Severity of Lewy body pathology in the brain

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.”

A Lewy body is an abnormal clump of alpha-synuclein protein.  These clumps were described by Dr. Frederic Lewy, a neurologist.

Lewy bodies are present in the brains of those with Parkinson’s Disease and Lewy Body Dementia.  It can be somewhat of a fine line to determine if someone has Parkinson’s Disease or Lewy Body Dementia because both disorders include Lewy bodies in the brain.  Neuropathologists are guided by WHERE in the brain the Lewy bodies are located in order to make a diagnosis.

Most of the neuropathology reports I read are from the Mayo Clinic in Jacksonville.  The neuropathologist there, Dr. Dennis Dickson, considers four levels of Lewy Body Disease severity:

* incidental
* brainstem
* transitional
* diffuse

Other brain banks occasionally call “diffuse Lewy body disease” something like “neocortical Lewy body disease.”

“Incidental” means that there are a small number of Lewy bodies in the brain and these are largely irrelevant.  There are no clinical symptoms.  Something like 10% of neurologically normal people are found to have had an incidental level of Lewy bodies in the brain.

“Brainstem” means that the Lewy bodies are in the brainstem.  A diagnosis of “brainstem Lewy body disease” is basically Parkinson’s Disease.

Let’s skip to “diffuse.”  A diagnosis of “diffuse Lewy body disease” means that the Lewy bodies are diffuse throughout the brain — even in the cortex of the brain.  Generally, it’s appropriate to say that someone with a DLBD diagnosis had Lewy Body Dementia, which means either Parkinson’s Disease Dementia or Dementia with Lewy Bodies.

In between “brainstem” and “diffuse” is transitional. This is an intermediate stage of Lewy body disease where the Lewy bodies are outside of the brainstem but not diffuse throughout the brain.  Some brain banks use the term “limbic” rather than “transitional” to refer to the fact that the Lewy bodies are in the limbic system of the brain.  Often those with TLBD had Lewy Body Dementia as well. Perhaps dementia symptoms were not as severe as someone with DLBD.

Interestingly, neuropathologists don’t say that someone had Lewy Body Dementia. 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.”  This means that Lewy Body Dementia is a clinical diagnosis — not a pathological one.

Here’s a related post on the topic of “likelihood” of having dementia with Lewy bodies:

Let me know if you have questions!