A couple of posts ago, I mentioned that my father had both cerebral amyloid angiopathy (CAA) and Alzheimer's disease. This isn't unusual - one study estimates 25% of people with Alzheimer's have moderate to severe CAA.
It turns out that the protein in the deposits on CAA patients' blood vessel walls is closely related to the protein seen in the plaques associated with Alzheimer's. Researchers don't understand why excess levels of these proteins build up in some people's brains, or exactly what the connection is between CAA and Alzheimer's.
One recent study shows that a kind of CAA concentrated in small capillaries, rather than in larger blood vessels, is linked to Alzheimer's disease. But Dad's CAA was not concentrated in his capillaries. In fact it seems his CAA and Alzheimer's were not really connected. "The burden of CAA in the brain vastly exceeds that seen in even the most severe and advanced cases of AD [Alzheimer's disease], indicating that this is likely to have been an independent disease process," Dad's autopsy report says.
There's growing recognition that CAA can cause or contribute to dementia, as well as cause hemorrhagic strokes like the one my dad had. The fact that cerebral microbleeds, which can be caused by CAA, were common in Dutch memory clinic patients in a recent study seems to support this.
Whether or not CAA and Alzheimer's disease are evil twins, they were double trouble for Dad.