Genetics and Neurodegenerative Dementias: A Complex Interplay

Recent progress in neurogenetics and molecular pathology has improved our understanding of the complex pathogenetic changes associated with neurodegenerative dementias.

In this episode, Katie Grouse, MD, FAAN, speaks with Sonja W. Scholz, MD, PhD, FAAN, an author of the article “Genetics and Neuropathology of Neurodegenerative Dementias,” in the Continuum® December 2024 Dementia issue.

Dr. Grouse is a Continuum® Audio interviewer and a clinical assistant professor at the University of California San Francisco in San Francisco, California.

Dr. Scholz is a senior investigator at the National Institutes of Health in Bethesda, Maryland and an adjunct professor of neurology at Johns Hopkins University in Baltimore, Maryland.

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Read the article: Genetics and Neuropathology of Neurodegenerative Dementias

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Full episode transcript available here: 

Dr Jones: This is Dr Lyell Jones, Editor-in-Chief of Continuum, the premier topic-based neurology clinical review and CME journal from the American Academy of Neurology. Thank you for joining us on Continuum Audio, which features conversations with Continuum's guest editors and authors who are the leading experts in their fields. Subscribers to the Continuum journal can read the full article or listen to verbatim recordings of the article and have access to exclusive interviews not featured on the podcast. Please visit the link in the episode notes for more information on the article, subscribing to the journal, and how to get CME.

Dr Grouse: This is Dr Katie Grouse. Today I'm interviewing Dr Sonia Scholz about her article on genetics and neuropathy of neurodegenerative dementias, which appears in the December 2024 Continuum issue on dementia. Welcome to the podcast, and please introduce yourself to our audience. 

Dr Scholz: Thank you so much for inviting me. My name is Sonia Scholz. I'm a neurologist working at the National Institutes of Health. My main focus of research and clinical work are neurodegenerative diseases, and I have a particular interest in using modern genomic tools to understand these diseases and potentially leverage it for new translational applications.

Dr Grouse: Sonia, we're really excited to have you today and thanks for joining us. 

Dr Scholz: I'm pleased to be here. 

Dr Grouse: I'd like to start by asking what you think is the most important message or takeaway point from your article?

Dr Scholz: So, this is an article that really captures a very broad and exciting field. So, one thing I wanted to really highlight is that there's a lot of heterogeneity, clinical, pathological, molecular heterogeneity in age-related neurodegenerative dementia syndromes. Our article was really aimed at providing a bird's eye view of the pertinent pathological characteristics, but also important genetic advances and insights and how we can leverage that, particularly in the new physician medicine era, hopefully come up with better treatments and better ways to counsel our patients. 

Dr Grouse: What do you think is the most challenging aspect of understanding the genetics and neuropathologic basis of neurodegenerative dementias? 

Dr. Scholz: That's a good question. There’re many big and challenging questions, but I think one of the things we struggle the most with is really the heterogeneity. I see patients with one and the same Mendelian form of dementia. One patient is in their forties another patient is in their eighties, and the clinical manifestations can be very different from one patient to another. There's a lot of heterogeneity, also, on the pathological level. Not every patient has exactly the same distribution. And so, we're starting to slowly define what the underlying causes are, but it's still quite baffling and quite challenging to put them together and understand them.

Dr Grouse: Do you feel that the genome-wide association studies has helped our understanding of these diseases, specifically the heterogeneity? And if so how? 

Dr Scholz: That's a great question, but you're talking to a geneticist here. And I definitely would say genome-wide association studies have helped us a lot in identifying what the underlying disease pathways are and what the relationships between neurodegenerative disease entities are. It really also gave us a better understanding of apparently sporadic diseases where genetic factors are still playing a role. And we can leverage that type of knowledge increasingly to highlight high-risk groups, but also, we can increasingly use it to stratify patients for clinical trials, for example. And that's really exciting and there's still a lot of knowledge that we have to garner very quickly, especially in the non-Alzheimer dementia space. 

Dr Grouse: You've mentioned, of course, the heterogeneity and these syndromes. And in your article, you go into a lot of the issue of the significant crossover between the genetic links and the neuropathological findings for the various types of neurodegenerative dementias. Do you think that this crossover has been more of a help or a hindrance in better understanding these diseases?

Dr Scholz: Yeah, it can be a little bit, you know, challenging to wrap one 's mind around it. But by and large, I think it’s actually good news because it highlights that there is a shared biology between many of the neurodegenerative disease entities. And by figuring out which the pathways are that are very often involved, we can prioritize certain targets for therapy development. But we can also be smarter about how we developed treatments. We could repurpose a drug that has been developed for Alzheimer's disease very easily for Lewy body dementia because we increasingly understand the overlap. And we can also leverage new clinical trials design, like basket trials. This is something that has been really transformative in the oncology sphere and now, increasingly, neurodegeneration. We're trying to apply that kind of thinking as well to our patient populations.

Dr Grouse: What do you think our listeners will find to be most surprising when they read the article?

Dr Scholz: We often present these diseases in our textbooks as these black-and-white entities, but the reality is that there's a lot of overlap. And we also see that co-pathologies are actually the norm and not the exception, and a lot of the molecular risk factors are shared. It's not really surprising. And I think that overlap and crosstalk between the various diseases is something that's a little bit strange to think about, but it actually makes increasingly sense now that we see the genetic risk profiles coming up.

Dr Grouse: In reading your article, I was really struck by how many, or how much the prior studies have been lacking in inclusion of different ethno-racial backgrounds in the patients who've been studied. How can this be improved going forward? 

Dr Scholz: Yeah, thank you. That's a really important and crucial question, and I think it really takes the collective effort of everybody in the healthcare research community to improve upon that. We need to talk to our patients about genetic testing, about brain donation programs, about referrals to clinical trials, and don't feel shy about reaching out to our colleagues and academic centers, even if you don't have the resources in a smaller institution. We also not only need to engage with the communities, we also need to build up a healthcare research community that has representatives from these various communities. So, it's really a collective effort that we build up and are proactive about building a more equitable healthcare system and research system that works for all of us and that really is going to provide us with the precision medicines that work for everybody.

Dr Grouse: What do you think is the biggest debate or controversy related to the genetics and neuropathology of neurodegenerative dementias? 

Dr Scholz: Yeah, there are loads of interesting debates, but I think in my field, in particular in the genetics is what to do with risk variance. What is it that I actually communicate to the patient? Obviously, I can learn a lot on the bench and I think I can use a lot of the genetic risk factors for molecular modeling, etc. But to which extent should I share that information? Because genetic information is something that we cannot alter and many of the risk factors are actually mild, that they may never result in disease. And so, communicating risk with patients is something that's very challenging and we used to just steer away from it. But now the discussion is starting to shift a little bit. You know, nowadays we are starting to offer, for example, testing for the APOE4 allele in individuals who are considering antiamyloid therapies. And this really, this is precision medicine in his earliest days because it allows us to stratify patients into those that are high-risk versus low-risk and those that need more frequent follow-up or may be advised not to pursue this treatment. And we're probably going to see more of those discussions and the ethics around it. And it's even harder in an aged population where you know, you may never manifest any of the symptoms despite carrying a lot of these risk deals.

Dr Grouse: You mentioned, you know, that testing, APOE4 testing for certain populations when deciding to do the antiamyloid immunotherapies. Apart from that, which I think is a really good example of where genetic testing makes sense, what other scenarios do you think it makes sense at this point in time to recommend genetic testing for symptomatic patients who are concerned about neurodegenerative dementias?

Dr Scholz: Yeah. So, I usually have a very frank discussion with patients in whom I suspect the genetic etiology. So those are individuals who have a strong family history, individuals from very early onset of the disease where genetic testing may allow us to establish a molecular diagnosis, individualize and refine our counseling, and potentially get them into targeted clinical trials that may be suitable for that. Those are always very nuanced discussions, but I usually start with those high-risk individuals. Increasingly patients are, even with the apparently sporadic forms, are asking me about it. And then I have a frank discussions about the pros and cons and offer it to the patients who really would like to pursue it. 

Dr Grouse: That makes a lot of sense. What about in the case of patients who are asymptomatic but might have high risks because of, well, family members with certain types of neurodegenerative dementias? When would it make sense, if ever, to do genetic testing for them?

Dr Scholz: Yeah, that's a that's a tough situation, to be honest. By and large, I would say I would like to understand what the motivation is to learn about the genetic status. If the motivation is something like family planning, future care planning, etc, then it may be a reasonable thing. But I also want to make it very clear upfront that knowing a genetic status, at least aside from APOE status, at least for now, doesn't actually change the clinical management. And I want to make sure patients understand if they are trying to lower their risk, knowing that genetic status is not going to lower their risk. There are other things, brain health habits, that are really important, that patients should double down on: avoiding vascular disease, avoiding traumatic brain injury, excessive alcohol use, etcetera. It's a discussion that really tries to understand the motivations behind the testing. But some patients are very frank and they want to have it. They may want to contribute to the research community, and so in those instances we may offer it, but I also really want to make them understand that knowing a genetic diagnosis may be acceptable to them, but family members who are related to them may not wish to know. And they can really cause a lot of psychological stress that extends beyond the individual. And then that's something to really consider before actually pursuing testing.

Dr Grouse: I think that's a really good reminder, especially about how this can even affect people outside of the patient themselves. I think a lot of us don't even think about that. And certainly, our patients may not either. Taking it a step further, thinking about newly available biomarkers, imaging modalities, how should we incorporate the use of these for our patients when we're suspicious of things like Alzheimer's disease or dementia with the Lewy bodies?

Dr Scholz: So by and large these biomarkers are used in in the research area, but we can, in a given patient where maybe the clinical presentation is somewhat atypical, we can use it to help with our diagnostic impression. It doesn't get rid of the clinical evaluation, but at least it gives us a little bit more certainty. Here are the you know, the molecular features, the abnormal amyloid tau deposits, for example, that we're there we're detecting supports diagnosis. May also sometimes help in patients where we suspect there could be even the co-pathology going on where we get a mixture of features, where we can counsel the patients and you know, detecting copathologies is something that is certainly challenging. We know that patients who have more pathologies on average are not doing as well as the ones who have relatively pure disease forms. But this is also an area of intense research and as long as it's used judiciously to help with the diagnostic compression, to reduce a diagnostic odyssey, I think there's a lot of potential there to improve the clinical evaluations nowadays.

Dr Grouse: It is really exciting to see the options that are opening up as the years go by, which brings me to my next question. There is certainly, as we know, this new category of disease modifying therapies that are available in the form of the anti-amyloid immunotherapies. What else do you think's on the horizon for treatment and prevention, neurodegenerative dementias, going down the road five, ten, fifteen years down the line? 

Dr Scholz: Yeah, I think we're entering the era of precision medicine already and we're, we're seeing it already with the anti-amyloid therapies. By and large, I think the standard of care is going to be a multidisciplinary individualized treatment plan that incorporates a more holistic view. It incorporates diet, lifestyle factors, symptomatic management, but also disease modification strategies and potentially even multitarget disease modifying strategies. I think there's a lot more work that we have to do, especially in in the non-Alzheimer’s dementia field. But overall, we're becoming much better in refining our diagnostic impression and in treating some of the complications that arise in these very complex diseases. 

Dr Grouse: I'm curious, with the future of dementia care and diagnosis being more of a precision medicine model, how do you think this will be possible in an aging population with already, I think, probably a limited access to neurologists even in current state?

Dr Scholz: Yeah, this is- these are these are very challenging societal questions. Increasingly, you know, we can use modern technologies such as televisits for follow up, but also, you know, remote monitoring devices. We have to educate the next generation, we need more neurologists, we can't do it alone; but we also need to empower primary care doctors who are usually the first go-to person. And perhaps biomarker testing will become much more common even in the primary care setting. I think overall, you know, we can tackle it by educating the community, empowering participants in various clinical trials, and being flexible of embracing certain new technologies.

Dr Grouse: Absolutely. I think that makes a lot of sense and hopefully this will be another call to arms to try to get the word out, get more access to neurology and more people interested and like you said, getting our other colleagues involved and being able to manage it as well. 

Dr Scholz: Yeah. 

Dr Grouse: I wanted to transition a little bit into learning more about you. How did you become interested in genetics of neurodegenerative dementias?

Dr Scholz: Yeah, it's something, it's an interest that has grown gradually. I started out as a neuroscientist in in Austria, where I was fortunate to work with a group that was very strongly involved in Parkinson's disease care. And I was so thrilled to see patients, you know, treated with deep brain stimulation. But yet in the same clinic, I also saw the patients who were not eligible because they had atypical neurodegenerative diseases. And it's the realization that there is such a broad spectrum of diseases that we frankly don't understand very well, that we really need to work with, understand and hopefully develop the treatments with. That's really has resonated with me. And I've since then really built my entire career around it through different countries at the United Kingdom and the United States. And I'm very fortunate to work at the National Institutes of Health, where I can pursue a lot of these research passions and work with interesting patients and colleagues. 

Dr Grouse: Well, I've learned a lot today, and I'm sure our listeners would agree. Thank you so much for joining us. It's really been a pleasure speaking with you. 

Dr Scholz: Well, thank you so much for allowing me to contribute. And, you know, I hope the review article conveys a lot of the exciting developments in this really challenging field. But there's loads of hope that we will eventually get to the point to tackle these conditions. 

Dr Grouse: I encourage all of our listeners to check out Dr Scholz 's article. It is a great overview of these conditions and the genetics and neuropathology underlining them. Again, thank you so much. 

Dr Scholz: Thank you for having me.

Dr Grouse: Again, today I've been interviewing Dr Sonia Scholz, whose article on genetics and neuropathology of neurodegenerative dementias appears in the most recent issue of Continuum on dementia. Be sure to check out Continuum audio episodes from this and other issues. And thank you to our listeners for joining today.

Dr Monteith: This is Dr Teshamae Monteith, associate editor of Continuum Audio. If you've enjoyed this episode, you'll love the journal, which is full of in-depth and clinically relevant information important for neurology practitioners. Use this link in the episode notes to learn more and subscribe. AAN members, you can get CME for listening to this interview by completing the evaluation at continpub.com/AudioCME. Thank you for listening to Continuum Audio.