Background: A positive effect of motor cortex stimulation (MCS) (defined as subjective estimations
of pain relief ≥ 30%) has been reported in 55 – 64% of patients. Repetitive magnetic cortical
stimulation (rTMS) is considered a predictor of MCS effect. These figures are, however, mostly based
on 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 cortex
stimulation 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 cortex
stimulation, 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, before
being submitted to MCS surgery. Measurement: Postoperative pain relief was evaluated at 6 months
and 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) a
short questionnaire (HowRu) exploring discomfort, distress, disability, and dependence.
Results: Pain scores were significantly reduced by active (but not sham) rTMS and by subsequent
MCS. Ten out of 20 patients kept a long-term benefit from MCS, both on raw pain scores and on
CPA. The CPA results were strictly comparable when obtained by the surgeon or by a third-party
on telephonic survey (r = 0.9). CPA scores following rTMS and long-term MCS were significantly
associated (Fisher P = 0.02), with 90% positive predictive value and 67% negative predictive value
of preoperative rTMS over long-term MCS results. On the HowRu questionnaire, long-term MCSrelated improvement concerned “discomfort” (physical pain) and “dependence” (autonomy for daily
activities), 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 the
reported items by the patient after a variable and long delay after surgery. Predictive evaluation based
on a single rTMS session compared to chronic MCS.
Conclusions: Half of the patients still retain a significant benefit after 2 – 9 years of continuous
MCS, and this can be reasonably predicted by preoperative rTMS. Adding drug intake and QoL
estimates to raw pain scores allows a more realistic assessment of long-term benefits and enhance
the rTMS predictive value.
The aims of this study and its design were approved by the local ethics committee (University Hospitals
St 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
A systematic review of the proposed mechanisms underpinning pain relief by primary motor cortex stimulation in animals
