Postherpetic Neuralgia clinical trials at UCSF

Chronic pain affects 1 in 4 US adults, and many cases are resistant to almost any treatment. Deep brain stimulation (DBS) holds promise as a new option for patients suffering from treatment-resistant chronic pain, but traditional approaches target only brain regions involved in one aspect of the pain experience and provide continuous 24/7 brain stimulation which may lose effect over time. By developing new technology that targets multiple, complimentary brain regions in an adaptive fashion, the investigators will test a new therapy for chronic pain that has potential for better, more enduring analgesia.

Chronic neuropathic pain is defined as pain caused by a lesion or disease of the somatosensory nervous system. It is highly prevalent, debilitating, and challenging to treat. Current available treatments have low efficacy, high side effect burden, and are prone to misuse and dependence. Emerging evidence suggests that the transition from acute to chronic neuropathic pain is associated with reorganization of central brain circuits involved in pain processing. Repetitive transcranial magnetic stimulation (rTMS) is a promising alternative treatment that uses focused magnetic pulses to non-invasively modulate brain activity, a strategy that can potentially circumvent the adverse effects of available treatments for pain. RTMS is FDA-approved for the treatment of major depressive disorder, obsessive-compulsive disorder, and migraine, and has been shown to reduce pain scores when applied to the contralateral motor cortex (M1). However, available studies of rTMS for chronic neuropathic pain typically show variable and often short-lived benefits, and many aspects of optimal treatment remain unknown, including ideal rTMS stimulation parameters, duration of treatment, and relationship to the underlying pain etiology. Here the investigators propose to evaluate the efficacy of high frequency rTMS to M1, the region with most evidence of benefit in chronic neuropathic pain, and to use functional magnetic resonance imaging (fMRI) to identify alternative rTMS targets for participants that do not respond to stimulation at M1. The central aim is to evaluate the pain relieving efficacy of multi-session high-frequency M1 TMS for pain. In secondary exploratory analyses, the investigator propose to investigate patient characteristic that are predictive of responsive to M1 rTMS and identify viable alternative stimulation targets in non-responders to M1 rTMS.