Ballooned neurons in select neurodegenerative diseases contain phosphorylated neurofilament epitopes.

Ballooned neurons are histological features of several neurodegenerative diseases of the central nervous system. We describe the immunocytochemical staining of ballooned neurons in Pick's disease, unclassified dementia, corticonigral degeneration, pigment-spheroid degeneration and Alzheimer's disease. In all of these conditions the ballooned neurons contain phosphorylated epitopes recognized by monoclonal antibodies to neurofilaments, but not epitopes unique to Alzheimer neurofibrillary tangles and Pick bodies. The morphological features and immunohistochemical properties of ballooned neurons in these disorders bear resemblance to swollen neurons produced by neurotoxins that impair axoplasmic transport of neurofilaments. This finding, by analogy, suggests that impaired axoplasmic transport of neurofilaments may be a common mechanism in various dementing neurodegenerative diseases.