Dr. Rudolph Schrot at the 2023 Cedars-Sinai Intracranial Hypotension Conference, Day Two
Dr. Rudolph Schrot, a neurosurgeon at Sutter Medical Center in Sacramento, CA, presented this talk on surgical approaches for sacral Tarlov cysts 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] I just want to thank Dr. Schievink for inviting me. This is a really great honor to present at this conference. So, I’m a consultant for some things that really don’t have to do with CSF leaks or Tarlov cysts.
[00:00:31] So they can be a source of CSF leak. But often they’re coming to the clinic for other reasons. So typically they’re found in the sacral region. They can have a broad impact. These sacral nerve roots are very multivalent in their their activity, bowel, bladder, sensory motor function. So patients have a lot of different symptoms.
[00:00:54] However, it is very important to think about these in the context of CSF leak and intracranial hypotension. As was mentioned earlier, probably a minority of Tarlov cysts that are really causing the kind of overt symptoms that you have with the various types of CSF leak. But the potential source of CSF leak is important. And so, while acknowledging the other symptoms that they cause, we have to also acknowledge their potential for CSF leak.
[00:01:27] So just some definitions: they’re variously referred to as perineural cysts, which I’ll talk about this distinction; intra-sacral meningeal cysts; and then we have to be concerned about a differential diagnosis of a meningeal diverticulum. That figure shows sort of conceptually these things. Meningeal diverticulum don’t have nerve roots or ganglion cells. Tarlov cysts do. And also dural ectasia.
[00:01:51] There are a few other things here that can be read as cysts, but often it’s just the way they’re sliced. For example, a prolonged subarachnoid space over the root can look like a cyst, but it’s not actually a cyst.
[00:02:04] I want to kind of shout out to Reta Hiers, who’s the founder and president of the Tarlov Cyst Disease Foundation, which is an advocacy group. And we went in 2017 to present at the coordination and maintenance committee, because up until that time, the the only code was one of these sort of wastebasket codes, “G54.8, other nerve root and plexus disorders.” You know, you have, for example, these, you know, silly codes like “W55.22XA, struck by a cow,” uh, “spacecraft collision.”
[00:02:39] You know, they have a code for this, but there’s no code for, you know, for Tarlov cysts. So, that was changed. So we have G96.191. So it gives us a little more specificity and ability to kind of look at these things retrospectively.
[00:02:53] So considerations are the cauda equina type symptoms. In addition to, in some patients, the intracranial hypotension symptoms. It’s at the lowest end of the pressure column. So you have this hydrostatic pressure, you have a very extensive venous anastamotic network. The sacral bone can really kind of gives way and erodes. It’s not really a weight supporting part of the sacrum. So the you know, the bone. doesn’t have much resistance. Oftentimes you can have extensive erosion. And the sacral nerve roots and their dorsal root ganglia: elsewhere in the spine, they’re protected by a bony foramen. And that’s not, they’re all sort of clustered together in in the sacrum and the sacral canal. So one cyst can affect multiple nerve roots or you can have multiple cysts.
[00:03:38] But the point I think to make, though, is that the surgical approach, whether it’s you know, and as I said, most of these patients are coming for other symptoms, and they may have orthostatic headaches as well, but it’s, the indication is often for the other symptoms. But the techniques are going to be the same and an approach, surgical approach, is going to be the same, whether it’s for the compressive symptoms or whether you suspect that the cyst or a cyst is leaking.
[00:04:07] So, incidence, we don’t really know it’s heavily weighted towards females about 9 to 1. There’s one study estimated about a 4.6 incidence in patients coming for MRI. So they had something, so they’re getting an MRI. And it’s estimated that about 20 to 40 percent may be symptomatic. 95 percent of them are in the sacrum, although the sacrum just represents a small portion of the spine.
[00:04:33] And these are probably different— a lot of times you see these patients with little dots of cysts all down, like we saw a lot of images, and those are probably different animals. And often those patients that present with that may be presenting more with leaks. Sometimes they don’t even have sacral Tarlov cysts all the time in those patients, so there’s probably something else going on, and the thoracic ones are often more diverticula, the type two leak, meningeal diverticula. It’s a sort of pedunculated cyst coming off where the axial of the nerve root is that can just be, like, clipped or ligated.
[00:05:08] So forms between the epineurium and perineurium, it’s usually proximal to the dorsal root ganglion. Compartmentalized pressure: basically a compartment syndrome gets formed in the sacral canal. You get plastic deformation of the nerve root, loss of axons and ganglion cells, which Tarlov demonstrated in 1938. Erosion and remodeling of the sacrum. And then you can have the CSF egress. So it’s important I think when they’re described, a lot of times the neuro radiology reports will not be very specific. They’ll kind of mention them in passing: “you know, yeah, we also see cysts incidentally, unlikely to be symptomatic,” but there’s not a drill down as far as, you know, how many of them are there; are they small, medium, large or giant; the anatomic location; and in particular, whether it’s central within the canal foraminal or presacral extension, and which nerve root is often involved. S3 is very common. It’s often described as an S2 because that’s the vertebral level you see it, but it’s actually the S3 nerve root, often compressing the S2 nerve root and causing symptoms. And is there any interval change in these over time?
[00:06:15] So these are all surgical cases of mine over the probably the past couple of years, but this just shows you some of the variety of these cysts that you’ll see. And so it’s probably would be helpful to have additional classification for these types. And here’s a giant, this is actually a meningeal diverticulum, but surgical approach for this is the same, extensive remodeling and both dorsally and ventrally.
[00:06:41] So, this was a early series of patients that I was seeing in conjunction with a urogynecologist and conspicuously absent are any CSF leak symptoms. These are all more cauda equina type symptoms, but in the survey from Tarlov Cyst Disease Foundation, you do have, you know, headaches, tinnitus, loss of balance, equilibrium, patients complaining of photophobia, hyperacusis. So these CSF leak symptoms can happen. How? Maybe transudation to the cyst dome, cyst rupture is pretty unusual, I have seen it, can be often mistaken for a subarachnoid hemorrhage, it’s often cataclysmic, but very rare. CSF venous fistula: I haven’t actually observed one on imaging in the sacrum. I’m sure they exist. I mean, with the extensive venous anastomotic network, you have veins running over the system.
[00:07:35] And again, they’re not always leaking. If they are having these symptoms, often the patients, many of them have a connective tissue, Ehlers Danlos. They could be leaking from somewhere else. And the treatment indications are often for their sacral radiculopathies. And if their headaches are better, that’s a big bonus and a big plus. And, but no symptoms, no treatment. So you don’t I don’t typically treat them even if they’re growing larger, but the patient doesn’t have any symptoms. I don’t typically treat them in that case.
[00:08:01] So just the historical perspective: 1938, Tarlov was working at the Royal Victoria Hospital in Montreal, was 33 years old, and he was dissecting an area that was kind of a no man’s land, which was the sacral canal, which not a lot of people were familiar with, and he was looking specifically at the filum terminale, and in these 30 cadaver specimens, he found six of them that had these cysts that he described and published.
[00:08:28] He referenced another paper in Germany by Marburg that was written, I think, in 1903 that had also described some similar cysts. Some of those were in the thoracic spine. At the same time, Rexed was— there wasn’t good Transatlantic communication. So he also described these cysts sort of independently. Different theories: Tarlov thought that it was from subarachnoid hemorrhage because he was observing some hemorrhagic debris and some inflammatory changes around the region of the dorsal root ganglia. And then Rexed had this theory that you had these arachnoidal proliferations, maybe congenital, that were resulting in these cysts.
[00:09:07] So here’s one of Tarlov’s drawings, you can see in the middle the filum terminale coming down, and then these cysts, and he has various phases of cyst development, some of them very tiny. And most of them were associated forming around the location of the dorsal root ganglion. And then various sizes, various levels of communication with the thecal sac.
[00:09:26] So just to talk a little bit etymology, I think that’s always interesting to look at where words come from to understand what a thing really is. So we all remember from medical school, the peripheral nerve has an endoneurium, a perineurium and epineurium. So the perineurium forms a perineurial space, which is topologically continuous with the subarachnoid space and the endoneurium is continuous with the pia.
[00:09:50] So, so he was able to trace out in serial sections that these cysts were arising in the perineurial space. So he called them perineurial cysts because this [was the] space [where they] were so. Somewhere I think in the 1970s, there was a publication where all of a sudden it started being called a perineural cyst.
[00:10:05] So I think it was probably a typo, but that’s resulted in a really different connotation, because people think, you know, you say “perineural,” you think “next to the nerve.” So it’s resulted in sort of this one publication here where they’re trying to redefine or reclassify perineural, and it really doesn’t harken back to the original sense of the term, which describes the histology.
[00:10:28] So when he concluded from this, that the clinical significance remains to be determined, that was sort of interpreted as “the clinical significance is uncertain.” You know, doubtful clinical significance. That was probably not his intention, but they sort of have gotten a bad sort of reputation as not causing symptoms and just being incidentally there.
[00:10:51] So. He changed his mind about that when he was operating on a patient for sciatica, couldn’t find the disc, explored a little further, took off some of the sacral lamina, which is usually not done, and found a cyst and resected it. And the patient got better. But the method was that he actually took the cyst out. And so I think he probably got lucky with that. But that technique, I think, if repeated, where you’re actually taking out the cyst, you risk actually removing the nerve roots, removing nerve tissue. And plus, as far as CSF leaks are concerned, you’re not really fixing the problem. And you could be a very high risk of developing postoperative pseudomeningocele.
[00:11:34] And so I suspect that some of the adventures in Tarlov cyst surgery, if they were based on Tarlov’s technique, would have resulted in failure. So, one of the common things that I hear [from] patients is they get told that they don’t cause symptoms, they’re incidental findings. Or that, okay, fine, maybe they’re causing symptoms, but don’t ever let anybody operate on this, you’re going to lose all your bowel, bladder function, it’s terrible. But, you know, the surgical techniques have been described. It’s not a very coherent literature, there’s a variety of techniques that are used: imbrication, fenestrating the cyst, marsupializing it, packing it with gel foam, packing it with, you know, injecting fibrin glue, or shunting. There’s some discussion about going intrathecally with a thecascope, trying to find the ostium.
[00:12:18] And so I think you can kind of broadly classify these approaches into intrinsic and extrinsic. So, intrinsic approaches would be where you’re actually into the perineurial space, you’re into that space that’s contiguous with the arachnoid. You’re trying to find the ostium, plug it, you may do a rotational muscle flap. And this would also, I think, include the interventional fibrin glue injections where your goal is to kind of seal off whatever is leaking into the cyst.
[00:12:45] And then in an extrinsic approach, where you’re actually either closing the wall through imbrication, that’s folding it together, or doing a dural graph to reconstruct it. If you think that they’re caused by that connective tissue problem where the nerve root sheath is giving way, then actually reinforcing the nerve root sheath kind of rationally makes sense to correct the problem.
[00:13:07] And this would also include surgical clipping, you know, in order to decrease the dome, but you’re not really, you want to kind of stay out of that perineurial space that is contiguous with arachnoid. And that is one of the risks, especially if there’s a large ostium, of injecting these and getting some of the inflammatory material into the subarachnoid space.
[00:13:25] So there’s pros and cons. So, pro, I mean if somebody told me they could heal me with a needle, I mean I’d much rather go for that. There’s less nerve root dissection, less vein coagulation, which you have to do when you’re in this area, but also then you’re into the space, you’re violating the cyst wall if it’s open, even placing a needle, you could risk actually going through fibers that are there. Potential for arachnoiditis or intraneural adhesions recurrence and problems with recurrence can occur with that, too.
[00:13:56] So, extrinsically, you’re avoiding that space. You’re preserving the wall. You’re trying to compensate for the defect. There’s this nerve gliding, which is maybe a bit controversial, but the, you know, the ability of a nerve to move back and forth when the legs move. It’s seen in the lumbar spine. I think it would be interesting to see how much that occurs in the sacral spine. And then you can also, you can fill the fat defect.
[00:14:19] Obviously cons, you’ve increased surgical time, you have to do a lot of dissection. Some of these patients will get a little bit of neuropraxia, maybe some saddle numbness. It’s usually temporary, but there’s a risk for that. And there’s no real minimally invasive option for doing a wrapping technique.
[00:14:36] So which is better. This article tried to compare surgeries. The problem is, it’s really a potpourri of studies and various surgical techniques. It’s very difficult to make any kind of valid conclusion. It did find that the recurrence of the cyst was higher using non surgery, would be considered a percutaneous technique, which is, it is surgery, but they’re classifying it as non surgery. And, however, CSF leak in a surgery series found that it was higher. But again, that’s a variety of studies. There’s, you can see here there are 32 surgery studies and only six percutaneous studies. So not really comparable here. Also more of the patients that they looked at in surgery studies had this orthostatic headaches compared to the non surgeries, presumably more compressive symptoms.
[00:15:29] So I got into this probably around 2007, and we were having a discussion last night with with Dr Beck about how I started with this. I had a patient in my clinic. I just called, tried to find out everything I knew about it. I called Fraser Henderson, I talked to Donlin Long, I talked to Frank Feigenbaum that had been doing these, and looked up the literature and sort of did a few cases.
[00:15:55] The first 12 I did were doing sort of a marsupialization or fenestration and then I started more folding the nerve root on itself and sewing it together. And with this you know, with this group there were a little bit, in the fenestration, a little bit higher pseudomeningocele, which is really not surprising given that, it’s left wide open. So I’ve kind of abandoned doing it that way.
[00:16:23] So my current surgical procedure is, you know, first after we’ve decided to go ahead with surgery, they’re asleep. My acute pain service does something called an erector spinae plane block, which is ultrasound guided, which is very helpful, we’ve been using this for the Tarlov cyst surgery, but also for other spine surgery, very helpful for perioperative pain control.
[00:16:44] So they’re asleep. I do nerve monitoring, started using an EMG Foley catheter as well to monitor BCR and pudendalis SSEPs during surgery. Localizing, doing a laminotomy first, depending on the location where the cyst is, either between S1 and S2 or just undermining the ligamentum flavum.
[00:17:01] I’m doing a laminaplasty with an ultrasonic bone knife. I first started doing a craniotome router, done hundreds of cases with that without a problem, and then I got a nerve root injury doing it, and I had to look at something else. I’m using this Sonopet, which has a bone tip knife that you can sort of carve out very nicely, cuts the bone, but not soft tissue. Doing the dissection circumferentially, dissecting and wrapping and sewing it. And then doing autologous free fat tissue transfer, either from the margin of the incision. And then I put the bone piece back in place.
[00:17:35] So that’s the localization, this is a sacrum, and then that just shows the area of the laminoplasty that’s done, and that can vary based on where the cysts are. This article was published last year in Japan, they have a beautiful illustration of this very similar technique.
[00:17:53] Now they were using Gore-Tex to wrap the cyst with, I kind of responded to this because there was some discussion yesterday about what the best graft material to use is. I had been using Durepair. I switched over to Synthecel, which is a biosynthesized cellulose. It’s very non inflammatory, it’s very bio inert, but it’s also bio permanent and can be removed. One time had it on a brain tumor, had to go back, and it lifted off quite nicely. But it also provides a pretty good watertight closure. And it’s just very easy to work with. And it’s also appealing to patients because there’s no animal product in it. It’s not like a xenograft like, bovine pericardium.
[00:18:35] So here is just a case. Ehlers Danlos, she had a lot of other—she has. I actually, I should say, all these cases are from the past couple of weeks. So she’s actually still in house right now. Insensate bladder, she’s self cathing, she has endometriosis and dyspareunia. So this is just to show the dissection. . So she had essentially, there were, this just shows the dissection, sharp dissection to avoid any any pressure, just to define the anatomy, getting that out there, getting that, that’s a piece of vascular background.
[00:19:08] Sometimes you can aspirate them. Sometimes you can kind of push the fluid rostrally to to decompress it. You could see the nerve root, actually the CSF is going circumferentially around and then that’s the Synthecel, and then suturing it with a 6-0 prolene, just doing a running, running stitch across it on the right side. That’s the dorsal root ganglion there. And then, you know, I have the neuro monitoring people telling me if there’s any, if they’re getting any activity. There was a, that’s the extradural attachment of the phylum terminology. So her, so I will often section that, the, the uh, that’s putting a bead of of fibrin glue and and then packing a fat graft in there.
[00:19:49] And then this is just replacing the bone flap. And then I put a little bit of additional fibrin glue around the bone flap and then and then close that down. So, the end of the conus tends to be on the lower side of normal in a lot of these patients for whatever reason, like ending around mid L2.
[00:20:05] And, you know, and I’ll look at that. I don’t think there’s much risk or harm in sectioning that, sometimes just to do the dural graft repair, especially if I have to wrap around the end of the thecal tip, you sort of have to get to section that to get the wrap all the way around. So, there have been described a few coccygeal nerve roots, at least that’s what Tarlov had described, but I haven’t seen any problem with actually doing that sectioning, and, you know, they may have some element of tethering that’s going on that it could be helpful there.
[00:20:34] So this is another another case. She’s also in house, also happens to be 26 years old, from Kentucky, that last patient was from Georgia. So she has urinary retention. She does have very prominent orthostatic headaches, and she had actually undergone a prior treatment with fibrin glue injection, cyst completely refilled in seven days.
[00:20:55] And just to to get a sense here of the extent. Sometimes these single images don’t don’t really do justice to the extent of the the problem.
[00:21:09] Those just shows pretty extensive pre sacral extension.
[00:21:31] So anyway, after the bone flap came off, just the CSF just like shot out, which I expect was being decompressed from the from the the pelvis. So this is just really trying to define the anatomy. I mean, this was a very long case. I mean, this is probably took about four hours, and it was very difficult at first to sort of figure out what was going on with the anatomy.
[00:21:52] But this was a meningeal diverticulum. I think, although I was available, you can see sort of some CSF pouring out of that ostium on the top edge of the of the of the view and and there was a nerve root coming out from it. So, whether this was a true, I mean, if it’s truly a meningeal diverticulum, there shouldn’t be a nerve root there but I ended up just closing over that, that ostium, I, I did a valsalva, there was still leak after the valsalva through that, so I did wrap with the Synthocel there, and then, and then close that.
[00:22:25] And after, after doing this, there wasn’t a leak anymore on valsalva, but the thecal tip, which is on the left side, it was pretty thinned out, that dura, because that had been covered by that membrane. And so I decided to put another piece just for good measure and kind of move it up more on the thecal tip to sort of further reinforce that.
[00:22:49] So those nerve roots that are just so, so that nerve root there on the top that’s S2, and this is the extradural filum attachment, which I sectioned as well. And she did have a fairly low-ish lying conus, but probably still within normal limits. I left the cyst membrane more distally. I thought it was too dangerous to try to, or, and unnecessary to remove it from all those lower sacral nerve roots. So this is just the fat harvest. And then and I think fat, it seems pretty permanent. I get MRIs about 6 months, it seems like it’s still viable. And it’s the natural thing that would be in the epidural space. So, I think using fat to fill in the defect makes a lot of sense. So, that’s just… and in this case, I actually did an L5 laminoplasty as well, because it was extending rostrally.
[00:23:41] So, this is just a 3rd case of a 67-year-old with sacral back pain, feeling of sitting on rocks, burning rectal pain. She did have headaches as well, and urinary frequency. So, and this is just a technique to occlude the thecal tip. Sometimes you try to drain the cyst, and then if there’s a big ostium, it just fills right back up again before you can decompress it.
[00:24:06] So, so kind of packing a little bit there to, to avoid the CSF refilling it. These are multiple multiple cysts involved, and this is the giant one, and this was really interesting case because there was, near the ostium, there was like, here I’m stimulating with a triggered EMG with a monopolar to find a silent area of the cyst wall where I can open, and there was actually an ossified mass within the cyst that was right next to the ostium where it’s coming out. So I thought it would be necessary to remove this, because I really couldn’t get it really tightly closed because of this ossified mass. There has been one case report of this that I found, and pathology did come back with bone. So, inside the cyst itself. So I thought that was kind of an interesting thing, but that allowed a more you know, a better wrap on it
[00:24:56] and just fill it, filling in with the fat graft and then remove. She had a dehiscent area that I used a piece of mesh, you know, where the cyst was coming out and eroding, you know, it completely eroded the bone.
[00:25:09] And then just the last case here, 48 year old female, also with EDS. She had her filum sectioned. She had a horrible CSF leak after that procedure because her dura was extremely thin, extremely friable. She has orthostatic headaches. She has also the photophobia and hyperacusis. So I just have some pictures for this, but this just shows the extent of the dural repair.
[00:25:33] So the top upper left shows the initial exposure, and that blue mass that’s the end of the thecal sac, so it’s kind of like ballooning out very thin. So I ended up wrapping not only the cysts, but doing a terminal thecal tip duroplasty as well. She is out of the hospital. She said that this is the first time in like over a decade that she’s not had headaches when she stands up.
[00:25:59] So I’m doing an outcome. This is very preliminary data. It’s funded by Sutter Institute for Medical Research. REDcap database. It’s IRB approved. The algorithm we used, I tried to remove myself from this process as much as possible. So I have some study personnel that had reached out to the patients.
[00:26:21] Patient reported outcomes. And there were 272 charts that they identified. I’ve done SlicerDicer on EPIC and come up with about 600 or 700 since I’ve been there for about nine years, but their algorithm, that’s what they come up with. We had a very low response rate of people that actually was 17%.
[00:26:38] So there are 47 patients that completed a post op questionnaire. So the study design is that they got their questionnaire, but the small, the sample size was representative. The, these outcome measures, treatment met the expectation in the vast majority, but there was that group that felt that they were worse and wouldn’t have done the surgery again. Oswestry disability index improved with surgery. The urinal genital disability index improved. This just shows a scatter plot, various times of follow up changing a baseline from ODI. And then urogenital disability index clustering around zero, or better, which we hope, but there are some outliers that did worse.
[00:27:17] And then looking at complications, no CSF leak post-op in those patients, but some cauda equina type symptoms. I tried to cluster all of these into total amount of bowel or bladder post-operative new symptoms, of which there were there were six. So, you know, obviously trying to identify prognostic factors. Tend to be older patients, tend to be patients with larger cysts or multiple cysts.
[00:27:40] Some acknowledgements. And then here’s just some takeaway points, but I’ll just end there.