Conventional transcutaneous electrical nerve stimulation shows no short-term safety signal in painful cervical dystonia: a pilot prospective study.

Abstract

Background and purpose: Cervical dystonia (CD) is frequently associated with chronic cervical pain refractory to botulinum neurotoxin (BoNT) therapy. Transcutaneous electrical nerve stimulation (TENS), a non-invasive neuromodulation technique with established analgesic properties, has not been formally evaluated in CD. This pilot study assessed the safety and tolerability of conventional TENS in painful CD, with exploratory evaluation of pain outcomes.

Methods: This prospective, observational, single-arm study (NCT04949594) included patients with painful CD treated or not with BoNT. The primary outcome was the mean change in Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) total score between peak BoNT efficacy time points before (T1) and after TENS introduction (T2), assessed against an exploratory -8-point safety threshold. Secondary outcomes included TWSTRS subscores and Pain Numeric Rating Scale (PNRS).

Results: Fifteen patients completed the study. The mean T1-T2 TWSTRS total score change was +3.42 (95% CI - 0.86 to 7.69), remaining above the exploratory -8-point safety threshold, with no group-level signal of clinically meaningful worsening. At the individual level, only three patients (20%) showed a worsening, two of whom (13.3%) exceeded the -8-point threshold (-11.5 and -9.5 points). TWSTRS subscores and PNRS showed no statistically significant changes after correction for multiple comparisons. Adverse events were mild and transient, and 80% of patients reported satisfaction and continued TENS use at follow-up.

Conclusion: Conventional TENS showed no short-term safety signal and was well tolerated in painful CD, supporting its feasibility as an adjunctive neuromodulation approach in this small, uncontrolled pilot cohort, pending confirmation in randomized sham-controlled trials.