Basivertebral Nerve Ablation: A Physician's Guide

[Dr. Jacob Fleming]
Very nice. I think the advantages of that multifaceted approach are pretty obvious for anyone from the radiology background to understand the typical difficulties, which you alluded to in terms of we have the imaging technology, but going to the next level and being able to directly evaluate the patient and perform the procedure for them, it's a gap that can be difficult to fill. Very cool to hear about your success with that, and I'm sure amidst your practice, something that has been crucial to expand this, is the treatment of anterior column pain, and so I'd like to dive right in and talk about vertebrogenic pain. First of all, we'll just start with the elephant in the room. What the heck is the basivertebral nerve? What is it and why ablate it? Just tell us about it.

[Dr. Olivier Clerk-Lamalice]
Yes. It is definitively a nerve in the anatomical structure that gained lots of momentum and lots of interest in the last few years. I would say even 10 years ago, most of the radiologists or interventionalists did not even know about this structure that now is, in my opinion, essential for any type of pain practice. The basivertebral nerve is a non-myelinating nerve. That's one of the key points that differentiate this nerve from, let's say, the medial branch nerve or any other peripheral nerve that you may want to ablate that will regrow with time.

This one, once treated with thermal ablation, will not grow back. This has been very well described with ex vivo studies and also consolidated now with the SMART clinical trial that we have patients, that, the trial went up to five years, but we now have patients coming out at seven and eight years, that have actually virtually no pain still after treatment. That's a first really key point of this nerve. This nerve is located within the central portion of the vertebral body, so, midpoint from superior endplate to inferior endplate, and about a third ventral to the posterior wall of the vertebral body.

If you take a look on a sagittal T2 sequence, normally you see within the posterior aspects that at the midpoint of the vertebral body, you see a small triangle that starts from the posterior wall. That is called the basivertebral canal. This canal will contain a small nerve called the basivertebral nerve, an artery and a vein, and we can treat that nerve by ablation. This nerve will arborize toward the endplates and will bring all the pain afferents from under the endplates, the superior and the inferior endplates back to the central portion of the basivertebral canal where the nerve lies.

Then the neural afferents will go back to the brain. In a nutshell, the basivertebral nerve will be responsible for what we call vertebrogenic pain, so, pain arising from the vertebral body. There always is a question, how can you differentiate this pain from discogenic pain?

[Dr. Jacob Fleming]
Yes.

[Dr. Olivier Clerk-Lamalice]
It can be very challenging, and in my opinion, it's virtually impossible to differentiate both. The reason is, continuing with the pain and the neural afferent back to the brain, the basivertebral nerve will pass through the sinuvertebral nerve, and the sinuvertebral nerve is also responsible for the innervation of the disc. Because of that neural connection there, it's very difficult to differentiate both. To determine if the patient has more vertebrogenic pain, we will rely heavily on MRI. Obviously, first, a physical examination, the patient will have low back pain with flexion maneuvers, sitting.

Often sitting at 15 degrees that stress is more basic for the anterior column. Will the patient have pain when he bends forward with weights, pain with vibration in the car and in the plane? All those that are typical for anterior column pain. That's one of the first things that we'll see. Then after that, if the patient has evidence of endplates, Modic Type 1 or Type 2 changes, then the patient becomes amenable for a basivertebral ablation procedure. That's a little bit how we can select those patients. That's a little bit of what we see. There's a big component that will be relying on physical examination and also on imaging for that specific treatment.

[Dr. Jacob Fleming]
Thank you for that wonderful overview of the pathophysiology and the workup for these patients. Just as a review for our listeners who are maybe a little bit more removed from diagnostic spine or neuroradiology, the Modic changes, like you mentioned, being the absolute hallmark of vertebrogenic pain. To review, the Modic Type 1 changes are the edematous changes of the endplate. That would be bright on T2 weighted or obviously stir and dark on T1. Then the Modic Type 2 changes, fibrofatty endplate changes, which are bright on both T1 and T2 sequences.

I appreciate you mentioning the difficulty of differentiating discogenic and vertebrogenic pain and the sinuvertebral nerve specifically, that connection is quite interesting. I understand it's something that that overlap can actually be taken advantage of. One of the next things I wanted to talk about is you mentioned some of the things that make the BVN different from other nerves in terms of it's not myelinated, it's intraosseous. Because of the intraosseous location, there's not really a great specific diagnostic block in the same way that we would say, for example, medial branch RFA, where the injection, the diagnostic block of the medial branch is very analogous to the ablation procedure itself.

Due to just the anatomy, it's not amenable to that, but the overlap with the sinuvertebral nerve pathway is something that could be taken advantage of with the anesthetic discogram. I'm curious, is that something that you use in your approach as sort of a diagnostic block? If so, can you tell in what context you may use it, or are there times where you're just convinced that it is vertebrogenic pain and to proceed ahead with the ablation procedure?

[Dr. Olivier Clerk-Lamalice]
Yes, absolutely. This is a crucial procedure also within my practice. Yes, I do use a lot of diagnostic and therapeutic anesthetic discograms quite frequently to confirm that the pain is coming from this specific disc level or from endplates that seem to be degenerated or have Modic Type 1 or Type 2. Also, the Modic Type 1 changes will be very frequently painful, so that the edematous endplate, so, bright on T2, hypo-intense on T1, very, very highly related to pain. I think the last time I checked, about 75% of those patients, of those type of imaging changes will be correlated with pain, versus the Type 2, you have early changes, and you have later changes.

Later changes sometimes may be less painful. It is kind of worth it to really determine if the patient would benefit from a procedure, and determine and confirm also that this is really anterior column pain. It's not coming from a different level. It's not coming from facets or any other area that could also be a confounding factor in that aspect. Definitively, diagnostic and therapeutic, and mainly anesthetic discogram is essential. We're doing it on every patient. If the patient responded well, meaning that the pain will decrease from a 7, 8, 9 on the VAS scale, to a 0, 1, 2, 3, at least 50% to 70% pain decrease. Then you have also the hallmark of vertebrogenic pain, which is on the MRI, the Modic Type 1 and Type 2. In a skeletally immature patient, patient did not respond to conservative care for at least 6 months, then you can proceed with the ablation.

[Dr. Jacob Fleming]
With that excellent segue into the allusion to discogenic pain, I do want to talk about some of the even further bleeding edge techniques that you're working on. You mentioned earlier, disc augmentation. I want to talk to you about your work with that, with the disc hydrogel. You've been working on a clinical trial with this. Just tell us about what's involved with this. Where does this fall into the anterior column pain treatment option melange? Where are we right now? Where do we expect to see that go?

[Dr. Olivier Clerk-Lamalice]
Yes, absolutely. The way that we set up our practice is also to provide high-level and high-quality clinical trial. We're running quite a few of these. A good portion of the interest right now is on the anterior column because we all know that most of the low back pain is not facetogenic mediated, but rather 60% or even more is mediated by the disc, the vertebral body. Currently, until, we just talked about BVN ablation, but there's not other minimally invasive treatments that will reliably treat the region of pain.

To palliate to this, there has been, for multiple years, an attempt to inject a gel inside the disc, try to rehydrate, basically, those discs, and provide some support. There was in the year early 2000, a hydrogel called Gelifex that was tested, but they noted lots of expulsion of the material, and unfortunately, this did not go too far. That was the first generation of a hydrogel that was tested. Now, there's a second generation that is available that is made with PVA, PVP, and PEG. Basically, it is a gel that you need to heat prior to injecting.

You're heating at 65 degrees celsius, this gel becomes liquid, and you can inject it through a 17-gauge needle. You're using the classic Kambin triangle approach. You're making sure that the tip of the needle is centrally located within the disc, and then you inject that disc. So far we've treated, in my center, 35 patients. Overall, in the world, I think we're past the 100 patients. In North America, we're actually the only recruiting center right now, and the results are just good. They're phenomenal. The average pain decrease of patients with stable discogenic back pain that had one or two levels of disc generation, decreased their pain score from a 6.8 to a 0.9, which is to be permanent.

[Dr. Jacob Fleming]
Wow.

[Dr. Olivier Clerk-Lamalice]
We're continuing to follow those patients, but so far, the results at one year seems to be quite sustained with no significant adverse events that are device-related that we saw within my cohort. Really good results so far. Very exciting technology. It's interesting to see also where the gel lies. Sometimes the gel lies whenever there's less stress within the disc, which is often where you see either radial or circumferential annular tear. Sometimes the gel will migrate up to the borders of the disc, which initially can seems a little bit concerning.

This is purely part of the gel. It will just provide support where there is no support, and a follow-up of patients of now two years plus in the other center, the gel just lay there and should be good for actually about 40 years.

[Dr. Jacob Fleming]
Wow.

[Dr. Olivier Clerk-Lamalice]
Seems to be so far a very promising treatment. We're still getting data on this treatment, but so far, very, very promising and excellent patient satisfaction. I think 95% plus of patients would suggest this treatment to family members or other individuals that they know. Lots of the individuals that we treated were out of work because obviously if he got back pain, they went back actually to work.

[Dr. Jacob Fleming]
That's incredible. It really reminds me of what we were talking about with vertebrogenic pain, in general, is that prior to a few years ago, this was a problem we didn't really have a good mousetrap for. A lot of different things have been tried in the disc over the years, from things that are more a nuclear lytic, to things that are actually trying to augment. As you said, the augmentation approach just, it doesn't have anything good available for it, or really, anything outside of a clinical trial at this moment. That just sounds like a really exciting frontier.

As anyone who's read spine MRI for more than a day will know that the issues of disc degeneration and annular tears, and this whole spectrum is just incredibly common, and debilitating. Like you said, some of these patients can't work because of it. What are you going to do to use them or put in an intrathecal pain pump? Those are things that happen. It's not to throw shade on that, and certainly, depending on the individual situation and context, sometimes more aggressive things are necessary, but in general, the entire approach that you're working on, is it seems to be getting the absolutely most ultra minimally invasive way to deal with the given problem.

This sounds like just that for the specific category of discogenic pain. We definitely look forward to hearing more about that and certainly hope to have you back at some point in the future to give us an update on that and what we can hope to see in the future.

[Dr. Olivier Clerk-Lamalice]
Oh, absolutely. I have no doubts that we'll hear lots of new developments on the anterior column treatments, on the disc injectables. I think that that's one that it seems to be very promising, but there'll probably be others also that may be able to help with larger type annular tear, also that normally that we cannot inject gel in those annular gap or larger torn other annulus. That will probably be coming also at some point, but lots of new developments within that field. I think, at the end of the day, everything that we're doing is for the patient and to provide better outcomes and less time in the hospital, and faster recovery.

I think really, everything that is happening currently is spearheading in that direction. It's a very exciting field, and I definitively convinced that within the next couple of years, we'll have very good therapies for the anterior column.

[Dr. Jacob Fleming]
Agreed completely. That's just really exciting. Speaking of new developments and frontiers and spine interventions, are there any other particular developments that you're excited about outside of the disc and the disc augmentation, and basivertebral nerve ablation? Any other particular things on the horizon that you're really excited to see where it goes in the next few years?

[Dr. Olivier Clerk-Lamalice]
Yes, absolutely. The only thing that we didn't talk and maybe that's going to be a topic for another podcast, but all those patients that have single or dual-level registered symptoms, secondary to a herniated disc, what do you do with those patients? Basically, there's more and more treatments that are minimally invasive, allowed to resorb or mechanically extract, physically, this herniated disc. One of them that we're working currently is with, we're performing nuclear lysis. Basically, you can inject a gas, ozone gas that basically will shrink a small portion of the nucleus pulposus right behind the herniated fragments, and will resorb the disc protrusion.

I did five or six cases right before Christmas, and all of those patient, they're all doing amazing. They have either significant decrease in their registered symptoms or completely gone. I have even followed on a firefighter that was completely out of work, had a herniated disc. I imaged the patient before the procedure, and after the procedure, and it looks like there's no neural impingements. The herniated fragment is completely resorbed. Quite remarkable for a procedure that you can do in such a short amount of time as well.

[Dr. Jacob Fleming]
Fantastic. Yes, I have to agree. I think that minimally invasive treatments for HNP as we call it for short, herniation of the nucleus pulposus, is another one of these omnipresent problems that plagues adult patients. There are a lot of exciting things coming out on there. We'll definitely need to have a specific discussion of nuclear lysis techniques and of course, one of my particular interests is the endoscopic spine surgical approaches, which are obviously gaining a lot of traction among the surgical community. I think that's another area that is absolutely the frontier. As we go further into that era, there's going to be no turning back, which, in the best way possible to making treatments for these debilitating conditions as ultra-minimally invasive as possible. Really exciting to see what comes out in the next few years.