rTMS and Retraining in Focal Hand Dystonia

The Arm Dystonia Disability Scale (ADDS) is a survey where participants rate task difficulty for activities such as writing, handling utensils, and buttoning on a scale of 1-4 (1 = no difficulty ,4 = not able or marked difficulty). This is a subjective assessment of impairment due to focal hand dystonia. Scores are determined using an equation: total points scored, divided by the maximum possible (23), multiplied by the quotient by 90 and subtract from 90%. Scores range from 0%-90% with higher scores indicating more function.

Examinations included two point discrimination. Two-point discrimination threshold was completed using a Disk-Criminator™. Participants were asked to reply "one" or "two" after each presentation. Static and dynamic stimuli were presented to the index and ring fingers bilaterally, meaning it was presented as a static stimuli or it was slowly swept across the skin (dynamic).

Cortical silent period (CSP) testing was completed during an isometric contraction of the target muscle whereby the motor evoked potential is followed by a short duration of electromyographic quiescence. The maximal voluntary contraction for finger abduction was recorded using a custom strain gauge placed around the index finger. Real-time visual feedback was given on a laptop screen to project the force produced by the participant and 20% of the maximum of three trials was calculated and displayed on a target line. For the CSP, participants were asked to contract until the target line was met, then a single transcranial magnetic stimulation pulse was delivered to the motor cortex. Ten trials were collected with a short rest period to prevent fatigue.

CSP duration was calculated in milliseconds (ms). CSP EMG data were first rectified, and then a 10-ms moving average calculation was applied to the data. The onset of the CSP was set as the time point of the delivery of the TM

Digitized handwriting was assessed using a computerized tablet (WACOM Co., Ltd., japan) with MovAlyzeR® (Neuroscript LLC, Tempe, AZ) hardware and software. Participants used a custom modified digitized pen (Kiko Software, Netherlands) to write in a self-selected pace and style on the tablet with real-time visual feedback. Writing tasks included "My country tis of thee" at a self-selected pace, repeated eight times. Data were sampled at 215 Hz (resolution: 5080 lpi, accuracy: ±0.01 pressure range: 0-800 g). Writing samples were segmented by points of minimal velocity into single strokes for analysis. Pressure for each stroke was automatically calculated within the software.

Video recordings were made as participants wrote on a pad of paper with pen. Participants were asked to draw a series of 10 loops across the pad of paper followed by "The dog is barking" and their signature, each repeated four times. A physician blinded to participant allocation rated recordings. Scoring criteria were adapted from a standardized writer's cramp rating scale (WCRS) (Wissel et al., 1996), rating pathological flexion or extension at the wrist, fingers and elbow, presence of tremor, dystonic posture, writing speed and latency of dystonic symptoms. Final scores are expressed as a rating listed as a movement score.

Participants completed the full SF-36 assessment with subsection of interest: "physical functioning".