Clinical efficacy of neuromodulation in isolated dystonia: A systematic review of motor function improvement

Isolated dystonia is a disabling movement disorder for which neuromodulation represents a key therapeutic option in medically refractory cases. Deep brain stimulation (DBS) of the globus pallidus internus (GPi) is the current standard target, while subthalamic nucleus (STN) stimulation and non-invasive techniques such as repetitive transcranial magnetic stimulation (rTMS) and transcranial direct current stimulation (tDCS) have been investigated as alternative or adjunctive approaches. To systematically evaluate the efficacy and safety of invasive and non-invasive neuromodulation techniques for motor symptom improvement in adults with isolated dystonia. A systematic search of PubMed, Embase and Cochrane Library (January 2007–December 2020) was conducted according to PRISMA guidelines. Randomized and non-randomized clinical studies assessing motor outcomes after GPi-DBS, STN-DBS, rTMS or tDCS were included. Risk of bias was assessed using design-specific tools. Twelve studies met the inclusion criteria. GPi-DBS provided consistent and sustained motor improvement across dystonia phenotypes with an acceptable safety profile. STN-DBS showed comparable efficacy in selected cohorts, with faster early clinical response and lower energy consumption, although the lack of prospective head-to-head trials prevents definitive conclusions. Non-invasive techniques (rTMS and tDCS) yielded modest but clinically meaningful benefits, particularly when combined with structured rehabilitation. Study heterogeneity precluded quantitative synthesis. Neuromodulation is an effective and safe treatment for isolated dystonia. GPi-DBS remains the best-supported approach, STN-DBS a promising option in selected patients, and non-invasive techniques a potential adjunct. Prospective comparative trials and standardized, phenotype-driven strategies are still needed.