Alzheimer’s Disease as a Capillary Dementia

Published in 1989 by Scheibel et al.

Apart from the presence of amyloid plaques and neurofibrillary tangles that typically identifies the presence of Alzheimer’s disease (AD), the small blood vessels around the outer layer of the brain also have a bumpy appearance. Also, the basement membrane which acts as a form of structural support for these small blood vessels become thickened.

Typically, a network of nerves known as the perivascular neural plexus surrounds blood vessels and helps with the regulation of the dilation and constriction of blood vessels for blood flow movement. In AD patients, these neural plexus is lost which is postulated to be the reason for the bumpy appearance of the blood vessel. The authors also stated that this neural plexus is responsible to protect the blood-brain barrier and when these neural plexus is lost, the blood vessels are not separated from the surrounding tissue which may further lead to the progression of the disease.

With the help of scanning of electron microscopy, we can visualize the changes that happen in small blood vessels from having a thin wall which contains endothelial lining, pericytes, basement membrane in control patients to a small blood vessels having thick walls.

Figure 1A and 1B shows the capillary image from the mid-brain of an healthy subject. The perivascular neural plexus is VERY obvious. In Figure 2A and 2B, it is again very obvious that perivascular neural plexus is missing. Yes, you are right. 2A and 2B is from an AD patient.

Finally, the authors suggest that the absence of the perivascular neural plexus in a certain region of the brain could indicate that the region is potentially impacted by Alzheimer's disease.