Objective: To investigate the role of brain dopamine function in writing and drawing micrographia of patients with parkinsonism.

Background: Micrographia, an abnormally small or progressively decreasing handwriting or drawing, is a common symptom in parkinsonism, but it may also occur in other neurodegenerative diseases [1]. The pathological mechanism of micrographia is poorly understood although it is likely to be related with dysfunctional basal ganglia motor circuits [2]. Levodopa improves micrographia, which suggests that dopaminergic modulation could be important. However, brain in vivo dopamine function has not previously been studied in relation to micrographia.

Method: Altogether 322 patients with tremor or parkinsonism underwent brain dopamine transporter (DAT) [123I]FP-CIT SPECT imaging for diagnostic purposes. Immediately before scanning, the patients provided writing and drawing samples. Detailed clinical examinations including MDS-UPDRS part III were performed. Striatal DAT binding was analyzed using semi-automated region of interest method. Associations between different types of micrographia and DAT binding were analyzed using linear regression models with and without covariates.

Results: There were significant associations between mean putamen DAT binding and both severity of progressive (B=-0.478 [-0.825, -0.130], p=0.007, n=310) and consistent writing micrographia (B=0.006 [0.002, 0,011], p=0.009, n=306). However, height of the drawing sample was not associated with mean putamen DAT binding (B=-0.001 [-0.005, 0.003] p=0.617, n=316). The relationship between DAT binding and writing micrographia remained significant when including age, sex, cognition, motor symptom duration and severity as covariates.

Conclusion: Striatal dopamine function is associated with writing but not drawing micrographia in patients with unclear parkinsonism or tremor. The observed association only with writing, without a similar relationship in drawing, suggests a specific interplay between dopamine and motor performance required in handwriting.

References: [1] Inzelberg R, Plotnik M, Harpaz NK, Flash T. Micrographia, much beyond the writer’s hand. Parkinsonism Relat Disord. 2016;26:1-9. [2] Wu T, Zhang J, Hallett M, Feng T, Hou Y, Chan P. Neural correlates underlying micrographia in Parkinson’s disease. Brain. 2016;139(Pt 1):144-60.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/striatal-dopaminergic-regulation-of-micrographia-in-parkinsonism/