Ultrasound in the Evaluation of the Brachial Plexus - HD

Introduction

Hello, I am Michael d Pietro from Ann Arbor, Michigan.

I'm a pediatric radiologist and professor of radiology and of pediatrics at the University of Michigan.

And today I'm gonna talk to you about ultrasound in the evaluation of the brachial plexus and infants following perinatal brachial plexopathy and the possibility of nerve repair.

And this is specifically regarding evaluation and preoperative planning for nerve graft.

This is work doing with my colleague Dr. Yang, University of Michigan, who is a neurosurgeon and is now performing all these surgeries.

It's a very multidisciplinary approach to these children, which includes neurosurgery and radiology and sonography and orthotics and physical medicine and orthopedics.

And anyhow, we, there's a role now that sonography has, and she has found it very helpful.

It's a little bit esoteric.

There aren't many places that actually have full fledged programs of trying to repair.

Perinatal Brachial Plexopathy

Now these are children at birth, difficult delivery, let's say traction on the neck.

And any of the cervical nerve roots or any of the nerves of the brachial plexus can be damaged.

The damage can occur at multiple levels and it can occur at two sites.

One is a root avulsion, which is within the spinal canal.

And for that, we do not evaluate with sonography.

Actually, I have a lot of experience looking at the cervical spinal canal and under actually ideal conditions, I looked and could see roots, but it just was not reliable enough.

And for that, we really rely on MRI.

But where sonography is useful is outside the spinal canal 'cause they can be broken there.

Now, some of these kids will have a brachial plexopathy of different degrees of extent, and they'll get better.

Not the ones where the nerve is actually torn, but sometimes it's just been pulled, it's been injured and they'll get better.

But the approach that Dr. Yang and her team uses is that if the child is not improving and you're now at about 3, 4, 5 months of age, the likelihood of a spontaneous return of function then is not very good.

So then she will evaluate these children for the possibility of doing a nerve graft.

And this is where we fit in, a role we're kind of doing some reconnaissance and we're gonna do is we're gonna look at what portions of the brachial plexus we think are okay, which aren't, because what you'll do is take sural nerve out down along the Achilles tendon and going up the leg, and then use that as material to lay in basically a patch to go from a good nerve across a bad area to another good nerve, and therefore to try to restore some function.

She says she can't make them normal, but she can make them better.

And that's where we get involved with that.

And it's kind of like electrician laying down a patch with some wires or something like that.

So this is our role.

We wanna make sure she's gonna be able to go from viable proximal nerve to a viable distal nerve.

What did she do before we got involved with sonography?

Well, basically it was based on EMG and physical exam and that, but that was limited.

And a lot of it was just figuring out while she's in there.

But she says we've done over 60 cases now that actually the work that we've been doing in ultrasound has actually been helping her.

She has a better idea of what to expect, which she can maybe offer, which she can do.

And so we've continued and it's been a great experience for us because we're learning quite a bit.

Most of you that have gone through medical school, remember the brachial plexus as something you took great pain to learn about and then promptly forgot the day after you took the test.

So we had to go back to it.

Now we've come up with an approach that's both a direct and indirect.

And in the direct approach, we actually look at the nerves.

And in a moment I'll show you how we do that.

Indirect is we look at specific muscles knowing their innervation, that can tell us what's going on with those particular nerves over that in a minute.

Anatomy of the Brachial Plexus

The brachial plexus is interesting as a numerical palindrome.

You know, palindrome is a word that's the same whether you pronounce it forwards or backwards.

And Dr. Yang pointed this out to me because we all start out with five roots brachial plexus, C 5, 6, 7, 8, and T one, which then merge to become three trunks.

So the five and six become the upper trunk.

C seven stays by itself.

The middle trunk C eight and T one become the inferior trunks.

You go from five to three.

Each of these trunks now divide into anterior posterior divisions.

That gives us six now by the divisions we're getting out here now into getting close by the clavicle.

They then do some merging, which is a little more complicated to show here, but end up with three cords and they're in relation to the subclavian artery.

Now we're getting into the axillary region here.

And this portion I don't specifically evaluate with regard to these studies.

And then they then become the five major nerves of the arm by the way that they merged.

So really we're concentrating on this portion up here with the roots coming out and then forming the trunks and the divisions.

I really wanna give credit to a friend and colleague in Genoa, Dr. Martin Leys, certainly well known to anyone who does musculoskeletal ultrasound, Carlo has done a lot of wonderful work in many areas of musculoskeletal ultrasound, but really has introduced most of us to evaluating nerves.

And it seems like every year he comes back and showing us in greater and greater and greater detail things he can see.

But I first learned about doing this.

And then when the neurosurgeon found out that I knew a little bit or had a little experience or exposure looking at the nerves, then she asked, would we be able to help her with her studies?

And this is how it all happened.

Direct Evaluation of Nerves

So I told you we look at the nerves directly because although not part of the brachial plexus, the phrenic nerve is also valuable.

We look at the diaphragm while the patient's breathing spontaneously because it's nearby and sometimes they can have a phrenic nerve injury.

I have seen one at birth, but at the time that we're studying these kids of the 60 cases, they've all had intact phrenic nerves.

We look at the rhomboid muscle on the medial aspect of the scapula 'cause that's predominantly innervated just by C five and it's the dorsal scapular nerve, which comes off quite proximally.

Therefore, if we see rhomboid atrophy, probably that proximal aspect of C five is not gonna be suitable as a jumping off point for a nerve graft.

The serratus anterior muscle also in relation to the scapula, but going anterior laterally to it, and I'll show you in a moment how we find them is innervated by the long thoracic nerve, which comes off even more proximally on these roots.

But it has three contributions and the supraspinatus infraspinatus not as useful, but we do look at it.

And that's from the suprascapular nerve, which comes off the more peripheral aspect of a C five going C five and six in the upper trunk.

And then we also have been evaluating the shoulder for laxity or subluxation.

Usually as later in the series because we also have an independent group of kids at an older age.

We've been following them.

So we're trying to see what they have even at this very early age.

So the direct evaluation, looking at the brachial plexus, this is the work again that one of the pioneers is Dr. Martin Ole.

We're gonna be looking at them right there where they pass between the anterior and middle scalene muscles and the lateral aspect of the neck.

So here's the kind of view we're gonna take.

Now the tape is because this child's intubated, this child is asleep, so it does make the exam a lot easier.

Actually just last week I did one in an awake kid and it was fine, but it's a little bit harder 'cause the kid's moving around, why are they asleep?

They're asleep because they've just come out of MR looking at the actual spinal cord and the roots, the intracanalicular portion, we keep them asleep for this portion and then also for brace fitting, 'cause orthotics comes too.

So this is all done in the recovery room and it helps the exam go a lot faster.

You can see here I'm using a small footprint, high frequency transducer.

I'm in the long axis to the neck.

This is actually basically to get this view that we're seeing here.

And this is what you see, this is superior, inferior.

You see the vertebral artery, the nerve roots are coming out now they're posterior to the artery.

And then with some practice now you can get pretty good at telling which one is which.

But that's how we get started.

Notice here, this is in short axis now.

So you have anterior scalene muscles here.

They are coming out and we're gonna scan in this way.

And what do we see there?

So here we are, how we would do the scan and we look at it now, the thyroid is over here, so this is on the right side.

And this is the anterior scalene muscle.

The middle scalene muscle, and see how they line up like this coming down.

So this is probably C five, C six, C seven, et cetera.

And you can see them as you move up and down them coming out.

But this is what they look like.

Nice discreet circles 'cause the nerves are coming out at you and between the anterior middle scalene muscle, here's when we did anterior scalene middle scalene.

And again, when we're up high, we just see this one, we could see it coming from behind the vertebral artery and then going into the space.

And then this one joins it and this one joins it.

So we think we see that's 5, 6, 7 maybe that's T one that we're seeing here.

And in some of them you can actually see the little fascicles, which is how you identify nerves.

And this is the orientation.

So this is where the anterior scalene would be the middle scalene.

And you can see how this all works out.

Now one of the things we also do is follow it out towards the clavicle and then you can see how orientation will change a little bit as you're going out.

And here you can see subclavian artery.

And these are all nerves.

These are all nerves there around the subclavian artery.

Now I'm not trying to identify which is which.

I'm really just gonna be evaluating, just seeing a moment how cleanly seen they are.

Going to the anatomy lab using a skeleton.

There are some landmarks, and this is a feature again that Dr. Martin Oli has brought to our attention is that by looking at the transverse processes, you can get an idea of where you are.

And if you'll notice that they're not all the same, like C five looks like a U and then C six is a U but has a big anterior process, which actually the neurosurgeons use as a landmark when they're in the OR.

And then when you get down to C seven, it has a very small anterior process.

And that's how we can do it.

So here we are in short axis to the neck.

And I've shown in this diagram this just happens to be the anterior tubercle, posterior tubercle for vertebral artery.

The nerve comes out behind it.

And that's the orientation here.

And in kids it's a little more complicated because a lot of it is cartilage.

So this is C five anterior tubercle, posterior tubercle cartilage in the bone, there's the vertebral artery.

If you're not sure, put color on and there's the nerve coming out from behind it.

Then you move down a little bit and you can see that the anterior tubercle on this one now is big.

And that's called the eg next tubercle.

It's a landmark to the neurosurgeons when they're doing this surgery.

But you can actually see it.

Here's the nerve.

There's already one up here in between in the interscalene area.

Now this one's joining it, so that's probably six.

Here's the posterior vertebral artery.

You go down a little bit farther.

Now there are a couple up here, see within the canal it's probably like five and six already.

Now this is C seven because you have a posterior tubercle but no anterior tubercle or it's minimal.

So anterior scalene, middle scalene.

And here they are lining up here.

So using these landmarks is how you can kind of figure out where you are.

You can also do it on the coronal.

So here I'm shown 'cause C six has that larger anterior process.

And as you come more anteriorly, you can see it here, it really stands out.

And then as you go a little bit posteriorly, staying coronal, you see the vertebral artery and then a little bit more posterior.

You see the nerves coming out.

And again, the one with this one is, that's where the C six nerve will be coming out.

So that'll help you figure out where you are now as a teaching aid.

It dawned on me, when you look at the interscalene area, the normal, it looks like a Ryan's belt.

I mean they're just nicely, clearly seen.

In the picture and in a moment when you see what the abnormal looks like, it looks like I call it the meatball.

So this is normal and see the nerves lined up here.

Now you may say, why are there so many black things?

It's because these nerves are actually some of 'em are multivesicular.

So that's actually like all of this may actually be C six, even though you see multiple black things here.

But look at the abnormal side.

You don't have any of this clarity anymore.

These nerves are just all this big mass of thickened echogenic tissue.

And that's why I call it the meatball.

Sometimes it's quite big, sometimes it isn't.

Sometimes you also see the nerve roots as they're coming outta the spinal canal are actually already thickened.

So here's the vertebral artery and they're a little hard to see, but they're thick and echogenic.

And then you're getting in and this is actually the meatball is actually called the neuroma.

It's not a neoplasm, it's just, it's really a scar.

But that's the neuroma.

And look at the normal side in contrast that compared to these, at least you see three, at least three roots here and here they're all very echogenic and thick, right where they emanate from the canal.

So disqualifiers for being any one of those nerve roots as being a jump off point for a nerve graft would be one.

If the MR shows that that root is actually avulsed within the canal, then it's shot, it can't be used.

Or if we're getting evidence that it's damaged either by its appearance, its involvement in the neuroma or else indirectly what muscles are involved.

Here's a short axis view of the neck, the anterior scalene muscle, middle scalene muscle.

Thyroid would be over here.

Vertebral artery, nerve coming out, right where it comes outta the canal, it's all echogenic.

And then it joins this big, the big meatball here, this huge neuroma that we're seeing now.

One of the things that I try to figure out what roots are involved as best I can also, the neurosurgeon wants to know, does this neuroma extend all the way to the clavicle?

'cause it used to be that she didn't know that.

And then she goes in and finds that it does and she has to go further distally to hook up a nerve.

And then she has to extend her incision.

So this way she knows upfront the length of the excision exposure that she needs.

And this is what we see as we go towards the clavicle.

It's subclavian artery.

You can see there is a nerve here, but there's a lot of abnormal tissue here.

This one looks like it may be relatively spared.

And on this coronal view, you have roots coming out.

And look how this one, these are very thick right away.

We're probably seeing four roots right here.

And here's another one.

And then it goes and joins this neuroma.

A very big one.

Now this case is interesting because these upper roots are going enjoining the neuroma, but this one seems to be spared right there.

See, it looks intact as it goes underneath it.

Okay, so we scan in this way.

Here's a recent case where we think it involved only C five and C six 'cause this nerve looks pretty good on the short axis view.

And then this is the normal for comparison where they all look normal.

So in this case, this one and this one are very thick and echogenic and part of the neuroma, this one down here looks okay.

So we thought that this is an upper trunk neuroma, which is C five and C six.

And then you wanna follow it towards the clavicle.

And this is more normal with nerve roots here.

And this one you can see some, but it's kind of echogenic.

So that's what we look for.

Another patient which really had only upper involvement and you can see on the coronal view looks actually pretty good coming out of the canal.

And then it gets the neuroma here.

So it is possible that you could have a normal, you could have a graft site for a jump off very approximately.

And the but these nerve roots here look like they're spared.

So this is the kind of thing we're doing, we're trying to figure out.

Indirect Evaluation via Muscles

Now the indirect evaluation is at the muscles.

This is an idea that was really by a colleague, Dr. Konz at an emeritus professor with us now.

And he suggested that we look at these muscles.

So here's the rhomboid underneath the trapezius, and it's innervated by the dorsal scapular nerve, which is off very proximally off a C five.

Now we don't find that nerve or see that nerve, but we can infer by the condition of the rhomboid, the condition of that portion of C five.

So how do you find it?

The kids now prone or scanning across the back, you find the scapula, you go medial towards the spine and your rhomboids are right here.

An example, midline is right square down the middle.

Same pictures with and without labels.

Normal right side, left side, you find the scapula.

Now being a kid, there's gonna be cartilage in the medial aspect of it.

And this triangular structure here is the rhomboid muscle.

This is the normal side.

We always do comparisons.

There's the trapezius look on this side is that it's you don't have that nice triangle, it's smaller, it's echogenic.

So this kid has atrophy of the left rhomboid.

So probably the proximal C five is not in good shape.

Also looking at the serratus anterior, which is more laterally coming around, it's underneath the latissimus dorsi, and that's innervated by the long thoracic nerve, which comes off even more proximally.

But it has five, six, and seven.

So if one of those is okay, the serratus might be all right.

Here's how you find it.

You find the scapula and you kind of go anterior laterally, and you can do it short axis to the body.

You can do it long axis to the body.

And in this case, I'm gonna show it long axis to the body, which is actually short axis to the muscles.

Now you can, and we have seen the long thoracic nerve, but the business end that we're concerned about is way up in the neck, not down here.

So here's what you see, this is on the normal side.

Here's rib, which actually has a lot of cartilage in little kids.

And here's the serratus muscle over it here, just like you're seeing here.

And on this side, it's really thin and scrawny and atrophied.

So we know that there's so five, six and seven approximately are not in good shape.

We do look at the supraspinatus and infraspinatus from the suprascapular nerve.

This has a little bit more of a distal takeoff on related to the upper trunk, it's they're important muscles because they're external rotators.

And we find later on that kids who have atrophy and of those are kind of permanently internally rotated because the internal rotators are unopposed.

That's an unstable position.

And the hip and the hip, well, it is analogous to the hip and the femur, the humerus is displaced posteriorly.

And you see posterior subluxation or dislocation.

So let me show you here's how we look at the supraspinatus right there in long axis, you're coming across, there's the supraspinatus, there's the spine of the scapula.

Here's the infraspinatus.

You do it on the normal side, you do it on the involved side.

You compare 'em for thickness for echogenicity to see if they may be atrophied.

Another thing that we've been looking at is looking at the shoulder for laxity.

Now this is analogous to the developmental dysplasia of the hip in some ways this is the normal side.

The kid's prone, here's the middle, here's the humeral head, here's the glenoid.

And then look on the abnormal side, how it's displaced.

Actually dislocated posteriorly.

Sometimes now this happens to be a little bit of a, this is an older kid where we look at 'em, but we've been doing it now in the babies and actually I just had one last week that actually was like this at five months.

But sometimes it's in, but you compare the two sides and on the abnormal side there could be a lot more laxity.

So that tells you there's gonna be a problem.

Summary

So in summary, we look at the nerves themselves as the direct approach.

These are the qualities that we look for, the information we try to find out, we do the indirect approach, looking at the muscles, knowing these muscles specifically looking for atrophy.

And in putting all that together, that's just another part of the equation.

Neurosurgeon puts it together with clinical data, neurological examination, et cetera, and then comes up with a plan.

And she says, actually, it's been very useful.

So we're really happy to be a part of this work and thank you very much.