy should be used [7,19].…”

Cyclization of Motor Cortex Stimulation for Neuropathic Pain: A Prospective, Randomized, Blinded Trial

“…Programing MCS can be a time‐consuming process and a failure to find the optimal stimulation settings could be a contributing factor to the lack of efficacy reported in number of recent publications . Previously, our team published an algorithm for programming MCS in which we suggested using 60% of the Motor Threshold (60 PMT) as the starting voltage and then adjusting the voltage up (e.g., 65 PMT) or down (e.g., 55 PMT) depending on the individual's response .…”

“…Case series , retrospective cohort studies , open label trials , and prospective, randomized, double‐blinded trials have demonstrated the efficacy of MCS in the treatment of patients with neuropathic pain of heterogeneous etiologies. More recently, however, two RCTs failed to demonstrate the efficacy of this therapy and several have cautioned against the use of this surgical procedure for pain management . If MCS is effective for neuropathic pain, then why does the therapy not work every time or in all centers?…”

“…Cyclization refers to how long the stimulation is “on” or “off” during a given time period. MCS cyclization strategies reported in the literature vary greatly and include a spectrum from continuous stimulation (“on” all the time) to pulse stimulation (“on” for a few minutes and “off” for hours) . The time spent “on” and “off” during each cycle may be another important variable that could potentially influence the efficacy of MCS.…”

The Current State of Deep Brain Stimulation for Chronic Pain and Its Context in Other Forms of Neuromodulation

“…Later results have shown mixed success. Two studies have effectively reported MCS to be ineffective, but are hampered by issues surrounded by patient retention, patient selection, and administration of the treatment [127,128]. Lefaucher et al reported an RCT of MCS for peripheral neuropathic pain, where 13 patients had a significant reduction in some measurements of pain when the device was ‘on’ compared to ‘off’.…”