Handwriting patterns in Isolated Rapid Eye Movement Sleep Behaviour Disorder

BackgroundHandwriting changes, such as micrographia, are recognised as an early manifestation of Parkinsons disease (PD). Whilst isolated rapid eye movement sleep behaviour disorder (iRBD) is strongly associated with future PD diagnosis, changes in handwriting remain under-explored. ObjectiveTo assess the handwriting of people with iRBD and develop a rating scale for detection of early disease clinical hallmarks. MethodsThis is a cross-sectional study involving 33 people with polysomnography (PSG)- confirmed iRBD and 29 healthy controls. Participants copied a standard sentence using a pen and paper. A graphologist analysed each handwriting script blindly and designed a scale based on observed abnormal patterns which included: micrographia, sentence slope, hidden tremor, retracing, resting marks, irregular shape, excessive pen pressure, and inconsistent word spacing. Each item was scored 0/1 based on their absence/presence. Separately, three blinded movement disorders experts assessed the scripts based on their global clinical impression as well as using the developed rating scale. ResultsPeople with iRBD were slower to complete the task than controls (76.70s (SD = 30.39) vs 61s (SD = 10.71); p=0.004). Hidden tremor was the most common feature amongst the iRBD group (72.0% vs 34.5%; p=0.005), followed by sentence slope (60% vs 24% p=0.005) and pen pressure (48% vs 14%; p=0.006). Micrographia was equally observed in both groups (iRBD 45.4%, controls 41.4% p=0.801). Classification accuracy of the scale for iRBD was higher than expert global assessment (AUC 0.76 vs AUC 0.62, p = 0.029). ConclusionsWriting speed, tremor, pen pressure and sentence slope are handwriting features that warrant further investigation to define early patterns in people with iRBD.