Article
Chronic motor cortex stimulation and the predictive value of rTMS
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Published: | April 28, 2011 |
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Objective: Chronic motor cortex stimulation (MCS) has been used as a treatment for neuropathic pain for two decades. The aim of this study was to retrospectively analyze a patient group from two centers with long-term follow-up of 2 years and to compare MCS analgesic efficacy between "ON"- and "OFF"- stimulation.
Methods: 10 patients with chronic neuropathic pain were treated with contralateral epidural stimulation electrodes over the precentral gyrus. There were 2 cases of trigeminal neuropathic pain (TNP), 1 case of post-stroke pain (PSP), one case of a posttraumatic brachial plexus lesion and 1 case of pain post-irradiation of an AVM. 5 patients suffered from CRPS II. Preoperatively all patients underwent rTMS to estimate the MCS effect. The placement of the electrodes (Specify®, Medtronic, Minneapolis, MN, USA) was performed under local anesthesia using frame-based stereotactic neuronavigation. Placement of the electrode was confirmed using postoperative stereotactic CT and re-fusion. A test trial of three to five days including double-blind testing was conducted and pain intensity was measured using a visual analog scale (VAS) prior to stimulator insertion.
Results: We only included patients with a positive response in rTMS. In TNP and in PSP, a positive effect with a 50% pain reduction (median VAS 9 to 5) was observed. In posttraumatic pain the relief was 60% (VAS 8 to 6). Post-irradiation pain resulted in complete relief (VAS 9 to 0) of pain. In CRPS the median pain reduction was 80% (VAS 8 to 2). The overall response was 75%. The mean follow-up period was 2.6 years (range 1–4 years). No complications have occurred so far.
Conclusions: Stimulation of the motor cortex is a promising treatment option for patients with chronic neuropathic pain localized in the face, head, trunk or upper extremity. Non-responders may be identified with rTMS. It has some predictive value for the effects. Since all patients benefited from surgery, a prospective MCT is highly warranted.