[Visual hallucination in the hemianopic field caused by dural arteriovenous malformation].

We presented a 65-year-old man with the right occipital dural arteriovenous malformation (AVM) who first experienced photopsia in his left inferior quadrantanopic field and then developed formed hallucinations 8 days later. His visual hallucinations disappeared with saccadic eye movements. EEG showed no epileptic discharge. MRI revealed hyperintensity in the right medial occipital lobe on proton density image. 123I-IMP SPECT during the hallucinations revealed decrease of regional cerebral blood flow (r-CBF) not only in the right medial occipital lobe but also in the right lateral occipital and in the right medial temporal lobe. Both left inferior quadrantanopia and visual hallucinations disappeared following the treatment of the dural AVM by transarterial embolizations. Because the lesion on MRI improved after the treatment, we considered that the lesion was brain edema, not infarction. Additionally decreased r-CBF in the temporo-occipital lesion on SPECT improved after the treatment, we emphasized the role of the temporo-occipital lesion as the cause of visual hallucinations in the hemianopic field.