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

Friday, April 19, 2019

Decoding the DLB Diagnostic Criteria, #3: Biomarkers

This series of blogs will attempt to decode the scientific language used to write the latest DLB diagnostic criteria and come up with a plainer version. If you haven't read the previous blogs, please go back and read them before you read more.

A biomarker is a fancy word used to describe a something measurable that can indicate the presence and severity of whatever you are testing for. We are all familiar with blood, urine and saliva tests. These are all used to test for biomarkers for a variety of conditions from pregnancy to strep throat to HIV and much more.

Presently, biomarkers are mainly used for confirming a diagnosis. However, they are the hope of the future. They can reach inside cells to fine minute, early signs of a disease well before there are symptoms, and before it grows too big to eliminate. Many people are now living healthy lives after being treated for a cancer that was found while it was still small enough to treat successfully. Until recently, that was not possible with neurological diseases like DLB. One had to wait for the symptoms to show up to know it was present--and by then the disease is so entrenched that one can do little but treat the symptoms. However, researchers can now focus on finding ways to stop it from growing.

But that is for tomorrow. Today, biomarkers help to diagnose DLB by signaling the presence of Lewy bodies in a tested item and providing a measurement of how plentiful they are--or of the damage they have done.

The criteria divides the biomarkers into "Indicative" (strong) and "Supportive" (helpful). Today's blog will discuss the three Indicative Biomarkers. Next week's blog will go on to discuss the Supportive ones.

The first two indicative biomarkers involve radio-active imaging. To go deep into the body tissues, they use a tiny amount of a radio-active tracer substance that goes to a targeted area and then normally exits the body within 48 hours.

1. Reduced dopamine transporter (DaT) uptake in basal ganglia demonstrated by SPECT or PET scans.
  • dopamine (DA): A brain chemical that is involved in the control of many tasks, including voluntary movement.
  • dopamine transporter (DaT): A protein that the body uses to move dopamine in and out of a cell.
  • uptake: the process of absorbing the dopamine so that it can be released on the other side of the cell.
  • basal ganglia: Area of the brain where movement, speech, posture and much more is regulated.
  • SPECT and PET scans: 3-D imaging technologies that measure the presence and progress of specific radio-active tracer substances inside body cells. See this article for a discussion about these two imaging processes.
What are they looking for? Signs of an inadequate amount of dopamine inside the cells.

Why? Lewy bodies are known to target and damage dopamine in these cells, which require the chemical to function properly.

In plain English: Lewy bodies are probably present if the scan shows signs of inadequate amounts of a dopamine in cells that control functions related to several LBD symptoms.
    2.  Abnormal (low uptake) 123iodineMIBG myocardial scintigraphy
    • Abnormal (low uptake): unusually low activity
    • 123iodineMIBG: a radio-active tracer substance
    • myocardial: of the heart muscle. From myo (muscle) and cardia (heart)
    • scintigraphy: 2-D imaging that measure the presence and progress of specific radio-active tracer substances inside body organs. (More about MIBG imaging)
    What are they looking for? Damage to nerves that control autonomic heart function.

    Why? Lewy bodies are known to damage the nerves that control autonomic functions such as heart beat and blood pressure. (More about LBD's autonomic symptoms.)

    In plain English: DLB is probable if an image of lower than normal tracer activity shows the type of heart muscle nerve damage connected with several DLB symptoms.
      3. Polysomographic confirmation of REM sleep without atonia (muscle relaxation).
      • poly (many) somno (sleep) graph (test): Sleep study that measures brain waves, blood oxygen level, heart rate, breathing, eye movements and leg movements.
      • Rapid Eye Movement (REM) sleep: The part of the sleep cycle when a person dreams.
      • atonia: Muscle relaxation. 
      What they are looking for? Evidence of muscle activity during dreams.

      Why? During REM sleep a person's muscles are normally so relaxed that they can't physically act out their dreams.

      In plain English: DLB is probably present if a sleep study confirms the presence of muscle activity during dream sequences.

      Or: DLB is probably present if a sleep study confirms the presence of REM sleep behavior disorder (RBD), a core DLB symptom. (more about RBD, also called Active Dreams)
        The above biomarkers provide objective tests for inadequate dopamine, a body chemical necessary for good cognition, heart nerve damage known to cause certain DLB-related autonomic dysfunctions, and Active Dreams, a core DLB symptom. None of the tests are considered 100% reliable alone but used with the more subjective clinical symptoms, they make a diagnosis about as accurate as it gets.

        Next week: Exploring the Supportive Biomarkers.

        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.
        Probable Diagnosis: almost--but not quite!-100% accurate.
        Possible diagnosis: Likely, but unproven without further evidence.
        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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