Pain
Conditions
Brief summary
Studies have shown that transcranial magnetic stimulation (TMS), a non-invasive form of brain stimulation, can reduce pain in the laboratory and in the clinic. The purpose of this study is to investigate how TMS relieves pain and affects pain circuitry in the brain. One of the primary study hypotheses is that opioid blockade will significantly reduce the pain relief produced by left prefrontal cortex TMS.
Detailed description
Non-invasive forms of brain stimulation such as transcranial direct current stimulation (tDCS) and transcranial magnetic stimulation (TMS) are currently being investigated as alternative or adjunctive therapies for pain. Clinical interest in these techniques continues to grow because of rising opiate abuse and inadequate pain management strategies. Despite this enthusiasm, studies on the efficacy of repetitive TMS (rTMS) for pain have produced mixed results. Some of the most promising and informative research has focused on rTMS for perioperative pain. In two different postoperative studies, a single session of left dorsolateral prefrontal cortex (DLPFC) rTMS after gastric bypass surgery reduced morphine self-administration by 40% when compared to sham stimulation. These data are particularly fascinating given the role of the DLPFC in top-down pain processing. Centered at the juncture of Brodmann Areas (BAs) 9 and 46, the DLPFC remains a popular therapeutic target for rTMS given its accessible location and presumed role in high-order cognition and emotional valence. Animal and human studies suggest that cingulofrontal regions like DLPFC may modulate pain perception via recruitment of opioidergic midbrain and brainstem structures like the periaqueductal gray (PAG) and the rostroventromedial medulla (RVM), respectively. These data outline the functional circuitry that might be involved in the analgesic effects of DLPFC rTMS. While many studies aim to evaluate the clinical efficacy of DLPFC rTMS for pain management, few have examined how it affects pain processing. Imaging the cerebral signature of pain before and after left DLPFC rTMS might reveal information about pain circuitry and help to elucidate the mechanism by which prefrontal rTMS may produce analgesia. Previous studies suggest that opioid blockade abolishes left but not right DLPFC rTMS-induced analgesia. In this study, our a priori hypothesis was that left DLPFC rTMS would attenuate blood oxygenation-level dependent (BOLD) signal response to painful stimuli in pain processing regions. More specifically, we anticipated that midbrain and medulla BOLD signal changes induced by left DLPFC rTMS would be abolished by pretreatment with the μ-opioid antagonist naloxone.
Interventions
PROCEDURESham rTMS
The eSham system was implemented in conjunction with a specialized Neuronetics sham TMS coil. This coil has a metal plate hidden inside of it that blocks the magnetic field from affecting the brain. Scalp electrodes were used to mimic the feel of real rTMS. This approach has been validated in previous studies.
PROCEDUREReal rTMS
An iron-core, solid-state figure-of-8 coil was used to stimulate the dorsolateral prefrontal cortex. The site of stimulation was estimated using the Beam F3 method based on the 10-20 EEG system.
Sponsors
National Institute on Drug Abuse (NIDA)
Medical University of South Carolina
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
BASIC_SCIENCE
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
ALL
Age
18 Years to 45 Years
Healthy volunteers
Yes
Inclusion criteria
* healthy volunteers * no history of depression or pain * no metal in body * no medications that lower seizure threshold
Exclusion criteria
* history of depression or pain * history of seizures or epilepsy * metal implants in body * medications that lower seizure threshold * psychiatric medications
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Pain Rating | Baseline (60 minutes into experiment), Post-Sham (90 minutes), Post-Real (120 minutes) | There are two experimental visits separated by one week. During each experiment, pain ratings will be measured every 30 minutes. Preliminary testing will be done 30 minutes into the experiment. The purpose of preliminary testing is to select the temperature that will be used to induce pain throughout the experiment. Baseline testing will be done 60 minutes into the experiment. After sham rTMS will be done 90 minutes into the experiment. After real rTMS will be done 120 minutes into the study. The pain scale used in a Visual Analog Scale (VAS). There was an 11-point rating system where 0 represented no pain and 10 represented unbearable pain. |
| Change in BOLD Signal in Pain Processing Regions During Pain, Including Supraspinal Opioidergic Structures | Baseline (60 minutes into experiment), Post-Sham (90 minutes), Post-Real (120 minutes) | There are two experimental visits separated by one week. During each experiment, blood oxygen level dependent (BOLD) signal will be measured at baseline (60 minutes into the experiment), post-sham rTMS (90 minutes into the experiment) and post-real (120 minutes into the experiment). |
Countries
United States
Participant flow
Recruitment details
Prospective participants were interviewed over the phone prior to being invited to a screening visit in the Brain Stimulation Laboratory at MUSC. Risks and benefits were explained and consent was obtained. All participants were tested for opiate use and females were tested for pregnancy. Recruitment began in 2011 and ended in early 2012.
Pre-assignment details
Healthy volunteers were randomized to receive I.V. saline or naloxone immediately prior to sham and real rTMS on the same experimental visit. One week later, each participant received the novel pretreatment but the same stimulation paradigm. One participant dropped out after her first experimental visit. These data were not included.
Participants by arm
| Arm | Count |
|---|---|
| Pretreatment & Stimulation Outside of the 3T magnetic resonance imaging (MRI) scanner, participants underwent resting motor threshold assessment, left dorsolateral prefrontal cortex localization and preliminary pain testing. Next, participants were placed in the scanner for baseline pain testing. After baseline testing, participants were asked to rate the pain that they had experienced. Participants were subsequently removed from the scanner and randomized to receive approximately 10 ml intravenous naloxone (0.1mg/kg) or saline immediately prior to 20 minutes of sham left DLFPC rTMS. Following sham rTMS, participants returned to the scanner for the same block testing performed at baseline. After rating their pain, participants were removed from the scanner for 20 minutes of real left DLPFC rTMS. Participants then returned to the scanner for the final block test. | 15 |
| Total | 15 |
Withdrawals & dropouts
| Period | Reason | FG000 | FG001 |
|---|---|---|---|
| Pretreatment 1 and Stimulation | Withdrawal by Subject | 1 | 0 |
Baseline characteristics
| Characteristic | Pretreatment & Stimulation |
|---|---|
| Age, Categorical <=18 years | 0 Participants |
| Age, Categorical >=65 years | 0 Participants |
| Age, Categorical Between 18 and 65 years | 15 Participants |
| Age, Continuous | 26 years STANDARD_DEVIATION 4 |
| Sex: Female, Male Female | 6 Participants |
| Sex: Female, Male Male | 9 Participants |
Adverse events
| Event type | EG000 affected / at risk |
|---|---|
| deaths Total, all-cause mortality | — / — |
| other Total, other adverse events | 0 / 15 |
| serious Total, serious adverse events | 0 / 15 |
Outcome results
Primary
Change in BOLD Signal in Pain Processing Regions During Pain, Including Supraspinal Opioidergic Structures
There are two experimental visits separated by one week. During each experiment, blood oxygen level dependent (BOLD) signal will be measured at baseline (60 minutes into the experiment), post-sham rTMS (90 minutes into the experiment) and post-real (120 minutes into the experiment).
Time frame: Baseline (60 minutes into experiment), Post-Sham (90 minutes), Post-Real (120 minutes)
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Sham rTMS With Saline | Change in BOLD Signal in Pain Processing Regions During Pain, Including Supraspinal Opioidergic Structures | 0.15 mean percentage of BOLD signal change | Standard Error 0.03 |
| Real rTMS With Saline | Change in BOLD Signal in Pain Processing Regions During Pain, Including Supraspinal Opioidergic Structures | 0.00 mean percentage of BOLD signal change | Standard Error 0.04 |
| Sham rTMS With Naloxone | Change in BOLD Signal in Pain Processing Regions During Pain, Including Supraspinal Opioidergic Structures | 0.10 mean percentage of BOLD signal change | Standard Error 0.03 |
| Real rTMS With Naloxone | Change in BOLD Signal in Pain Processing Regions During Pain, Including Supraspinal Opioidergic Structures | 0.13 mean percentage of BOLD signal change | Standard Error 0.05 |
p-value: 0.0003ANOVA
p-value: 0.794ANOVA
Primary
Pain Rating
There are two experimental visits separated by one week. During each experiment, pain ratings will be measured every 30 minutes. Preliminary testing will be done 30 minutes into the experiment. The purpose of preliminary testing is to select the temperature that will be used to induce pain throughout the experiment. Baseline testing will be done 60 minutes into the experiment. After sham rTMS will be done 90 minutes into the experiment. After real rTMS will be done 120 minutes into the study. The pain scale used in a Visual Analog Scale (VAS). There was an 11-point rating system where 0 represented no pain and 10 represented unbearable pain.
Time frame: Baseline (60 minutes into experiment), Post-Sham (90 minutes), Post-Real (120 minutes)
| Arm | Measure | Value (MEAN) | Dispersion |
|---|---|---|---|
| Sham rTMS With Saline | Pain Rating | 7.36 units on a scale | Standard Error 0.24 |
| Real rTMS With Saline | Pain Rating | 5.61 units on a scale | Standard Error 0.26 |
| Sham rTMS With Naloxone | Pain Rating | 7.54 units on a scale | Standard Error 0.15 |
| Real rTMS With Naloxone | Pain Rating | 6.75 units on a scale | Standard Error 0.21 |
p-value: <0.001ANOVA
p-value: 0.04ANOVA