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BackTable / MSK / Podcast / Transcript #55
Podcast Transcript: BackTable Basics: Lumbar Epidural Injections
with. Dr. Chris Beck
Today, we have a BackTable basics episode. I'm joined by my friend and colleague, Chris Beck. We're coming at you live, not actually live, from Dallas, Texas, and Paris. That's Paris, France, not Paris, Texas, for anybody keeping track. Chris, how are you, man?
Table of Contents
Referral Pathways & Procedural Training
Patient Selection & Setting Expectations
When to use Lumbar Epidural Injections
Technical Considerations: Interlaminar Injections
Steroid Cocktails, Spinal Stenosis, & Motor Block
Intrathecal Entry: When to Abort the Procedure
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[Dr. Jacob Fleming]
Welcome back to the BackTable MSK podcast. Today, we have a BackTable basics episode. I'm joined by my friend and colleague, Chris Beck. We're coming at you live, not actually live, from Dallas, Texas, and Paris. That's Paris, France, not Paris, Texas, for anybody keeping track. Chris, how are you, man?
[Dr. Chris Beck]
Good, Jacob. Thanks for having me on the BackTable MSK show. Long-time listener, first-time guest. I appreciate it, man. I love the show. Actually, I don't know how many of your audience members know that you did the intro music. That's Jacob Fleming original.
[Dr. Jacob Fleming]
Oh, God. Aaron asked me, he was like, "Hey, do you want a credit at the end of the show for that?" I was like, "No."
[Dr. Chris Beck]
Of course. Of course I do.
[Dr. Jacob Fleming]
I just didn’t want it be honest, but now the cat's out of the bag.
[Dr. Chris Beck]:
Its a nice easter egg for his hardcore fans.
Referral Pathways & Procedural Training
[Dr. Jacob Fleming]
Today, we're going to be talking about a very important topic, epidural steroid injections. I think this is going to be fun. I think this is going to be fun for us and our listeners because your perspective is coming at it as an interventional radiologist who had to learn to do them out of necessity without really much, if any, exposure and fellowship. I've just finished my own fellowship, which is very spine-focused, and did several 100 epidurals. I'd really like to share our tips and tricks and different approaches.
One thing that I found with these is there are many different ways to skin a cat. I think we can talk about the different techniques and maybe some pearls. While we just jump in, we'll start with some talk about lumbar. Just tell me, what's been your experience with ESIs?
[Dr. Chris Beck]
You nailed it. When I went through fellowship, I was classically interventional trained in the old model in which I did diagnostic radiology for four years and then one year of fellowship. I did a total of zero epidural steroid injections. I did have a little bit of exposure in residency. We had a diagnostic neuro-rad who would, just when you were on a neuro-rotation, you might do some. Maybe I had done 20 or 30, some of them but a relatively low number, definitely under 50.
I really conceptually understood a lot of the times what I was doing, because it was so spotty. I just wasn't doing them with like a lot of reps. Then when I got out, I took a private practice job and the role that I stepped into, there was a lot of bread and butter interventional radiology, but then there was all these things that were just little add-ons. One of them was, we had a small pain service, but it comprised maybe 10% of the practice because we'd preserve one Friday morning. We had a little OBL that was attached to the hospital where we would do all of our pain procedures, which was joint injections, back injections. Some of the other guys were doing fetal bundle branch blocks and ablations.
I fell into this practice where I had to learn it, had to learn it quickly. We also had a practice where they put you out on an island and it was like, "Swim." Hold on, is that the expression? They just put you out on-- I don't know what that said, but they put you out on an island and you were expected to be able to do these procedures and do them quickly. There wasn't a lot of shadowing involved.
Then, now it's 10 years later and it's a procedure I feel very comfortable with, but I didn't have an academic approach to coming at these procedures. It's just something I had to learn on the go. Then I've developed my own way of working or navigating these patients with our referral patterns, which we'll get into talk about too.
[Dr. Jacob Fleming]
For sure. My experience in residency, I think was somewhat similar to yours. We had a pretty robust neuroradiology spine service which performed-- The bulk of the work was definitely like LPs, intrathecal chemo and myelograms, but did a pretty decent amount of both targeted and non-targeted blood patches. ESIs would come along once in a blue moon, but so many of those procedures were done under CT. That's an approach I became very familiar with.
I will say now to our radiology colleagues who are listening to this, because no other specialty uses CTs for ESIs, I will say that in my opinion, fluoro is far and away the superior option. It's quicker. I don't really care too much for doing those injections under CT because you're committed to doing just a straight axial approach unless you can tilt the gantry. For me, having a bit of an angle with the ESIs is something that's just really, really important and just makes it more versatile. Why don't you walk us through, first of all, what are the most common patients you're getting ESIs for?
[Dr. Chris Beck]
I think we have a nice patient mix in that we get a lot of referral from an orthopedic group. I think there's a couple spine surgeons and a lot of orthopedists. A lot of these patients have a pretty good workup coming in. I think we have a good patient mix in that it's patients who are interested in conservative therapy. They're either passing on a surgery or aren't surgical candidates. They come with a lot of openness to epidural steroid injections. I've already been briefed on it pretty substantially. Then we get some referrals from the community where we do a little bit more legwork on the beginning.
Referrals can be all over the map in that sometimes the spine surgeons want a specific level, specific number of injections. They can be very prescriptive about it to maybe one of the other orthopedics who does a lot of hips or something. He's just like," I just want to try and tease apart," whether it's a back issue or a hip issue. They give us a lot of leeway. They just say just do your workup and go through the motions of seeing the patient, looking at the imaging, and then choosing the level that we think is most appropriate. I think we have a nice mix. That's been a fun patient population to practice on.
Patient Selection & Setting Expectations
[Dr. Jacob Fleming]
I agree. My fellowship, like I said, was probably about 85%, 90% spine related. As you alluded to, a lot of these patients come in and they have leg pain. They've got sciatica and a lot of them attribute it to their hip or their knee because referral patterns can be complicated. I think this is something that's always worthwhile to keep in mind. It really comes down to, in my opinion, the MRI, the lumbar spine, figuring out where are you going to go and what is actually causing it. One of the nice things about the ESI is it is a diagnostic tool as well. You can get pretty quick feedback on whether you targeted the right level of pathology. Although I will say that most ESIs, they're not very selective per level.
That's something that we can get into. The indications for lumbar epidural steroid injections would be lower extremity radiculopathy with or without back pain. Notice that back pain alone is not a very good indication for ESI. Those of us who have done it know that for just solely axial back pain, you might get a little bit of relief, but it typically doesn't last. It's definitely not a good durable treatment. Then spinal stenosis is another one. I look at that more of a diagnostic tool to figure out if their neurogenic claudication is coming from that particular area.
Usually there's not a whole lot of doubt about it, but prepare the patient that with any of these injections, it's hard to say the durability of the relief that you'll get, you'll certainly get some, and we'll know today if that's the right switch, but it could last for two hours, could last for two years. It's very difficult to approach this. For example, my dad needed just a simple ESI, he's got some stenosis, had fairly significant neurogenic claudication, and now, seven months later, he's still fine. It's extremely variable, I find. Those are the indications we talk about. I think at some other point, you alluded to medial branch blocks and facet interventions and disc injections. I'll just put solely back pain off the table for now and say we'll cover that at some other point. Tell me about, you've got ESI on the schedule today, you've talked to the patient already. Patients on the table, just run me through your technique, how you take care of this.
[Dr. Chris Beck]
One other thing I wanted to touch on, I just wanted to drill down on it, but you did a good job in talking about just the reasons patients were referred. The two categories I'm always trying to put patients in a box to choose what procedure I'm going to do, I try and select the patients who are primarily neurogenic claudication, and those are the ones I'm primarily thinking, let's start with interlaminar injections, and then the patients who are primarily radicular symptoms.
Everyone who treats back pain knows that this is a messy category, but I really drill down with my patients, do some targeted H&P and some physical exam maneuvers to try and tease those two apart. If they have both, I'll just ask them, I'll say, "What's bothering you the most? If I were to take away your leg pain today, do you think you could start gardening or riding motorcycles tomorrow?" That's how I'll start the conversation with also leaving the door open to my patients and telling them, "Look, let's dig in for the long haul because back pain is something-- Everything that we do today, it's just to control the symptoms." I just broadly talk about it in broad strokes, but it's like, "All that arthritis, all those pinched nerves, they're still there. What we're doing is just symptom management. There's going to be opportunities to try different therapies or try different things to get you dialed in."
The other thing I was going to say, my preamble to the procedure is, I always take pain assessment score and I think people can get a little bogged down in the numbers. What's your pain score at, what's your pain score at it's worse, when it's at its best, whatever. I always tell them that those numbers are important to me, but what I'm really trying to do is restore them to a certain symptom relief to where I don't care if they're at a three or a 10 or a 6/10. If 3/10 means that they can go do the things that they love to do, like ballroom dancing or jumping out of airplanes, then that's a success.
If that number needs to be two for them or if that number needs to be four for them, that's the goal of therapy for me, is to chip away at this back pain to where they're going to be able to do the things that they love to do and not be afraid of back pain or ridiculous symptoms getting in the way of that, lifestyle limiting symptoms. I just wanted to say that.
When to use Lumbar Epidural Injections
[Dr. Jacob Fleming]
For sure. I'm glad you brought that up because, that actually brings up, I think the differentiation between a chronic and more subacute presentation. I'm sure you've had these patients who they present and they have just terrible sciatica. One of the things that I've learned is that sciatica is one of those types of pain that really can be a 10/10. I also put up there vertebral compression fractures and just a few other things. Usually when a patient comes to you and they're just having terrible pain, there's a very good possibility that it's an acute or subacute disc herniation. That could definitely be compressing the nerve in a lateral recess or the foramen.
I will say that my experience so far has been that the vast majority of patients who have radiculopathy do not have any lateral recess or foraminal stenosis. What I learned that this seemed to be due to, and what Dr. Beal has corroborated is that the inflammatory mediators that leak out of the disc, even if you just have an annular tear, but not any real significant amount of nucleus expelled, it's the inflammatory mediators that really rile up the surrounding nerve. In those patients with an acute or subacute presentation of a sciatica due to an annular tear or certainly any herniation, a lot of times you can knock it out with a single ESI, because the natural history of these HNPs is that they will heal on their own.
In the meantime, if the patient can't walk, they can't do anything because their sciatica is so bad, a lot of times you can just kick that out and it often is enough to get them by. I think that's a really important consideration too. I find that for more chronic issues, you tend to get a little more temporary relief. Like I said, it's very hard to predict this different patient by patient.
[Dr. Chris Beck]
I agree. I usually tell patients, similar to you, this is just talking in broad strokes. I'm just thinking about all my patients as a whole, as I'll say, anywhere between two days and two years worth of symptom relief with the average, our average internally within our group is somewhere between three and four months if we're hitting the right area. That's like the presumption that I've targeted the correct area and we land a successful injection. All the caveats there, but I think that it's good expectation management that you might only get a week worth of symptom relief and depending on the situation, it can still give you some diagnostic information that can help with therapy after that, things that maybe are not in the IR bag.
[Dr. Jacob Fleming]
Absolutely. Some things that are, and it's just a sidebar is that there's this dichotomy that I've heard over and over again, is that it's either injections or surgery. I think that there's a lot in between there that can be maximized. That's a different subject, but I will say, it depends on your relationship with your referents, especially if they're surgeons. A lot of times if they're a little more prescriptive about what they're asking for, then the conversation with the patient can go a little bit differently in terms of what could be the next thing.
Most of the time, if a spine surgeon is already involved in their care and just running the ship, I was going to say, look, I'm going to defer to Dr. so-and-so says we're happy to do anything to help you out. That's a different situation than if the patient is referred directly to us from primary care or another source and they're eval and treat. That conversation can go a little bit differently.
[Dr. Chris Beck]
Totally agree.
Technical Considerations: Interlaminar Injections
[Dr. Jacob Fleming]
I jumped the gun a little bit earlier, but let's jump into the technique, the technical. Patient's on the table--
[Dr. Chris Beck]
I'm going to do an interlaminar or transforaminal.
[Dr. Jacob Fleming]
Let's talk interlaminar first.
[Dr. Chris Beck]
Interlaminar, patient's prone, I will stand on patient's left. We have a table that can airplane, tilt side to side. I usually just start with the patient in the just regular prone position and just take a spot of the back. I'll have looked at their cross-sectional imaging at a time, one, to know the level that I want to target and corroborate that with the symptoms. Also it's helpful to me to know about any variant anatomy that might be there, if they have transitional anatomy. I just take a spot, identify where I want to be. I'll do a little level count from the bottom and find the exact location.
One of the things that is important for me and everyone's got their own method, but I'll usually try and flatten out the end plates with a little bit of cranial caudal tilt and true up the end plates. Maybe if I'm going L3, L4, then I'm going to true up the superior end plate of L4, the inferior end plate of L3. Sometimes I have to throw all that out the window and then I'm just looking for this little white space where I'm just rocking the II, either cranial, caudal and sometimes right to left. Usually if it's interlaminar, I'll ask the patients, just tell me which side's the worst.
If it's dead even, that's fine. I'll just pick a side that I think is easier to get into. I find that I always start pyramid line and just try and direct it as towards the center as possible. That's sometimes easier said than done. Sometimes a side can be totally blocked off to you, but with a little needle steerage, I can get it close to midline. If they tell me pain is mostly right sided, then I'm going to go right sided. I also feel like there's a patient in between the ears component that if they tell you all their pains on the right side or majority's on the right side and they have a bandage on the left side, they're like, "Eh."
[Dr. Jacob Fleming]
They didn't get the right spot.
[Dr. Chris Beck]
Exactly.
[Dr. Jacob Fleming]
They didn't get into the right epidural space. I totally agree with that.
[Dr. Chris Beck]
I understand that.
[Dr. Jacob Fleming]
I think that's totally reasonable too. I do the same if there is a laterality to it, then I'll target that. One thing that I learned during residency really is that if you've ever done these under CT, either ESI or blood patch, you'll see regardless of where you inject it, it goes everywhere. It goes ventral, it goes left, it goes right, it goes up, it goes down. For me, the selectivity of the transforaminal, which we'll get to in a second, is, it's not too important, but I think like you said, from the psychological perspective, it's just better, "Oh yes, we went on the left side." Oh wow. My leg pain is gone now." I wouldn't worry too much about that. If we have sciatica, just leg pain in both legs, we go from a left sided approach. You can still expect to get relief bilaterally, but probably the more of the concentration of the medication will be on that laterality.
[Dr. Chris Beck]
I agree. That's a good point to bring up. If you're done in CT, you really see how much coverage you get both ventral, left, right, dorsal. I'm just looking for that little lighter area, which is in between the bony elements. I'll advance the needle, I use a 20-gauge Tuohy needle. Sometimes I use a 22-gauge. The kits come with a 22-gauge, but my preference is to use a 20-gauge. I once had an attending who told me, this was an IR fellowship, Keith Horton. Although I know he doesn't listen. Keith, he told me that anything worth sticking with a 22-gauge needle is worth sticking with a 20-gauge needle. I've taken that to heart with whether it's kidneys, liver, or whatever, abscess drainages. I usually use 20-gauge.
I'll just go with a 20-gauge needle. I used to direct it at a posterior element and then walk it down. I've gotten away from that. I'll just go for the clear space. I have a feel for it when I'm meeting a little bit of resistance and have a LOR or loss of resistance syringe on the back filled with saline. I'll just like poke it along. I have a little bit of pressure with my thumb on the syringe. As soon as I feel like it give, then take the LOR syringe off. The rad tech is rotating the II into the lateral position.
This all happens, it's like an organized dance, but as they're putting the II in the lateral position for me, I've already injected contrast. My next picture is it in the lateral position and I can see if I'm epidural or not, which I also look at the needle, am I getting CSF return or if I'm getting blood return, but ideally nothing. I do that injection.
Once I see a nice epidural gram, we save that picture in addition to the PA picture. Then I just give the steroids and for better, for worse, I'll give the steroids. I think of the 2E, if it's in the 12 o'clock position, if the stylet or the bevel is open towards the 12 o'clock, I'll give a little bit in the 12 o'clock and then I'm rotating at 360 degrees. I'm dosing it in. I would say there's probably some voodoo to that. Every now and then, there's one clock face that doesn't want to accept it. I don't sweat it. I just keep putting it in wherever it's receiving it. Normally its where I'm putting the meds.
[Dr. Jacob Fleming]
Got you. Do you have a specific cocktail that you prefer?
[Dr. Chris Beck]
For interlaminars, I do 30. It's 5ml of Celestone, which is probably 6mg/ml, so 30mg of Celestone and 1ml of bupivacaine 0.25%.
[Dr. Jacob Fleming]
Nice. The mixture that I learned in fellowship is a little more like the inverse of that. We would typically, in the lumbar, we'd typically use Kenalog or Triamcinolone. That'd be 40mg in 1cc. We would typically do a total injectable in about 8ccs. Dr. Beal's style, which a lot of people are like, "What?" Is to, for the rest to be 0.25% bupivacaine.
Personally, having learned with that, I really like it. I will say that there are some times where I don't want to give that entire volume of bupivacaine. Certainly I know that there are some people who just use saline, some people will use lidocaine. The good thing about bupivacaine is that it is a much lower concentration than the lidocaine, you can end up with a motor block, and don't ask me how I know that in certain situations. I've noticed that to be more common in post-surgical state, even if the patient has had something just like a discectomy at that level, there's still enough post-surgical change between the epidural space and the dura that you have this friable dura.
It seems to be that you can get a partial spinal block doing that. The patient will be-- You get them off the table and they're like, "Oh, my legs are really weak." It's like, "It's going to be okay." As the bupivacaine sets in, and like I said, if you have that partial spinal effect, they can get a temporary motor block there and that's fine. It can be concerning for the patient. You just have to let them know you're not paralyzed. This is the thing that unfortunately happens. It'll be okay in a little bit.
Hopefully most of the time it's within about an hour or so, but I had one that lasted about six hours. The thing that you can really do to help dissipate that I found is try to stand up the patient as much as possible. Obviously you need help to do this. At least two people helping them up and stand up even for a few seconds at a time. It just lets that medication settle out a little bit more. I feel like that can accelerate it a little bit. The other situation where I would say I would cut the bupivacaine a bit, either with saline or lidocaine, depending on your preference, is significant spinal stenosis. Which is obviously one of the situations we're doing.
I've gotten to the point where if they've got severe stenosis, personally, I don't typically like going at that level. I'll typically go the level above. Like we said, it will run down. That's just because if you're injecting at a stenotic level, it's more difficult. You can puncture the dura more easily. If you're doing a nice LOR technique, you shouldn't, but it's certainly within the realm of possibility.
The other thing is when you're injecting at a stenotic level, it can be really painful for the patient, frankly, just because of the volume of the injectate before the local anesthetic, let alone the steroid kicks in. Those are some of the caveats that I learned through experience as they say, good judgment comes from experience and experience comes from poor judgment. Those are some of the things I learned.
[Dr. Chris Beck]
One of the things I want to say – I was also experienced in motor block and actually, I told you that when I started, I didn't have a lot of practical experience with these. I'd read some papers and everything, the textbooks that I could get my hands on before I started these. Man, it must've been one of my first six months. I had a motor block. It certainly made me very nervous. I knew it was something that could happen, but until it actually happens to you, it's hard to know how you react to it. My mind went to all the worst things that could have happened.
There are different patients that it can happen to and it couldn't have happened to a better patient. The guy was a complete prince. I remember after we did the procedure, I came and checked on him afterwards, and I said, "How are you doing?" He goes, "I'm great." He goes, "I feel fantastic." He was an old guy. I was like, "All right. Good." We always did these on a Friday. I said, "Have a nice weekend." He goes, "The only thing is, can't move my legs." He just mentioned it as if it's just passing. [crosstalk] Just can't move my legs. He had to hang around for a little bit afterwards until it wore off, but it took about like three or four hours before I was comfortable turning him loose.
Although I think now with having the experience that occasionally these things do happen, I could turn them loose a little bit earlier. That's the first time I've ever heard that, standing them up. Does it still work if you sit the patient up or if you can get them in a wheelchair or something, or?
[Dr. Jacob Fleming]
Most of the time they are sitting. That's okay. Of course once you get to the lumbosacral junction towards that area, the flexion you have from sitting, I think prevents the medication from spreading out more evenly. Maybe this is a voodoo thing, but I do feel like just getting gravity involved, getting them upright for even just a few seconds can let that settle out. I would say that's especially true for the stenosis. We talked about that spinal thing, but you can have motor block even without prior surgery with stenosis and patients can be a bit uncomfortable sometimes just from the injection.
I found that if you can get them up and stand them up, obviously if they have any sort of motor block, but if they're just feeling uncomfortable, but they can still walk, then getting up and walking around a little bit in recovery, obviously with supervision and assistance can really help that disperse down through the epidural space. I think that mechanistically makes a lot of sense to me where the standing up for a motor block, I think for-- Maybe that's something that just makes me feel better, but anecdotally in my end of two, it does seem to speed the process up a little bit.
Steroid Cocktails, Spinal Stenosis, & Motor Block
[Dr. Chris Beck]
You're clearly more constantly trained in these procedures than I was or than I am. When it comes to caudate equina and going at the stenosis level, I totally agree, but actually go at the level below the stenosis. If they have an L3, L4 stenosis, actually try and go lower than that. The idea behind it is certainly, one, I'll say that those are definitely the patients you can't just blast in the steroid. Actually, I'll say, I think it's usually poor form if you're just blasting this in as quickly as you can get the steroid. It's a nice control. If it feels good, then okay, take it.
That's a real point in the procedure where you can pay attention to your patient. We do all of ours under moderate sedation. Every now and then there's a player who just wants to be local, which is fantastic and fine with me. If they're coming off the table, you can slow down your injection rate. There's no race to get these done. Certainly I'll do a much slower injection rate for patients who are experiencing discomfort when I'm going below the level of stenosis. I just thought, oh, below that way I'm tackling all the nerves that are below the level of stenosis. Then also assume that some of it is tracking up above the stenosis.
[Dr. Jacob Fleming]
For sure. I think that works basically equally as well, just going adjacent to either the surgical or the particularly stenotic level. I agree, we also do the vast majority under moderate, although sometimes we'll do one under local. This might just be if we're having a clinic day and the patient shows up and they have very easy issue to just throw an epidural at. Most insurance plans don't require prior auth for an ESI. Getting them done the same day, even if we don't have our sedation nurse in the office, we can just do it under local. You have to eyeball these patients and get a feel for them, because there are some patients who, they're not going to do well under local, typically white males who are age 20 to 40, no offense to you or me, but we are the biggest wimps just statistically.
[Dr. Chris Beck]
I'm above 40, so it's really just you.
[Dr. Jacob Fleming]
You have the face of a 20 year old, so it works out. Actually there's been some interesting research on this that vasovagal episodes happen less often with moderate sedation. That's one thing that's nice. Especially in the super jacked, 25 year old dude with a big beard comes in and you're like, "That dude's going to vagal." I do feel that moderate sedation for me is definitely preferable. When we talk about the cervicals in a little bit, we'll talk about why going deeper than that I think is ill-advised. I agree, moderate sedation is great. When pushing in the medication, I totally agree with what you said, it's not a race. Typical patient, I'll probably inject it over a span of 30 seconds to a minute.
I like to let them know, "Hey, you'll probably feel some weird sensation down your legs. That's normal." It's very common to get a paresthesia with the injection of the medication, especially if you're using, lidocaine or bupivacaine in there, which I do. Just tell them that's normal. Some of them get freaked out by it. The patients who've had multiple injections in the past, they're probably fine. I just find that the sensation associated with a lot of these things can be very disconcerting for some patients. I like to let them know, "Hey, this is normal." Having them at a level of sedation where they can appreciate what I'm saying helps a lot.
[Dr. Chris Beck]
Totally agree.
[Dr. Jacob Fleming]
We'll say like technique-wise, I think my approach is pretty similar to yours. Usually get a little bit of oblique to whichever direction you're going to go from, because that can help open up the interlaminar space. However, I would say that's the way that I learned it or I was made to learn it was using just a standard AP view with no oblique. That took me a while to understand. I struggled with that for quite some time. Now I will say I haven't been forced to do that.
It definitely was more versatile and helps me understand the process for, for example, spinal cord stimulator. Blake previously has talked about this, the approach for how you put in the needle for placing a spinal cord stimulator lead. I will say that actually most of the time I do an ESI, I do a very similar trajectory to that of an SES placement. For that, I will start with an AP view, do a little bit of cranial caudal tilt first to crisp up the end plates, like you said. Then some patients just don't have a great interlaminar window. Obviously the patients who have degenerative stenosis is almost always related to degenerative disc disease and collapse of the inner body space and the interlaminar space tends to go with it.
Angulating more caudal gets you more of a view, which makes sense if you think about it, we're coming up from below. That helps a lot. In that case, if I'm not doing any oblique and the interlaminar space is open enough on the straight AP, typically where I will start is around the level of the pedicle below. This is something Dr. Beal referred to as the epidural highway. The way I understand this is basically between the pedicles, the medial borders of the pedicles and basically the laminate below. As long as you go through that path, you have a very good chance of getting into the epidural space.
This allows you to do it without doing an on-foss technique. That being said, I think the on-foss technique, which would be typically what you described as obliquing a little bit, opening up the interlaminar window, and then just starting to place the needle down the barrel, I think that's totally fine. Having learned both ways, I will say that I now prefer the way on a direct AP, but it takes a little bit because you have to, unlike the on-foss approach where you're really just moving in one axis, so to speak, this one you're moving in two or three different axes. You just have to get your brain used to it.
It's very similar. Blake made this point too, in a recent episode is that access to the epidural space is a similar angle to how you would access an artery or a vein for angiogram. Those in IR, I think will understand that pretty well. I think especially starting out, I would recommend going with more of an on-foss approach. A shout out I wanted to put out there before we get further and I forget is I think a really great resource for this is this textbook Atlas of Image-Guided Spinal Procedures by Furman et al. This is-- [crosstalk]
[Dr. Chris Beck]
I know exactly the one that you're talking about. It's a reference in the reading room.
[Dr. Jacob Fleming]
Yes. I think it's a fantastic resource and it's got great images and it's very thorough walking you through, "Here's your trajectory view and everything." I would suggest anybody, frankly, any specialty who's going to do a significant amount of interventional spine work, but especially IRs. If you have that, you'll see that, "Oh, wow, these procedures are fairly straightforward," and you just follow. Make sure you understand the imaging and go at it. Most of these procedures are fairly straightforward compared to the other stuff we do. I would wholeheartedly recommend that one to have as a resource.
[Dr. Chris Beck]
You talked about the AP projection. Do you ever flip to the lateral projection to see an injection?
[Dr. Jacob Fleming]
Yes. Absolutely do. Thank you for bringing that up. Personally, the way I would do it is, part of it is by feel and part of it is-- You can be a little more methodical about it by measuring roughly the distance on the cross-sectional imaging. Then you can know that, my needle is going to be this many centimeters in before I'm even close to the ligamentum. Once I get to that point where I'm like, "The needle is in a bit," then you can go to the lateral projection.
Some people would use the contralateral oblique. I think there are upsides and downsides to that. I personally prefer a true lateral. What I would do at this point is, I would switch off for my loss of resistance syringe. The way that I've learned this is actually, we didn't use a true loss of resistance syringe, which I think is a great instrument to have available, but we would use our contrast syringe, so 3cc contrast syringe. You see where you are on lateral and you're going to start injecting when you're just posterior to the spinal laminar line. That's the base of the spinous process where it joins with the lamina on the superior aspect. You're drawing this line in your mind's eye from that, the top of the spinal laminar line.
Once you get in there, you're going to feel the resistance. It took me an embarrassing long time to understand, "What the hell is loss of resistance? What is it?" What we're looking for is that feeling of loss of resistance as you go through the ligamentum flavum, because typically the inside the ligament, the pressure is such that you're not going to be able to inject contrast. Obviously if you just slam it in, you can get a sub-ligamentous injection.
Go in, and whether you're going to use a real loss of resistance or the combo LOR contrast thing, which I love that, I don't think I'll ever go back, do that, and then you'll get your epidurogram. If you feel really comfortable and based on where you are, then I think it's fine to start doing the LOR from an AP, but from a true safety perspective, the true lateral I think is the way to go. Once you do that and then you feel the loss of resistance and then in your case, injected, or in my case, that's the same as the LOR, then you step on floor and you get the nice epidurogram.
Of course, if you have any question, if the patient has real severe stenosis, then you can do this under fluoro too. I would do it. I personally don't do it live in the lumbar, but I would say 99% of the time I am getting lateral view. Then epidurogram has a pretty characteristic appearance, but sometimes it can be like, "Oh, that intrathecal, is it?" I think that's an important thing to talk about. The true epidurogram that is epidural, you can see that the contrast will pass over the pedicle. Whereas the thecal sac does not extend to the pedicle. You won't see that so much.
Those of us who've done a lot of myelography are pretty comfortable seeing what it looks like, but sometimes for whatever reason, you get more of a ventral epidurogram. That can look quite a bit like when you first start injecting for a myelogram, and that can get a little bit tricky. In that case, I would say never be shy about putting in more contrast to get a better feel for where you are. There's a few other characteristic findings, the subarachnoid pattern will be more of an hourglass shape and goes straight up. Like I said, it doesn't drape over the pedicles as the epidurogram does. If you see that nice epidurogram, even from the lateral aspect and you know you're in, I think that's fine. If there's ever any question, come back to AP, take a look there. Just do not, under any circumstances, inject unless where you are for sure. Like I said, because then you definitely will get a motor block and the patient will not be happy with you.
Intrathecal Entry: When to Abort the Procedure
[Dr. Chris Beck]
Let me ask you this. If you say you're doing your injection for whatever reason, you end up intrathecal, what's your next step as far as completing the procedure? Do you abandon the procedure? Do you go to a different level? I've just heard people are just all over the map and their approach to this. Some people can be very dogmatic. I'm interested in your take.
[Dr. Jacob Fleming]
Sure. It's a really great question. I've frankly been taught different ways. In residency, it was, if you got CSF back while doing an ESI, you got to abort the procedure for the day, call it a day and go home. I don't think that's necessarily true. I would say abandon that level, for sure, and go to an adjacent level. I really don't think that it is the end of the world to get intrathecal, but you need to be aware. I think it's appropriate to tell the patient about this that they may have a spinal headache after.
In that case, if they have that, and it persists for a few days, I would tell them, "Look, take--" Fioricet can actually really help and just hydration. Most of these dural punctures are going to be just fine without any further intervention. If after a few days, they're still having that spinal headache, blood patch is an easy thing. We can talk about that some other time.
The access for a blood patch is exactly the same as an ESI. In that case, I would go at the level where you either presumably or definitely had the dural puncture and do that. What I learned in my fellowship is that it's not a contraindication to go ahead with the ESI, but go at a different level so that you have a much less chance of getting any of that spinal action.
[Dr. Chris Beck]
I agree with that. It's strange that I also learned in training, when I got a little bit of training on these, that there were some neurorads who just abandoned the whole process like, "Oh, we got to bring them back on a different day. My practice currently is if for some reason I'm an intrathecal, then just take that needle out." Sometimes it's a little bit painful. It's not often with interlaminar, but sometimes you're working to get into this one spot and then you finally get in and then it doesn't work out and so you have to drop into another level.
Podcast Contributors
Dr. Christopher Beck
Dr. Chris Beck is a practicing interventional radiologist with Regional Radiology Group in New Orleans.
Dr. Jacob Fleming
Dr. Jacob Fleming is a diagnostic radiology resident and future MSK interventional radiologist in Dallas, Texas.
Cite This Podcast
BackTable, LLC (Producer). (2024, August 6). Ep. 55 – BackTable Basics: Lumbar Epidural Injections [Audio podcast]. Retrieved from https://www.backtable.com
Disclaimer: The Materials available on BackTable.com are for informational and educational purposes only and are not a substitute for the professional judgment of a healthcare professional in diagnosing and treating patients. The opinions expressed by participants of the BackTable Podcast belong solely to the participants, and do not necessarily reflect the views of BackTable.
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