The fine structure of neurofibrillary tangles in a case of atypical presenile dementia.

The neurofibrillary tangles in a case of atypical presenile dementia were studied by electron microscopy. The tangles consisted of 2 types of tubule: one straight, measuring about 15--20 nm in width, the other twisted. Both types of tubule appeared separately in each neuron; however, occasionally twisted tubules seemed to be distributed among the straight tubules. The implications of these findings are briefly discussed.