AN IMMUNOHISTOCHEMICAL STUDY OF NEUROFIBRILLARY TANGLE FORMATION IN POST-ENCEPHALITIC PARKINSONISM

Neurofibrillary tangle (NFT) formation is a feature of postencephaliti c Parkinsonism (PEP) and Alzheimer's disease (AD). Tangle formation ha s been compared immunohistochemically in these 2 conditions. Staining patterns for tau protein, ubiquitin and beta/A4 amyloid protein were s tudied in frontal lobe, hippocampus, and midbrain in 2 classical cases of PEP, 2 cases of AD and 2 controls matched for age and sex. NFTs we re present in all cases, but with varying frequency: all tangles were tau-positive and many were ubiquitinated. In the frontal cortex and hi ppocampus, irrespective of the case category, tangle formation was ass ociated with beta/A4 amyloid deposition. A similar association was pre sent in the 2 AD cases in the midbrain. However, in PEP tangle formati on in the midbrain was not associated with adjacent beta/A4 amyloid de position. This finding raises the possibility that the pathogenetic me chanism of tangle formation in PEP is different from that of AD, altho ugh the final cellular morphological expression of abnormality in both conditions is similar.