The immediate effect of peripheral stimulation on cervical dystonia disease outcomes: single-case experimental design

Limited cervical range of motion (CROM) and pain are among the most common symptoms of cervical dystonia (CD), which are treated with botulinum neurotoxin (BoNT) injections. However, adjunctive interventions may offer additional benefit. Therefore, this study evaluated the immediate effects of peripheral stimulation comprising conventional transcutaneous electrical nerve stimulation (TENS), muscle stimulation (NMES), and muscle vibration on CROM and pain in patients with CD.

A single-case experiment design (SCED), alternating treatment design was conducted with 19 CD patients, recruited at the Antwerp University Hospital (UZA). Participants randomly received conventional TENS, NMES and muscle vibration on three different days. Main outcome measures were CROM, measured using a 3D-stereophotogrammetric scanning system (3dMD Inc., GA, USA) and pain, quantified by Visual Analog Scale (VAS).

Mean age of participants was 59.87 ± 8.9 years. Baseline CROM for rotation ranged from 87^° to 137.6^° and from 79^° to 132.4^° for flexion/extension. Improvements in neck rotation were observed in 5 (33.3%) participants after conventional TENS, 8 (42.1%) after NMES, and 8 (42.1%) after muscle vibration. Similarly, improvement in flexion and extension was observed in 10 (55.6%) after conventional TENS, 8 (53.3%) after NMES, and 7 (46.7%) after muscle vibration. Significant reductions in pain shortly after the three interventions were observed in patients experiencing pain.

These findings suggest that peripheral stimulation may provide immediate symptomatic relief in CD, particularly for improving CROM and reducing pain. While promising, these results should be considered as exploratory and warrant further investigation in larger, controlled studies.