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This episode of SciShow is brought to you in partnership with Gates Notes.
Head to Gatesnotes.com to learn more about some of the latest breakthroughs
in creating reliable, affordable, and accessible Alzheimer’s Diagnostics.
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Detecting Alzheimer’s Disease early on can be a huge challenge.
But it’s crucial to helping patients maintain a
higher quality of life for a longer period of time.
You might already know that Alzheimer’s is a devastating form of dementia,
it causes cognitive decline and memory loss that interferes with a person's daily life.
But there’s a small group of brain cells that starts changing an average of
25 years before that cognitive decline starts.
And it could be a key to catching Alzheimer’s decades earlier.
One of the hallmarks of Alzheimer’s Disease is
the accumulation of tau proteins in the brain.
Tau proteins help healthy brains develop their cellular structure.
But in Alzheimer’s brains, they seem to change in
a way that makes them harmful rather than helpful.
There’s a strong correlation between tau accumulation
in the brain and cognitive impairment.
While we don’t exactly know how, tau sometimes clumps up within neurons
to make a toxic tangle that can damage connections and destroy brain cells.
Tangles got their name because they literally look like
something is tangled around your brain cells.
And they’re found in the memory center, or hippocampus, of many aging brains.
But previous studies have only found them widespread outside the hippocampus
in the brains of patients with dementia.
Scientists have compared the post-mortem brains of people who were diagnosed
with Alzheimer’s and people who weren’t and found that the brains of
those with Alzheimer’s have fewer cells and are smaller overall.
The tangles kill off more and more brain cells as Alzheimer’s progresses.
So these tangles across the brain are bad news.
But if we find them early, it’s possible that people could start preventative treatment
before cognitive decline, rather than after it’s too late to be effective.
One of the first places that tangles form outside of the hippocampus is
a small group of cells called the locus coeruleus, located in the brainstem,
at the back of the brain where it meets the spine.
Tangles can start accumulating there about 25 years
before cognitive decline starts.
And the locus coeruleus is connected to pretty much the entire brain.
It’s involved in regulating arousal and memory, among other things, by transporting
the chemical norepinephrine to parts of the brain that control those behaviors.
These are all processes that people with Alzheimer’s have difficulty with.
As Alzheimer’s continues progressing, the locus coeruleus starts getting smaller
by both volume and cell number.
And this also affects the amount of norepinephrine
in the brain and the central nervous system.
In a 2017 study, scientists compared the brains of individuals with no symptoms
and those with mild cognitive impairment and found that,
in the group with mild cognitive impairment, the locus coeruleus was 30% smaller.
Then stepping that up from mild cognitive impairment to moderate
Alzheimer’s symptoms, the locus coeruleus was an additional 25% smaller.
But importantly, the locus coeruleus appears to start to get smaller
even before a person usually gets an Alzheimer’s diagnosis.
This means that the locus coeruleus might be a good place to keep an eye on
if someone is at higher risk for developing Alzheimer’s.
So using brain imaging technologies, it could be possible to give people
regular check-ups to monitor locus coeruleus size
or norepinephrine concentration in the brain.
One technology that makes this possible is an MRI.
The locus coeruleus is a very small part of the brain,
so it can be hard to see in an MRI.
But MRIs that highlight the chemicals the
locus coeruleus makes would show where it is.
Another option is to get a PET scan.
This technology can highlight cells with a lot of something called NET,
which is the norepinephrine transporter and it’s found in high amounts
where there’s a lot of norepinephrine.
So a PET searching for NET could also monitor the locus coeruleus.
A sample of norepinephrine levels can also be taken from your plasma.
A 2020 study found that low levels of plasma norepinephrine
correlated with lower levels of tau in the brain.
They also found that these plasma levels correlated with
the mental state of the sampled Alzheimer’s patients.
This is just one study, and there’s definitely a lot more research that
needs to be done, but it’s a promising starting point.
If a professional sees a noticeable change in these characteristics,
it could be a flag to look deeper and consider starting treatments before
the tangles spread to other parts of the brain and cognition deteriorates.
Preventative medicine is so important in many aspects of human health.
And the earlier we are able to detect Alzheimer’s,
the better care we can provide for patients.
Learning more about the complex ways it changes
different parts of the brain can help get us closer to doing just that.
Thank you for watching!
And thank you to Gates Notes for sponsoring this episode of SciShow.
If you’re interested in learning more about the latest advancements
in Alzheimer’s Diagnostics testing, from a simple blood test being developed
in Sweden to highly sophisticated apps you might one day have access to
on your smartphone, head to GatesNotes.com or click the link in the description.
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