This transcript has been slightly edited for clarity:
Andy Lee, MD:
Hello and welcome back to the NeuroOp Guru. I’m here with my good friend Elizabeth Fortin, MD. Hello, Elizabeth.
Elizabeth Fortin, MD:
Hi.
Andy Lee, MD
And today we are going to talk about a recent article. Should visual snow syndrome have an evaluation outside the norm in clinical ophthalmological tests? The two participants were Claire Fraser, MD, and Michael S. Vaphiades, DO. Elizabeth, maybe you could tell us what visual snow is.
Elizabeth Fortin, MD:
Snow visual syndrome is a spectrum of symptoms we see in people who describe having small spots or dots in their visual field. So normally these are black and white dots all over the visual field. It is often described as an out of tune TV, like an old TV. And it persists over time. So it takes at least 3 months to call it visual snow syndrome. And it is often associated with other visual symptoms such as photophobia or other visual and thematic phenomena.
Andy Lee, MD:
And their exams are normal?
Elizabeth Fortin, MD:
Yeah, so people called primary visual snow syndrome have a perfectly normal exam. They often describe the symptoms I just talked about, in a very classic way. They have no other neurological symptoms and their examination is completely normal, unlike people who have, for example, secondary visual snow, who may have other symptoms or other examination findings.
Andy Lee, MD:
So you’re okay with us doing a visual field, automated perimetry, and macular OCT on all these people?
Elizabeth Fortin, MD:
Of course, you have to do a full eye exam, including a dilated fundus exam, I believe. And in the clinic at the office, it is easy to get a macular OCT to assess the retinal layers. More importantly, probably the outer retinal layers in the visual field tests that we should have done in all of these people.
Andy Lee, MD:
And have you ever found anything about these people?
Elizabeth Fortin, MD:
It’s very rare. If you do a good exam, questionnaire or history with these people, and there really are no other symptoms, it is extremely rare to find any other results on your exam, but it can certainly happen. But I would say it’s pretty rare. Have you found any?
Andy Lee, MD:
No, I never found anything. So the problem is that Claire Frazier is saying that although most cases are idiopathic, there are certain atomic and neurological conditions that can mimic visual snow in the literature. And so the question is, first of all, does it exist? And second, should we do an MRI, EEG, and ERG?
Elizabeth Fortin, MD:
Yeah, so I think like we just said, what’s really important is to take a really good story. And first you need to know what the idiopathic version of visual snow syndrome looks like and what does it look like. It is therefore necessary to make sure to have a good anamnesis and to do a complete examination, including what we have just mentioned, that is to say that it is absolutely necessary to have a visual field and a macular OCT . She also suggests that you could get fundus autofluorescence, which I don’t do regularly in my practice, but I think it might be a good idea if you’re unsure about the symptoms because you’re wondering if some patients who have a normal examination might have, for example, certain retinal diseases which are often present without any findings or fundus examination. So it’s a good addition to consider if you’re not completely sure you have the idiopathic version of visual snow syndrome. But otherwise, I think if you really do a good story and a good review, you should be fine, without doing any other tests outside of the office.
Andy Lee, MD:
Do you recommend they get an MRI?
Elizabeth Fortin, MD:
No, normally I do not recommend it myself. What do you think?
Elizabeth Fortin, MD:
Most of the patients I see have already had an MRI. So it’s very rare that I see someone who hasn’t already had an MRI. Probably a little different maybe in Canada, but I don’t really recommend that they test. There have been studies with fMRI and PET that have shown that the lingual gyrus is overactive. I do not order any of these tests. Did you order PET or fMRI scans or anything?
Elizabeth Fortin, MD:
Not at all because it does not change my management with these patients. There are therefore not really any treatments whose effectiveness in these patients has been convincingly demonstrated. So I don’t do them all the time. I think it’s used more for research purposes as of now. And maybe we will eventually find a treatment that works for these patients, but personally, I haven’t followed them.
Andy Lee, MD:
I usually show patients other patients who have had an fMRI and a PET scan so they know I believe them. But I don’t order a new one on them. How about the EEG. You order this?
Elizabeth Fortin, MD:
So EEG No. This is a good question because one always wonders if there could be patients who have, for example, occipital seizures who could present with visual snow. But often these people have other neurological symptoms, or their symptoms are intermittent, which may suggest that they have another condition, such as migraine or seizures. I therefore do not systematically order an EEG. What do you think?
Andy Lee, MD:
No. Some patients with occipital crisis have small circles, but they are larger and they are not as diffuse as snow and they contain colored spots. Unless there is other evidence of seizure activity, I have not routinely recommended EEG, electroencephalography. How about WRG? Should you do ERG on these people?
Elizabeth Fortin, MD:
It’s the same thing, pretty much the same answer. So if the exam is completely normal, again, including an OCT and visual field, I normally don’t. If you have any doubts too, a good way to approach these patients is to follow them over time. If you think there is something not quite typical, you can review these people, and if there is a change in their visual field or their appearance of the other retinal layer on the OCT, then you can probably think of doing an ERG. Now, again, there are usually findings either on the peripheral visual field and patients who have outer retinal diseases, or they may have findings on fundus examination. Specifically, if you have no fundus findings, if you do fundus autofluorescence, as Dr. Fraser suggested, you will likely find out if there is retinal pathology. . So, unless there is one, I don’t routinely order ERGs, just also for a matter of access, because it’s not very easy, where I work to order to get an erg. What do you think?
Andy Lee, MD:
I don’t order electrophysiology unless there’s something on the exam that suggests it’s retinol, about a word on the treatment. Do you use a treatment on does anything work?
Elizabeth Fortin, MD:
I did not use any treatments. So what I would say is probably happened once or twice in people who were very, very anxious about the symptoms and were about to change careers because of the symptoms. Because of the symptoms. I haven’t had much success with them. There are drugs that have been used like lamotrigine, sertraline, topiramate, but I don’t use them personally. What do you think?
Andy Lee, MD:
We offer it to patients, mainly anti-anxiety agents help them with coping mechanisms. And is simply reassuring themselves and dealing with their normal underlying anxiety treatments helpful about Diamox? I used Dynavox. What about acetazolamide?
Elizabeth Fortin, MD:
So, I don’t want to say, unless there are suggestions of raising intracranial pressure, I know there’s no harm in doing that. But I don’t use them personally.
Andy Lee, MD:
And what happens to these people? They just walk away. They seem not to come back after a while in my practice.
Elizabeth Fortin, MD:
Yes, they are not coming back. After a while the symptoms don’t tend to go away in my experience. I think they stay there. But, reassured, some people feel sufficiently confident and know that they will not lose their sight. Often I feel like reassurance is probably the most important part of what we do in the office. And, of course, you have to base your reassurance on a very complete and normal examination. And I think that often that is enough to reassure them. I mean, maybe some end up going to see my colleagues elsewhere, but I don’t think so.
Andy Lee, MD:
I don’t think so either, as I don’t see many second and third opinions on snow. I think first person is probably all they need. Well, maybe you could just give the take home message then, from your point of view, should visual snow have further testing?
Elizabeth Fortin, MD:
Yes, so I think the takeaway is that you need to take a very thorough history of these patients and make sure that you have a full eye exam, including a dilated fundus exam, you need to get an O CT of the macula and get a visual field trial. And if you’re in any doubt, there’s no harm in getting an MRI and/or a slash erg EEG depending on the results. But, if you’re confident enough and have classic symptoms of idiopathic snow visual syndrome, I think it’s okay to just do the exam, the eye exam in the clinic.
Elizabeth Fortin, MD:
I agree, Elizabeth. Well, that concludes another adventure with the NeuroOp Guru, and we’ll see you next week. Thanks again Elizabeth. Goodbye.
