Neuropathology of Alzheimer's Disease

Gross Brain Changes

The following are the gross changes in the brains of people with Alzheimer’s disease:

1. Reduced weight of the brain
2. Reduced cortical volume
3. Dilated ventricles
4. Deepening of sulci

Magnetic Resonance Imaging

On magnetic resonance imaging, the diagnostically most important finding is atrophy, especially of the medial temporal lobe. It affects the entorhinal cortex the earliest but then it spreads to other regions of the temporal lobe and limbic lobe for example hippocampus, amygdala, and parahippocampus. Later, the pathology extends to the parietal lobe and eventually causes global atrophy. It spares frontal lobes until the late stage. The progression of atrophy occurs in a similar pattern as the progression of neuropathology.

Dilated ventricles can show global atrophy, but the most reliable method is a direct measurement of volume. Expansion of the fissures is the indirect, and less reliable way to measure the atrophy. For Alzheimer’s disease, fissures/sulci in the temporal lobe and parietal lobe are more important.

>> Parietal atrophy relates to the early onset subtype of Alzheimer’s Dementia.

References

1. Johnson, K. A., Fox, N. C., Sperling, R. A., & Klunk, W. E. (2012). Brain imaging in Alzheimer disease. Cold Spring Harbor perspectives in medicine, 2(4), a006213. doi:10.1101/cshperspect.a006213
2. Alzheimer disease | Radiology Reference Article | Radiopaedia.org. (n.d.). Retrieved January 17, 2020, from https://radiopaedia.org/articles/alzheimer-disease-1