左前頭葉腫瘍摘出後にタイピング障害を呈した熟練タイピストの1例

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

左前頭葉腫瘍摘出術後にタイピング障害を呈した1例を報告した。失語症は軽微でかな文字失書はなく，両手のタイピング障害と右手の軽度巧緻運動障害を認めた。タイピングでは非隣接キーエラーを単語のみに認め，それは巧緻運動障害のない左手に多く生じた。このエラーの発現機序として，単語単位のタイピング運動記憶の出力過程の障害が想定され，左前頭葉損傷との関連が考えられた。一方，隣接キーエラーは単語と無意味語ともに右手に多く認め，左前頭葉損傷による右手の巧緻運動障害により生じたと考えられた。

Abstract

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)