Fixation on Histology

Bielschowsky’s Silver Stain for Alzheimer’s


Bielschowsky StainMax Bielschowsky was a German neuropathologist at the beginning of the 20th century. Most of his life’s work was centered on the study of neurodegenerative diseases such as Alzheimer’s, Huntington’s, and Parkinson’s. In the aftermath of the first World War, he also studied neurological trauma caused by injury.

The Bielschowsky stain, which Max is credited with developing, is a type of silver stain which is used primarily to demonstrate nerve fibers, neurofibrillary tangles and senile plaques in the central nervous system. Sections are placed in silver nitrate, followed by a secondary impregnation by an ammoniacal silver solution. This process deposits silver on the neurofibrillary tangles and senile plaques which is then reduced by formaldehyde to stain the neurofibrils, senile plaques, axons, dendrites, and nerve bodies black, with a brown/yellow background.

Senile plaques, otherwise known as amyloid plaques, are deposits of the amyloid beta protein, that when present in large numbers, along with neurofibrillary tangles, which are made up of the protein tau, are characteristics indicating Alzheimer's disease, which is why the Bielschowsky stain is used in suspected Alzheimer’s cases.

Research into early diagnosis of Alzheimer’s disease has focused on ways to measure these levels of amyloid and tau proteins, either through analysis of cerebrospinal fluid, or molecular imaging of the brain. Positron emission tomography (PET) scans use a tracer to measure either detection of the amyloid proteins, tau proteins, or glucose, as dementia patients have exhibited low glucose use in the brain. These methods are not yet heavily used in the routine clinical setting, but primarily in research and selecting patients for clinical trials.

Learn more about the Bielschowsky stain in NSH’s HT Prep Course, which covers histology basics, such as staining, microtomy, processing, and fixation, to prepare you for the HT exam.