Agraphia for Kana Predominance Induced by a Cerebral Infarction Involving the Left Middle Frontal Gyrus (Exner’s Area)

The foot of the left middle frontal gyrus has been considered as the site of graphemic motor image center since Sigmund Exner’s work in 1881. However, there have been only a few cases supporting the hypothesis. Recently, direct electrical stimulation and studies using functional MRI or PET have indicated the functional role of the area in handwriting. We herein report an ischemic stroke patient who showed apraxia of speech and agraphia. In her handwriting, kana (Japanese syllabograms) was predominantly disturbed compared with kanji (Japanese ideograms). Lesion analysis with MRI clearly showed the involvement of the middle part of the left precentral gyrus expanding to the caudal part of the middle frontal gyrus (rostral to the primary motor hand area). The former was considered to be responsible for her apraxia of speech, and the latter for her agraphia. In Japanese handwriting, “the writing center” of kana and that of kanji might be separate in the Exner’s area, as was in the case in left posteroinferior temporal lobe lesions.