Micrographia prevalent in Parkinson’s

Jul 19 2012

By Andrew Czyzewski

Around half of patients with Parkinson's disease (PD) display symptoms of micrographia, a case-control study shows.

Notably, micrographia correlated with disease severity, cognitive impairment, bradykinesia, and hypophonia "suggesting a possible overlap in their pathophysiology," report Aparna Shukla (University of Florida, Gainesville, USA) and colleagues in BMJ Open.

Micrographia has been defined as an impairment of a fine motor skill manifesting mainly as a progressive reduction in amplitude during a writing task. Micrographia can manifest in two dimensions; handwriting may decrease in amplitude across a single line or manifest as each line gets added with continued writing.

In questionnaire-based cross-sectional studies, the prevalence has ranged from as low as 9% to as high as 75%.

In the current study, the researchers used systematic clinical assessments to: identify the prevalence of micrographia in a large cohort; document the clinical profile of micrographia; and to determine if a correlation exists between micrographia, bradykinesia or hypophonia.

They enrolled 68 male patients with PD, aged an average of 72.3 years, from a movement disorders clinic located in a veterans administration medical centre. The team also enrolled controls matched for age, gender, and handedness for validation of handwriting test scores and decibel meter recordings.

Shukla et al report that 63.2% of the cohort reported symptoms of micrographia when interviewed, and in 50.0% of the patients proved to have micrographia when they undertook a handwriting test.

Micrographia was associated with bradykinesia and hypophonia determined by history and decibel meter recordings.

It also correlated significantly with disease severity defined by Hoehn and Yahr stage, motor impairment on the Unified Parkinson's Disease Rating Scale, and cognitive impairment determined by Mini-Mental State Examination, but not with disease duration.

Discussing the findings, Shukla et al speculate that the underlying mechanisms linking bradykinesia and hypophonia with micrographia could be inappropriate scaling of the dynamic muscle force to the movement parameters.

"Future studies of PD-related micrographia should be directed towards functional imaging and electrophysiological assessment of the cerebral cortex and its basal ganglia connections and the on/off effects of dopaminergic medications," they comment.

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