PubMed · 1922836
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J C Horton, W F Hoyt. 1991. Alexia without agraphia.. https://doi.org/10.1212/wnl.41.10.1708-d
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We examined a drawing ability in a case with pure agraphia. The patient, having lesions in the left middle frontal gyrus and inferior parietal lobule, could not write in both dictation and spontaneous writing tasks, with the ability to copy letters being well spared. Correspondingly, he showed a deficit of spontaneous drawing, with the ability to copy complex figures being well spared. These findings suggest that he could have an impairment of retrieving visual image, not restricted to letter image. Although some previous cases with pure agraphia were attributed to an impairment of retrieving visual letter image, drawing ability which seemed to be related to retrieving visual image had not been investigated. In the present case, disability of both writing and drawing could be attributed to a common mechanism, that was an impairment of retrieving visual image. In addition, the patient did not show a significant difference between the performance on Kana writing and on Kanji writing. But it has been said that an impairment of retrieving visual letter image could be related to a deficit of Kanji writing more than of Kana writing. Then, it could be assumed that the mechanism of Kana writing involved not only the pathway depending on graphical motor pattern but one depending on visual image.
A strongly right-handed Japanese man showed an unusual writing disorder associated with Broca-type aphasia after suffering a right hemispheric infarction. Writing with his right hand produced a fluent output in contrast to his nonfluent speech. The patient's agraphia disproportionately affected the writing of kana (Japanese syllabograms), leaving relatively intact the writing of kanji (Japanese ideograms). His kana agraphia, consisting of substitutions, intrusions, transpositions, and deletions, became apparent as the number of syllables in target words increased. Quantitative analysis of the substitutions in terms of their phonological similarity to the target revealed that most of the substitutions were phonologically dissimilar. Those errors were distributed almost identically for familiar and novel words. Moreover, the errors were observed asymmetrically across the target: more errors occurred near the end than at the beginning of a word. The kana agraphia in association with fluent writing output resulted in kana jargonagraphia. These observations suggest that our patient's selective kana jargonagraphia is best explained by selective damage to the hypothesized kana graphemic buffer and by disinhibition of the motor engrams of writing behavior, both of which resulted from right hemispheric damage.