23. Senile plaques and neurofibrillar degeneration

Staining: Silver stain (Bielschowsky)

Overview

Organ: Brain, hippocampus

Description: The hippocampus is visible and that’s where the characteristic findings are visible on this slide.

Senile plaques are extracellular deposits of β-amyloid that are surrounded by silver-positive proteins. The amyloids themselves aren’t stained by silver and are therefore pale. These plaques are therefore visible as large black foci with a pale core. Neurofibrillary tangles are intracellular bundles of hyperphosphorylated tau. These tangles are stained by silver and causes the neurons to be stained black.

Diagnosis: Alzheimer disease (senile plaques, neurofibrillary tangles)

Senile plaques and amyloid cores

Risk factors:

• Genetic factors
• Down syndrome
• Lack of physical activity
• Traumatic brain injury
• Old age

Theory: Alzheimer’s disease most commonly affects the hippocampus first, and then the frontal and temporal lobes before it becomes a diffuse process. This slide is overstained, so the characteristic findings are therefore hard to distinguish from background noise.

These nerve cell bodies are stained black as they contain neurofibrillary tangles