Transcranial direct current stimulation in the management of phantom limb pain: a systematic review of randomized controlled trials

Abstract

Introduction: Phantom limb pain (PLP) after amputation is a frequent entity that conditions the life of those who suffer it. Current treatment methods are not sufficiently effective for PLP management. We aim to analyze the clinical application of transcranial direct current (tDCS) in people with amputation suffering from PLP.

Evidence acquisition: The following databases were consulted in September 2021: MEDLINE, EMBASE, The Web of Science, PEDro, SCOPUS and SciELO. Randomized controlled trials investigating the use of tDCS in people with amputation undergoing PLP were selected. Demographic data, type and cause of amputation, time since amputation, stimulation parameters, and outcomes were extracted.

Evidence synthesis: Six articles were included in this review (seven studies were considered because one study performed two individual protocols). All included studies evaluated PLP; six evaluated the phantom limb sensations (PLS) and two evaluated the psychiatric disorders. In all included studies the intensity and frequency of PLP was reduced, in three PLS were reduced, and in none study psychiatric symptoms were modified.

Conclusions: Anodic tDCS over the contralateral M1 to the affected limb, with an intensity of 1-2 mA, for 15-20 minutes seems to significantly reduce PLP in people with amputation. Single-session treatment could modify PLP intensity for hours, and multi-session treatment could modify PLP for months. Limited evidence suggests that PLS and psychiatric disorders should be treated with different PLP electrode placements. Further studies with larger sample size and longer follow-up times are needed to establish the priority of tDCS application in the PLP management.

Figure 1

—PRISMA flow diagram. Flowchart of selection process: 171 studies were retrieved; after eliminating duplicates, 75 studies were read by title and abstract. Finally, for detailed reasons, 6 studies were included in the review.

Figure 2

—Revised Cochrane risk-of-bias tool for randomized trials. Depending on the color, the different types of bias evaluated in the included studies are represented. Green: low risk of bias; yellow: unclear risk of bias; red: high risk of bias.