From Nerve to Brain: Toward a Mechanistic Understanding of Spinal Cord Stimulation in Human Subjects

Inclusion Criteria:

* Aged 18 to 80
* Capable of providing informed consent and following trial procedures, including capacity to complete self-reported measures of pain, function, and other outcomes
* Stably implanted spinal cord or dorsal root ganglion stimulator
* Device is to treat back/radicular lower extremity pain or neck/arm pain
* Device with a paresthesia-free setting

Exclusion Criteria:

* Patients who are not on a stable dose of opioids or are on a stable dose greater than 100 MME/day per day within the two months prior to enrollment, or those who are unwilling to maintain a stable dose of opioids throughout the duration of the study
* The investigator concludes that the participant is unable to differentiate back or neck/arm pain from other pains
* Systemic or psychiatric illness that in the opinion of the site investigator would interfere with the individual's ability to participate in the trial
* Other factor that in the opinion of the site investigator would interfere with the individual's ability to participate in the trial or tolerate the study procedures

Dropout Criteria for Optional Imaging

* Stimulation device is not 3 Tesla magnetic resonance imaging compliant
* Contraindications to magnetic resonance imaging and/or positron emission tomography scanning (including presence of a cardiac pacemaker or pacemaker wires, vascular clips in the head or previous neurosurgery, prosthetic heart valves, claustrophobia)
* Pregnant or breastfeeding
* Participants with a low affinity binder phenotype based off testing for the Ala147Thr polymorphism.
* Current or recent use of benzodiazepines (except for alprazolam, clonazepam, and lorazepam). Recent use will be defined based off the benzodiazepines half-life, such that patients who stopped taking the medication at least five half-lives ago will be considered eligible for scanning.
* Subjects who have exceeded (or would exceed if they were to participate) the yearly amount of allowable radiation, as defined by the Radiation Safety Committee
* In the opinion of the investigators, unable to safely participate in this study and/or provide reliable data (e.g., unlikely to remain still during the imaging procedures).