Are PET Scans for Alzheimer’s Disease Accurate?

Are you caring for a loved one with dementia? You don't have to figure this out all on your own. Welcome to Truth, Lies Alzheimer's, the show that helps you reimagine a new relationship with your loved one, a relationship a little more free of stress and anxiety. Join host Lisa Skinner and her 30+ years of experience as she guides you on a new path to a better relationship with those you care for. Here's Lisa.

Hi everybody, welcome back to the Truth, Lies 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, um, 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 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 plaque 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 an 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 healthcare 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 the 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, and this is called the preclinical 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 healthcare 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 result 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 integrating 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 for identifying the plaques, but not definitive for diagnosing Alzheimer's disease on its own. How do 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 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. 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, Pick's disease, Ataxia, frontotemporal lobe dementia, cerebral degeneration, strokes and post-stroke dementia, meningitis and encephalitis, hydrocephalus, HIV-associated dementia. Myasthenia gravis, muscular dystrophy and neuromuscular diseases, cerebral palsy, 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. Um, 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 3 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, mindingdementia.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. So much, and I will be back next week with another episode of The Truth, Lies Alzheimer's Show. I'm Lisa Skinner, your host. Take care for now. Bye-bye.

Thank you for listening to Truth, Lies Alzheimer's. We hope you found something in today's episode that helps. We understand that caring for a loved one with dementia can be the challenge of a lifetime. But you don't have to do it alone. If you're ready for exclusive access to even more great content and resources, head on over to Facebook and join Lisa Skinner's Minding Dementia support group. We're a community of like-minded caregivers, and we're here to help.