Title : Transcranial direct current stimulation: From mechanisms to clinical applicability. Why is a promising, safe, and accessible therapy still underutilized?
Abstract:
Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technique that applies low-intensity direct electrical current through scalp electrodes to modulate neuronal membrane potentials, cortical excitability, synaptic plasticity, and distributed brain networks. Although modern tDCS has expanded rapidly over the past two decades, therapeutic electrical stimulation has ancient roots. In the first century AD, the Roman physician Scribonius Largus described the electric torpedo fish for headache and pain. Later, Luigi Galvani, Alessandro Volta, and Giovanni Aldini established key links between electricity and nervous-system function, while twentieth-century experiments demonstrated lasting changes in cortical excitability after weak direct-current stimulation. This presentation reviews the historical development, neurophysiological mechanisms, safety, and clinical applicability of tDCS. Evidence from experimental studies, randomized trials, systematic reviews, meta-analyses, and evidence-based guidelines will be discussed, with emphasis on chronic pain, major depressive disorder, stroke rehabilitation, migraine, multiple sclerosis-related fatigue, Parkinson’s disease, and cognitive impairment. Clinical effects vary according to cortical target, electrode montage, current intensity and density, number of sessions, concomitant therapies, and individual neurobiological characteristics. When established safety recommendations are followed, adverse effects are generally mild and transient. Despite its relative safety, portability, low cost, and growing evidence base, tDCS remains underutilized in routine practice. Major barriers include protocol heterogeneity, insufficient standardization, small and heterogeneous trials, inconsistent replication, limited long-term data, interindividual variability, regulatory differences, and insufficient professional training. Its inexpensive, device-based nature may also provide fewer commercial incentives for large industry-funded multicenter trials. Wider clinical integration will require standardized protocols, adequately powered studies, individualized electric-field modeling, biomarkers and predictors of response, and clearer evidence-based implementation pathways.
