From micrographia to Parkinson's disease dysgraphia

Abstract

Micrographia, an abnormal reduction in writing size, is a specific behavioral deficit associated with Parkinson's disease (PD). In recent years, the availability of graphic tablets has made it possible to study micrographia in unprecedented detail. Consequently, a growing number of studies show that PD patients also exhibit impaired handwriting kinematics. Is micrographia still the most characteristic feature of PD-related handwriting deficits? To answer this question, we identified studies that investigated handwriting in PD, either with conventional pencil-and-paper measures or with graphic tablets, and we reported their findings on key spatiotemporal and kinematic variables. We found that kinematic variables (velocity, fluency) differentiate better between control participants and PD patients, and between off- and on-treatment PD patients, than the traditional measure of static writing size. Although reduced writing size is an important feature of PD handwriting, the deficit is not restricted to micrographia stricto sensu. Therefore, we propose the term PD dysgraphia, which encompasses all deficits characteristic of Parkinsonian handwriting. We conclude that the computerized analysis of handwriting movements is a simple and useful tool that can contribute to both diagnosis and follow-up of PD.

Handwriting as a Marker for PD Progression: A Shift in Paradigm

“…This large range mainly results from the number of patients studied, the heterogeneity of symptoms and the nature of the analyses (quantitative vs self-questionnaires). In fact, according to the published studies, it should be noted that less than 50% of patients studied presented micrographia [14].…”

“…Similarly, for writing duration, 56% failed to demonstrate any significant difference between patients and age-matched controls [14]. However, the comparisons of kinematic variables (velocity, fluency) between control subjects and PD patients, as well as between treatment states (with and without medication), were much more distinguishable.…”

“…Indeed, based on studies carried out during the last decade, we proposed that four main variables are of crucial interest for analysis of handwriting impairment: size, duration, speed and fluency [15]. More recently, from an exhaustive identification of the studies investigating the impact of PD on handwriting, we questioned the meaning of micrographia in PD and the relevance of continuing to use this term in light of the findings raised by graphics tablet evaluations [14].…”

“…may affect the handwriting kinematics without necessarily affecting its size. Second, it implies that dynamical and kinematical variables are more suited for the diagnosis and follow-up of PD, or for e valuating the efficiency of a given treatment" [14].…”

“…If we consider dysgraphia in PD from this point of view, we reach the following conclusions: handwriting impairment was found to be positively correlated with an accurate diagnosis of PD [17,18]; correlations between handwriting variables and clinical evaluations in PD patients (motor part of the Unified Parkinson's Disease Rating Scale [19]) were found in several studies (e.g., [9,12]); changes in handwriting increase with PD progression [7]; there is still a need to confirm the preclinical status of handwriting impairment; many studies led by experts have specifically targeted an understanding of handwriting impairment in PD (for a review, see [14,20]). In addition, it has been reported that short and routine writing tasks based on kinematics analyses could help to distinguish PD patients from controls [7].…”