The Importance of Neuroimaging in Optic Neuropathies

Optic neuropathies encompass all congenital or acquired conditions affecting the optic nerve and are often a harbinger of systemic and central nervous system disorders. A systematic approach to identifying the clinical manifestations of specific optic neuropathies is imperative for directing diagnostic assessments, formulating tailored treatment regimens, and identifying broader central nervous system and systemic disorders.

In this episode, Gordon Smith, MD, FAAN speaks with Lindsey De Lott, MD, MS, author of the article “Optic Neuropathies” in the Continuum® April 2025 Neuro-ophthalmology 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. De Lott is an assistant professor of neurology and ophthalmology at the University of Michigan in Ann Arbor, Michigan.

Additional Resources

Read the article: Optic Neuropathies

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Host: @gordonsmithMD

Guest: @lindseydelott

Full episode transcript available here

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: Hello, this is Dr Gordon Smith. Today I'm interviewing Dr Lindsey De Lott about her article on optic neuropathies, which appears in the April 2025 Continuum issue on neuro-ophthalmology. Lindsey, welcome to the podcast, and perhaps you can introduce yourself to our audience.

Dr De Lott: Thank you, Dr Smith. My name is Lindsey De Lott and I am a neurologist and a neuro-ophthalmologist at the University of Michigan. I also serve as the section lead for the Division of Neuro-Ophthalmology, which is actually part of the ophthalmology department rather than the neurology department. And I spend a good portion of my time as a researcher in health services research, and that's now about 60% of my practice or so.

Dr Smith: I'm super excited to spend some time talking with you. One, I'm a Michigan person. As we were chatting before this, I trained with Wayne Cornblath and John Trobe, and it's great to have you. I wonder if we maybe can begin- and by the way, your article is outstanding. It is such a huge topic and it was actually really fun to read, so I encourage our listeners to check it out. But you begin by talking about misdiagnosis as being a common problem in this patient population. I wonder if you can talk through why that is and if you have any pearls or pitfalls in avoiding it?

Dr De Lott: Yeah, I think there's been a lot of great research looking at misdiagnosis in specific types of optic neuropathies; in particular, compressive optic neuropathies and optic neuritis. A lot of that work has come out of the group at Emory and the group at Washington University. But a lot of neuro-ophthalmologists across the country really contributed to those data. And one of the statistics that always strikes me is that, you know, for example, in patients with optic nerve sheath meningiomas, something like 70% of them are actually misdiagnosed. And a lot of those errors in diagnosis, whether it's for compressive optic neuropathy or some other type of optic neuropathy, really comes down to the way that physicians are really incorporating elements of the history in the physical. For example, in optic neuritis, we know that physicians tend to anchor pretty heavily on pain in general. And that often tends to lead them astray when optic neuritis was never the diagnosis to begin with. So, it's really overindexing on certain things and not paying attention to other features of the physical exam; for example, say presence of an afferent pupillary defect. So, I think it just really highlights the need to have a really relatively structured approach to patients that you think have an optic neuropathy when you're trying to sort of plan your diagnostic testing and your treatment.

Dr Smith: I do maybe five or six weeks on our hospital service each year, and I don't know if it's just a Richmond thing, but there's always at least two people in my week who come in with an optic neuropathy or acute vision loss. How common is this in medical practice? Or neurologic practice, I should say?

Dr De Lott: Optic neuropathies themselves… if you look across, unfortunately we don't have any great data that puts together all optic neuropathies and gives us an actual sort of prevalence estimate or an incidence estimate from year to year. We do have some of those data for specific types of optic neuropathies like optic neuritis and NAION, and you're probably looking around five-ish per one hundred thousand. So, these aren't that common, but at the same time they do get funneled to- often to emergency rooms and to neurologists from our ophthalmology colleagues and optometry colleagues in particular.

Dr Smith: So, one other question I had before kind of diving into the topic at hand is how facile neurologists need to be in recognizing other causes of acute visual loss. I mean, we see acute visual loss as neurologists, we think optic neuropathy, right? Optic neuritis is sort of the go-to in a younger patient, and NAION in someone older. But what do neurologists need to know about other ophthalmologic causes? So, glaucoma or acute retinal disorders, for instance?

Dr De Lott: Yeah, I think it's really important that neurologists are able to distinguish optic neuropathies from other causes of vision loss. And so, I would really encourage the listeners to take a look at the excellent article by Nancy Newman about vision loss in this issue where she really kind of breaks it down into vision loss that is acute and chronic and how you really think through distinguishing optic neuropathies from other causes of vision loss. But it is really important. For example, a patient with a central retinal artery occlusion may potentially be eligible for treatments. And that's very different from a patient with optic neuritis and acute vision loss. So, we want to be able to distinguish these things. 

Dr Smith: So maybe we can pivot to that a little bit. Just for our listeners, our focus today is going to be on- not so much on optic neuritis, although obviously we need to talk a little bit about how we differentiate optic neuritis from non-neuritis optic neuropathies. It seems like the two most common situations we encounter are ischemic optic neuropathies and optic neuritis. Maybe you can talk a little bit about how you distinguish these two? I mean, some of it’s age, some of it’s risk factors, some of it’s exam. What's the framework, of let's say, a fifty-year-old person comes into the emergency room with acute vision loss and you're worried about an optic neuropathy?

Dr De Lott: The first step whenever you are considering an optic neuropathy is just making sure that the features are present. I think, really going back to your earlier question, making sure that the patient has the features of an optic neuropathy that we expect. So, it's not only vision loss, but it's also the presence of an apparent pupillary defect in a patient with a unilateral optic neuropathy. In a person who has a bilateral optic neuropathy, that apparent pupillary defect may not be present because it is relative. So, you really would have to have asymmetric vision loss between the two eyes. They should also have impairment of their color vision, and they're probably going to have some kind of visual field defect, whether that's central scotoma or an arcuate scotoma or an altitudinal defect that really respects the horizontal meridian.

So, you want to make sure that, first and foremost, you've got a patient that really meets most of those- most of those features. And then from there, we're looking at the other features on their history. How acute is the onset of the vision loss? What is the progression over time? Is there pain associated or not associated with the vision loss? What other medical issues does the patient have? And you know, one of the things you already brought up, for example, is, what's the age of the patient? So, I'm going to be much more hesitant to make a diagnosis of optic neuritis in a much older patient or a diagnosis on the other side, of ischemic optic neuropathy, in a much younger patient, unless they have really clear features that push me in that direction.

Dr Smith: I wonder if maybe you could talk a little bit about features that would push you away from optic neuritis, because, I mean, people who are over fifty do get optic neuritis-

Dr De Lott: They do.

Dr Smith: -and people who get ischemic optic neuropathies who are younger. So, what features would push you away from optic neuritis and towards… let's be broad, just a different type of optic neuropathy?

Dr De Lott: Sure. We know that most patients with optic neuritis do have pain, but that pain is accompanied---within a few days, typically---with vision loss. So, pain alone going on for a number of days without any visual symptoms or any of those other things I listed, like the afferent papillary defect, the visual field defect, would push me away from optic neuritis. But in general, yes, most optic neuritis is indeed painful. So, the presence of optic disc edema is unfortunately one of those things that an optic neuritis may be present, may not be present, but in somebody with ischemia that is anterior---and that's the most common type of ischemic optic neuropathy, would be anterior ischemic optic neuropathy---they have to have optic disc edema for us to be able to make that diagnosis, and that is a diagnosis of NAION, or nonarteritic ischemic optic neuropathy. An APD in this case, again, that's just a feature of an optic neuropathy. It doesn't really help you to distinguish, individual field defects are going to be relatively similar between them.

So then in patients, I'm also looking, like I said, at their history. So, in a patient where I'm entertaining a diagnosis of ischemic optic neuropathy, I want to make sure that they have vascular risk factors or that I'm actually doing things like measuring their blood pressure in the office if they haven't seen a physician recently or checking a lipid panel, hemoglobin A1c, those kinds of things, to look for vascular risk factors. One of the other features on exam that might push me more- again, in a patient with ischemic optic neuropathy, where it might suggest ischemia over optic neuritis, would be some other features on exam like a crowded optic disc that we sometimes will see in patients with ischemic optic neuropathy. I feel like that was a bit of a convoluted answer.

Dr Smith: I thought that was a great answer. And when you say crowded optic disc, that's the- is that the “disc at risk”?

Dr De Lott: That is the “disk at risk,” yes. So, crowded optic disk is really a disk that is smaller than what we see in the average population, and the average cup to disk ratio is 0.3. So, I think that's where 30% of the disk should be. So, this extra wiggle room, as I sometimes will explain to my patients.

Dr Smith: And then, I wonder if you could talk a little bit about more- just more about exam, right? You raised the importance of recognizing optic disc edema. Are there aspects of that disc edema that really steer you away from optic neuritis and towards ischemia-like hemorrhages or whatnot? And then a similar question about the importance of careful visual field testing?

Dr De Lott: So, on the whole, optic disc edema is optic disc edema. And you can have very severe optic neuritis with hemorrhages, cotton wool spots, which is essentially just an infarction of the retinal nerve fiber layer either overlying the disc or other parts of the retina. And ischemia, you can have some of the same features. In patients who have giant cell arteritis, which is just one form of anterior ischemic optic neuropathy, patients can have a pallid optic disc edema where the optic disc is swollen and white-looking. But on the whole, swelling is swelling. So, I would caution anyone against using the features of the optic nerve swelling to make any type of, sort of, definitive kind of diagnosis. It's worth keeping in mind, but I just- I would caution against using specific features, optic nerve swelling.

And then for visual field testing, there are certain patterns that sometimes can be helpful. I think as I mentioned earlier, in patients with ischemic optic neuropathy, we’ll often see an altitudinal defect where either the top half or, more commonly, the bottom half of the vision is lost. And that vision loss in the field corresponds to the area of swelling on the disk, which is really rewarding when you're actually able to see sectoral swelling of the disk. So, say the top half of the disk is swollen and you see a really dense inferior defect. And other types of optic neuropathy such as hereditary optic neuropathies, toxic and nutritional optic neuropathies, they often cause more central field loss. And in patients who have optic neuropathies from elevated intracranial pressure, so papilladema, those folks often have more subtle visual field loss in an arcuate pattern. And it's only once the optic nerves have sustained a pretty significant injury that you start to see other patterns of field loss and actual decline in visual acuity in those patients. I do think a detailed visual field assessment can often be pretty helpful as an adjunct to the rest of the exam.

Dr Smith: So, we haven't talked a lot about neuroimaging, and obviously, neuroimaging is really important in patients who have optic neuritis. But how about an older patient in whom you suspect ischemic optic neuropathy? Do those patients all need a MRI scan? And if so, is it orbits and brain? How do you- how do you protocol it?

Dr De Lott: You're asking such a good question, totally controversial in in some ways. And so, in patients with ischemic optic neuropathy, if you are confident in your diagnosis: the patient is over the age of fifty, they have all the vascular, you know, they have vascular risk factors. And those vascular risk factors are things like diabetes, hypertension, high blood pressure, hyperlipidemia, obstructive sleep apnea. They have a “disc at risk” in the fellow eye. They don't have pain, they don't have a cancer history. Then doing an MRI of the orbits is probably not necessary to rule out another cause. But if you aren't confident that you have all of those features, then you should absolutely do an MRI of the orbit. The MRI of the brain probably doesn't provide you with much additional information. However, if you are trying to distinguish between an ischemic optic neuropathy and, say, maybe an optic neuritis, in those patients we do recommend MRI orbits and brain imaging because the brain does provide additional information about other CNS demyelinating disorders that might be actually the cause of a patient's optic neuritis.

Dr Smith: I wonder if you could talk a little bit about posterior ischemic optic neuropathy. That's much less common, and you mentioned earlier that those patients don't have optic disk edema. So, if there's a patient who has vision loss that- in a similar sort of clinical scenario that you talked about, how do you approach that and under what circumstances do we see patients who have posterior ischemic optic neuropathy?

Dr De Lott: So, you're going to most often see patients with posterior ischemic optic neuropathy who, for example, have undergone a recent surgery. These are often associated with things like spinal surgeries, cardiac surgeries. And there are a number of risk factors that are associated with it. Things like blood pressure, drain surgery, the amount of blood loss, positioning of patient. And this is something that the surgeons and anesthesiologists are very sensitive to at this point in time, and many patients are often- this can be part of the normal informed consent process at this point in time since this is something that is well-recognized for specific surgeries. In those patients, though… again, unless you're really certain, for example, maybe the inpatient neurology attending and you've been asked to consult on a patient and it's very clear that they went into surgery normal, they came out of surgery with vision loss, and all the rest of the features really seem to be present. I would recommend that in those cases you think about orbital imaging, making sure you're not missing anything else. Again, unless all of the features really are present- and I think that's one of the themes, definitely, throughout this article, is really the importance of neuroimaging in helping us to distinguish between different types of optic neuropathy.

Dr Smith: Yeah, I think one of the things that Eric Eggenberger talks about in his article is the need to use precise nomenclature too, which I plan on talking to him about. But I think having this very structured approach- and your article does it very well, I’ll tell our listeners who haven't seen it there's a series of really great tables in the article that outline a lot of these. I wonder, Lindsey, if we can switch to talk about arteritic optic neuropathy. Is that okay?

Dr De Lott: Sure. Yeah, absolutely.

Dr Smith: How do you sort that out in an older patient who comes in with an ischemic optic neuropathy?

Dr De Lott: Yeah. In patients who are over the age of fifty with an ischemic optic neuropathy, we always need to be thinking about giant cell arteritis. It is really a diagnosis we cannot afford to miss. If we do miss it, unfortunately, patients are likely to lose vision in their fellow eye about 1/3 to 1/2 the time. So, it is really one of those emergencies in neuro-ophthalmology and neurology. And so you want to do a thorough review systems for giant cell arteritis symptoms, things like headache, jaw claudication, myalgias, unintentional weight loss, fevers, things of that nature. You also want to check their inflammatory markers to look for evidence of an elevated ESR, elevated C-reactive protein. And then on exam, what you're going to find is that it can cause an anterior ischemic optic neuropathy, as I mentioned earlier. It can cause palette optic disc swelling. But giant cell arteritis can also cause posterior ischemic optic neuropathy. And so, it can be present without any swelling of the optic disc. And in fact, you know, you mentioned one of my mentors, John Trobe, who used to say that in a patient where you're entertaining the idea of posterior ischemic optic neuropathy, who is over the age of fifty with no optic disc swelling, you should be thinking about number one, giant cell arteritis; number two, giant cell arteritis; number three, giant cell arteritis. And so, I think that is a real take-home point is making sure that you're thinking of this diagnosis often in our patients who are over the age of fifty, have to rule it out.

Dr Smith: I'll ask maybe a simple question. And presumably just about everyone who you see with a presumed ischemic optic neuropathy, even if they don't have clinical features, you at least check a sed rate. Is that true?

Dr De Lott: I do. So, I do routinely check sedimentation rate and C-reactive protein. So, you need to check both. And the reason is that there are some patients who have a positive C-reactive protein but a normal sedimentation rate, so. And vice versa, although that is less common. And so both need to be checked. One other lab that sometimes can be helpful is looking at their CBC. You'll often find these patients with giant cell arteritis have elevated platelet counts. And if you can trend them over time, if you happen to have a patient that's had multiple, you'll see it sort of increasing over time.

Dr Smith: I'm just thinking about how you sort things out in the middle, right? I mean, so that not all patients with GCF, sky-high sed rate and CRP…. And I'm just thinking of Dr Trobe's wisdom. So, when you're in an uncertain situation, presumably you go ahead and treat with steroids and move to biopsy. Maybe you can talk a bit about that pathway?

Dr De Lott: Yeah, sure.

Dr Smith: What's the definitive diagnostic process? Do you- for instance, the sed rate is sky-high, do you still get a biopsy?

Dr De Lott: Yes. So, biopsy is still our gold-standard diagnosis here in the United States. I will say that is not the case in all parts of the world. In fact, many parts of Europe are moving toward using other ancillary tests in combination with labs and exam, the history, to make a definitive diagnosis of giant cell arteritis. And those tests are things like temporal artery ultrasound. We also, even though we call it temporal artery ultrasound, we actually need to image not only the temporal arteries but also the axillary arteries. The sensitivity and specificity is actually greater in those cases. And then there's high-resolution imaging of the vessels and the- both the intracranial and extracranial distributions. And both of those have shown some promise in their predictive values of patients actually having giant cell arteritis. One caution I would give to our listeners, though, is that, you know, currently in the US, temporal artery biopsy is still the gold standard. And reading the ultrasounds and the MRIs takes a really experienced radiologist. So, unless you really know the diagnostic accuracy at your institution, again, temporal artery biopsy remains the gold standard here. So, when you are considering giant cell arteritis, start the patient on steroids and- that's high dose, high dose steroids. In patients with vision loss, we use high dose intravenous methylprednisolone and then go ahead and get the biopsy.

Dr Smith: Super helpful. And are there other treatments, other than steroids? Maybe how long do you keep people on steroids? And let's say you've got a patient who's, you know, diabetic or has other factors that make you want to avoid the course of steroids. Are there other options available?

Dr De Lott: So, in the acute phase steroids are the only option. There is no other option. However, long term, yes, we do pretty quickly put patients on tocilizumab, which is really our first-line treatment. And I do that in conjunction with our rheumatology colleagues, who are incredibly helpful in managing and monitoring the tocilizumab for our patients. But when you're seeing the patients, you know, whether it's in the emergency room or in the hospital, those patients need steroids immediately. There are other steroid-sparing agents that have been tried, but the efficacy is not as good as tocilizumab. So, the American College of Rheumatology is really recommending tocilizumab as our first line steroid-sparing agent at this point.

Dr Smith: Outstanding. So again, I will refer our listeners to your article. It's just chock-full of great stuff. This has been a great conversation. Thank you so much for joining me today.

Dr De Lott: Thank you, Dr Smith. I really appreciate it. 

Dr Smith: The pleasure has been all mine, and I know our listeners will be enjoying this as well. Again, today I've been interviewing Dr Lindsey De Lott about her article on optic neuropathies, which appears in the most recent issue of Continuum on neuro-ophthalmology. Be sure to check out Continuum Audio episodes from this and other issues. I already mentioned Dr Eggenberger and I will be talking about optic neuritis, which will be a great companion to this discussion. Listeners, thank you 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.