Abnormal tau deposition in neurons, but not in glial cells in the cerebral tissue surrounding arteriovenous malformation.

We report an autopsy case of arteriovenous malformation (AVM) of the right frontal lobe in a 50-year-old man, in whom post mortem examination revealed massive tau deposition in the affected cerebral cortex. The patient was diagnosed as having AVM at the age of 21 years, and died of unknown cause at the age of 50 years. Immunostaining with anti-phosphorylated tau antibody (AT8) revealed many NFTs and neuropil threads, but not glial tau accumulation, in the right frontal cortex surrounding the AVM. The NFTs and neuropil threads contained both 3-repeat and 4-repeat tau. Ultrastructurally, the NFTs consisted of paired helical filaments. In the other brain areas, a few NFTs were found in the parahippocampal gyrus. There was no amyloid deposition in the brain. A variety of disease conditions, including brain tumor, viral encephalitis, angioma and cervical spondylotic myelopathy, have been reported to show Alzheimer-type NFTs. The present findings indicate that abnormal tau deposition can occur in neurons, but not in glial cells, of the affected cerebral cortex surrounding AVM.