Handwriting training in Parkinson’s disease: A trade-off between size, speed and fluency

Background
In previous work, we found that intensive amplitude training successfully improved micrographia in Parkinson’s disease (PD). Handwriting abnormalities in PD also express themselves in stroke duration and writing fluency. It is currently unknown whether training changes these dysgraphic features.
Objective
To determine the differential effects of amplitude training on various hallmarks of handwriting abnormalities in PD.
Methods
We randomized 38 right-handed subjects in early to mid-stage of PD into an experimental group (n = 18), receiving training focused at improving writing size during 30 minutes/day, five days/week for six weeks, and a placebo group (n = 20), receiving stretch and relaxation exercises at equal intensity. Writing skills were assessed using a touch-sensitive tablet pre- and post-training, and after a six-week retention period. Tests encompassed a transfer task, evaluating trained and untrained sequences, and an automatization task, comparing single- and dual-task handwriting. Outcome parameters were stroke duration (s), writing velocity (cm/s) and normalized jerk (i.e. fluency).
Results
In contrast to the reported positive effects of training on writing size, the current results showed increases in stroke duration and normalized jerk after amplitude training, which were absent in the placebo group. These increases remained after the six-week retention period. In contrast, velocity remained unchanged throughout the study.
Conclusion
While intensive amplitude training is beneficial to improve writing size in PD, it comes at a cost as fluency and stroke duration deteriorated after training. The findings imply that PD patients can redistribute movement priorities after training within a compromised motor system.

研究背景
过往研究表明，幅度强化训练可有效改善帕金森病（Parkinson’s disease, PD）患者的小写症。帕金森病患者的书写异常还体现在笔画时长与书写流畅度方面，目前尚不清楚训练是否会改变这类书写障碍特征。

研究目的
本研究旨在明确幅度强化训练对帕金森病患者各类书写异常特征的差异化影响。

研究方法
本研究将38名帕金森病早中期右利手受试者随机分为两组：实验组（n=18）接受以提升书写字号为目标的训练，每日30分钟、每周5天，持续6周；安慰剂对照组（n=20）接受强度与实验组一致的拉伸与放松训练。分别在训练前、训练后以及6周随访保留期后，采用触控平板对受试者的书写能力进行评估。评估内容包含两项任务：一是迁移任务，用于测试已训练与未训练的书写序列；二是自动化任务，用于对比单任务与双任务书写表现。本研究的结局指标包括：笔画时长（单位：秒）、书写速度（单位：厘米/秒）以及归一化jerk（即流畅度）。

研究结果
与此前报道的训练对书写字号的改善效果相反，本研究结果显示，幅度强化训练后受试者的笔画时长与归一化jerk值均出现上升，而安慰剂对照组未出现此类变化。上述指标升高的情况在6周随访保留期后依然存在。与之相反，书写速度在整个研究期间均未出现明显变化。

研究结论
尽管幅度强化训练可有效改善帕金森病患者的书写字号，但该训练同时存在代价：训练后患者的书写流畅度与笔画时长均出现恶化。本研究结果提示，在受损的运动系统中，帕金森病患者可在训练后重新分配运动优先级。