Unruptured Intracranial Aneurysms and Arteriovenous Malformations With Dr. Edgar A Samaneigo

Unruptured intracranial aneurysms and arteriovenous malformations are frequently discovered incidentally on neuroimaging, presenting complex decisions around monitoring, referral, and treatment. This episode highlights key risk factors for rupture, the role of imaging in evaluation, and practical approaches to triage and management, including when specialist intervention is warranted.

In this episode, Gordon Smith, MD, FAAN, speaks with Edgar Samaniego, MD, FAAN, authors of the article “Unruptured Intracranial Aneurysms and Arteriovenous Malformations” in the Continuum® June 2026 Cerebrovascular Disease issue.

Dr. Smith is a Continuum® Audio interviewer and a professor and chair of neurology at Kenneth and Dianne Wright Distinguished Chair in Clinical and Translational Research at Virginia Commonwealth University in Richmond, Virginia.

Dr. Samaniego is a professor of neurology, neurosurgery, and radiology and the director of the vascular neurology fellowship at the University of Iowa in Iowa City, Iowa.

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Read the article: Unruptured Intracranial Aneurysms and Arteriovenous Malformations

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Host: @GordonSmithMD

Guest: @esamaniego

Full episode transcript available here

Dr Smith: Have you ever ordered an MRI of the brain and found a coincidental unruptured aneurysm or perhaps an arteriovenous malformation? If so, are you up to speed on how to manage this common situation, how to monitor, when to refer, and how to counsel your patients? If your answers to these two questions are yes and or no, then please keep listening. 

Dr Jones: This is Dr. Lyell Jones, Editor-in-Chief of Continuum. Thank you for listening to Continuum Audio. Be sure to visit the links in the episode notes for information about earning CME, subscribing to the journal, and exclusive access to interviews not featured on the podcast. 

Dr Smith: This is Dr. Gordon Smith. Today, I'm interviewing Dr. Edgar Samaniego about his article on unruptured intracranial aneurysms and arteriovenous malformations. This article appears in the June two thousand twenty-six Continuum issue on cerebrovascular disease. Edgar, welcome to the podcast, and maybe you can briefly introduce yourself to our listeners. 

Dr Samaniego: Yeah. Thank you, Gordon. So, I'm an interventional neurologist. I'm practicing at the University of Iowa. I've been in Iowa for the last ten years. I'm originally from Ecuador. Did my residency in Wisconsin, and then I went to Stanford for neuro critical care and stroke. And then I did my neurointerventional fellowship at the Baptist Cardiac and Vascular Institute in Miami. 

Dr Smith: You're a triple threat in the world of vascular and critical care, which I want to get to later. But your article's really great. I'll admit one of the first things I do when I read an article for Continuum Audio is I see how long it is. I saw yours was as long as the rest, and I was a little surprised because this sounded like a simple topic. But having read it, it's anything but simple. This is really important and complex stuff. I wonder if maybe you can orient our listeners to the importance of this. We frequently find unruptured aneurysms or vascular malformations on brain imaging that we order for something else. I mean, how common is that, and why do you think our listeners need to be particularly attentive to our conversation today? 

Dr Samaniego: It's pretty frequent that we see patients with unruptured brain aneurysms. A lot of times, you know, we do imaging like CT angiograms, or magnetic, resonance angiography. Patients come to the ER with headaches, and we find an unruptured aneurysm. And you know, the question always comes, "What should we do with this aneurysm that we found?" We know that a lot of these aneurysms will not rupture, but the caveat is that when they rupture, like fifty percent of these patients may die or have bad outcomes. So, it's always a puzzling question, you know. What should we do with the aneurysm? 

Dr Smith: Well, thanks, Edgar. I mean, this is certainly something that I come across. I'm glad to hear that other people struggle with this as well. What actually is the prevalence of aneurysms in the general population? How common is this? 

Dr Samaniego: It's more common than what we think, you know. The, the estimates talk about like one in every fifty people have a brain aneurysm, and about every eighteen minutes an aneurysm will rupture. In the United States, there's approximately thirty thousand ruptures per year. So, there's a significant number of, of patients affected by brain aneurysms. And, and the key thing is that affects usually younger patients who are in the most productive years of their lives. So that's why it shouldn't be ignored, and once we find an aneurysm, we have to have all the information for triaging and deciding on treatment of these aneurysms. 

Dr Smith: Well, it's a great way to begin our conversation. I mean, this is not a rare problem. It's a common problem, and there's actually a really great section of the article I'll refer people to about medical malpractice and the importance of recognizing and dealing with this thoughtfully. It's an empowering section, not a scary one, but this is important for our listeners to know about. Pretty high-stakes stuff. Maybe you can orient listeners like me or maybe simple neuromuscular people. What different types of aneurysms are there? 

Dr Samaniego: That's the interesting question because there's multiple types of aneurysms, and there is a whole spectrum of aneurysm. When we say aneurysm, you can be talking about a fusiform versus a saccular aneurysm. We tend to classify them based on shape, also location. But the two main classifications for brain aneurysms will be saccular, which, you know, has a sac kind of morphology shape, and then you have the fusiform aneurysms. Those are the main morphological classifications. Then on top of that, you have two other subtypes that you see quite often. The one that we see is mycotic aneurysms that is like a misnomer because it's not a fungal aneurysm. It's just an infectious aneurysm that most of the time we see on the setting of endocarditis. These behave a little bit different than the typical saccular or fusiform aneurysms. And then also you have other more rare types of aneurysms like blister aneurysms that are sometimes located in the anterior wall of the carotid artery. So, you know, within this spectrum, we have those main aneurysms. The typical aneurysms, which can be fusiform or saccular, and also the more atypical, which can be mycotic and also blister-like aneurysms. 

Dr Smith: I wonder if you might comment a little bit on the relevance of the type of aneurysm, fusiform, saccular, blister, and then location on rupture risk or prognosis.You have a really great figure about anatomic classification in the article actually that I encourage everyone to check out when they hopefully read it. But what do these characteristics imply for risk? 

Dr Samaniego: Yeah. This is very complex question because, you know, entails different characteristics of aneurysms such as shape, the location, morphology. So, we know that some locations, for example, the anterior communicating artery has a high risk of rupturing as opposed to patients such as the part of ophthalmic aneurysm, which are usually located at the origin of the ophthalmic artery in the internal carotid artery. So, by risk of rupturing, the highest risk is usually the anterior communicating. Then you have posterior communicating artery aneurysms, which are usually located in the internal carotid artery, but because of their proximity to the origin of the posterior communicating artery, they're called posterior communicating artery aneurysms. Then you have the posterior circulation aneurysms on top of risk of rupturing is the top of the basilar artery location. Those three are the highest risk for rupturing: ACOM, PCOM, and top of the basilar. In terms of morphology, I always tell my patients, you know, if it's like a nice-looking aneurysm that has this rounded shape is a benign morphology. If you have the aneurysm that's having these Mickey Mouse ears that has these blebs or daughter sacs, those are aneurysms that usually scare us because those are the ones that usually rupture. So that's another criteria, morphology. And then the other criteria would be size. There is this magnificent study called ISUIA, which was published several years ago, and basically what it demonstrated was that aneurysms that are seven millimeters or larger are more likely to rupture versus smaller aneurysms. So those are the three criteria that I'm looking into when talking to patients about morphology, location, size, and the, the shape or morphology of the aneurysm. 

Dr Smith: So, let's say a general neurologist or comprehensive neurologist practicing in a community setting in a rural area orders a, let's just say a CT or CTA for a patient with a TIA and finds what looks like an aneurysm. What's the next step in terms of imaging? What's the best next step? I mean, there are a bunch of different imaging modalities. Do you get an MRA? Is it time-of-flight, contrasted? You know, when do you get a DSA and so forth? 

Dr Samaniego: Yeah. The first thing to do is to better characterize the aneurysm. Order of more accurate imaging that we can obtain without being invasive with a diagnostic cerebral angiogram. The rest will be a magnetic resonance angiography with contrast that, you know, gives you really good detailed information about the aneurysm. Similar in terms of quality and precision will be a CT angiography. The caveat there is with CT angiography is that, you know, you use radiation, and the patient has to get iodine. And then under those two, you will have a time-of-flight magnetic resonance angiography, which doesn't use any contrast, but then you lose a little bit of quality in terms of the imaging and some morphological features you might miss. So usually what we do in my practice, I don't wanna do a diagnostic cerebral angiogram, and somebody has to refer an unruptured aneurysm. I try to do CT angiogram as a baseline, see how the aneurysm looks, and then for follow-up, I usually do magnetic resonance an- angiograms with with contrast. If there is a concern that the aneurysm has some dangerous features like it's irregular in shape, it's, it's larger, it's in one of these high-risk locations, might be better just to refer the, the patient to a specialist for a diagnostic cerebral angiography. 

Dr Smith: So, you know, there are these scales that you talk about in the article. There's phases in the UIATS that are used to predict rupture risk and guide decision-making. Are these scales that general neurologists or non-vascular neurologists can use to guide care? I'm thinking of like Chad-Baskin, ASBAD, which, you know, all our residents know about. Should we all be familiar with these scores? 

Dr Samaniego: I think they're very helpful in the sense that it will give us some guidance. Some of the characteristics of the scale might be up- outdated. For example, like ancestry. Although it's been described more in Japanese and Finnish populations, and North American, not as much as these two other populations. We do see a lot of aneurysms in people from North America and other backgrounds. For example, one of the biggest critiques for the phases is that doesn't take into account smoking history. Smoking that we know is a risk factor. And the other critiques for phases is that, for example, if you are older than seventy years old, you will score one point, which will increase your risk of aneurysm rupturing. Having said that, we do see like tons of aneurysms on younger patients, actually the most productive years of their lives that they rupture. So, it gives you some parameters like the presence of hypertension, the size, as I said, seven or larger, previous history of subarachnoid hemorrhage, and the location of the aneurysm. But it doesn't take into account other factors like smoking or morphological features of the aneurysm.

Dr Smith: Now, you mentioned size. I'd like to maybe go back and talk about a case from your article, which I found really impactful. For our listeners, this is a sixty-four-year-old woman who had a five-millimeter ACOM aneurysm. She was imaged serially, didn't change over the time period, and then two years later ruptured with devastating consequence, right? And so that's a small aneurysm. Most aneurysms, I guess, are small aneurysms. I just wonder, when you see a patient like that, how do you handle the discussion regarding risk? And how do you decide when to refer them for an intervention? 

Dr Samaniego: Yeah. It's always puzzling when we see these smaller aneurysms. And this example is a typical example of a patient that doesn't follow the rule of seven or larger aneurysm size for rupturing. We see that quite often on aneurysms located in the anterior communicating artery. Just this last week, I treated two patients with similar characteristics, with smaller aneurysms, like average size between four and five, that rupture, and both were located in the anterior communicating artery. So, we know that there is definitely a linear relationship between size and risk and rupture, but we do see a lot of patients that have smaller aneurysms, like three, four, five millimeters that rupture, and we don't really understand very well the, biology of these aneurysms. So, when we see these aneurysms, we try to maximize the characterization of the aneurysm with better imaging, try to see the morphology. And usually when an aneurysm is discovered, what we do for follow-up is a six-month follow-up with some type of imaging, CTA, MRA with contrast, and see if there's has been any change in, on the aneurysm. 

Dr Smith: So, is it fair to say that a knowledgeable non-vascular neurologist can safely manage these patients, follow them over time using what they learned from reviewing your article, identify patients who have higher risk aneurysms based on the characteristics you summarize, and refer them to a tertiary center? When I get these, it's easy for me to have our vascular neurosurgeon see them or a vascular neurologist, right? But in a community where you may not have ready access to that subspecialist, is it still important to get all of these patients to a tertiary center? Are there select instances where a community-based general neurologist can follow them and then refer if there's change in size, for instance? 

Dr Samaniego: Yeah. I think that everything else that we do in neurology, it's important to do some type of triage in referring some of these patients for further studying and  expert opinion. I think age and size of the aneurysm, age of the patient and size of the aneurysm are huge factors. For example, if we have an older patient in their nineties and has incidentally found two-millimeter aneurysm in a low-risk location like the parathalmic, that patient probably needs to be seen locally. I don't think merits a full workup. As opposed to a younger patient with a three-millimeter aneurysm located in the ACOM. I think that type of patient probably needs to be referred to a tertiary s-stroke center for workup. I mean, most of the time what's gonna happen is that if it's a small aneurysm with benign characteristics, you know, it's gonna be seen by the specialist and they're gonna determine some type of follow-up, which can be done locally. 

Dr Smith: So maybe we can pivot a little bit and talk about AVMs, if that's okay. What's your approach to a coincidentally discovered AVM, right? I mean, presumably, we need to think about symptomatic AVMs a little differently, I would think. So maybe we can start with the same scenario we've been talking about. You get an imaging study for something else, and, well, we find an AVM. What's the approach to that situation? 

Dr Samaniego: Yeah. AVMs are fascinating vascular lesions because they're very complex, they're very heterogeneous. If we're talking about the morphological features with aneurysms, this, in the case of AVMs, is way more complex in terms of location size. The complexity added to AVMs is that you have a feeding artery, you have a nidus, and then you have draining veins. So, all of these can be very heterogeneous. In case of AVMs, I think those definitely need to be referred to a tertiary center because the management of AVMs is multidisciplinary, even in the tertiary centers. You know, we don't have a magic wand that will say, you know, all these AVMs need to be treated this way. Sometimes they don't even need to be treated because we know from some studies that just watching them will be good enough. 

Dr Smith: You raised management of AVMs. Maybe we can go back and talk a little bit about what's the latest in management of aneurysms. You manage aneurysms from soup to nuts and as an endovascular interventional neurologist. What's the latest in management of aneurysms? 

Dr Samaniego: The latest is that, which falls within management, is that we have tools that they have not really been validated a hundred percent because we're still understanding the biology of some of these aneurysms. But high-resolution MRI will help us to define if there is some enhancement of the aneurysm. There is the thought that if there is enhancement after the administration of contrast, might be more of an inflammatory process. So that can be used for management, triage, and follow-up of some of these aneurysms. In terms of endovascular treatment, it has been really a revolution of how we treat these lesions. You know, we have a lot of new devices, better catheters to access the aneurysms.There is devices that you can place inside the aneurysm sac and it'll completely shut down flow into the aneurysm. There is other special stents called flow diverters that can take the flow away from the aneurysm and bypassing the aneurysm. So, all of these things have really revolutionized how we treat them. Having said that, you know, there's always a risk with any of these procedures, and that's why we gotta be mindful when we decide to treat these patients with unruptured incidentally found aneurysm. 

Dr Smith: I've got just one more question, Edgar, which I kind of led with. You've got training as a vascular neurologist, a neurointensivist, and an interventional neurologist. And you know, Ralph Sacco, as you probably know, used to like to talk about the neurologist, and part of the neurologist was interventional. I wonder what wisdom you have to trainees that are listening to us right now who might be interested in pursuing a career as a neuroendovascular neurologist. What wisdom do you have for them about how to go about doing that? 

Dr Samaniego: It has been really rewarding to be part of this process and evolution of treating a stroke and aneurysms and AVMs because I remember when I was a resident at the University of Wisconsin, we only had, like, thrombolysis and only one device for, retrieving some of these clots. But now we have, like, 10 different devices. We have two different indications or two, two different thrombolytics. So, my best advice for trainees that want to pursue neuroendovascular is to get engaged early on, understand very well the biology and the thought process because it's not only a technical field. You have to have really good judgment on when to do and when not to do the procedure, and try to find mentorship. You know, there is a lot of neurointerventional neurologists out there right now. Having a good mentor will really facilitate your career choices and getting into training. 

Dr Smith: Well, Edgar, thanks so much. What an exciting conversation. It's just another great example of how exciting neurology is these days. Many exciting advances and innovations, and we just scratched the surface. I encourage all of our listeners to read the article. It's actually really, really informative. So, thank you very much. 

Dr Samaniego: Thank you so much, Gordon. 

Dr Smith: Again, today I've been interviewing Dr. Edgar Samaniego about his article on unruptured intracranial aneurysms and AVMs. This article appears in the June 2026 issue of Continuum on Cerebrovascular Disease. Be sure to check out other Continuum Audio episodes from this and other issues, and thanks to you, our listeners, for joining us 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 the 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.