Dystextia due to impairment in spatial operation on a smartphone: A case report.

Smartphone texting has become indispensable in modern life. Although dystextia (texting disability) has been reported, dystextia without aphasia or other cognitive impairment remains rare, and its pathophysiology is not fully understood. In Japanese text entry, the consonant is selected first on the screen, and the vowel is then determined by slide direction. Thus, accurate text input likely requires a sequence of processes, including segmentation of morae into consonants and vowels, followed by the spatial operation corresponding to each. Here, we report a patient with dystextia associated with impaired key-position and slide-direction processing. A 57-year-old right-handed Japanese woman developed difficulty with texting. Standard neuropsychological testing showed no aphasia, agraphia, or other cognitive impairment except for apraxia of speech and mild attention/executive dysfunction. Accordingly, dystextia was diagnosed. In addition, the patient had difficulty identifying keys corresponding to consonants and the slide direction corresponding to vowels. Magnetic resonance imaging showed a subcortical infarction in the left cerebral hemisphere. Single-photon emission tomography showed hypoperfusion, including in the left dorsolateral frontal lobe. The left frontal lobe is thought to contribute to spatial operations on digital devices. Therefore, diaschisis of the left dorsolateral frontal lobe secondary to the subcortical lesion may be associated with impairment of key-position and flick-direction processing, which may have contributed to dystextia in this patient.