[A Skilled Typist with Typing Disorder Following Resection of a Left Frontal Lobe Tumor]

We reported a male who showed typing disorders after resection of a tumor in the left posterior superior and middle frontal gyri. He was a right-handed Japanese in his 50s and was good at touch typing as a system engineer. After the tumor resection, he presented typing errors and slightly impaired dexterity of his right fingers. The results of neuropsychological examinations indicated that his typing impairment was not due to aphasia or agraphia of kana letters (Japanese syllabogram). Typing errors were classified into adjacent key, non-adjacent key, omission, and insertion errors. Adjacent key, omission, and insertion errors were commonly found in both words and non-words. Adjacent key errors appeared more frequently in the right hand than the left-hand assigned keys, which may be explained by impaired dexterity of the right fingers associated with the left frontal lesion. Non-adjacent key errors were found exclusively for words and more frequently with the left hand than with the right hand. We consider that the patient's left frontal lesion may have impaired the motor engrams of word typing or its output process necessary to type individual words as a programmed series of pushing keys. (Received November 2, 2018; Accepted July 16, 2019; Published October 1, 2019).