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To Operate or Not to Operate: Implications for Management of Arachnoid and Pineal Cysts

Cormac Maher

June 29, 2011


- Hello, ladies and gentlemen, thank you for joining us, find out this session on the AANS Operative Grand Rounds. Today we have with us Dr. Cormac Maher, from university of Michigan. Our discussion will be about, management of controversial lesions, such as arachnoid cysts and pineal cysts. Actually, this is the first session of a series of three sessions, which we'll be discussing management of controversial cerebral lesions. The second and third conferences or the web conferences, we'll be discussing management of Chiari malformations as well as incidental vascular lesions respectively. Cormac, thank you again for joining us, and we're looking forward to hearing your valuable information.

- Thanks, Aaron, I appreciate the invitation to present today, on a topic that I think is of interest hopefully to many neurosurgeons. I have no financial disclosures, I do have many people to acknowledge that I've worked with, over the past several years on these topics. So you can see here and some of them will be named later in the presentation. I believe that the intercranial cysts are a important topic because they present a neurosurgical outpatient practice with a great frequency, and frequently they are associated with symptoms that are also very, very common in normal children or in children with abnormalities that aren't necessarily related to the cysts. I have here a list of common neurological symptoms that can occur in children with or without any associated pathology that can be seen on the MRI scan. Headaches, as we'll get into in this presentation are a relatively common symptom in children, not necessarily although they might be associated with pathological entities, are not necessarily associated with pathological entities of interest to neurosurgeons. Developmental delay also very common, childhood seizures common, failure to thrive depending on how it's defined, very, very common and macrocranium, again, depending on how it's defined can be very, very common. I mentioned that headaches are frequent occurrence in children, and in fact, a recent survey appearing in the British Journal of General Practice, to find at least in the British population, that 20% of adolescents had complained of a headache, one or more times each week. And that 6% of adolescents had a headache several times a week or even every day. So headaches at least in adolescents are not particularly rare, seizures as this audience knows very well is also very common at least single seizures. Turning that issue on its head, looking at MRI findings. Now, there are also very, very common findings on MRI that are not necessarily of at least treatment interest to neurosurgeons, vascular entities, such as DVA anomaly, postnatal hematomas, very common if we image newborn babies, Chiari malformations, lipomas cysts and so on, all maybe found is incidental findings in the pediatric population. And this raises what I regard as an important issue, which is that there are common incidental findings in pediatric neuro imaging. And there are common symptoms in children which may or may not be related to these common findings on MRI imaging. And I think it's up to the neurosurgeon to be very, very cautious when ascribing anything more than the coincidental association to these entities. This slide I've taken from the New England Journal of Medicine and excellent article written in 1986 by Mold and others, where they described something that they called the cascade effect. And I think this is an important point to understand for any pediatric practice, especially a pediatric neurosurgical practice. In many cases, the primary care physician will order a test to be cautious because there is a symptom and they don't want to miss anything potentially serious, A test is ordered and that test is abnormal, for instance, it might show arachnoid cysts, it might show a Chiari malformation or any number of other relatively common findings on neuroimaging. This leads to parental or patient anxiety. A specialist is consulted sometimes leading to more tests and then down this cascade a little bit, the parents are anxious. In some cases, the treating physicians are anxious and occasionally a surgical treatment can be perceived as a safe alternative to doing nothing, and a surgical procedure is carried out. Sometimes without completely understanding whether or not that needed to be done. And this leads to the concept of the fully ajar where a pair of people, a patient or their family, as well as the treating physician can sometimes enter into a relationship where something is done, that is improper. Even with the best of intentions, the patient or the family they have good intentions. They're looking for an explanation for the child's symptoms. They want the symptoms to be taken seriously by a care provider, and they're looking for a chance for a cure, the surgeon or the care providers, in most cases, also looking for an opportunity to help, although reimbursement issues have to be considered. And in many cases, these treatments are very technically simple. For instance, many surgeons know how to treat arachnoid cysts, it's a very simple operation, the thing that I think nobody in the world right now is very clear on is exactly when that surgery is necessary. And that's something that I hope will be better defined in the coming years. So with that said I'll go on to part one of our discussion now which will be on arachnoids cysts. As shown in this slide, arachnoid cysts come in all different shapes and sizes, they can occur in virtually any parts of the intracranial compartment, and here this slide illustrates I think very well, all of the different varieties of arachnoid cysts locations of arachnoid cysts. As show you in the upcoming slides, some of these I think should be properly surgically treated. And many of these in my opinion should be properly left alone, started with this case is a very typical left middle fossa arachnoid cysts, this patient presented to us after a fall and wanted a neurosurgical opinion for other treatment should be advised. I recommended... Yes Aaron.

- Let me ask you for my concentricity. So you see this arachnoid cysts in the young child, this is one of the most common things we see in children that are incidental and the patient has only headaches. I mean, what would you... I mean, how do you even console the family in terms of what is the natural, that's a history of these lesions and what needs to be done in terms of surveillance imaging? I'm sure you're going to go into these more detailed.

- I think that's a great question. And many of these answers are frankly not clear in a matter of opinion rather than fact, for a cysts such as this one, which I regard as being relatively small size and was discovered incidentally, I believe it's very clear that no surgical treatment should be recommended. In your scenario which you brought up with a patient may have been experiencing headaches, which were bothering the patient and bothering the patient's family. I think that makes it a more difficult decision, although at least in my practice, I would still hesitate to recommend surgery for cysts this small I'd be very reluctant to offer surgery for anything like the size of this cysts. I would recommend referral to a pediatric neurologist for headache treatment, I would recommend taking time being very conservative, recommending serial imaging that lets the family know that we're taking this lesion seriously and that we are interested in treating this child, but that we're also trying very hard to avoid it, but in my opinion would be an unnecessary surgical treatment. In terms of the interval for follow-up imaging, again, there's no data here in my opinion, that can provide a strong guideline for that, in my own practice for the young children, I recommend imaging at at least a six month interval, sometimes a nine month interval, if that looks okay, sometimes we'll go 12 months. At that point in my own practice, I usually don't follow these anymore, although some reasonable surgeons do. And again, I don't think we have the information right now to provide a strong guideline for that. I think this is an important point though, I also don't think we have the information to provide a strong guideline that people would be remiss for not ordering follow-up imaging for this sort of cysts, even in a young person. I wouldn't find fault with a surgeon who didn't get follow up imaging in this situation, certainly in adults which we're not talking about today. It's very common also define these lesions in adults and I believe it would be a typical practice to not get follow-up imaging and this cysts an adult. But again, there's not really a standard guidelines to guide any of us in that treatment strategy. This is another patient who interestingly as two lesions, there's quadrigeminal arachnoid cyst, which is eccentric to the right. And there's also a pineal cysts just showing the two lesions side-by-side here. Some have made the point that it can be difficult to tell a true pineal cysts apart from quadrigeminal cysts. And I think this case example shows very nicely, the fact that actually it's very easy to tell the two entities apart. And I think that's important when we get into issues like, what should the follow-up be? And should we be concerned about this lesion? I've tend to be a little bit less concerned about pineal cysts, arachnoid cysts. I follow up tends to be less strict, so I think identifying these two lesions and separating them in your mind, is an important point.

- Cormac, I may ask you in the previous pineal cysts, that you showed, some patients at least the ones that I have and if you don't mind, I'm going to go back and thank you. People the young woman come in their early 20s, really bad headaches and I've heard occasionally people, say well, these headaches are related to this cysts because the neurovascular systems in that region are getting compressed. And if we do an endoscopic fenestration, the headaches will get better. Do you believe that's a reasonable practice? I personally don't. I don't believe these lesions are responsible for headaches, I believe they have been there for a long time. And I think a neurological evaluation and more aggressive management of headaches through a neurologist is appropriate. What are your thoughts in terms of fenestrating these just for headaches?

- Yeah, thank you for raising that question Aaron. And I think it's a very important point and one that we'll get into in more detail later in this presentation, but I couldn't agree with you more, pineal cysts we'll show a very common neuroimaging findings in older children as well as in adults. Headaches are also a very common symptoms, and I think neurosurgeons have to be very, very cautious when describing headache symptoms, the presence of a pineal cysts. In my opinion it rarely I've ever happened and I personally in my practice never use headache as a reason for treating a pineal cysts. If a pineal cysts is very, very large and is causing obstruction of CSF pathways with results in hydrocephalus and headaches, that might be a rare exception where pineal cysts can be treated for headache symptoms, but is clearly another associated finding, which is the associated hydrocephalus. I personally would never treat a pineal cysts for headache. It has been done, it has been done by very good surgeons, but I think just to have a difference of opinion with me on this matter, but in my opinion there's no data to tell us that we should be treating pineal cysts for headaches symptoms. In my view, that's a mistake. Unfortunately it is being done. Here's another patient, again, a young child that presented to us after a head injury and clearly has this left middle fossa arachnoid cysts. It's larger than the last example of a middle fossa arachnoid cyst that I showed you. And here we see we elected to follow them without surgery, and here we see six months later that this cysts has grown. And this raises, I think a very troubling issue for what to do with an arachnoid cysts, which you think is largely asymptomatic and yet which has grown on a serial imaging. I don't pretend to have the right answer for this, I don't think there is a right answer for this, but I will say it's a troubling issue and I think it's defensible to treat this surgically since there is obvious serial growth on follow-up imaging in a medium-sized metal fossa arachnoid cyst. If there are no symptoms though, I also think it's defensible to not treat it surgically and to continue to follow serial imaging, but my entire projection will be a very close follow up. There's another example of a patient with an arachnoid cyst, this one is actually quite massive as you can see, and this child presented again asymptomatic and was followed with serial imaging. And unfortunately this child's head it was a very young child, less than two years of age. This child's head expanded rapidly, another scan was carried out and you see a very significant expansion of this arachnoid cyst. And here I think is a very clear case if the treatment is indicated for this arachnoid cyst. And this cyst is treated at our hospital. So I've shown you several examples of arachnoid cyst. Some of which I thought were very difficult treatment decisions such as the last case, some of which I think were very easy treatment decisions such as this case, Aaron.

- May I ask, Cormac, would you recommend endoscopic fenestration through the basilar assistance for this patient, the same thing or different procedures?

- Yeah, I don't think that there's any great data proving definitively that any of those procedures are better than any of those other procedures. I think it depends on an individual surgeons practice and experience. At our hospital we would perform an endoscopic fenestration as a first step and if that doesn't work we would at least consider Cisto-peritoneal shunting. There are surgeons who prefer to essentially never but Cisto-peritoneal shunt because it makes the child shunt dependent and that's a really big problem. On the other hand endoscopic fenestration success rate is simply lower in the young children. And I feel strongly about that, although there are some controversial points to be made about that as well. Suffice it to say, I think fenestration procedures or shunting procedures are reasonable. They're both within the standard and I think surgeons can't be faulted for choosing one or the other.

- Thank you.

- In 2008, this really interesting paper came out by Tambarrini and others. And it was a very simple study design, they simply showed this image, which is projecting in front of you two pediatric neurosurgeons and they asked the question, would you recommend treatment for this arachnoid cyst and various clinical scenarios? And if this cyst was an incidental finding, I thought this was interesting. 37% of pediatric neurosurgeons, at least in 2008 would recommend treatment for this. I think I personally would put myself in the majority and would not recommend treatment for this cyst if there was an incidental finding. But I think it's relevant to now that many experts disagree with that. At least a large minority of experts would consider treatment for this. Yes, Aaron.

- Cormac, on the previous slide, it seems like a lot of surgeons are doing surgery because prophylactic to decrease the bleeding risk, but there is no data to support that there is a higher bleeding risk with these arachnoid cysts. So their mentality in terms of offering surgery to these patients to prevent prophylactic surgery to prevent bleeding is really not based on any data. Is that correct?

- And I couldn't agree with you more, in my personal opinion, I don't think that there's any significant evidence to suggest that we're helping people by performing prophylactic operations to try to mitigate against any future bleeding risk. I have some slides on that issue coming up, but in my own practice, I would never recommend surgery. If the only thing I thought I could offer a patient is prophylactic against bleeding risk. I don't view that as a good indication for surgery. And, yeah, you're right, that is one of the interesting findings of this Tamburrini and other study is that many of the surgeries that were being offered to these asymptomatic individuals were being justified just on that basis. And in my opinion that can't be justified. So I think there's a lot of troubling issues with the arachnoid cyst there's a lot we don't know about arachnoid cyst as a neurosurgical community. When we see a patient with an arachnoid cyst, we need to know, should this cyst be treated? If we elect to not treat that arachnoid cyst with surgery, do we need to follow the cyst over time? If the patient has symptoms perhaps non-specific symptoms, could be symptoms 'cause by the cyst or are they unrelated? And then I think finally the most troubling of all that the least amount of information right now is if we elect to not treat arachnoid cyst, should we place any activity restrictions on these children? So there are several things that I think we'd like to know about arachnoid cyst that we don't know enough about already. Number one, how unusual or common is it to find a cyst on imaging, i.e what is the MRI prevalence? In my opinion, if we establish that it's actually a very common finding on children undergoing neuroimaging. You might be slightly less concerned about a patient that presents to your clinic with a small cyst. You might come to the conclusion that's not such an unusual event. What do we know about the natural history of arachnoid cyst? Again, this is a critical point, if a family of a three-year-old boy with a smaller arachnoid cyst presents to your office, they will want to know, well, if you don't operate will it get bigger? Will it get smaller? Will they have trouble 10 years from now? We need to know much more about this topic and much more is being learned all the time. Treatment morbidity, what is the treatment morbidity for endoscopic fenestration for cyst patient? Actually, we do have some information about that. In general, these operations are thought to be safe and that they're relatively easy to carry out, but the complications from these treatments are usually not caused by the surgeon because of a mistake or misadventure during surgery. They're caused because we've done something to an arachnoid cyst. We've changed the intracranial pressure dynamics in this child's head sometimes for the worst. And then finally, what's the risk of injury for untreated cysts? We'll get into some of these topics now. A couple of years ago, we did a study looking at the MRI prevalence of arachnoid cyst and a large population of children that underwent neuroimaging at our institution. We studied over 10,000 consecutive children that underwent neuroimaging for any indication. And we found that a relatively large percentage of these children had cysts. You can see slightly over 3% of boys and slightly approximately 2% of girls had arachnoid cyst on imaging. Just last year, we extended this study into the adult age range now looking at over 40,000 consecutive adults that underwent neuroimaging and arachnoid cyst stayed prevalent throughout the entire adult age range. And, again, interestingly you continue to find more cyst in men than women. But these things never go away, they do stay present throughout the life span, at least we're able to find them throughout the life span of individuals. Looking at the location of arachnoid cyst, this is now back to our pediatric survey. They were marked cyst on the left and the right, which is interesting. And I think handedness here is an issue that will require future analysis. Middle fossa cyst were very, very common as you can see here, and we did break them down by the glossy classification. Although the usefulness of that classification, I think has been called into question. Posterior fossa is also a very, very common location of arachnoid cysts. Looking at our pediatric series over the last few years, the last 321 consecutive patients that we've seen with interact cyst, 21 of those underwent surgery at our institution. Now, any survey like this is gonna be very subjective, it's gonna depend on what our own indications are for surgical treatment of arachnoid cyst. And other hospitals that might be more aggressive with treating these would obviously operate on a larger percentage, but for us fewer than 10% of the patients presenting with the arachnoid cyst ended up having surgical treatment. And I believe this number is actually going down over time. We're becoming more conservative now than we used to be when our survey started. There's just no doubt about that. You can see listed here, the indications that we use for surgical treatment, some of these are objective indications, progressive macrocephaly, hydrocephalus, increased intracranial pressure if a monitor was placed, these are relatively objective indications for treatment of arachnoid cyst. There were some subjective decisions though, patients with large cysts and headaches, for instance, or occasionally treated in our institution, I believe we're becoming significantly more conservative about that treatment recommendation now than we used to be. Turning to the natural history. There's lots of case reports on natural history, some of them suggest that they have arachnoid cyst got bigger, some that got smaller, some that disappeared completely. We recently reported on 111 consecutive patients and followed them for three and a half years. These were all children, most of them didn't change at all in size, 13 of them decreased in size and 11 got bigger, so the bottom line is most don't unchanged. Some get bigger, some get smaller. Trying to predict which patients get bigger and which patients get smaller is interesting. What we found is that the ones that got bigger, at least in our series which is a relatively small series, although it's the biggest in the literature, the patients that got bigger over time were all younger patients at the time of presentation. We didn't have any patients over four years of age that got bigger. Now I believe that that can happen and as we expand our own series, I expect that we will see that that happens, but you should understand that it's rare. It's a very rare event for an older patient to have a significantly expanding arachnoid cysts. What about symptoms? I touched on in our own surgical series. I believe that there are some specific symptoms of arachnoid cysts, hydrocephalus secondary to obstruction of the CSF pathways is obviously a relatively sound indication for surgery, definitely sounded indication for surgery. Macrocrania also a good indication for surgery with an expanding arachnoid cysts. Suprasellar cysts of their own presentations as we'll get into later with endocrinopathy or extremely rarely but the bobble head doll syndrome. The trouble is that most people don't present with these relatively specific symptoms that are good surgical indications. Most patients come in with relatively non-specific and common symptoms such as headache. You were asking earlier, Aaron about headache. And assuming that we have a 2.6% arachnoid cysts prevalence, which is what we found in our pediatric series. That means 2.5% of at least patients, undergoing cranial imaging have an arachnoid cyst. And then using that British data for the prevalence of headache in the teenager population, we can presume that the chance of a teenager having an arachnoid cyst and a weekly headache is about 0.5%. That's if we don't know anything else about this patient and the chance of a teenager having arachnoid cysts and a daily headache is 0.16%. These aren't very high percentages, but when the applied to the entire US population, that leaves us with a staggering number of children that could be affected by this. So 75 million children are in the United States. If the number is even kind of correct, that's two million children with arachnoid cysts, 375,000, that could be expected to have arachnoid cysts a weekly headache and 120,000 with arachnoid cysts in a daily headache. I think it's fair to quibble with these numbers and suggest that the MRI prevalence is a significant overall estimate of the population prevalence. Nevertheless, I think it does raise the issue very well that we have to be very cautious when describing a causative relationships between a common finding, like arachnoid cysts and common symptoms like a headache. You had the question earlier about treatment, Aaron. and I think there are three well-established treatments for this Cisto-peritoneal shunting or fenestration procedures carried out either with a craniotomy or an endoscope. Certain surgeons feel very strongly that one of these types of operations is significantly better than other types of operations. And in my opinion, we don't have any data right now to defend that statement. I think that they're all options, they're all valid in different settings and I prefer when possible to avoid shunting. Although I think in the very young kids with the very, very large cysts, occasionally shunting can at least lead to the most dramatic results. Looking at our surgical series and trying to predict exactly who had surgery and who didn't. These were subjective decisions that we made, but nevertheless, I did find it interesting that anterior fossa cysts were much more likely to get surgery in our center then posterior fossa cyst. And again, at our center we try to be very cautious and conservative and we try as much as possible to limit operations to relatively objective findings, such as macrocephaly, hydrocephalus, or documented increased intracranial pressure. I'd like to talk a little bit about the special case, Suprasellar arachnoid cysts and our series, these represented about 1.5% of all arachnoids cysts on imaging, but in our series as well as others, they represent a much larger percentage of those patients who are undergoing surgical treatment. And that's because in my view, they're more likely to be symptomatic. Why is that? Well because of the structures they're near, they can impair the optic pathways causing visual impairment, they can cause endocrinopathy such as precocious puberty and they can obstruct CSF pathways causing hydrocephalus. Finally, the bobble-head doll syndrome is considered the classic presentation of a suprasellar arachnoid cyst. I've never seen it, although I've now seen quite a large number of suprasellar arachnoid cyst. I've never seen a patient present with bobble-head doll syndrome. And the literature also suggests that this is actually quite a rare presentation, but it is the most classic presentation of this cyst type. Let me see a very typical axial image of a suprasellar arachnoid cyst. You can see a large cyst in what appears to be the third ventricle, but in fact is a large cyst with ventriculomegaly and you can see trans dependable flow of the CSF indicating that there is a hydrocephalus.

- Cormac, I have a question? How do you differentiate this? I'm sure you're going to maybe go into it from a regular hydrocephalus. If I look at that actual MRI, it looks like just a diffuse ventriculomegaly maybe at the level of aqueduct or something since I don't have the other actual images. So what are the differentiating factors?

- Yeah, I think that's a great question, Aaron. And if all you have is actual imaging, for instance, actual CT scan it can be challenging. It seems like the third ventricle or what could be the third ventricle is large out of proportion to the lateral ventricles and you call it the Mickey mouse here appearance. And this to me does appear to be a suprasellar arachnoid cyst rather than just a few ventriculomegaly, the proportions are different than what we'd expect. Furthermore, the sagittal really tells the tale. If you have access to sagittal imaging, this is the unmistakable appearance of a suprasellar arachnoid cyst. And what should be the floor of the third ventricle, we don't see mammillary bodies. We don't see any of the structures that we should identify on the floor of the third ventricle the reason being is that the floor or the third ventricle is elevated. Here, this is now the floor of the third ventricle being blown up from the midbrain up to contact with the lateral ventricle, and here this is not the floor of the third ventricle. This is the basal membrane of that suprasellar arachnoid cyst. We see the same thing on T1 imaging over here. So again, classic sagittal MRI appearance on the Suprasellar arachnoid cyst. And that to me is the easiest way to differentiate between the two, but I think it's a very important point that you raised down. It's important to differentiate Suprasellar arachnoid cyst from hydrocephalus because the treatment will be different as I'll show in these next slides. Again, coronal imaging, Mickey mouse appearance, very large cyst lowing up the floor of the third ventricle. And, again, here depicted graphically is the suprasellar arachnoid cyst. The standard treatment for Suprasellar arachnoid cyst has become endoscopic fenestration in my view, and there are two accepted types of endoscopic fenestration for Suprasellar arachnoid cyst, there's a ventriculocystostomy or VC procedure or ventriculocystocisternostomy or VCC procedure. And the difference between those two procedures is the membranes that are perforated. In the VC procedure we perforate the atypical membrane of the cyst into the lateral ventricle and some surgeons continue to coagulate the cyst and even shrink it, which I think is a reasonable treatment option. In the VCC procedure, the surgeon doesn't stop with the apical perforation, but continues to go through the cyst and then perforates the basal membrane of the cyst in front of the basilar artery, and that's the VCC operation. I'll show them a VCC operation here on these slides. On the right-hand side of the screen now you can see the typical endoscopic appearance of the foramen of Monro, and you see this apical membrane of the cyst filling the foramen of Monro. We start to endoscopically coagulate the system membrane, we make a hole in it. And here we're about to enter into that cyst and now are inside the cyst itself. You can see the basilar artery here with the posterior cerebral arteries, and you might think the operation's done, well, would be done if you're performing a VC operation, but to perform that VCC operation, you still have another membrane to perforate, left this membrane in front of the basilar artery, as we're about to perform here, we'll pop through and there you see the structures in front of the parts with the basilar artery, that's a VCC operation. And you may say, well, what's the point of making that final perforation? Oh, I think if it can be done safely, there's a few papers coming out now, we had a paper last year in the journal of neurosurgery and another appeared and this month's copy of the journal of neurosurgery indicating that... Although both operations are reasonable to perform and although both operations do treat most of these cysts successfully. The recurrence rate the need for future treatment does seem to be lower if you can perforate that basilar membrane and make a VCC perforation rather than just the VC operation. And here you see the classic appearance after fenestration again, before fenestration flare the third membrane of the third ventricle all the way up here, following fenestration it's come down nicely. Here's a better example even again, before fenestration flared the third ventricle all the way up here following fenestration, you can see the flared returned nicely bodies and floor of the third ventricle down here. So what about bleeding risk? I mentioned too earlier that I thought that this was not a good indication for surgical treatment of arachnoid cyst. The Tamburrini and other survey indicated that some very good pediatric neurosurgeons appear to disagree with me on that, and we're using this as an indication for surgery and our own series of the 309 patients that we initially had in our pediatric series with arachnoid cyst. Only one of them presented with a bleed at the time of presentation. And here you see depicted on this slide, a patient with it arachnoid cyst also had aneurysm, the bled into this arachnoid cyst. This patient did very well, they didn't bleed into the subarachnoid space, they bled into the cyst. The aneurysm was easier than usual to treat and the hemorrhage didn't significantly harm this patient. I think this brings up the point that although it's certainly possible for a hemorrhage into arachnoid cyst to be a catastrophe for a patient, the experience of most surgeons with these hemorrhages is that they hemorrhages into the cyst, and they're not as distressing as a typical intercranial hemorrhage would be in the absence of the cyst. No patients that are natural history, harm experienced hemorrhage during the time of follow up. That was true at the time of our report two years ago and it remains true today with now approximately double the number of cases. When you look at the world literature, there are 42 reported cases of hemorrhage into an arachnoid cyst, 26 of these at an immediate prior history of head injury, now 42 cases may sound like a lot, but if you consider the MIR prevalence of arachnoid cyst, 2.5% of all of those patients undergoing neuroimaging at our institution, 42 patients is a very small number. And again, in my opinion, it's a simple issue of math numerator, 42, denominator, thousands, tens of thousands, hundreds of thousands. The that doesn't add up. If we're doing prophylactic surgery for a risk, that's not tiny in my opinion. And finally, the most controversial topic of all in terms of arachnoid cyst is what do we tell these patients or their families in terms of activity restrictions? And we know nothing about this, we literally know nothing about this. We certainly know, as I've just shared with you that some patients have post-traumatic hemorrhages into arachnoid cyst. I think it's up to a surgeon's best judgment right now to make a recommendation for their individual patients. We're trying to accumulate data on this topic right now, and I hope that within six months or at most a year, we'll be able to make a presentation on these data and hopefully provide some sort of evidence-based recommendations for people going forward. I will say that in my own practice, I try very hard not to limit the activity of children with the arachnoid cysts. I would conceivably make exceptions for cases of massive arachnoid cyst in patients that want to participate in significant contact sports. But I try very hard to not limit a patient's activities, if they have a typical appearing arachnoid cyst or small appearing arachnoid cyst, even when it comes to contact sports. I believe that my opinion that I've just stated is extremely controversial. And I believe that other surgeons are justified if they feel that's the right thing to do to limit the activity of children with arachnoid cysts.

- If I may ask a question. So if you have a 18 year old boy who presents with some headaches has an MRI shows interact, sizeable arachnoid cyst really wants to play football. You will let them do it, understanding that this is a very controversial topic.

- I would counsel that boy and his family than it is a controversial topic and that we don't have great information about it. I would tell them that I believe that there is some leading risks, but that I don't think it's very great. I think that I would feel uncomfortable if the cysts was very massive. And if this child wanted to participate in sports that involved a lot of contact, but again, I try very hard to limit the number of times that I limit children's activities with these cysts. I think the scenario that you painted an older child, participating in football with a large cyst is definitely in that gray area for me, where I even, I become slightly reluctant to give the all-clear to participate in sports, very controversial topic. I hope we're going to have some more information about it within half a year or a year. So in conclusion, arachnoid cyst are common. The prevalence does not change significantly with advancing age. It's always about 2% to 2.5%. It's a frequent finding in asymptomatic patients, as well as a frequent finding in patients with common non-specific symptoms and the relevance of these non-specific symptoms have to be judged very carefully. The locations are diverse, surgical treatment is occasionally necessary. I have to guard against a tendency to suggest that surgery is just not necessary for cysts. I don't even believe that I do treat some of these cysts with surgery. I just try to exercise a good deal of caution with that recommendation, and that the need for clinical or radiographic follow up. In my view, hasn't been firmly established for older children or adults I think that's up to the surgeon's own discretion. Next we'll talk about pineal cysts and we'll hit on many of the same themes that were covered in the arachnoid cyst section. Like arachnoid cysts, pineal cysts can be a great cause of concern for your patients. And I think it's important for we as neurosurgeons to understand that when patients present to us with a finding of a pineal cyst on an MRI scan, we may look at it and think that it's nothing, but you should understand that not all of your patients do. There's a lot of information on the internet about pineal cysts most of which or at least much of which is incorrect. And so I think part of our jobs as neurosurgeons right now is to correct some of these misunderstandings that exists in the internet and in the public sphere about pineal cysts and pineal cyst surgery. Part of the misunderstanding of course, is that we have very little information about pineal cysts. Here's a typical patient, a teenager that presented with a headache and had this pineal cysts. I recommended no surgery, but the family reasonably wanted to know well, what does the future hold? Will this get bigger? Will this gets smaller? And I think until recently we didn't really know. Here's another example of the teenager that presented with the pineal cysts. This one is quite large and you can see that it got even larger on follow-up imaging. I think a relevant question here, is what does this mean? The fact that it's getting larger, does this necessarily mean that it's a bad actor and requires surgical treatment? What if the patient had headaches? What if the patient didn't have any symptoms? Is growth enough of a surgical indication? Where have I been into in the next several slides, I definitely think the growth is not by itself, an indication for surgical treatment. And I'll try to explain why I think that. We recently completed a survey again, of all patients undergoing intracranial imaging at our hospital. For this series we looked at almost 63,000 consecutive patients at all age groups that underwent neuroimaging at our hospital, looking for pineal cysts on their neuroimaging. And I think the results were interesting, at least to me, you can see that pineal cysts were relatively less common in the very early age groups became more and more common throughout childhood and then became less and less and less common throughout the adult age range and they were distinctly unusual in the octogenarians. I think this is very interesting prevalence data by itself, doesn't tell us natural history, but this is a relatively compelling prevalence curve I think that tells us that the fact that we're finding new cysts in teenagers that didn't exist before does not necessarily spell a bad prognosis for that cyst. Does not necessarily imply that, that's just going to grow indefinitely until it's treated surgically. And it certainly led me to be very, very conservative with treatment of pineal cysts. In fact, I've got to the point where I basically do not treat pineal cysts in the absence of the extremely rare cases that are associated headache or paranoid syndrome. And those are almost never seeing. Comparing pineal cysts to arachnoid cyst with this table very quickly. I just want to make the point again, that pineal cysts prevalence decreases throughout the adult age range. As you can see in the purple bars on these more blue bars, arachnoid cyst prevalence doesn't change. So the cysts do behave differently although they're both cysts types. They're different from a pathophysiological standpoint and the treatment and recommendations therefore should be different as well. When we looked at the pineal cyst natural history in our adult series, the vast majority of adults over adults over a several year follow up had no change in the pineal cyst size over time, but a fair substantial minority of them did have a decrease in size. Very few of them increased in size and this increase was not substantial in my view in any of these cases. But I think what this tells us is that this reflects the prevalence curve that I showed you. It's not all that unusual for cysts to get smaller in the adult age range. And when I looked at the pediatric natural history, it wasn't all that unusual for cysts to get larger in kids, they get larger and kids, they get smaller and adults. And I think that fits nicely with what we know about the prevalence now. Here's a good example in my view, this child presented 17 or 18 years of age to emergency department after a car accident, a CT scan that was done demonstrated a cystic lesion in the vicinity of his pineal gland and this MRI scan was carried out. This scan shows a slightly larger than average pineal cyst, the radiologist read it as having mass effects. We elected to not treat it surgically, but did recommend follow up imaging. And here's what we found, constantly one year later the cysts looked relatively similar in terms of size, but several years after that it was definitely smaller. And now most recently just in January of this year, there's been a definite substantial decrease in the size of that pineal cyst. In conclusion, I believe that pineal cysts are extremely common. The prevalence on MRI decreases with advancing age and the adult age range. We showed this in our own study, as I've already described to you and in an earlier study by Sawamura and colleagues from 1995 and a relatively smaller group of patients that shattered startlingly I think similar curve. So this data in my opinion is sound. Given the frequency and the normal population, pineal cysts can be expected to coincidental finding in patients with headaches or other non-specific neurological symptoms. The fact that the patient has a headache and the pineal cysts in my view does not prove that the pineal cysts is causing the headache. And in my view should not be an indication for surgical treatment. Again, getting to the idea of common incidental finding and common symptom. That's does not prove causation. I should say the same thing about the numerous case reports in the literature of pineal cysts that are associated with tumor syndrome, that are associated with precocious puberty, that are associated with headache types and all sorts of other problems. Psychiatric conditions everything you can name to me it does not seem surprising that somebody has been able to find a patient with a psychiatric condition at a pineal cyst, given how common pineal cysts imaging. These case reports are not useful and in my opinion shouldn't be used as a justification for surgical treatment of pineal cysts. So I never treat asymptomatic pineal cysts, I would consider the treatment of the pineal cyst with hydrocephalus although that is extremely rare. And in all of the 100 of cysts that I've seen in the last few years, I've seen one case that was definitely causing hydrocephalus. And another case that was sent to me from an outside surgeon following treatment that did have hydrocephalus, but that let me emphasize is a very rare presentation. So neurosurgeons should exercise extreme caution in selecting patients with non-specific symptoms for surgery. So what can be done going forward? I think we need rational use of diagnostic imaging and the primary care physician's office. The main reason we're seeing all of these cases now is because neuroimaging is becoming so much more common in the general population. And surgery as this isn't going to solve the problem, because there is some irreducible minimum number of unexpected findings that we're going to identify on neuroimaging. So the bottom line is we really need better information, we need more prevalence studies, we need more age specific prevalence studies, which tell us a little bit, give us some insight into the natural history. And we need real natural history studies that are information will hopefully I believe lead to better treatment decisions going forward into the future. So as neurosurgeons, I think one thing we can do is accumulate data, we're seeing these patients, we're imaging these patients, we're accumulating databases that hopefully will help us in the future. We need to consider the natural history of these cysts carefully. And we need to measure what we know about the natural history against what we know of our own treatment morbidity. Again, there's going to be a tendency for your patients in many cases to want you to treat their cyst and don't go Leopold and Loeb on them. Don't get into that folly where they want you to treat the cysts. And therefore you decide to treat the cyst for that reason. I think neurosurgeons have to exercise independent thinking and only treat patients who they believe they can really help. And finally, if a patient is sent to you after an unsuccessful initial treatment, if the headaches are persisting, never reinforced failure. One of my favorite quotes from I believe Napoleon Bonaparte, at least he's credited with it when asked why he wouldn't send a reinforcement to align, that was a breaking in battle. And he said, "Never reinforced failure." I believe that's good advice for neurosurgeons as well. If a patient is treated for headaches and then cysts and the headaches do not get better, I believe that's not an invitation to continue to do more and more cysts surgery on these patients. So thanks very much, Aaron, for inviting me to give this presentation today, I really appreciate the opportunity and also I want to thank all the other people listed on this slide who have participated in many of the studies that I cited here today, especially in Liliana Goumnerova who participated in the suprasellar cysts study with me published last year, and then the large group of people at University of Michigan.

- Cormac, I want to thank you again for this really very worthwhile discussion. I think this is so critical in terms of describing when it's important to operate when it's not. And based on my impression is that for arachnoid cyst, really their requirement for treatment is extremely rare. And only if there's bonafide symptoms such as hydrocephalus, such as symptoms that can be clearly related to mass effect because of a giant cyst are clear indications again that is extremely rare, especially for pineal cyst. Even if the indications are most strict. And you would say that almost nobody should ever operate on pineal cysts which I completely agree with you unless there is clear evidence of hydrocephalus-

- And the other exception would be a clear, apparent out syndrome, although I've never seen it, it's been reported. And I believe that's a reasonable indication as well. Their extraocular movement difficulties with a massive pineal cyst probably a reasonable indication for surgery. I've never seen it. I believe that it can happen rarely. And I'm sure surgeons watching today have seeing such things. So I never say never and I never say always, but I do believe caution is the operative word here.

- Okay. I think that's a very short way to end the discussion today. And the statement you made is obviously very well stated. Cormac, thanks very much for your information. And we'll look forward to having with us related to the same topic of incidental lesions, including Chiari malformation, which we hope to have Dr. Mark Proctor with us as well. I'm very much looking forward to that discussion because Chiari malformation is a very challenging topic to manage and select the appropriate patients. And also the last session would be a discussion of incidental vascular lesions. Those will be very exciting and I personally look forward to that. Thank you, again. Thanks to our viewers and have a good day.

- Thanks, Aaron.

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