credit: NeuroscienceNews
One of Brain Support Network’s mission is to help families with brain donation arrangements. We’ve seen lots of neuropathology reports come back with references to “Lewy body disease” and, occasionally, “Lewy body dementia.” Terms such as “low,” “intermediate,” and “high likelihood” are used. This post attempts to explain that terminology.
Most of the neuropathology reports I read are from the Mayo Clinic in Jacksonville. The neuropathologist there, Dr. Dennis Dickson, is one of the top in the world. He co-authored the diagnostic criteria for Dementia with Lewy Bodies. That criteria can be found in this important paper:
Neurology. 2005 Dec 27;65(12):1863-72.
Diagnosis and management of dementia with Lewy bodies: third report of the DLB Consortium.
McKeith IG, many others, and Consortium on DLB.
Interestingly, neuropathologists don’t say that someone had Lewy Body Dementia (or Dementia with Lewy Bodies) as that’s a clinical diagnosis, not a neuropathologic one.
It’s important to know that Lewy Body pathology and Alzheimer’s pathology typically co-occur in the brain of someone with Lewy body dementia. Curiously, for a neuropathologist to suggest someone had Lewy body dementia, the neuropathologist must consider the level of Alzheimer’s pathology in the brain!
A neuropathologist may say something like:
“Based on the clinical picture, the level of Lewy bodies, and the level of Alzheimer’s pathology, the likelihood [emphasis added] this donor had symptoms of Dementia with Lewy Bodies is high/intermediate/low.”
To make such a statement, neuropathologists rely on a chart, titled “Assessment of the likelihood that the pathologic findings are associated with a DLB clinical syndrome,” in that McKeith paper:
- On one axis is “Lewy body type pathology,” where the choices are Brainstem, Limbic (transitional), and Diffuse Neocortical.
- On the other axis is “Alzheimer’s type pathology,” where the choices are NIA-Reagan Low (Braak stage 0-2), NIA-Reagan Intermediate (Braak stage 3-4), and NIA-Reagan High (Braak stage 5-6).
If the Lewy body pathology is Limbic or Diffuse and the amount of Alzheimer’s pathology in the brain is low, the “likelihood that the pathologic findings are associated with a DLB clinical syndrome” are “high.” When we see this outcome, it’s very likely that, while alive, the person had a diagnosis of Lewy body dementia (which is PD Dementia or Dementia with Lewy bodies).
Conversely, if the LB pathology is Brainstem or Limbic and the amount of Alzheimer’s pathology in the brain is high, the “likelihood that the pathologic findings are associated with a DLB clinical syndrome” are “low.” When we see this outcome, it’s very likely that, while alive, the person had a diagnosis of Parkinson’s disease.
The “tricky” area is when the “likelihood” is “intermediate.” In these cases, I suggest families decide based upon the person’s symptoms whether they had “Lewy body dementia” or not.
My layperson explanation is that if the Alzheimer’s pathology is severe, the chances of Lewy body dementia symptoms revealing themselves are smaller than if the Alzheimer’s pathology is not as severe.
Here’s a related post about the severity of Lewy bodies in the brain that explains brainstem, limbic (transitional), and diffuse.
Let me know if you have questions!
Robin
Brain Support Network