Pragmatic Trial of Remote TDCS and Somatosensory Training for Phantom Limb Pain with Machine Learning to Predict Treatment Response

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.

The investigators have designed a pragmatic trial of home-based tDCS for 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 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.

The investigators will perform a pragmatic, parallel randomized clinical trial. Investigators will recruit 290 participants with upper and/or lower bilateral or unilateral limb amputation and phantom limb pain in the chronic phase. All participants will be randomized to receive 20 daily sessions (4 weeks) of active anodal M1 home-based tDCS combined with somatosensory training or usual care. The participants will participate in 23 visits over 12 weeks.

Eligibility Criteria:
Inclusion Criteria:

1. Age - older than 18 years
2. Limb amputation
3. Patients who experience PLP regularly (at least once a week)
4. Pain not attributable to other causes, such as peripheral inflammation
5. Current chronic pain as defined by an average pain of at least 4 on the numeric rating scale (NRS, 0: no pain, 10: worst imaginable pain)

Exclusion Criteria:

1. Any clinically significant or unstable medical or psychiatric disorder
2. History of substance abuse in the past 6 months (according to the DSM-V criteria for substance use disorder with six or more symptoms)
3. Uncompensated psychiatric disorder
4. Previous significant neurological history with current significant neurological deficits
5. Previous neurosurgical procedure with craniectomy that would affect current distribution of tDCS
6. Contraindications to tDCS (implanted brain medical devices)