The Whitworths of Arizona, bringing science to you in everyday language.

Friday, April 19, 2019

Decoding the DLB Diagnostic Criteria: #4, More Biomarkers

The 2017 diagnostic criteria for dementia with Lewy bodies (DLB) is important for care partners to know but this part of it especially is written in scientific language that is difficult for even a well-educated person to understand. This series of blogs attempts some decoding.

Last week introduced a two-part biomarker section and the three indicative biomarkers. This week's blog presents the three suggestive biomarkers. If you haven't read the previous blogs in this series, please go back and read them now so that you will better understand this one.

Supportive biomarkers are signs indicating the presence and intensity of DLB that cannot stand alone but can support a diagnosis based on other symptoms and biomarkers.

Supportive Biomarker 1. Relative preservation of medial temporal lobe structures on CT/MRI scan.
  • relative preservation: maintenance of function in relation to the norm
  • medial temporal lobe: The part of the brain responsible for memory of facts and events.
  • CT/MRI scans: Two types of 2-D scans of organ tissues.
What are they testing for? The amount of shrinkage in a part of the brain involved with memory.

Why? Shrinkage of this area is significantly related to Alzheimer's, but not to DLB.

In plain English: Little shrinkage of the area of the brain involved with memory of facts and events supports a DLB diagnosis.

Supportive Biomarker 2.  Generalized low uptake on SPECT/PET profusion/metabolism scan with reduced occipital activity +/- the cingulate island sign on FDG-PET imaging.

Let's divide this one into two parts:

Supportive Biomarker 2a. Generalized low uptake on SPECT/PET profusion/metabolism scan with reduced occipital activity
posterier cingulate cortex
location of  the posterier
cingulate cortex
  • Generalized low uptake: All-around low activity
  • SPECT/PET scans: 3D scans using radio-active tracers.
  • Profusion/metabolism scan: scan for brain activity
  • Occipital (lobe): an area at the back of the brain.
What are they looking for? Low levels of activity in the occipital lobe.

Why? This area of the brain controls visual functions related to DLB symptoms, including the core symptom of visual hallucinations. It is usually less damaged by Alzheimer's.

Supportive Biomarker 2b. The cingulate island sign on FDG-PET imaging may or may not accompany 2a.
  • FDG: A radio-active tracer used with PET scanning.
  • Cingulate island sign: a finding of preserved metabolism in the posterior cingulate cortex
  • Preserved metabolism: normal activity
  • Posterior cingulate cortex: An area deep in the back of the brain.
What are they looking for? Fairly normal levels of activity in an area of the brain ordinarily damaged by Alzheimer's.

Why? Brain damage in this area is common with Alzheimer's. The more normal brain activity called "cingulate island sign" is usually present with DLB.

2a and 2b together in plain English: A scan that shows decreased brain activity in the occipital cortex supports a DLB vs. a Alzheimer's diagnosis, as does the presence of the cingulate island sign.

Supportive Biomarker 3. Prominent posterior slow wave activity on EEG with periodic fluctuations in the pre-alpha/theta range.
  • EEG: (Electroencephalogram): measures electrical waves of brain activity through the scalp.
  • posterior slow-wave activity: Slower than normal brain wave activity.
  • periodic fluctuations: periods of changes in wave activity.
  • the pre-alpha/theta range: Alpha waves occur when a person is awake and alert. Theta waves occur during relaxation and light sleep. (I could not find a definition for "pre-alpha/theta range." Help invited!)
What are they looking for? Slow brain activity with periodic episodes of higher functioning.

Why? Cognitive fluctuations are common with DLB but not with Alzheimer's.

In plain English: An EEG that shows slow cognitive activity with periods of an increased level of functioning is supportive of a diagnosis of DLB vs. Alzheimer's.

Next week: The "clinical features" or symptoms.

LBD is an umbrella term for all Lewy body diseases and starts with an L for Lewy.
DLB is for Dementia with Lewy bodies and starts with a D for the way the disease starts.
PDD is for Parkinson's disease with dementia and starts with a P for the way that disease starts.
Biomarker: Something measurable that can indicate the presence and severity of whatever you are testing for.
Indicative: A strong sign.
Supportive: A weaker sign that can still be helpful.
Radio-active imaging: An imaging process that uses a radio-active tracer.
Radio-active tracer: biomarker that can enter the tissues or cells of the body.
Uptake: The process of absorbing a substance so that it can be released on the other side of the cell.

For more information about Lewy body disorders, read our books:
A Caregivers’ Guide to Lewy Body Dementia
Managing Cognitive Issues in Parkinson's and Lewy Body Dementia
Responsive Dementia Care: Fewer Behaviors Fewer Drugs
Riding A Roller Coaster with Lewy Body Dementia: A Manual for Staff

Helen and James Whitworth are not doctors, lawyers or social workers. As informed caregivers, they share the information here for educational purposes only. It should never be used instead of a professional's advice.

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