Developing Brain Stimulation as a Treatment for Chronic Pain in Opiate Dependent

Effective control of chronic pain is a top priority in the United States, as approximately 10% of adults have severe chronic pain - most of which is chronic lower back pain (CLBP). However, despite the advances in neuroscience over the past 20 years, chronic pain is still largely treated with opiate narcotics, much as was done in the Civil War. In addition to the high abuse liability and dependence potential, only 30-40% of chronic pain patients declare they receive satisfactory (\>50%) relief from their pain through pharmacological treatment. In these patients a common clinical practice is to escalate the dose of opiates as tolerance develops - which unfortunately has contributed to escalation in opiate overdose deaths, a resurgence of intravenous heroin use, and $55 billion in societal costs. Consequently there is a critical need for new, treatments that can treat pain and reduce reliance on opiates in individuals with chronic pain. Aim 1. Evaluate repetitive Transcranial Magnetic Stimulation (rTMS) to the dorsolateral prefrontal cortex (DLPFC) as a tool to dampen pain and the engagement of the Pain Network. Hypothesis 1: DLPFC TMS will attenuate the baseline brain response to pain (Pain Network activity) and increase activity in the Executive Control Network (ECN) when the patient is given instructions to 'control' the pain. Aim 2. Evaluate Medial Prefrontal Cortex (MPFC) rTMS as a tool to dampen pain and the engagement of the Pain Network. Hypothesis 1: MPFC TMS will also attenuate the baseline brain response to pain (Pain Network activity) but will not effect the ECN or the Salience Network (SN) when the patient is given instructions to 'control' the pain.

The goal of this proposal is to evaluate two novel non-invasive brain stimulation strategies to mitigate pain and the brain's response to pain in CLBP patients. Transcranial Magnetic Stimulation (TMS), can induce long term potentiation (LTP-like) and long term depression (LTD-like) effects on brain activity in a frequency dependent manner. The investigators have previously demonstrated that LTP-like TMS to the dorsolateral prefrontal cortex (DLPFC, a node in the Executive Control Network (ECN)) can decrease perceived pain and corresponding Blood Oxygen Level Dependent (BOLD) signal in the "Pain Network'. The Pain Network is an expansion of the Salience Network (SN; insula, dorsal anterior cingulate) which includes the thalamus and somatosensory cortex. The analgesic effects of DLPFC TMS can be blocked by naloxone - suggesting that the analgesic effects of LTP-like DLPFC TMS are opiate mediated. Additionally, DLPFC TMS delivered postoperatively leads to less patient administered morphine use (PCA-pump) in the hospital and less opiate use in the outpatient setting. These data all suggest that LTP-like DLPFC TMS is a promising candidate for treating pain. An alternative strategy is to apply LTD-like stimulation to the medial prefrontal cortex (LTD-like mPFC rTMS. This strategy is based on the understanding of functional neural architecture, wherein the SN is modulated by two other core networks: the ECN and the default mode network (DMN). As stated above, it is possible to attenuate activity in the SN through LTP-like TMS to the DLPFC, a node in the ECN. It is also possible to attenuate the SN through LTD-like TMS to the ventral medial prefrontal cortex (a node in the DMN). The proposed study will be the first to employ a randomized, double-blind, sham-controlled design to parametrically evaluate the longitudinal effects of 16 days of rTMS to the DLPFC (Aim 1) or the MPFC (Aim 2) on self-reported pain and the brain's response to pain. This will be done in a cohort of patients recruited from the community as well as Medical University of South Carolina clinics with chronic lower back pain that may or may not be using prescription opiates for 3 or more months without adequate pain relief. Participants will be randomized to receive rTMS to the DLPFC (10Hz), MPFC (cTBS), or sham (50% at each site), using a Latin square randomization. Resting state connectivity will be collected along with data from a standardized thermal pain paradigm wherein individuals are exposed to pain and instructed to try to "control' the pain. MRI data will be collected 3 times: before the 1st day of TMS, after the 12th day of TMS, and before the 16th day of TMS (the last day administered).