Selection criteria for offering patients motor cortex stimulation (MCS) for refractory neuropathic pain are a critical topic of research. A single session of repetitive transcranial magnetic stimulation (rTMS) has been advocated for selecting MCS candidates, but it has a low negative predictive value. Here the authors investigated whether multiple rTMS sessions would more accurately predict MCS efficacy.
Patients included in this longitudinal study could access MCS after at least four rTMS sessions performed 3–4 weeks apart. The positive (PPV) and negative (NPV) predictive values of the four rTMS sessions and the correlation between the analgesic effects of the two treatments were assessed.
Twelve MCS patients underwent an average of 15.9 rTMS sessions prior to surgery; nine of the patients were rTMS responders. Postoperative follow-up was 57.8 ± 15.6 months (mean ± standard deviation). Mean percentage of pain relief (%R) was 21% and 40% after the first and fourth rTMS sessions, respectively. The corresponding mean durations of pain relief were respectively 2.4 and 12.9 days. A cumulative effect of the rTMS sessions was observed on both %R and duration of pain relief (p < 0.01). The %R value obtained with MCS was 35% after 6 months and 43% at the last follow-up. Both the PPV and NPV of rTMS were 100% after the fourth rTMS session (p = 0.0045). A significant correlation was found between %R or duration of pain relief after the fourth rTMS session and %R at the last MCS follow-up (R2 = 0.83, p = 0.0003).
Four rTMS sessions predicted MCS efficacy better than a single session in neuropathic pain patients. Taking into account the cumulative effects of rTMS, the authors found a high-level correlation between the analgesic effects of rTMS and MCS.
ABBREVIATIONSLEP = laser evoked potential; MCS = motor cortex stimulation; MEP = motor evoked potential; NPV = negative predictive value; NRS = Numerical Rating Scale; PPV = positive predictive value; ROC = receiver operating characteristic; rTMS = repetitive transcranial magnetic stimulation; SSEP = somatosensory evoked potential; %R MCS = percentage of pain relief following MCS; %R rTMS = percentage of pain relief following rTMS.