Agraphia due to the left parietal lobe dysfunction is a condition characterized by various symptoms, including distortion of character morphology, errors in stroke order, and impaired character recall. These errors can differ depending on the writing system, which differs across languages; for example, complex Chinese characters in Japanese and Chinese require visuospatial processing for accurate writing. Despite these observations, the establishment of clear and consistent classification criteria for these errors remains a challenge. In this study, the error response classification for Chinese character in degenerative diseases, proposed by Tee et al. (2022), was applied to a Japanese case of agraphia caused by a focal left parietal lobe lesion. Our aim was to evaluate the usefulness of the assessment and to investigate the underlying mechanisms of agraphia caused by damage to the left parietal lobe. The patient was a right-handed male aged in his 70s who presented with agraphia due to a brain tumour on the left parietal lobe. The patient exhibited characteristics of apraxic agraphia, such as distorted character shapes, disorder of sequencing writing strokes, and repeated self-corrections, as well as a characteristic of pure agraphia, namely the inability to recall character. The analysis revealed that in the early stages, "stroke errors", characterized by distorted character shapes, were highly prevalent, clearly indicating the features of apraxic agraphia. However, as the patient's condition improved, the frequency of "stroke errors" decreased, while "radical errors", which involve substituting or omitting parts of a character, and "blank responses", typically associated with pure agraphia, became more prominent. These results suggest that the apraxic agraphia, which was noticeable in the early stages, improved significantly over time. This classification method proved beneficial in comprehending the intricacies of the errors observed in this case. However, it was deemed essential to augment the prevailing cognitive model to elucidate the underlying mechanisms of apraxic agraphia caused by focal damage, particularly to the left parietal lobe.
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