Dr. Geoffrey Parker at the 2023 Cedars-Sinai Intracranial Hypotension Conference
Dr. Geoffrey Parker, of Macquarie University Hospital in Australia, presented this talk on endovascular approaches for idiopathic intracranial hypertension at the 2023 Cedars-Sinai Intracranial Hypotension Conference on July 9, 2023. The conference was hosted by Cedars-Sinai with generous support from the Spinal CSF Leak Foundation in Kohala Coast, Hawaii.
Transcript
[00:00:12] Idiopathic intracranial hypertension is a name, and so is benign intracranial hypertension, but they’re not good names because the disease is neither idiopathic or benign, and I suppose we should call it pseudotumor cerebri. Everyone knows population figures, nine to one female, majority are obese, headache, visual disturbances, as have been mentioned.
[00:00:36] Transient visual obscurations are sensitive, a very specific sign. So if the patient coughs and their vision goes completely black, then that’s a very helpful indicator. Papilledema. And the majority have pulsatile tinnitus. The diagnostic criteria, would have been mentioned in the last talk, the Dandy criteria modified by Kathleen Digre [and] Alastair Corbett is one that we use, but it doesn’t mention, it mentions imaging studies, but it doesn’t say anything about veins.
[00:01:10] We think the best quality imaging is done with ATECO MRV, which was described by the group from Toronto. And so we use intravenous gadolinium enhanced MRV, and it is set up so that the contrast resolution part of the image is obtained when the gadolinium is present in the image, and the rest of the image in three to five minutes later is completed when the gadolinium is largely passed.
[00:01:37] So you get these extraordinary images here where you can see the veins and the cortical venous tributaries. It’s also, it’s very important to look at the jugular veins, as you can see there, and their relationship to the styloid process over here, and to look at normal images there.
[00:01:57] It’s also important to realize that there is asymmetry in the transverse sinuses very frequently. And so you can discuss which of those is dominant. So this is a case where there is narrowing of the transverse sinus. We typically don’t worry if one is small as long as the other is large, because what you need not to have venogenic BIH is one good transverse sinus.
[00:02:26] And this is a study that was read as normal, but I hope people in this audience can identify that patient has severe bilateral jugular venous compression. So, apart from the skull base collaterals, which can come out here, this is almost functionally the same as transverse sinus stenosis.
[00:02:49] You can also have SVC obstruction as a cause for this condition. And you know, similar to the patient with malignant SVC obstruction, this patient had pacemaker leads in for many years because of a congenital cardiac disease, and the pacemaker leads were changed, and during that procedure the SVC was damaged, and she had to have a stent put in and then she developed a stenosis in the stent, and so that had to be angioplastied, and and she recovered.
[00:03:25] It’s also important to realize that some of these patients are on this bizarre seesaw that we’ve been talking about where sometimes they have BIH and sometimes they have SIH, and that’s a very important consideration.
[00:03:43] So, the steps in diagnostic and therapeutic evaluation where IIH patients can be shown to have venous sinus stenosis on ATECO MRV, they can be further investigated with a direct retrograde cerebral venogram and manometry if they’re not controlled with medical therapy. And if they can be shown to have increased venous sinus pressure above a stenosis and a venous pressure gradient, or, as we’ve discovered, lots of collateral veins that relieve the pressure without getting rid of the stenosis, we hypothesize that release of the venous narrowing could result in increased CSF absorption into the venous sinuses through arachnoid granulations and therefore a decrease in intracranial pressure.
[00:04:34] We avoid focusing on whether the stenosis is primary or secondary, because, as has been mentioned, it is a feedback loop and there is no answer to the question about what comes first, the chicken or the egg. IIH can exist without papilledema if the patient has optic nerve atrophy, and we’ve seen a number of patients.
[00:04:55] So here’s one of our venograms, and you can see we’ve placed a catheter from the femoral vein up into the superior sagittal sinus. And, there it is there. And we’ve injected contrast medium, and you can see that the patient—we’re recognizing these as an important feature now. So you can see these collateral veins, and patient has a stenosis of the left transverse sinus. When you pull the catheter back across that, you can see the pressures that you measure.
[00:05:25] We were measuring, 27, 28, 27, 28. And then all of a sudden it drops down to 15 across that stenosis right there. And if you do a chart recording, it shows beautifully that the pressure falls. And also, the pulsatility decreases, because the venous system is more compliant under lower pressure. So the pressures are very important. The study is meaningless unless you have pressures, and this is our current record holder, a patient from Broken Hill with a pressure in the superior saggital sinus of 94, psychotic sixth nerve palsies, and we treated that stenosis and she got better. Of course she had, in order to have a venous pressure of 94, she had an arterial pressure of 200.
[00:06:16] So there are numbers of different kinds of stenoses. There are intrinsic stenoses, which are giant arachnoid granulations. There have been papers in the literature that say that they’re a normal finding, one of them from Australia. But it’s just it, you know, it is untrue in the vast majority of cases.
[00:06:34] There can be extrinsic compression. So there’s compression of a collapsible sinus by raised intracranial pressure, possibly due to compression by the weight of the brain. Bear in mind that this condition has never been recognized in quadrupeds. So where the transverse sinus is in a vertical orientation, you don’t get this condition. And it can be septae and dural bands. But thrombosis is also a cause of stenosis, but it’s excluded from the definition in the Dandy criteria.
[00:07:07] So this is a picture from Ian Johnston’s book, and this is an arachnoid granulation, and they get large because they get a hernia of brain tissue, or meninges, or just CSF, through the stalk of the cauliflower into this structure here. And this is a paper that we, from a paper we published in the AJNR in 1998. Before we recognized this and we had a giant arachnoid granulation for histological evaluation because the transverse sinus had been resected to treat a dural fistula.
[00:07:43] And there was a giant arachnoid granulation in it. And we published and we said, wow, there’s some brain inside this fistula, this arachnoid granulation. And we said, well, this is ectopic brain tissue. But it wasn’t. It was a hernia of brain tissue into the arachnoid granulation. And sometimes you can even see these hernias on MRI. So that’s CSF and brain tissue into the granulation.
[00:08:09] The other type of stenosis, other main type of stenosis is extrinsic. So in this patient, they’ve got a giant AG on one side and an extrinsic stenosis on the other side. And an extrinsic stenosis is a Starling resistor, rather like the gastroesophageal junction, where the resistance is proportional to the external pressure because the resistor is collapsible.
[00:08:33] And that’s quite different to an Ohmian resistor, where there is no effect on the resistance through the resistor due to external pressure. There are also these strange septae that are seen in the transverse sinuses, like that fibrous band there. Bear in mind that the transverse sinuses form embryologically because of coalescence of venous, small venous lakes.
[00:08:58] And so sometimes there’s a bit of a residuum of one of the septae between the lakes, and that can cause narrowing of the transverse sinus. The critical thing to understand about this disease is that there is raised intracranial pressure for some reason, and that causes narrowing of the venous sinuses, venous outflow obstruction, venous hypertension, decreased CSF absorption, and the disordered positive biofeedback loop, which raises intracranial pressure.
[00:09:29] And so the intracranial pressure then rises until another resorptive mechanism takes over, or, very occasionally, the patient can have an ICP crisis and pass away. We’ve seen that once. So how do you treat this by stenting? Well, what you have to do is your venogram. You have to identify the stenosis, show that there is a gradient across it.
[00:09:55] Then you have to get a guiding catheter up there through that tortuous section. Then you have to get the guiding catheter across the stenosis and up to that point there. And that can be quite difficult. And then you advance the stent across the stenosis and deploy the stent ,and that’s what you end up with.
[00:10:14] We’ve had to use, essentially off label, although that doesn’t apply to us in Australia, we’ve had to use peripheral vascular stents for this procedure all along. But there are now, I think Ferdinand, you were saying, three companies that are coming out with purpose designed stents for intracranial veins.
[00:10:34] So, there’s a stent before deployment. There’s a stent after deployment. So what issues might we consider? Do we need to treat one side or two sides? We only treat the dominant side. There are people who publish that there is a need to treat both sides. We don’t believe that. We’ve treated two sides, I think, in one patient in our 350 cases.
[00:10:59] The question of how long to make the stent, if the stenosis is just due to an arachnoid granulation, we can use a short stent across the stenosis. But when the stenosis is an extrinsic stenosis, a long segment stenosis, we tend to use longer stents because what you frequently see is that if you have not treated the whole length of the transverse sinus, you’ll get a recurrence stenosis above the stent.
[00:11:28] We don’t tend to do what David Kumpke in Denver does, which is to pass stents all the way up into the superior sagittal sinus, which we occasionally, you know, once in a while, we’ve gone around the bend through the torcula into the superior, just the bottom of the superior sagittal sinus. Recurrent stenoses are usually from extrinsic stenoses. Sometimes stenoses can be evanescent.
[00:11:51] We’ve had patients where we’ve had to do a number of venograms in order to see the stenosis. We had one young lady from Canberra who had terrible problems with BIH and it was only on the third occasion that all of a sudden the stenosis appeared and we were able to treat her. In-stent stenoses are very rare.
[00:12:12] And in-stent thromboses are very rare. The best anticoagulant regime is worth discussing. We’ve always used combination of aspirin and clopidogrel or aspirin and prasugrel, but the hematologists say, well, actually you’re not treating an arterial problem and you really need some anticoagulant as well as antiplatelet agent. So they are now recommending we use aspirin and apixaban.
[00:12:40] After stenting, most patients get some headache. And you say to them, “how are you feeling?” And they say, “Oh, I’ve a terrible headache.” “Well, how does that compare? Is that your normal headache?” And they say, “No, it’s not my normal headache at all. It’s only on, it’s only on the side of the stent, just around my eye.” And what they have is durally mediated pain on the ipsilateral to the stent, and it lasts usually two to five days and then resolves. So we tell them about that and they don’t worry about it.
[00:13:13] Occasionally you can see a recurrent stenosis above the end of a stent that’s too short in a patient with an extrinsic stenosis that I mentioned. These are our results published in the AJNR in 2012, and you can, this was 70 patients, and 58 had papilledema before stenting and none had papilledema after stenting. Sixteen had some visual acuity loss, and that resolved in some patients, not all.
[00:13:44] Visual field loss also improved. Sixty patients had headache, and nine patients had headache after the stent. So headache doesn’t always resolve. Sometimes they can have headache from multiple causes. And you know that the part that’s not due to BIH doesn’t resolve. The TVOs and the pulsatile tinnitus and the diplopia all resolved.
[00:14:09] There was a meta analysis published in 2015, where 185 patients with 221 stents were reviewed and they measured the gradient before and after, so did we actually; but they measured the gradient before and after and showed that the gradient resolved. They had complications of 5.4 percent, major complications in almost 2 percent, headache improved in 78, and the other things like papilledema improved in a large number of patients. They had to re-stent 10 patients in 185. And then last year there was a paper published from Australia which had similar results. 89 percent were able to cease Diamox after stenting.
[00:14:58] So, stenting usually cures papilledema and pulsatile tinnitus and saves vision. It doesn’t always cure headache, because the patient may have headache from multiple causes. And you need to exercise a great deal of care in patients who present with pulsatile tinnitus, for example, without a full set of IIH criteria. Because, you know, you may be dealing with a different condition.
[00:15:23] There’s a paper published in Neurointerventional Surgery 2022, which talked about the major complications of this procedure. Ferdinand was one of the authors. And that is, you know, there are complications that occur. They include acute subdurals, intraprocedural in-stent thrombosis, delayed in-stent thrombosis, cerebellar hemorrhage, vascular perforation during venography, and SAH and SDH after cerebellar cortical venous perforation. So in, in their paper, they found six patients with major complications and listed them there. I would add two other complications being Vein of Labbe occlusion and also problems with anaesthetic management. I’ll speak more about that in a moment.
[00:16:14] So, major complications. Hemorrhage: of course, you’re dealing with a patient who has dual antiplatelet agents and is on heparin and has raised intracranial pressure. And any hemorrhage can be absolutely catastrophic. It is crucially important to say to the anesthetist, the anesthesiologist, that you are dealing with a patient with raised intracranial pressure. You need a full neuro anesthetic so that they do not make the patient hypercapnic during the emergence phase from anesthesia, because otherwise that will push the RICP up. And you know, can lead to, we’ve had one patient where that caused a critical Cushingoid response.
[00:16:59] Occlusion of the Vein of Labbe is important. There’s another, there’s a paper published in 2015 which said that you could put a stent across the vein of the orifice of the Vein of Labbe with no problems. We’ve had one issue where, you know, where the Vein of Labbe comes down to the transverse sinus. Occasionally, there’s a thing that looks like the delta of a river with an arachnoid granulation sitting in it. And we’ve had a situation where the stent pushed that arachnoid granulation up into the Vein of Labbe, blocked the Vein of Labbe, and the patient had a bleed, which was catastrophic. So that’s one point to watch out for. This was that patient and she did not survive. It is very important to be extremely careful.
[00:17:48] This is a patient who who had a bleed during the procedure because of perforation of a venous tributary. And we had to reverse the heparin with protamine, and you can see we got thrombosis in the sinus. She needed an emergency craniotomy, which was done and she survived, but it was a very nasty experience. That’s her and afterwards, that’s the craniotomy, and she had a hemianopia as a result of that.
[00:18:21] This is just an illustration of the Munro Kelly hypothesis and what happens with rising PCO2 levels and ICP rises. So it’s very important to, to emphasize that to the anesthetist. These patients can be very brutal because, unlike the patient who has a craniotomy, where the raised intracranial pressure is released, the raised venous pressure goes away straight away, but the raised CSF pressure can take a fair bit of time.
[00:18:53] So in conclusion, the actual precipitating cause of BIH is often not known, but something tips the patient into an abnormal positive biofeedback cycle and leads to persisting symptoms. The purpose of the stent is the purpose of the stent is to break that positive feedback cycle, and not to treat a venous stenosis, which may or may not be reversible. We have found good results from venous sinus stenting. They’re at least as good as shunting without the high repeat procedure rate. And we think that stenting should be the primary therapeutic option when medical treatment fails.
[00:19:37] Occasionally, we still do optic nerve fenestration in a patient with fulminant BIH who presents before a stent can be put in. Or when there are reversible causes like BIH secondary to minocycline therapy and vision is failing. That’s all I have. Thank you for your attention.