VLOG: NeuroOp Guru: Nonleaking CRF and SRF out of proportion to optic disc edema from IIH

Andrew Lee, MD, and Andrew Carey, MD, sit down on another episode of the NeuroOp Guru to discuss nonleaking CME and subretinal fluid out of proportion to optic disc edema in idiopathic intracranial hypertension in the setting of optic atrophy.

Video Transcript

Editor's note - This transcript has been edited for clarity.

Andy Lee, MD:

Hello, and welcome to another edition of the NeuroOp Guru. I'm here with my good friend Drew Carey. Hi, Dr Carey.

Drew Carey, MD:

Hi, Andy.

Andy Lee, MD:

And today we're gonna be talking about non leaking cystoid macular edema, CME, and subretinal fluid that seems out of proportion to optic disc edema in idiopathic intracranial hypertension, but in the setting of optic atrophy. So Dr. Carey, maybe you could just tell us why is this even an issue? And why is it coming up now?

Drew Carey, MD:

That's a great question, Andy. I think there's this thought that in some patients who have optic disc atrophy from whatever cause, but very commonly papilledema, that maybe the disc is to atrophic to swell, and that the disc is not a good barometer for ICP, in that setting. And patients may be having IIH relapses and elevation of their ICP or shunt failure, if they were treated with a shunt. And we're not going to be able to detect it with looking at their optic nerves. Because they're already very pale, and there's not a lot of nerve fiber layer left there. And the question is, maybe we could have other ocular biomarkers that might help us detect ICP elevation in these patients. And in this case, the OCT of the RNFL, I think is helpful. Clinically, this patient did not have any disc edema, and their RNFL thickness was fairly average. But in a patient with known disc pallor atrophy, having a normal range RNFL might be a little bit of a red flag.

Drew Carey, MD:

And, so that's one tool. But this case identified, perhaps another tool that we might be able to use to help to identify intracranial pressure elevation, and in other cases of really severe swollen optic nerves in other etiologies, like in really bad NAION. Sometimes we can see fluid that leaks out from the disk also in conditions like hypertensive–stage 4 hypertensive retinopathy, where we get fluid that leaks into the macula. And even underneath the macula with subretinal fluid. And of course, we're all familiar with like neuro-retinitis where that may happen, obviously, this is a little bit of a different etiology. And so seeing that retinal fluid is a sign in those other cases that there's really severe optic nerve swelling, and even in acute really severe papilledema, you can see that. Now this patient didn't have really severe papilledema, because the nerves are a little bit atrophic. But we did see on the OCT, that this fluid had leaked out of the retina, and that can lead to decreased visual acuity. Which from papilledema alone, you don't really expect to see decreased visual acuity.

So if you had a patient coming in with a history of papilledema, and they're saying, "Hey, I'm really having a really hard time reading and not doing well on the eye chart," and you do their field and you see essential scotoma, you're like what's going on, that's not a typical finding for papilledema. It would be good idea to look at the macula. And this could be one of the reasons that's happening. And then retina doctors like to talk about leaking and non-leaking CME. And so for me, who does a little bit of retina and a little bit of narrow, I thought it was really interesting that on the fluorescein we saw this CME in the subretinal fluid, there's obviously some leaking going on. But we don't see the petaloid leakage in the macula, it's not coming from the retina.

Andy Lee, MD:

So maybe you could walk us through these figures, and then just highlight not only what you just said, non-leaking CME and how this fluorescein helps, and then maybe you could also comment on where is the fluid coming from.

Drew Carey, MD:

So on the top left, labeled A and B, we have the cross-sectional peripapillary OCT, from the ring scan. And it's a cross sectional, there's a little bit of segmentation error in the right eye where we see this dip in the RPE. But I think the RNFL and the internal limiting membrane are segmented pretty well. And on the average, it's in the green, it says it's normal. And when we look at the actual thickness tracing, we see that there's a little bit of thickening there, but certainly not severe, not the level that you would expect to have with fluid leaking out into the retina.

And in in the left eye. You know, it says again, average RNFL thickness in the green, now maybe there's a little bit of thinning in the red zone and a little bit of thickening over here on the cross-sectional or on the thickness map. Where we see it's it's elevated into the white so those balance each other out. But I think if we saw that in a patient with either of these eyes who came in and it was, you know, we said, that's pretty mild, you know. I don't think you're really at risk of vision loss. You know this isn't a big deal. In the panels below that, E and F, these are cross-sectional scans, OCT scans of the macula, right eye and left eye. And here we can see just like in the vitreous which is hyper reflective, it's it's black.

Underneath the retina, underneath the fovea, particularly, we see this area very similar reflectivity, so that's subretinal fluid. And then in the nasal macula, we get these cystoid changes, mostly in the outer nuclear layer. Running from the fovea all the way up to where you would expect the optic nerve to be where the scan is cut off and very similar mirrored appearance in the left eye, where you get this hyper reflective fluid in the subretinal space underneath the fovea and elongation of these outer segments. And then almost schisis like changes for the entire retinal fluid in the nasal macula.

Below that, we have a late phase of widefield fluorescein angiography and we see there's a little bit of staining in the optic nerve in the right eye, suggesting, yep, there's some vascular leakage in the optic disc. Which you would see in papilledema as well as other causes of optic disc edema. But we don't see any hyper fluorescence or petaloid pattern of leakage in the macula, corresponding to that cystoid fluid we're seeing on the OCT scan.

And in the left eye, the optic disc has really minimal hyper fluorescence that could even be normal there. But again, we don't see any leakage in the fovea, or in the nasal macula. To suggest that there's an exudative, retinal, vascular or chorioretinal vascular process, so no signs of the cradle neovascular membrane and no leaking of the, in the nasal macula petaloid pattern. So that that tells you that this is not a retinal exudative process and tells us this is probably coming from the nerve. And the fluid in this case, I don't think we've ever done any specific testing on the fluid to look to see if it's CSF or where it's coming from.

There's a lot of questions in patients who have optic disc pits is the fluid that leaks out, CSF fluid or something else, I don't think that's the question in here, I don't think we have a clear, clear pathway for communication in papilledema patients, or in this patient. So probably this is a transudative fluid coming from the optic disc vessels. Those capillaries that feed the optic nerve, when it becomes swollen from the pressure, the vessels become leaky and that's what leads to the optic nerve swelling. And that fluid can can leak out into the surrounding retina and subretinal space.

Andy Lee, MD:

They did a shunt and it went away?

Drew Carey, MD:

They did. So they did a shunt for the patient. And all the fluid went away, the optic disc became less thick, you know, it's a little bit of a stretch to say they were definitely swollen before, because they were normal thickness. But this is probably the patient's actual baseline thickness due to the optic disc atrophy. So we can see the average RNFL thickness is much lower, it's now in the red. So now we know, in hindsight, that that was swelling of the optic nerves on the RNFL. And we can see the fluid, the subretinal fluid, and the intraretinal fluid all went away. So that by lowering the intracranial pressure, we stopped this transudative process and allowed that retinal vasculature and optic dispatch vasculature to return to a normal state.

Andy Lee, MD:

So what do you think the take home message for audiences from this case?

Drew Carey, MD:

So this case is definitely a little bit atypical. It's not our standard papilledema IIH case. I think, you know, the take home points is this tells us a little bit about the pathophysiology of subretinal fluid and macular edema that we see in our patients who have papilledema. That we know that it is related to the optic disc swelling and the elevated intracranial pressure and treatment of that underlying process can help to reverse that fluid and help to protect the central vision. I do think it's important to remember that most patients with papilledema are not going to have central vision loss. So if you have a patient with papilledema or optic disc swelling and central vision loss, thinking about potentially other etiologies, like is it optic neuritis with optic disc edema? Or is it an NAION? Or is this a patient with papilledema who has fluid leaking out from the optic nerve underneath the macula?

Andy Lee, MD:

Well, thank you again, Dr. Carey. That concludes yet another edition of the NeuroOp Guru.

Drew Carey, MD:

Thanks again for thanks for having me.