This study is being done to see how well a new investigational medical device, the StimRouter System, will work to treat the chronic pain in people who have failed previous treatments for Carpal Tunnel Syndrome (CTS) pain, including surgery. These people have been treated for CTS pain before including surgical carpal tunnel release, but without good results, and they are still having pain. The study will look at both the good and bad effects of the StimRouter System for treating this kind of pain and as a general peripheral nerve stimulation device for treating chronic pain. The study will also help to understand other possible uses for the StimRouter System.

This is a prospective, single-center, open label study designed to evaluate the clinical use of the StimRouter as a peripheral nerve stimulation device for the treatment of chronic pain. The clinical study is proposed to serve as an evaluation of the preliminary StimRouter design, proposed implantation techniques, electrical stimulation parameters, and outcome measures for the StimRouter. The current study will utilize the median nerve (in the context of carpal tunnel syndrome (CTS), status-post a single failed carpal tunnel release (CTR) surgery)as a model to represent the device's more general intended use as a peripheral nerve stimulator to treat chronic pain.

• Eisenberg E, Waisbrod H, Gerbershagen HU. Long-term peripheral nerve stimulation for painful nerve injuries. Clin J Pain. 2004 May-Jun;20(3):143-6.
• Day M. Neuromodulation: spinal cord and peripheral nerve stimulation. Curr Rev Pain. 2000;4(5):374-82. Review.

Inclusion Criteria:

• 18 years of age or older
• Chronic peripheral pain persisting for greater than or equal to 3 months diagnosed previously as a mononeuropathy of the median nerve at the level of the carpal tunnel (i.e., diagnosed CTS)
• Average chronic pain level greater than or equal to 5/10 [on 0-10 numeric rating scale (NRS) (BPI#14)], where such pain is attributed to injury, irritation, or entrapment of the median nerve at the level of the carpal tunnel (i.e., diagnosed CTS)
• Failure of a single prior carpal tunnel release surgery to provide relief, where such failed surgery was performed greater than or equal to study entry
• Able to tolerate stimulation (TENS)
• Temporary pain relief is achieved by local anesthetic block of the target median nerve suspected to be the source of chronic pain symptoms
• Ability to give informed consent and understand study requirements
• Ability to quantify pain using a 0-10 numeric rating scale [A screening tool will be used to ensure that subjects can rate 3 common pain scenarios (mosquito bite, stubbed toe and broken bone) on a 0-10 NRS relative to each other, with mosquito bite < stubbed toe < broken bone]
• Willing and able to understand and comply with all study-related procedures during the course of the study
• Motivated to maintain an accurate diary for the study duration

Exclusion Criteria:

• Metal implants in the forearm
• Active infection
• Active or existing skin disorder or irritation which, at the physician's discretion, contraindications use of skin gel electrodes
• Allodynia
• Regular use of antiplatelet medications [e.g., aspirin, ticlopidine (Ticlid), clopidogrel (Plavix), tirofiban (Aggrastat), and eptifibatide (Integrilin)]
• Anticoagulated (taking warfarin or heparin, including fractionated heparin) or has a bleeding disorder
• Cardiac pacemaker
• Implanted neurostimulator (e.g., spinal cord, deep brain, vagus nerve stimulator) or implanted pump or infusion device
• History of cardiac arrhythmia with homodynamic instability
• Untreated drug habituation or dependence
• Psychologically or medically unstable
• Uncontrolled seizures (averaging > 2 seizures per month)
• Pregnant or plan on becoming pregnant or breastfeeding during the study period
• Currently require, or likely to require, diathermy and/or MRI during the study duration
• History of adverse reactions to local anesthetic (e.g., lidocaine)