[Development of pure alexia due to a lesion in the left fusiform gyrus in a patient with hypertrophic pachymeningitis].

We present the case of a patient with pure alexia due to a restricted lesion in the left fusiform gyrus. A 59-year-old right-handed female, with a 7-year history of rheumatoid hypertrophic pachymeningitis suddenly developed reading and writing difficulties. Neuropsychological examinations revealed the presence of alexia for both Japanese kanji (morphograms) and kana (phonograms); mild agraphia predominantly for kanji; and word-finding difficulty. Brain magnetic resonance imaging (MRI) revealed a high signal intensity lesion in the left fusiform gyrus on fluid attenuated inversion recovery (FLAIR) images in addition to marked thickness of the left cerebellar tentorium on contrast-enhanced T1-weighted images. The abnormal intensity lesion in the left fusiform gyrus was recognized as representing a cerebral edematous change due to venous insufficiency associated with dural thickness. After high-dose methyl-prednisolone therapy, there was a rapid improvement in the reading and writing abilities of the patient, and 5 days later all the symptoms had disappeared. Three months later, a repeat MRI showed that the abnormal intensity lesion in the left fusiform gyrus had disappeared completely. The present case suggests that damage to the left fusiform gyrus alone can cause pure alexia and mild agraphia. Furthermore, this case raises the possibility that the fusiform gyrus is a part of the writing center.