Prospective Clinical Study of a New Implantable Peripheral Nerve Stimulation Device to Treat Chronic Pain

Abstract

To evaluate clinical use of the StimRouter, an investigational implanted peripheral nerve stimulator for treating chronic neuropathic pain, using the median nerve as a model for that general application. Eight patients with carpal tunnel syndrome and chronic pain despite both carpal tunnel release and treatment with oral pain medications were enrolled in a single-center, open-label trial after institutional review board approval. Primary endpoints were successful implantation near the target peripheral nerve and safety. All 8 patients were implanted temporarily at the median nerve in at least one arm and 2 patients were implanted bilaterally, with 10 implants total. Each implant was considered a separate "patient." For 5 days, all patients received 6 hours of daily transdermal electrical stimulation targeting the median nerve. Pain was measured at baseline, during implant, and after explant. Two patients experienced clinically meaningful (>or=30%) pain reduction throughout the entire 5-day treatment period. Apparent carryover effect in pain reduction also was observed after daily stimulation. After explant, pain returned to baseline, increasing 36.8% to 45.6% relative to average reduced pain with daily stimulation. No significant or unexpected adverse events occurred. Mean patient study satisfaction was 96%, and 100% of patients indicated a preference for permanent implant. Temporary implant of the StimRouter device resulted in both pain reduction and reduced use of oral opioid pain medication during the 5-day stimulation period. The results suggest that permanent implant of the StimRouter System may be safe and effective for treating chronic peripheral neuropathic pain.