Episode 93: Imaging for Peripheral Nerve Disorders and Chronic Pain | Hernia Talk Live Q&A

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Speaker 1 (00:00:01):

Hi everyone, it’s Dr. Towfigh. Welcome to Hernia Talk Live where we do this every week, every Tuesday on our Hernia Talk Tuesdays. My name is Dr. Shirin Towfigh. I am your hernia and laparoscopic surgery specialist. You can follow me on Twitter and Instagram at hernia doc. Many of you’re joining me on Facebook at Dr. Towfigh and on Zoom as well. Thank you for joining me. At the end of this show, we’ll make sure that you have access to all these episodes, including today’s on my YouTube channel. I have the distinct pleasure of having a very lovely guest today, Dr. Jan Fritz is the musculoskeletal radiology specialist at NYU Langone. I’ve known Dr. Fritz for, I want to say maybe six years now, five or six years. You can follow him on Twitter at Jan Fritz M S K. And please welcome Dr. Fritz. Hi.

Speaker 2 (00:00:58):

Hi. Pleasure to be here.

Speaker 1 (00:01:03):

Let’s see if I can hear your voice.

Speaker 2 (00:01:05):

Yeah, can you hear me?

Speaker 1 (00:01:08):

All right. Very good. So Dr. Fritz, welcome.

Speaker 2 (00:01:14):

Thank you. Pleasure to be here.

Speaker 1 (00:01:15):

I’m so privileged to have you. So for the audience you may know, I love radiology myself. I’ve actually published about radiology and hernias, and you may want to know this. I actually got where my resident got an award from the R S N A for one of our presentations about imaging for hernia Mesh. So I love Mesh, I love radiology. I maybe should have been a radiologist and had a I maybe better lifestyle, I don’t know. But I feel like you’re like a surgeon in a radiologist body. And I’m a radi, I’m a, wait, hold on. How do I say this? I feel like you are a surgeon in a radiologist’s body and I’m a radiologist in a surgeon’s body.

Speaker 2 (00:02:03):

That’s a good way to put it.

Speaker 1 (00:02:05):

Yeah. So welcome. Thank you for coming to the show. I asked Dr. Fritz to join us because even though he’s on the exact opposite end of the United States to me, he has been able to help a lot of my patients. And actually one of my patients referred me to you because you were helping him and we’ve shared several patients since then and your availability and abilities have been just enormous. So thank you also for donating your time for today’s Hernia Talk session.

Speaker 2 (00:02:39):

Yeah, thanks for having me.

Speaker 1 (00:02:42):

Can I ask you initially to just give a very brief intro, how do people become radiologists? And you are spec, spec specifically a musculoskeletal radiologist. How does that happen and what kind of patients you see?

Speaker 2 (00:03:01):

Right, so radiology is like surgery, specialty of medicine. And so it starts with a medical school we all go to. And then after that you basically decide what you would like to be when you’re an adult physician. And so after medical school, you’re a medical doctor and then you start your, what we call specialty training. You make a decision whether you become a surgeon like you are or you go into medicine or you go into anesthesia like putting people to sleep or you become a radiologist and radiologists is basically all imaging. And then you do a residency, which is five years. And during that residency you work as a doctor, but you’re basically a doctor in training and you learn everything about imaging. So MRIs, CTs, ultrasound of course.

Speaker 2 (00:04:03):

And during those five years you also learn to do procedures. So the surgical part or if you want the minis surgery, part of the radiologists is that you interpret images and to look for abnormalities, injuries, certain conditions, but you also do procedures. And the procedures we do is not surgery. I want to here, but we use imaging to guide instruments. So for example, injections and biopsies. So we are often asked if something is seen on the images and we don’t want to do surgery like you would and get a specimen or a tissue sample for pathologists to look at it under the microscope and find out what it is. Sometimes the radiologists are being asked and say, Hey, can you do this under imaging guidance and maybe make a smaller incision in the skin and get a small sample out of it? Maybe we can get that way and find out what it’s, so we differentiate diagnostic radiology, which means looking at images and finding out what’s wrong and then add that to the evaluation of patients and then add that information to come up with a plan.

Speaker 2 (00:05:23):

And then what we call the minimally basic procedures on the imaging guidance is injections, mostly biopsies of bone or soft tissues. And sometimes we do something like ablations where we can treat abnormal tissues by just freezing or burning it. And then after that five years you have hopefully learned all of that. And then within radiology you decide what kind of radiologist you want to be. So it’s a little bit like in surgery. So after your first residency or surgeon, and then you try to, do you want to be a vascular surgeon or cardiac surgeon, and you may know this from TV and similar in radiology, you decide whether you want to be a neuroradiologist or a musculoskeletal radiologist. For example, pediatric radiologist. And so I’m a musculoskeletal radiologist, which is then a fellowship where you learn within radiology everything about bones, muscles, tendons, joints and nerves. And so you subspecialize and so you acquire additional skills that allow you to become more proficient in that.

Speaker 1 (00:06:31):

I just want to clarify for the audience. So surgical residency after medical school is typically minimum five years. That’s considered a very rigorous residency, but radiology is also five years of radiology as opposed to mental medicine, which is three years. Pediatrics is three years. Most of the other ones are in the three year range. And then in addition, they do extra training. So when you see a best radiologist like Dr. Fritz, it’s the same amount of training years that I’ve had. He’s had maybe more. So it’s pretty impressive how much we rely on good radiologists and how much training they get to do. But let me ask you this. I know currently you do a lot of nerves and pain and abdominal wall type imaging interventions, but when you were in the first five years, did you all get taught about hernias specifically? And in retrospect, do you think it was adequate how much hernias were kind of considered part of your differential diagnosis in reviewing imaging?

Speaker 2 (00:07:44):

Yeah, I would say it was a small part of it. So basically in those five years, you need to learn the body from top to bottom again. So in medical school you learn everything about anatomy and physiology. And then in residency you have to learn how all this looks on imaging normally. And then you have to learn everything that can go wrong. And so hernias are a part of that. But I think in residency it focuses more on the classic hernias, so growing hernias, right? And how they look on imaging, not so much on the nerves. So the nerve is really a topic. Maybe very early, maybe 10, 15, 20 years ago, we were actually not very good in imaging those because we didn’t have the technology and the tools, although we knew the anatomy and then for example, MRI, which is what we often employ for our patients, has evolved tremendously.

Speaker 2 (00:08:40):

There has been tremendous technological advances and the anatomic detail that we now see with MRI and specifically a specific technique of MRI is monography. Where you apply techniques where you specifically tune everything for the nerves. We can see a lot more detail now that we have not been able to see. Yeah, 15, 20 years ago. So if you can’t see it right, it’s not part of the textbooks. And now that we can see it, we know a lot more about it and we teach a lot more about it. But when I was in training, the amount of knowledge and the abilities technically was much more limited than it is now.

Speaker 1 (00:09:26):

So we have a lot of questions that are coming in live, but also that were submitted to me in advance. Most of ’em were about complicated situations, but maybe we can start simple. So for an abdominal wall hernia, and I’m going to talk about abdominal walls separately from inguinal or groin for an abdominal hernia, can you review what you as a radiologist would recommend for imaging to identify a primary abdominal wall hernia in the United States?

Speaker 2 (00:09:56):

Yeah, it typically starts with CT, right? So some of these are palpable or the diagnosis is readily made clinically. So basically experienced surgeons like you or also patients learn a lot of about their bodies, often already diagnosed it correctly. And then it is either visualized on ct, so for example, on an abdominal ct, which displays the muscles and the abdominal wall to actually good detail does not show the nerves, but it does show the muscles and it does show the relationship of, for example, bowel and the abdominal contents to the hernia pretty well. And that goes really from above the umbilicus down into the pelvis, all where these little hernias can occur. That’s usually the first time we pick it up. Sometimes we do it with ultrasound, so sometimes there has been a surgical evaluation clinically patient sees a surgeon like you and then you do a physical examination and then it’s already pretty established what it is. And then sometimes we do focused ultrasound, which can be done dynamically. You want to see are there bowel contents moving in and out for example, or is the hernia going medial and lateral to a vessel, all these different things.

Speaker 2 (00:11:20):

And then sometimes there’s emergency situations where hernia, where hernias complicate, right? So if they have a wide narrow neck in one of the bowel loop slips in for example, and twists around, then that can cause problems with first inflammation and then it can literally cause bowel obstruction. And some of these abdominal wall hernias are notorious to do that and then they can locate it, different anatomy, anatomic situations. And then sometimes we do CT even for surgery. So let’s say somebody comes in and needs acute surgery because then we often get a CT as a roadmap. The surgeons would like to know, okay, so where is this exactly? How bad does it look? How bad is the obstruction? Do I have time or would we need to rush to the or? If so, can we roadmap that and help make the incision maybe smaller than necessary or see if there’s anything else that needs to be addressed

Speaker 1 (00:12:20):

In terms of cost? Well, so the main imaging that we use for abdominal wall is ultrasound, CAT scan or CT scans, the same thing or MRI in terms of cost is the cheapest and MRI is the most expensive. Is that about correct?

Speaker 2 (00:12:36):

It’s about correct typically? Yeah. Yeah, typically that’s correct. It depends a little bit on how it’s done and where it’s done. The thing about ultrasound is that ultrasound itself, the ultrasound machine is cheap, but I would say a skilled ultrasound exam takes a while and you basically need a physician with the patient together to do the exam. So there’s actually a lot more time involved than for example, a CAT scan, right? CAT scan if you had it, you know, go in and these are so fast, it takes five seconds and it’s done. An ultrasound exam for such a specific location is sometimes in tough anatomic region. So the ultrasound probe, it’s not just in the belly, it might be in the groin, it might be in the buttocks region. And so you have to do specific maneuvers. So it depends a little bit on how much time needs to be invested, but from I think the way of the material cost MRI, yeah, is most involved in ultrasound is probably technically the cheapest.

Speaker 1 (00:13:41):

As surgeons, we’re very comfortable with the CAT scan and I think most doctors are most comfortable with a CT scan or a CAT scan. So when you go to the emergency room, that tends to be the first image that’s done. And so for emergencies, for example, we tend to just rely on the CT scan and so on. Okay, let’s move on to the more complicated situation, which is they’ve had surgery and now they’ve had Mesh or some other thing where there may be issues. Let’s talk still abdominal wall on the front of the belly and then we’ll move on to inguinal later because that’s much more more involved. Do you recommend any specific type of imaging to look for the Mesh and look for hernia recurrences, folding of the Mesh, infection of the Mesh? Any other reasons for chronic pain Ehlors, for example, do you recommend one imaging versus the other?

Speaker 2 (00:14:39):

Yeah, as you already outlined, it depends a little bit on the situation. So the major plus of CAT scans is that it’s very fast and like you said, it’s available in the western world in almost every ed. And the image quality is generally very good. The technology is very refined these days. CAT scan has been around for many decades and it’s the accessibility whereas everybody knows it has undergone MRI, it it, there’s fewer machines around, they’re usually not on at night and it takes a lot of longer to image. So in emergency situations it’s CT for certain questions. Even in non-emergency situation it’s still ct because CT is very good to see small fluid collections like you said in inflammation. Yeah, maybe a hernia recurrence, maybe a second hernia that was not the original hernia but is now somewhere else. All these things, CT is often sufficient and CTs good because you go to your radiology practice, get on the table and zip it’s done, right? And then yes,

Speaker 1 (00:15:53):

Very quick. It’s less than a minute, right?

Speaker 2 (00:15:56):

Oh yeah, it’s often the actual scan time is five seconds. It’s like, yeah, it’s literally this. It’s very good for bowel. So often if there is a question whether there’s bowel involved, some VA in abdominal wall hernias or inguinal hernias or obturator hernias, whenever there’s a question whether there’s bowel protruding through the hernia opening, then CT is very good because you can drink what’s called oral contrast material and then looks white on ct. So it’s dense, it outlines the bowel beautifully. And if you, so patients are usually asked to drink a substantial amount, usually order a gallon or so, and then you sit there and wait and you wait for the oral contrast material, it looks like water, but on CT it appears white. I have to say yes, I think they tastes better than they used to taste. So yes, and all radiologists taste that so that you know what you’re giving your patients it like very bitter, I think that tastes better.

Speaker 2 (00:16:55):

Now you can also edit a little bit of orange juice or so. Yes. So they ask you to drink that and then you sit there for maybe 90 minutes to two hours. And the purpose of that is that the oral contrast material travels through your bowels and then when you do the CAT scan, it’s outlined the bowel beautifully. That’s actually almost better than MRI. And then you can very well see where the bowel is and if it sits in the hernia sac or whether there is an obstruction or narrowing for the contrast material to go through so you get some functional information. So this is all ct, I would say almost every patient that I see or that you and I see had a CAT scan at some point and there’s valuable information in there. It’s also very good for bone. We can see bone really well in CAT scan.

Speaker 2 (00:17:40):

It’s basically a super x-ray. And so there’s helpful information that in some ways supplements or comp compliments, MRI. So it’s often not the case that you know, MRI is great and hey they gave me a ct. That’s bad. It’s really, it’s often the CT is the right imaging and then start with that. It’s quick, it’s fast, it gives all the information that is usually necessary for emergency situations when there’s a question whether surgery has to be done at night or so. And then MRI answers a lot of questions that you may not see on ct. So let’s see, let’s say you do the CT and like you said, there’s still questions about where the pain is coming from. Then there’s certain things that CT cannot show and one big thing is the nerves. So nerves are very small, they’re like a millimeter thick and less so really tiny, not like a hair but like a small bundle of hairs and that is too small for our ct. And so that’s where MRI comes in. So MRI excels in visualizing these nerves with a special technique, but in general, MRI is much better for small vessels and nerves and see how they curve in relationship to the hernia.

Speaker 1 (00:18:57):

So when imaging for the pelvis, usually for inguinal hernias or complications from inguinal hernia surgery for primary hernias, if you need to, again, what you said is very right, if there’s an obvious hernia, there’s really no need to do imaging usually unless there’s some planning that imaging will help. But usually that’s not the case. But if you have an ultrasound is often good enough, CT scan may be adequate for a simple hernia and MRI is definitely the most sensitive imaging modality for the groin. But let’s talk about the complications because that’s why most of the people here are looking at and that’s really where your gift is. So can you talk about the benefit of MRI for the pelvis, why it’s better than CT scan? And then secondly, a lot of these patients have chronic pain because they’ve had surgery, so they may even have an occult hernia, an occult infection or attackers that are causing pain. Mesh may be folded there or other Mesh related involvement with local organs. Can you explain why an MRI is better?

Speaker 2 (00:20:16):

Yeah, so yeah, for those situation, MRI is great and is the test that should follow if a CT doesn’t give the answer. So the basic difference between CT and MRI is that CT uses x-rays and MRI uses actually the protons of our body. So MRI does not need anything to be sent into the body or you know, drink at baseline with, you can give contrast material through the veins, but we can talk about this later, but at baseline, MRI just uses the water in your cells to make images. It’s actually, when you think about this pretty nifty because CT has to send x-rays through your body, you send it from one end and on the other end you see what comes out and then the thing rotates and you make an image. Yeah, in MRI you don’t do that. You use the water molecules of your body and you send in radiofrequency pulses and then you have magnetic fields that received the signal and then you make an image. So that’s why somebody got, or two people or three or four got the noble price for that because it’s such a genius way of doing it. So you’re using it basically the agent’s always ask and say, so what do I have to bring? And I say, bring yourself actually

Speaker 1 (00:21:31):

You’re protons,

Speaker 2 (00:21:32):

Bring your protons, that’s what you are. So we are 80% protons, I would say 90% protons,

Speaker 1 (00:21:39):

But it’s also why the muscle looks different than the Mesh, which looks different than the fat. Whereas a CAT scan it’s all muscle and Mesh all look the same. So it’s very hard for me to identify specifically how the Mesh interacts with the muscle when they both have the same color MRI, they’re distinctly different. So I really like that much better.

Speaker 2 (00:22:02):

Yeah, exactly. So for sake of a understandable model, CT can be thought of density. So the denser tissue like bone is very dense, the brighter it looks on ct, but for tissues that are not dense, which is everything soft tissue and that even includes water, it just looks grave like you said. Yeah. And there’s not much of a difference for CT between certain soft tissues. So a tendon in a nerve and a bowel wall in the liver looks very similar on CT because they’re not dense, whereas the bone is very dense, looks very white, everything else looks great. Now for certain situations it’s still enough to differentiate it, but there is not much of for recall contrast. So contrast between these grays is small, whereas with MR, where you image protons, this is very different. So a nerve looks very different to fatty tissues, looks very different to muscle, looks very different to fluid to bladder wall to bowel wall to organs like uterus, ovaries, prostate, right?

Speaker 2 (00:23:11):

Everything that’s around there, it’s excellent for joints, it’s fantastic for articular cartilage. So that’s why orthopedic surgeons use MRI a lot because we can see so many structures in the joint. Yes. Whereas a CT of the joint, you pretty much see the bone in nothing else, right? Yes. And so the same applies for the groin. The, it’s one of the most complex anatomic areas in the body that you probably would agree there is never, there’s so many structures in the groin, so many, it’s a genius anatomic construction. So evolution has done a masterpiece there. But for us to do surgery there or for you to do surgery, there is yes, certainly a microscopic challenge. And for us to look there is a lot to learn and a lot of image and you need the contrast of MRI. So MRI is very good to show you the little tissue differences much better than ct. So that’s why MRI is so good.

Speaker 1 (00:24:08):

Great. Okay, I’m going to run through a bunch of questions that are being posed so that we can answer as many as we can. Let’s talk about fat and bowel and hernias. Can a CT scan differentiate a hernia with fat content versus a hernia with bowel content?

Speaker 2 (00:24:24):

Yes. So this is actually where CT excels for that question and that’s often also in the emergency. So part of my job is also covering our emergency rooms here in Manhattan where what behind and they’re often hernias are there and they usually fat filled like the question correctly states and then if it goes wrong, then a bowel loop can slip in, it sometimes slips back out and it doesn’t do anything, but sometimes it stays there, they can get inflamed and if it’s an emergency situation, the twists and then the bowel, the contents can no longer pass. And so that is where CT is excellent. I actually would not get an MRI. Yeah for that, right? Often time is of the essence for that as sometimes you go to the ED and then you be called by the ED doctors and said, Hey, we need a surgeon. Can you at least take a look? This may need immediate attention. And so that’s where the CAT scan needs to be done quickly, search and radiologists look at it and then a decision needs to be made. And that’s actually not just because of availability, but CT is really the best for that question.

Speaker 1 (00:25:33):

Correct. And do you think the CAT scans should be done with bear down views? So for these

Speaker 2 (00:25:41):

That’s a good question. So should it be done? Yes. So I think actually we should do two runs. We should run, we should do a run just relaxed and then we should do one where you increase your abdominal pressure, your pelvic pressure, like the said of Valsalva, where you breathe into your belly and that’s often where we see that bowel is being pushed into hernias. I will say that’s a little bit more involved in at night in emergency situation, that’s challenging to do, but for an outpatient center where you have a specific question and we have time and patients are not in severe acute pain, we can do that. That can also be done with ultrasound. Some surgeons do it in their office where you can put the ultrasound probe on the groin for example, and then you say, okay, please bear down for me now. And then you see the bowel sliding in and out for example. And

Speaker 1 (00:26:34):

What’s the instructions that you give to actually perform a Valsalva or bear down?

Speaker 2 (00:26:39):

Yeah, so we say do the same thing that, so if you take a bath or you dive into the ocean and then you get up and you have water in your ears, you do it like this. That’s exactly what we tell the patients. Well that’s

Speaker 1 (00:26:54):

A good one.

Speaker 2 (00:26:55):

So you hold your nose and you breathe in your chest, but don’t let the air out. So I think closes to what gets to Valsalva. Yeah. And you can put it on the table. We say, okay, nothing’s happening. Do your thing and then breathe into your nose and then hold it. And when you hold it, we push the button

Speaker 1 (00:27:15):

And you’re clearing your ears. That’s perfect. Yeah, that’s great. Okay, questions about nerves. So MRI is specifically the imaging that can, I think ultrasound as well, but definitely not CT scan where you can look at peripheral nerves. So is there a fine tuning of the MRI you have to do for specific nerves to be viewed? Yes. Is that the MR Neurogram that some people order

Speaker 2 (00:27:40):


Speaker 1 (00:27:40):

And what is that?

Speaker 2 (00:27:41):

Yeah, so two parts. So actually ultrasound is also very good for nerves, but only if they are close to the skin surface. Oh, in the groin they’re often deep and also, so part of my practice, a big part is of course groin pain, which is what’s working, but also thigh pain and also pelvic pain. a lot of patients are with pelvic pain and they’re kind of interconnected and there a lot of the nerves are deep and it’s act very hard. So the one thing that ultrasound will suffer from is penetration depth. The ultrasound is not very good to look into deep tissues. That’s where MRI is excellent. However, let’s say you have an elbow, a arm that falls asleep and you have problems here at the elbow here, ultrasound is great because the nerve is right under the skin surface. But yes, for MRI, I think that that’s a differential answer. So it is very important how the MRI is being done.

Speaker 1 (00:28:42):


Speaker 2 (00:28:43):

So MRI itself is great for nerves but not all MRI it It does indeed. The questions suggest need a fine tuning and that is difficult. I will say often we get MRIs to look at and then we say, ah, that wasn’t geared towards nerves. This was maybe geared towards organs. Maybe this one’s more like a prostate MRI or something geared towards joints and then the nerves are not that well seen or so I would say two things that need to be done. It needs to be more modern equipment. So a scanner that’s 20 year old can likely not do it and then it needs to be tuned towards nerves and that needs to be done with some technical expertise. So you and I have transferred knowledge from the east coast to the west coast so that patients don’t always have to fly to New York and get these scans done. Yes, there’s certainly centers at the west coast and almost in every city that can do it. I think the challenge is to find these centers and knowing whether they have the technical expertise and the technique in place. So that is true. MR neurography means that is fine-tuned to nerves. Unfortunately it’s not a protected term and there are certain expectations for pornography, but there’s also a broader, it’s a broad term where many things are being mixed in. Sometimes

Speaker 1 (00:30:17):

I get a lot of MR neurography done and then the radiologist really doesn’t interpret it correctly. So yeah, besides getting the right imaging, you need the radiologist and understands that. It’s

Speaker 2 (00:30:27):

A very good point as well. So even if you use the best technique and you have done everything right, technically it takes a little experience to actually read these MR Know where those nerves course a lot of nerves have anatomic variations, meaning the textbook says this, but in reality there’s five different Oh yes versions of

Speaker 1 (00:30:45):


Speaker 2 (00:30:45):

Maybe more and this better than we do. When you do surgery, you look for the nerves and then you figure where they are and you say, oh, this one didn’t read the anatomy book. That is somewhere else. And so that takes expertise and in certain amount of training and also it takes time. These scans often take half an hour, hour to look at and interpret and so that all needs to be done.

Speaker 1 (00:31:12):

So there’s a disorder called acnes. A C N E S is anterior cutaneous nerve entrapment syndrome. The nerve itself is totally healthy. It’s just as it transfers from the back towards the front of the abdominal wall and it splits at the lateral border of the rectus muscle through the fascia or as it goes posterior splits to come up towards the front of the muscle, it gets entrapped. And so when the muscles of the abdominal wall contract, it kind of kinks that nerve. So technically the nerve is not abnormal. Can an MRI help identify entrapped nerves?

Speaker 2 (00:31:57):

Yes, it can. So I will say this is probably a high C of nerve imaging. So these vessels in the, the nerves in the abdominal wall, when they start at the spine, there are certain thickness which we can see and then they thin out as they run around the flank and the abdomen and then they thin out these small, you just explained those small branches into the abdominal wall. So I will say these very, very small end branches are tiny. They’re literally like hairs.

Speaker 1 (00:32:29):

Yeah, I wear wear high four X magnifying glasses when I operate on those.

Speaker 2 (00:32:38):

So what works with MR is that if they’re inflamed, they light up so then we can see them. I will say MRI is the best imaging technique to see those. They are very small and it’s challenging and unfortunately the abdomen moves during breathing and moving is the one thing that MRI is not good with. So another thing, your CAT scan is really great. It’s moving because breath, you can freeze the breathing motion with MRI. The breathing motion is an issue. It’s not an issue in the ankle because the ankle, there’s no breathing motion, but the abdomen naturally moves during breathing and that is also a challenge. So sometimes we do those belly down and try to stabilize the motion of the belly there so we can see those.

Speaker 1 (00:33:28):

How do you see the entrapment?

Speaker 2 (00:33:31):

Yeah, so sometimes there is what’s called a neuroma. So there’s like a sun swelling of the nerve a little. It’s almost like a dot. Yeah, a little dot that’s too big at that location. So that’s great that you can see sometimes it’s inflamed. So the nerve is basically aggravated by the entrapment and we can see that and you get nerve edema sometimes when there was an incision or there was an injury, step wound, gunshot wound, all these things, we can see the scar and then we can see how the nerve runs into the scar and literally gets what we call scar encase. So the scar, when the wound heals scar tissue is being formed and sometimes it grabs the nerve, it literally gets the nerve and then it circumferentially encases the nerve and constricts the nerve, right? Yes. So we can see that there are some cases where there’s none of these things and then it looks completely normal, but the symptoms, for example, are very suggestive in those instances.

Speaker 2 (00:34:30):

We use image-guided nerve blocks as the next step to help us out. So if we don’t see it morphologically, but the symptoms are obviously there, that’s why the patient come and see us, then we can use nerve blocks. We can block these nerves specifically selectively we call. So basically we use a small dot of anesthetic block the nerve upstream from where the entrapment is suspected to be. And then if we block that nerve and the symptom sees while the nerve is anesthetized during the block, then that’s a very good functional sign that there is entrapment somewhere. It might be very, very small, but we know it has to be that nerve.

Speaker 1 (00:35:14):

So is MRI the best imaging for scars or scar tissue I should say?

Speaker 2 (00:35:19):

Yes, yes. Okay. So yeah, that’s

Speaker 1 (00:35:23):

Both in the wound as well as adhesions or bowel adhesions.

Speaker 2 (00:35:28):

Yes, exactly. We can also see Mesh really well with MRI, so, so for example, for in inguinal hernia repairs, the mash that is being put in there so that the pelvic contents don’t no longer put true through there. You can see this very nicely with MRI and you can see how the nerves travel around or through that Mesh or a buffer below, and you can also see where scarring occurs and where those nerves are in relationship to that. So these relationships are seen very, very well. I will say the groin is easier to image than the abdominal wall. So the front of the abdominal wall here, that’s my chest, but kind of here, this is very hard to image. So we spend an enormous amount of time in doing that and often we use nerve blocks in combination and we basically need the information also from your clinical exam. When you say, okay, I looked at this, I think it’s right there. Often we mark the skin, we put a little marker on the skin and do this with a patient on their scan and say, tell us exactly where the area is. So we put that little marker on. So it helps us during imaging exactly to know, okay, that’s where the symptoms are. So it’s almost like an additional pointer to look closely there.

Speaker 1 (00:36:49):

And do you need a three Tesla or higher MRI for those?

Speaker 2 (00:36:53):

Yeah, so three Tesla is preferred for all of these. I will say there are some exceptions. If for example, we look in the buttocks or the groin region in patient’s head, a hip replacement, then sometimes 1.5 is actually better, the exam will be a little longer. Oh, but three Tesla gives more signal and more anatomic details without metal implants and joint replacements or spinal fixation hardware. I would say three Tesla is the way to

Speaker 1 (00:37:27):

Go. Okay. We have many questions about denervation injury. So some people have either surgery or an accident and they get injury to the nerve and therefore the muscle that nerve feeds becomes what we call it can thin out or just lose function. So do you see signs of denervation on CAT scan or MRI?

Speaker 2 (00:37:50):

Yes, both. But MRI sees it in much better detail and much earlier. So the way it oh

Speaker 1 (00:37:56):

Much earlier

Speaker 2 (00:37:57):

Now on MRI is, so there’s different grades of nerve injuries, right? Yes. And you still have written classifications right there. There’s one that’s called Dr. Satin has written, one there has three categories and then Dr. Sunderland has written one, and those are like five categories anyway. So the graduation is higher grade injuries where there is more nerve injury and less signals go through the muscle. And then there’s the lower grade injuries where more signals go through and the muscles spare better. And some of these low grade injuries will recover over time, whereas some of these higher grade injuries may need surgery, they need to be liberated from scar or they need to be crafted. So depending on that grading we see with MRI different grades of severity and MRI shows it as early as 24 hours after the injury. Wow. Much, much faster than CAT scan or ultrasound and also actually faster than nerve conduction studies.

Speaker 2 (00:39:01):

So neurologists are very skilled and very good doing nerve conduction studies. So basically yeah, they measure whether electric signals go from proximal in the nerve to distal in the nerve and see whether something is going through. And in general, when you have a nerve injury, you get muscle edema first. And MRI is very good for detecting edema and that’s why we see this right away. Later on the edema change goes down and then what happens is that the muscle wastes, it gets smaller and then muscle fibers get replaced with fatty tissue and then the muscle loses function. And so that is also very well seen with MRI At the later stage. You see it with CT as well. You can see with CT when the volume shrinks and when the fatty replacement happens. But in the early stage where it’s only edema, you can see the nerve itself. So often we can see the injury of the nerve and then we can help grading it, is it a high grade or a low grade? And then we see the effects of the muscle and that also helps you to see which nerve is injured and what the severity of the nerve of the nerve.

Speaker 1 (00:40:07):

I did not know that. That’s pretty impressive because sometimes you see thinning of the abdominal wall, but not always. That’s really end stage where the muscle thins, the early stages when the patient’s lying flat, which is how they are in an MRI or CAT scan, the belly looks normal, it’s when they get up and the gravity kicks in. That one side of their abdominal wall for example is more pooching out and the other because they’ve lost that function of the muscle. That’s interesting that you can, so do you need IV contrast for these studies?

Speaker 2 (00:40:48):

Yeah, so for most of these monography studies, we don’t need contrast. So the patient brings all the protons, which is what we need. Sometimes it is helpful, so if there is scarring, it’s a little bit when patients had spine surgery, let’s say there was a disc herniation and it gets removed and then later there’s a reassessment how it healed and there is inevitably a little bit of scarring. That’s how the body heals. And sometimes those scar areas contrast can be helpful. It’s very rare. I would say maybe one out of 10 needs contrast. What we often see is, and I would let the radiologist guide the decision there if I were a patient, sometimes we receive requests that say I need contrast. And then we look at it and we look very carefully at the requests, at the prescriptions and we talk to the referring physicians like you and I always talk and then we make sure we get the best exam and sometimes we determine contrast is not really needed. It’s a it’s, and sometimes there’s a strong belief that contrast needs to be done and often it’s not the case. I will say most often contrast is not needed or will not add anything, it will just prolong the exam, it will add cost and there’s a little small risk of anything even checked into the vein. So if you don’t need it, don’t get it.

Speaker 1 (00:42:20):

Yeah, very good. Thank you. So MRIs are very loud. The question is can you protect your ears during MRI? What about the transmission of all that noise through your bone? What do you know about that?

Speaker 2 (00:42:35):

Yeah, yeah. So MRI makes knocking noises, right? It makes all kinds of noises. Yeah. People have actually tuned MRIs to make music. So you can play a song off Adele or so on MRI. Whoa. Yes, yes. Aside from that MRI,

Speaker 1 (00:42:51):

But not while getting your MRI, you can’t do that while you’re in there though, right?

Speaker 2 (00:42:55):

No. The physicists have tuned MRIs to arrange these knocking noises into making music. But yes, MRI is loud, MRI is annoying. It takes a long time. And I know as a radiologist nobody likes MRI and nobody, while I’m fascinated by it, and it’s a great diagnostic tool, the process of obtaining MRI is cumbersome. Patients don’t like it. Some are scared. It’s really tight in there sometimes, although the bores yes are not that tight anymore. Our machines are bigger now. They almost look like more like CTs. But yes, that is true. So what we do is it’s mandatory to have those soft ear flu in. So if you’re not given those earplugs, ask for them, they have to be in the room. And then we put little, what we call Mickey mouse ears on top, on over the soft plug where we play music. So this double insulated and that usually takes care of the knocking noise. It’s almost like huge AirPods or so that have noise cancellation and we try to mitigate the noise as best as possible, but that’s true. Yeah, MRI is loud and that has, because if somebody is interested in the technical detail, the gradient, the physical gradients that change and make the MR signal that make that noise,

Speaker 1 (00:44:19):

Oh wow.

Speaker 2 (00:44:22):

Oh by the way, there was one part. It is not harmful. Not harmful, it does not vibrate the bone or so nothing like that has ever happened. But the ears need to be protected because for some people it is too loud.

Speaker 1 (00:44:38):

Here’s a question about directly just nerve. So when you deal with chronic pain patients that need peripheral nerves imaged, what kind of procedures do you do? Is it a nerve block? Do you do ablations?

Speaker 2 (00:44:57):

Yes. So as we use MRI to diagnose or visualize the nerves and diagnose and diagnose those abnormalities, we also use it to guide our blocks. And I think especially if you try to figure out pain syndromes. So in the groin there’s like three or four nerves that could cause the pain sometimes. And they’re all very close together. And like we said, there’s anatomic variations and sometimes what we end up doing is I think back in the days you can comment on that, things like triple neurectomy were done where all the nerves were cut out,

Speaker 1 (00:45:32):

Still done. Yeah.

Speaker 2 (00:45:34):

And I’ve learned that nowadays sometimes surgeons ask us to say, okay, let’s block these nerves for, and maybe we can find out which one is actually the pain generator and maybe I only need to cut out that one or

Speaker 1 (00:45:47):

Yeah, that’s good. I highly encourage that. Select neurectomy. Yeah,

Speaker 2 (00:45:50):

Yeah, exactly. And so we use MRI to do these nerve blocks. So you can use MRI to guide a needle next to the nerve and then inject the local anesthetic and then basically do a nerve block. So this is what we do at N by U every Thursday. And so that’s where we do our nerve blocks. And similarly I see a question there. You can also do a cryoablation of these nerves. So let’s say for some reason surgery is not the first choice or maybe surgery has been attempted and there’s some recurrence, but it doesn’t warrant to do surgery. Again, it’s different situations. Sometimes patients are too sick to get surgery or it’s too risky, then we could try to freeze the nerve and that is basically can be thought of as a very long nerve block, like months. If it’s successful it can put the nerve to sleep and can in select cases where we know which nerve is the nerve generator, we can do that too.

Speaker 2 (00:46:48):

And we can do that under CT or ultrasound or MRI guidance as well. And yeah, we have several papers published out on that. I see a question about lateral femoral cutaneous and anterior femoral cutaneous nerve. Yes. So that’s a very good area of thigh pain. So the lateral femoral cutaneous nerve is neuralgia. It’s like the more lateral thigh pain and the anterior femoral cutaneous nerve is more the frontal thigh pain, but they’re overlap and sometimes it’s hard to know which one it is. And so we do these blocks, sometimes differential on one day we block the lateral femoral cutaneous nerve and then we see how it, the symptoms react, and then we do the anterior femoral cutaneous nerve and then we just decide which one it is.

Speaker 1 (00:47:37):

Yeah. So the question is, I’ve had two attempts at cryoablation of the lateral femoral cutaneous nerve with that relief of symptoms in the front of my right thigh. This is a nerve problem that I’ve had, that I have after a large Mesh removal surgery, which implies that the Mesh that the nerve was, it’s either injured or entrapped in scar tissue either at the groin or proximal in the retroperitoneal space. It’s impossible that the anterior femoral continuous nerve could be the cause of the pain, tingling, and burning. Could this be addressed with MR guided nerve block of the anterior femoral cutaneous nerve even though the lateral femoral cutaneous nerve treatment failed? I read that the paper addressing anterior femoral cutaneous nerve nerve block for treating anterior thigh pain and I’m hopeful to screen my next step.

Speaker 2 (00:48:32):

Yes, I agree. I think sometimes it is the anterior femoral cutaneous nerve that clinically literally mimics the lateral femoral cutaneous nerve and the lateral femoral cutaneous nerve is much more common than the anterior femoral cutaneous nerve. But I think in situation where it is the interior femoral cutaneous nerve that can be clinically challenging and an MRI guided nerve block could help to differentiate that. We had several cases over the years, but this was where this was the case. So yes, MR guided nerve block or somebody that really is an expert in that could also do it under ultrasound if they can see the nerve. But the differential block between the AFCN and the LFCN sounds like the next good step.

Speaker 1 (00:49:18):

And so can you just clarify? So an MRI in layman’s term is a very, very strong huge magnet. And so anything in that room must be not magnet, magnet prone. I once had little bobby pins in my hair and I was in the room as a machine was running and you could feel the bobby pins like moving in my hair. So

Speaker 2 (00:49:43):

They should not have been in there.

Speaker 1 (00:49:44):

I should not have been there. So exactly. I didn’t know about the bobby pins. So the question is this, when you’re doing these nerve blocks, the machine is running and therefore every instrument you have there is not metallic.

Speaker 2 (00:50:00):

Yes. So basically what happens is before you there, there’s federal guidelines on that. So before you enter the MRI suite, there is a security check and it’s literally like the TSA. So you are being asked a lot of questions about implants, whether you have anything on you or in you that is metallic pacemakers, surgical implants, cochlear implants, all these things, even glasses, piercings nowadays, even some tattoos s have metallic ink, have the color of the ink is being achieved with small metal particles. So all this serves being asked. And then often we have a sensor device that you know, basically check every body part, whether it beeps and whether there’s metal in there. And then yes, some metals are okay, for example, knee implants, hip implants, ankle implants, spine implants, they’re usually okay, but some things are not. Okay. So pacemakers need special consideration. Cochlear implants can be scanned, but not like that. They basically need to be what’s called bandit. So an E M T doctor needs to help with that and so on. Like I said, some tattoos cannot undergo MRI, some piercings that cannot be removed. Bullet fragments is a big problem. We usually don’t know what metal that is. And there’s a concern that they either heat or move

Speaker 1 (00:51:32):

And also pain stimulators or pain, yes, implants.

Speaker 2 (00:51:37):

Yeah, exactly. Anything that has a battery pack in a lead, like a wire into the heart or to the spine or to a muscle or to a nerve, they need very, we basically need to know exactly what model that is and how old it is and who put it in. And then we will contact basically whoever implanted it and the manufacturer and figure out whether and how this can undergo MRI it need, it almost certainly needs modifications and some cannot undergo MRI safely. So in those cases we do ct, although MRI might be the best, but it could not be done safely.

Speaker 1 (00:52:14):

Then there are certain pain pumps and nerve stimulators that are MRI friendly. Yeah,

Speaker 2 (00:52:24):

Yeah. We talk about special techniques or special appointments for people with pacemakers, for example.

Speaker 1 (00:52:31):

Can you talk about pal Neuralgia? That’s a very difficult diagnosis and

Speaker 2 (00:52:36):

Yes it is. Yes. So a big part of my practice is a pelvic pain and so different,

Speaker 1 (00:52:44):

You’re such a masochist for radiologist, you’re such a masochist

Speaker 2 (00:52:50):


Speaker 1 (00:52:51):

There’s a reason why there’s very few of you in practice and I need to rely on someone across the nation for some of my patients. So thank you.

Speaker 2 (00:53:00):

Oh, you’re welcome. Yeah. So the pudendal nerve is, I will say a common pain generator of pelvic pain, especially after pelvic injuries and surgery, but also sometimes without any known inciting event. For example, interesting in cyclists have a higher incidence of Pudendal Neuralgia maybe because those long times in the settle compressed the pudendal nerve and over time. So yes, but the pudendal nerve is one major pain generator of pelvic pain. However, there’s probably three or four or five other nerves that can do it as well. And that’s why pelvic pain is difficult to diagnose and treat because often it is so difficult to figure out which nerve is actually causing the pain. And we have similar regimens where we sometimes end up blogging a blog, blogging these, we do monography and then we may or may not see something. But often we do nerve blocks, selective nerve blocks to figure out which of these nerves is actually transmitting the pain. And once you know that it’s easier to treat, you have a better chance for success than not knowing what it is.

Speaker 1 (00:54:14):

So how often do you, I feel like Pudendal neuraglia is over diagnosed. How often are you able to confirm Pudendal neuralgia based on imaging?

Speaker 2 (00:54:28):

So often? So I will say the diagnostic challenge is that there’s a set of criteria that is, that’s published for Pudendal Neuralgia, and you have four out five of those plus a nerve block. You have a pretty high accuracy. There is other nerves that can make similar symptoms. For example, the posterior femoral cutaneous nerve, that medicine only learned about five to 10 years and it’s still not well known. So that’s often a pain generator. Then confounds the diagnosis and it can make, in my experience, the exact identical symptoms. And sometimes if somebody gets treated for Pudendal Neuralgia, but it is the posterior pharmacal cutaneous nerve, then obviously the Pudendal Neuralgia treatment may not be as effective as suggested. And so we usually use the nerve blocks when the monography is normal. So let’s say the patients has clear pelvic pain symptoms well documented and the MRI is normal.

Speaker 2 (00:55:29):

Let’s say there was not a surgery and we don’t see scar entrapment and we don’t see a neuroma and the common things. Then we usually do MR guided selective nerve blocks, and we do those because we want to want to be as accurate as possible to selectively, which means block the Pudendal nerve, but only the pudendal nerve. So that pain response we get is specific to the pudendal nerve. So let’s say somebody has a suspected Pudendal Neuralgia and it’s on the right side and we selectively successfully block the right Pudendal nerve and the symptom sees for the time the local anesthetic is active. And that’s a very good sign that this is Pudendal Neuralgia. But if we do that in patients get numb and the pain doesn’t go away, that means it’s likely not Pudendal neuralgia and the surge continues and that’s good. It’s sometimes a disappointing result. But the way we look at it is that would we have gone down the treatment pathway probably would not have been successful. So it’s good that we figured it out now, right? Correct. So we can continue the search, which is difficult, but there’s other pain generators to check for.

Speaker 1 (00:56:33):

Correct. Going back to the anterior femoral cutaneous nerve patient, is this diagnostic procedure readily available at most large hospitals?

Speaker 2 (00:56:45):

I’m not sure about that. You can always come

Speaker 1 (00:56:46):


Speaker 2 (00:56:48):

Yeah, you can always come to NYU, but as the 10 mentioned, the papers are out there and it, it’s described. So maybe that’s something that is not often done in a hospital near nearby, but could be done based on the descriptions.

Speaker 1 (00:57:08):

Okay. Was that your cat that just came across the screen?

Speaker 2 (00:57:10):

Yes. Yes. Dinner time.

Speaker 1 (00:57:14):

That’s excellent.

Speaker 2 (00:57:16):

Get off the internet feed me.

Speaker 1 (00:57:19):

Very good. All right. Well let’s talk about Mesh plug and patch. That’s the kind of one of the different al hernia meshes where I get imaging always before removing those, mostly because I want to differentiate the anatomy. How close is this plug to the femoral vein bladder? Sometimes it involves a genital branch of the genital al nerve, not always. And then how close is it with the actual spermatic cord? So it helps me gauge the difficulty of the operation, helps me be a safer surgeon. What do you recommend in terms of identifying chronic pain in patients with an inguinal Mesh? Which imaging modality?

Speaker 2 (00:58:10):

Yeah, so I think you could see most of the structures with CT except for the channel branch of the genitofemoral nerve. That is a tough

Speaker 1 (00:58:21):

One, right?

Speaker 2 (00:58:22):

Yeah. So I would say ideally I would do that evaluation with high risk solution three T MRI by monography techniques. Yeah, you can see the vessels really well. You can see the spermatic cord really well. You can also see how the hernia repair was done, where the plug sits relative to the inguinal canal. And then you can usually see nicely where the genitofemoral nerve, but also the ilio inguinal nerve runs and what the relationships to that plugging is. And that’s a common indication that we get.

Speaker 1 (00:58:59):

Yeah, very true. And then on CT scan, you can see the metal spiral tacks that we sometimes use for hernia Mesh fixation, but the trend is now towards polypropylene or plastic based fixation, both sutures and also tacks. Those are not visible on ct. Correct. But you can see a foreign body effect on MRI, is that correct?

Speaker 2 (00:59:26):

Yes. So if it’s metal, they’re very well seen on ct. Yeah. If they’re not, then MRI is a better chance. In fact, the metal clips can make small metal artifacts in MRI that sometimes can obscure structures, right? So let’s say a nerve runs right to a metal part, then this can be exactly the area where we cannot get Mr Signal because of the metal. So I think for MRI, the non-metallic material is actually beneficial and we usually can see those.

Speaker 1 (01:00:03):

Got it. Wow, that was intense. That was such great information. I love it. Thank you so much.

Speaker 2 (01:00:10):

Thank you.

Speaker 1 (01:00:12):

All right, everyone, that was fantastic. Let’s say goodbye and thank you to Dr. Fritz. You were amazing. I love the fact that you’re able to answer so many questions so quickly. I always have more and more information and questions I have for radiology. When do you use contrast? I have a great radiologist that does his own ultrasounds. That’s very, very helpful to me. And I’m very grateful to you, Dr. Fritz, because you’ve taken care care of a lot of my patients, and I will continue to send you more. So thank you very much.

Speaker 2 (01:00:47):

Thank you for

Speaker 1 (01:00:48):

Having me. Thank you. And that ends today’s Hernia, Talk Live. Thank you everyone for joining us. Please go to my YouTube channel to watch this and all other, I think we’re close to 90 episodes of Hernia Talk Live. There’s so much to talk about hernias, and I will see you again next week with another lovely, very generous and very talented guest. Thank you, Dr. Fritz. Enjoy evening.

Speaker 2 (01:01:14):


Speaker 1 (01:01:14):

You. Thank you. Bye-bye.

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