Dysgraphia in Korean patients with Alzheimer's disease as a manifestation of bilateral hemispheric dysfunction.

BACKGROUND

In writing, linguistic (i.e., spelling) and nonlinguistic (i.e., arranging strokes or letters) functions are processed by the left and right hemispheres, respectively. The configuration of Korean alphabet, 'Hangul' invokes nonlinguistic, visuospatial functions that other writing systems use less extensively. Patients with Alzheimer's disease (AD) have bilateral involvement of temporoparietal-frontal areas that are responsible for processing language and visuospatial functions.

OBJECTIVES

The aim of this study was to examine the nature of Hangul writing dysfunction, which may be associated with bilateral hemispheric impairments in AD.

METHODS

A sample of 75 patients with AD and 20 healthy controls (HC) performed a Hangul writing task. Neuroimaging positron emission tomography (PET) data of 22 patients were utilized to measure the regional brain glucose metabolism associated with Hangul writing.

RESULTS

The writing performance of the AD group was significantly reduced and different types of errors were observed as the disease got worse. Glucose hypometabolism correlated with Hangul writing impairment was located in the right occipitotemporal lobe and left temporoparietal lobe.

CONCLUSIONS

The PET findings demonstrate that impairment in Hangul writing performance in Korean AD patients is closely related to a functional decline in both the right and left hemispheres. The study provides a unique contribution to the knowledge of dysgraphia in a non-alphabetical writing system as well as the underlying neuropathology of dysgraphic features in such languages.