Silver staining of senile plaques and neurofibrillary tangles in paraffin sections. A simple and effective method.

A one-step silver staining method using a protective colloidal developer of gelatin and formic acid was originally established for demonstration of argyrophilic nucleolus organizer regions by controlled reduction of silver. We describe here a new application of this silver technique that can easily be performed to demonstrate senile plaques (SP) and neurofibrillary tangles (NFT) on paraffin sections. Preliminary results in ten cases of senile dementia of Alzheimer type and five cases of amyloid congophilic angiopathy showed a reliable demonstration of amyloid and neuritic type SP as well as NFT in all 15 cases. In addition, deposits of perivascular amyloid and areas of fibrillar amyloid, the diffuse type of senile plaques, were revealed. The success seems to depend particularly on the low concentration of formic acid in the developer, which might be the responsible agent for the careful revealing of buried argyrophilic structures in SP and NFT. The staining features were quite similar to those with anti-beta and anti-tau immunostaining. This result suggests a high specificity of this method for extracellular and intraneuronal cerebral amyloid. The detailed staining of delicate morphological structures points to a high sensitivity for cerebral amyloids, senile plaques and neurofibrillary tangles, respectively, by this simple and inexpensive method.