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 various descriptions of “Lewy body disease” and the cover letters indicate the person had “Lewy body dementia.” Within the “comments” section of the reports terms such as “low,” “intermediate,” and “high” 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. They may say something like “based on the clinical picture, the level of Lewy bodies, and the level of Alzheimer’s pathology, the LIKELIHOOD this donor had Dementia with Lewy Bodies is high/intermediate/low.”
There’s a chart in the McKeith paper that neuropathologists rely on in making this statement. The table is titled “Assessment of the likelihood that the pathologic findings are associated with a DLB clinical syndrome.” 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.” 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.”
Here’s a related post about the severity of Lewy bodies in the brain that explains brainstem, limbic (transitional), and diffuse.
Typically, Lewy Body pathology and Alzheimer’s pathology co-occur in the brain of someone with Lewy body dementia. In my layperson’s mind, the low-intermediate-high language is basically a gauge to say which pathology is more important in terms of overall pathologies found in the brain — is it Lewy Body pathology or Alzheimer’s pathology?
Let me know if you have questions!