Vibro-tactile stimulation as a non-invasive treatment method for cervical dystonia

Abstract

Cervical dystonia (CD) is a form of focal dystonia associated with involuntary cervical muscle contractions that lead to sustained or intermittent abnormal, painful head movements or postures, which severely affect a CD patient’s daily life. Current treatment opportunities for CD are limited and mainly consist of Botulinum toxin (BoNT) injections in the dystonic muscles or deep brain stimulation. Both methods are invasive, and BoNT is not tolerated by all CD patients. This dissertation examined if superficial, vibro-tactile stimulation (VTS) of the cervical muscles can be an alternative method to provide temporary symptom relief for people with CD. Method: A total of 66 CD participants (44 female; mean age ± SD: 61.2 ±12.6 years) participated in the study. All participants were seen within two weeks before or one week after their new BoNT injection (i.e., their symptomatic period). The most often affected cervical muscles, sternocleidomastoid and trapezius, were stimulated. Participants completed up to 9 randomly ordered stimulations under different conditions (stimulating a single muscle or the combination of two muscles) based on their clinical manifestations (e.g., torticollis, laterocollis). Under each stimulation condition, VTS was applied continuously for 5 minutes. A head angle index (HAI), a composite measure reflecting the head deviation across the three head axes, and a self-reported pain score (100-point scale) were the primary outcome measures. Results: First, 83% of the participants showed 10% or higher improvement in HAI with 39% showing improvement higher than 30% under at least one stimulation condition. Approximately 58% of participants who experienced pain showed at least 10% or higher of improvement in pain score under at least one stimulation condition. Second, both therapeutic effects in normalizing abnormal head posture and reducing pain persisted immediately after cessation of VTS. However, the head normalization effect decayed quickly. Retention of pain relief was more stable and was observable up to 20 minutes after the cessation of VTS. Third, each CD manifestation does not have a distinct optimal stimulation profile. For a specific manifestation, several stimulation conditions could induce similarly large relative improvements or response rate. Conclusion: In summary, the findings of this study provide evidence that VTS can be used as a potential new treatment method for CD. Improvements in abnormal head posture and pain were observed among a large portion of participants during the application of VTS.