Efficacy of motor cortex stimulation in the treatment of neuropathic pain: a randomized double-blind trial.
OBJECTIVE
In this study the authors used a double-blind protocol to assess the efficacy of motor cortex stimulation (MCS) for treating neuropathic pain.


METHODS
Eleven patients with unilateral neuropathic pain (visual analog scale [VAS] score 8-10) of different origins and topography were selected for MCS. A 20-contact grid was implanted through a craniotomy centered over the motor cortex contralateral to the painful area. The motor cortex strip was identified using neuroimages, somatosensory evoked potentials, acute electrical stimulation, and corticocortical evoked potentials. Subacute therapeutic stimulation trials allowed the authors to determine the most efficient pair of contacts to use for long-term MCS. The grid was replaced with a 4-contact electrode connected to an internalized stimulator. Bipolar stimulation at a 40-Hz frequency, 90-micro sec pulse width, amplitude 2-7 V, and 1 hour in "ON" and 4 hours in "OFF" mode was used. Pain was evaluated using the VAS, Bourhis, and McGill pain scales applied each month for 1 year. At Day 60 or 90, the stimulators were turned to OFF mode for 30 days in a randomized, double-blind fashion. The statistical tool used was the Wilcoxon test.


RESULTS
Three patients did not report improvement in the subacute trial and were excluded from long-term MCS; the remaining patients underwent long-term stimulation. Significant improvement of pain was induced by MCS (p < 0.01); this persisted during the follow-up period. Turning stimulation to OFF mode increased pain significantly (p < 0.05). Improvement at 1 year was >or= 40% (40-86%) in all cases.


CONCLUSIONS
Motor cortex stimulation is an efficient treatment for neuropathic pain, according to an evaluation facilitated by a double-blind maneuver. Subacute stimulation trials are recommended to determine the optimum motor cortex area to be stimulated and to identify nonresponders.
Velasco
Francisco
F
Unit for Stereotactic Functional Neurosurgery and Radiosurgery, Service of Neurology and Neurosurgery, Mexico General Hospital, Mexico City, Mexico. slanfe@prodigy.net.mx
Argüelles
Carlos
C
Carrillo-Ruiz
José D
JD
Castro
Guillermo
G
Velasco
Ana Luisa
AL
Jiménez
Fiacro
F
Velasco
Marcos
M
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004311:Double-Blind Method; D004599:Electric Stimulation Therapy / Q000379:methods*; D004566:Electrodes; D005071:Evoked Potentials / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009044:Motor Cortex / Q000502:physiology*; D010146:Pain / Q000503:physiopathology*; D059408:Pain Management; D010147:Pain Measurement; D013997:Time Factors; D016896:Treatment Outcome