Are PET Scans for Alzheimer’s Disease Accurate?

Hi everybody. Welcome back to the truth, lies

and Alzheimer's show. I'm Lisa Skinner, your host. Today, I

want to address a topic that has spawned a bit of confusion for

people in one of my previous episodes, I did tell you, and

this was a while ago that the only way that we have to

definitively and accurately diagnose Alzheimer's disease was

upon autopsy. And one of my listeners wrote in, and I want

to thank you for bringing this to my attention, because what he

said was, I believe PET scans have the ability to accurately

diagnose Alzheimer's disease now. So of course, I was freaked

out about that, because I always strive to bring everybody the

most accurate information that I can find, and I do spend a lot

of time staying on top of these things. But I thought, Okay,

well, maybe I missed something. So I went back and did more

extensive research on the diagnostic ability of PET scans,

so I could bring you the updated information that is the most

current and the most accurate that I could find, which was as

of this year. Now I probably hit about 10 different resources,

and they all said exactly the same thing, and these are all

scientific journal researches and websites like the lancet and

NIH plus a lot more, and they will be listed in the show notes

for you, but it's really interesting what I learned, and

I'm going to share that with you today. So what did I uncover?

How accurate is a PET scan for diagnosing Alzheimer's disease

accurately, conclusively and definitively. Well, if you have

been experiencing notable changes in your memory or

thinking, your physician may recommend a PET scan to help

determine if you may have signs of Alzheimer's disease, an

amyloid PET scan is helpful. Is helpful in narrowing down and

ruling out causes of concern for brain changes, and can also help

identify what that source may be. So what exactly is a PET

scan, and what does it measure in our brain? A PET scan is an

imaging test that measures the levels of amyloid plaques in our

brains. And during a PET scan, a radioactive tracer which

attaches to amyloid plaques is given to the patient

intravenously. This tracer reveals the level of

accumulation of this protein in amyloid plaques that may be

accumulating in your brain. The amount and distribution of these

plaques are thought to be indicators that Alzheimer's

disease may be present, although they are not in themselves, a

definitive diagnosis. How do these plaques relate to

Alzheimer's disease, the characteristics of dementia can

include changes in thinking, memory and behavior. While

strong parallels do exist among dementia, not all types of

dementia are the same in origin or prognosis. One distinction

that is found in Alzheimer's is the presence of these amyloid

plaques buildup in our brains. A person who demonstrates

behaviors associated with dementia, who also has amyloid

buildup is most likely living with Alzheimer's is an amyloid

PET scan and accurate test for determining Alzheimer's disease.

Well, it actually can be between 58 and 90% accurate for

detecting the location. And extent of the amyloid plaques in

the brain. How your provider uses the PET scan along with

other tests for Alzheimer's, is what I'm going to talk about

next. So if your physician wants to investigate possible

dementia, an amyloid PET scan can help in ruling out

Alzheimer's disease if no plaques are present now,

additional scans, biomarker assessments, cognitive

evaluations and health history work to provide a clearer

diagnosis as part of this broad approach, the presence or

absence of these plaques is one piece of information

contributing to a diagnosis. It's a huge puzzle that you need

to have all the pieces and figure out how they fit

together. How will your health care provider use your pet scan

results to diagnose your condition? Well, your pet scan

results will indicate whether or not these plaques are present in

your brain, and while these plaques are associated with

Alzheimer's, a diagnosis is not made on the existence of these

plaques alone, and I think this is where it has become confusing

for everybody. So why did your provider even order these

cognitive tests and memory tests in addition to the PET scan?

Well, the PET scan, in and of itself, does not provide a

diagnosis of Alzheimer's disease or other dementia, while it is a

valuable tool in detecting the presence of amyloid plaques, it

is not a conclusive way to diagnose Alzheimer's disease. So

this is how MRI scans and CT scans can complement the PET

scan for diagnosing Alzheimer's. And while the amyloid PET scan

is considered a highly specific tool that can detect the

presence, location and extent of these plaques, it does not

reveal other information about the brain that may be valuable

in formulating a diagnosis.

Additional neuroimaging scans, such as the MRI scan, provide

detailed imagery about the brain's anatomy and health,

which a PET scan does not these scans can help identify atrophy

in the brain or shrinkage, and can also help identify other

causes of symptoms that may mimic dementia, like bleeding in

the brain or the presence of a tumor, the combination of these

imaging scans provides a more comprehensive picture of brain

activity and health, allowing for a more accurate explanation

of symptoms. I'm going to reveal how these PET scans can help

identify Alzheimer's disease in its early stages. Identifying

any dementia can be an involved process, as you've probably

picked up on now of diagnostic tools and assessments. It's a

long, complicated, drawn out process, and the PET scan is

just one tool that can help focus a potential diagnosis by

revealing the presence or absence of the plaques in the

brain. Plaques can be an indicator of potential

Alzheimer's disease even before symptoms become apparent the

presence or absence of amyloid plaques in the early stages of

dementia can help shape diagnosis and treatment for

Alzheimer's or for one of the other cognitive brain diseases

that causes dementia. How do this? Does the PET scan detect

changes in the brain before the symptoms even appear? Well, the

PET scan can identify the presence of amyloid plaques in

individuals who may not be presenting with any symptoms of

dementia. Dementia, and this is called the pre clinical

Alzheimer's disease phase. It can be helpful in watching for

developing symptoms that may appear later on, as well as

consideration for early treatments that may delay the

onset and severity of symptoms. How does this PET scan help

identify MCI or mild cognitive impairment that has not yet

progressed to dementia? Well, mild cognitive impairment or MCI

is a noticeable change in cognitive ability that does not

yet interfere significantly with life's activities. An amyloid

PET scan is helpful for individuals who may have mild

cognitive impairment, as it will reflect the presence or absence

of the amyloid plaques in the brain, which can be a helpful

guide to a treatment plan. If no plaques are found, other causes

of MCI, like a vascular condition, sleep issues or side

effects of medications, can be investigated if the plaques are

found, then the likelihood of Alzheimer's disease as the

source of MCI does increase, and your physician will help you to

consider what the treatment options for your specific

situation could be. So how does early detection of these plaques

in your brain help guide treatment and care decisions?

Early detection of the plaques helps your health care provider

understand more about the causes and prognosis of the cognitive

changes if the plaques are found, the likelihood of

Alzheimer's disease being present and progressing does

increase, but it doesn't necessarily mean that that's

100% what it is. So knowing this and taking appropriate

interventions and early treatment to delay the onset of

more significant symptoms can then take place. How does the

PET scan results fit into the diagnostic process? Well, the

PET scan helps narrow the possible reasons that you may be

experiencing your cognitive decline. If the plaques show up

on your results, then the likelihood of Alzheimer's

disease increases, and your provider may order further

imaging in conjunction with the PET scan, if no plaques are

found on your results, then other types of dementia or

underlying conditions are likely to be present, and then your

physician will develop an appropriate care plan for You.

What can you expect from your pet scan results? The PET scan

results are currently the best tool to find out if these

plaques are present in your brain. The detection of these

plaques can help guide interventions, treatment and

care by your physician. If no plaques are found on your

results, this result will also help guide your physician in

choices for intervention, treatment and a care plan

designed specifically for you. If your results show amyloid

plaques in your brain? Does it mean you have Alzheimer's

disease? I'm going to answer this question again, because it

really needs an emphasis. The presence of amyloid plaques is

not in itself a diagnosis of Alzheimer's disease, if your

provider finds any plaques, then additional comprehensive medical

and cognitive assessments will help form a more accurate

diagnosis that can then be addressed with appropriate

medical care and lifestyle interventions. Early detection

of the plaques helps shape a possible prognosis that can only

be confirmed with diagnostic tools like a physical exam,

extensive cognitive assessments, and then integrate. Getting your

personal medical history into the mix. So here are some

commonly asked questions pertaining to PET scans. What is

it and how does it measure in the brain? Well, it's again, a

scan that provides an imaging test that measures the buildup

of amyloid plaques, which is a key marker of Alzheimer's

disease in the brain. How are these plaques related to

Alzheimer's disease? These plaques are abnormal protein

deposits that can disrupt brain function and are strongly

associated with Alzheimer's disease. How accurate is an

amyloid PET scan for detecting Alzheimer's? It's now considered

highly accurate in identifying the plaques, but not definitive

for diagnosing Alzheimer's disease on its own. How to MRI

and CAT scans complement an amyloid PET scan in diagnosing

Alzheimer's the MRI and the cat or CT scans provide detailed

images of brain structure which can identify other conditions or

brain changes that an amyloid PET scan alone cannot and does

not show. Can an amyloid PET scan detect Alzheimer's disease

before symptoms appear, yes, the PET scan can detect amyloid

plaque buildup in the brain actually years before noticeable

symptoms develop. If your amyloid plaque, if your amyloid

PET scan shows plaques, does it mean that you definitely have

Alzheimer's? The answer is plainly, no period. But while

the plaques are a hallmark of Alzheimer's, their presence does

not necessarily mean that you have or will develop the

disease. How can early detection of amyloid plaques influence

treatment and care decisions? Well, early detection allows for

timely interventions, lifestyle changes and treatment plans that

may help slow disease progression and improve your

quality of life.

Losing a loved one with dementia, a brain injury or a

neurological disease can be a difficult experience and can

leave you and your family with a lot of unanswered questions. An

autopsy can help answer a lot of those questions. Most dementias

cannot be diagnosed with certainty without a tissue

diagnosis, and you cannot do a tissue diagnosis very well

without a huge risk of damaging the brain while you are still

living. The brain cannot generally be biopsied during

life due to its crucial functions. This means that

diseases such as Alzheimer's and Parkinson's, among many more,

can only be definitively diagnosed with an autopsy. The

autopsy is considered to be the gold standard of diagnosis for

dementia, and the final answer in documenting and explaining

the extent of disease and damage in other organic brain diseases

such as Alzheimer's, Parkinson's, multiple sclerosis,

traumatic brain injuries, Lewy, body dementia, picks disease,

ataxia, frontotemporal lobe dementia, Cerebral degeneration,

strokes and post stroke dementia, meningitis and

encephalitis, hydro Cephalus, HIV associated dementia,

myasthenia gravis, muscular dystrophy and neuromuscular

diseases, cerebral palsy. Alzy and ALS or Lou Gehrig's disease,

also brain tumors. So in conclusion, yes, a brain autopsy

is still the only way to definitively, positively,

conclusively, confirm Alzheimer's disease by examining

brain tissue for plaques and tangles, because it does involve

microscopic evaluation of brain tissue to find the definitive

signs of Alzheimer's, which are the plaques and tangles. Also

modern techniques like biomarker tests, which include blood or

spinal fluid and PET scans now allow doctors to diagnose it

with high accuracy, up to 90% while a person is living, and by

being able to rule out other causes, but while not 100%

certain without an autopsy, these advanced tests, alongside

clinical evaluations, provide strong evidence for a probable

diagnosis, guiding Treatment and Research, I have actually known

of several cases where people were diagnosed with Alzheimer's

disease and treated for it. I know of one gentleman for three

years, and it turned out that it was not an accurate diagnosis.

He actually had Lyme disease. So there you have it. They're doing

the best they can with the tools they have to work with.

Currently, they are definitely advancing. But again, the

autopsy is the only definitive way right now to diagnose

Alzheimer's. But of course, that can change like tomorrow, but I

will stay on top of it for you, to bring you the most current

and accurate information that I continue to find. So I want to

thank you for being here today to listen to this very important

update about how PET scans work and how they are able to help

with a diagnosis of Alzheimer's. And when you have a chance,

please visit our website, minding dementia.com. If you'd

like to subscribe to our free weekly newsletter and have that

sent to you. It's sent out every Monday, and it provides you with

updated tips and information that I constantly research for

everybody and also, you know, explore around the website,

because we do also upload current information, strategies,

tips, as they change, and I find out updates on them. So I hope

everybody has a wonderful, happy, healthy rest of your

week. Thanks again for being here. I do appreciate it so

much, and I will be back next week with another episode of the

truth lies and Alzheimer's show. I'm Lisa Skinner, your host,

Take care for now. Bye, bye.