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Standardized handwriting provides quantitative measures to assess bradykinesia, tremor and micrographia in Parkinson's disease

Smits, E. J. and Tolonen, A. and Cluitmans, L. and van Gils, M. and Conway, B. A. and Zietsma, R. C. and Maurits, N. M. (2012) Standardized handwriting provides quantitative measures to assess bradykinesia, tremor and micrographia in Parkinson's disease. Movement Disorders, 27 (S1). S213-S213. ISSN 0885-3185

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Abstract

To assess whether standardized handwriting can provide quantitative measures to distinguish patients diagnosed with Parkinson's disease (PD) from healthy controls (HC). Early symptoms of PD are often wrongly diagnosed by ascribing the signs of the disability to normal aging. Current diagnostic methods are based on a clinical neurological investigation and the clinician's subjective interpretation of the patients' performance on writing and daily living tasks, but this interpretation is not objective. A method that offers objective measures of the clinical symptoms of PD is required for (early) diagnosis and to monitor the course of the disease. Ten PD patients and ten healthy controls were included. The PD patients were tested after overnight withdrawal of their anti-Parkinsonian medication. The participants were instructed to perform circle, spiral and cross drawing and 'elelelel' and sentence writing. The tasks were executed with a pen whose pen-tip trajectories were recorded. The data was analyzed to quantify differences in writing production between PD patients and HC. Movement time and velocity were calculated using the position of the pen-tip to detect bradykinesia. Frequency analysis was performed to detect a rest or action-tremor and the size of handwriting was investigated to detect micrographia. The PD (mean age 69.0 years) and HC group (mean age 68.1 years) were gender matched (6 male) and the mean disease duration of the PD group was 4.4 years. Movement time and velocity in all tasks were highly sensitive (ranging from 0.7 to 0.8) and specific (ranging from 0.8 to 0.9) to PD presence, reflecting bradykinesia in this group. Micrographia was reflected particularly in the width of the letter 'e' in the 'elelelel' task (sensitivity: 0.9, specificity: 0.9). The presence of a tremor was confirmed by frequency analysis in all three patients who suffered from rest tremor. This study shows that standardized handwriting can provide objective measures for the assessment of bradykinesia, tremor and micrographia to distinguish PD patients in a relatively early stage of the disease from healthy controls. Therefore, these measures could be useful in clinical settings for (early) PD diagnosis and to monitor disease progression.