The investigators have designed a pragmatic trial of home-based transcranial direct current stimulation (tDCS) for phantom limb pain (PLP), the PLP-EVEREST trial (PLP-EffectiVEness pRagmatic Stimulation Trial) to test a portable device that would reach underrepresented populations and would validate this therapy in a more pragmatic setting. Subjects will be randomized to home-based tDCS of the primary motor cortex (M1) with somatosensory training or usual care only (including their current pharmacological treatments, physical therapy, and occupational therapy). The investigators will therefore test the effectiveness of home-based tDCS and somatosensory training in a real-world, home-based setting. The Investigator will compare patients randomized to this combined strategy vs. usual care alone (subjects from this group will be offered combined treatment at the end of the trial). The investigators hypothesize that the combined strategy will be associated with a significantly larger Cohen's d effect size (at least 1) compared to the control group.
Age - older than 18 years
Limb amputation
Patients who experience PLP regularly (at least once a week)
Pain not attributable to other causes, such as peripheral inflammation
Any clinically significant or unstable medical or psychiatric disorder
History of substance abuse in the past 6 months (according to the DSM-V criteria for substance use disorder with six or more symptoms)
Uncompensated psychiatric disorder
Previous significant neurological history with current significant neurological deficits
Parallel
M1 anodal home-based tDCS
DeviceDuring tDCS, low amplitude direct currents are applied via scalp electrodes and penetrate the skull to enter the brain. Direct current will be transferred by a saline-soaked pair of surface sponge electrodes (35 cm2) and delivered by a specially developed, battery-driven, constant current stimulator with a maximum output of 10 mA.
Somatosensory Training
BehavioralThe somatosensory training will be performed during the self-administration of tDCS, including 20 sessions over 4 weeks. Sessions will start with relaxation exercises using a body scan technique, whereby subjects in a relaxed state will be instructed to sequentially interchange their mind to different regions of the body while perceiving it and establishing contact with the body part. Subjects will be asked to concentrate on any feeling (kinetic, kinesthetic or exteroceptive) related to each body part. Phantom exercises will involve the use of imagined movements of the phantom limb. Therefore, patients will be asked to perform general exercises with their phantom limb. Exercises will include hip, knee, ankle, and toe movements.
Usual Care
Other interventionUsual care includes pharmacological treatments, physical therapy, occupational therapy and/or behavioral therapy that the subject is receiving.
Visual Analogue Scale (VAS) for Phantom Limb Pain
The VAS is a common assessment that asks subjects to self-reportedly measure their pain on a visual scale (i.e., unbearable to none). Investigators will use the VAS to determine subjects' pain scores. Subjects will rate their pain from 0 - indicating no pain at all, to 10 - indicating the worst pain felt. This scale is also colored, from green (at 0) to red (at 10), as a visual indicator of pain. This assessment tool is frequently used in many research studies evaluating pain levels in phantom limb.
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