Grand Rounds-The Oral Boards Review: Principles of Peripheral Nerve Surgery

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- Hello, ladies and gentlemen, and thank you for joining us. Today, we have a very special session with Dr. Robert Spinner from Mayo Clinic. His specialty is peripheral nerve surgery. He will giving us a general talk regarding management of peripheral nerve disorders. This talk will be also specially important for those who are preparing to take their oral boards. Rob, thank you for your time, and please go ahead.

- Thanks, Aaron, for having me. It's a pleasure to be here with you all to discuss some of the pearls of peripheral nerve surgery. In general, I'd like to talk about four different things today, all relating to the subspecialty and for boards: injury, entrapments, nerve tumors, and nerve pain. These topics will supplement and compliment some of the review courses that I do for other venues, including the Goodman course. So this will be presented in different fashion. I'd like to start with injury, focusing on nerve repair and nerve reconstruction. In general, there are many options ranging from nerve repair directly to neurolysis, nerve grafting, some new use of nerve tubes, nerve transfer, and some other items that I'm not going to discuss today. I think the items in white are the important ones for life and for your boards. So assuming favorable circumstances, nerve repair, neurolysis, nerve grafting, and nerve transfers work. Favorable circumstances to be divided into different topics. Items that you can control as a surgeon, the timing of the repair, and the technique of the reconstruction. And then items that you can't control, the patient, the place, the nerve and the location of the injury, and the type of injury, the pattern of injury. Timing. We as surgeons we like to operate, but it's important to operate at the right time whenever possible. There's a rule of threes that I've amended to a rule of threes plus one. Three days, three weeks, three months, and one year. Early surgery less than three days is indicated for lacerations or suspected lacerations when the nerve would be in discontinuity. Subacute would be three weeks, and that's for a transected injury that's blunt or ragged rather than a clean cut. A chronic injury three months or so, would be for lesions in continuity that are closed. Delayed surgery greater than one year is a salvage type approach that oftentime one needs plastic surgeons or hand surgeons to help with some of the options that are available. As I mentioned, early surgery less than three days, would be for sharp transection such as stab wounds that might occur from glass, knife, or razor injury. The advantage of early surgery in this setting is that the fascicular anatomy can be well-defined and easily opposed. And you can oftentime achieve a single suture line, which is better than having to interpose a nerve graft, which would then demand two sets of nerve repairs. The subacute repair would be something like this with a propeller blade or a chainsaw, where the nerve is suspected of being in discontinuity, but the ends may not be fresh and one would leave a certain amount of time, namely several weeks, for the nerve to define itself. So here are the definition of the extent of the nerve pathology, can be done several weeks later, the repair can be done at that time, after you can resect back to healthy tissue, because in other words, acutely, one might not be able to define where the injury starts and stops. So if exploring acutely and you see a jag it in, what many people would do would be to tack down the nerve ends on some tension to fascial planes using metallic staples so that you can find the ends when you go back in time. Delayed surgery is done for the vast majority of injuries. This is for lesions in continuity, stretch, contusive injuries, and gunshot wounds. And we'll talk about gunshot wounds in a moment. Non-operative treatment can be continued in cases where there was early sign of spontaneous recovery, or in some partial lesions. And that's important because 90% of nerves that recover do so within four months. Surgery is indicated when there's been no evidence of clinical or electrical recovery. Now, you have to usually have both, because oftentime the electrical recovery that you see on EMG, doesn't always have to correlate with clinical recovery. So if an EMG is optimistic without clinical recovery, then one might still need to do surgery. Late surgery greater than one year, those patients need a salvage type approach. Nerve surgery typically doesn't work, as we'll talk about. There are some newer types of distal nerve transfers, and there are some anecdotal reports describing cases of late recovery, but in general, these patients are better served with other reconstructive options that may not be neurosurgical. They may relate to the muscle, tendon, bone, or joint. And for the most part, these might be tendon transfers or fusions. And this is important to always have something else up your sleeve, because, for example, somebody who has a radial nerve palsy with a wrist drop, who comes to your office 15 or 18 months after the injury, there are some very well-defined reproducible tendon transfers that could be done that would allow good, useful, wrist transection finger extension. And those can be done any time assuming that the limb is supple by a plastic or reconstructive surgeon, but those would work better than any type of neurosurgery. Let's talk about nerve repair and end-to-end suture. This is done in two settings. One is when there's a short nerve gap from a transected nerve, or after you remove a focal neuroma in continuity that did not conduct a nerve action potential. In some cases, with mobilization of the two ends, you still can affect an end-to-end repair. So here in this cartoon, you can see that if you explored somebody early, the nerve ends would appear like this, and you can align them well. And then put in a few sutures using standard microsurgical technique without tension. So direct repair, whenever possible, is preferred. And as I mentioned, it allows you to deliver the proximal axons to the distal stump across a single fascicular, single suture line, allowing good alignment of the fascicles. But you want to avoid tension. Now, acutely, there are certain tricks that you can use such as seen in this cartoon. Whenever possible, you want to match fish and fish, and fowl and fowl, and you want to avoid mixing fish and fowl. So one trick would be as simply to align the vessels. You can match big fascicles to other fascicles, small ones to small ones. And then, in some cases, you can even use anatomical maps such as those described by Sir Sydney Sunderland to define important motor cortex of the nerve. The right technique is microsurgical technique using loops, or the intraoperative microscope, and standard microsurgical equipment. And then you perform a standard microsurgical technique. Minimal surgical trauma aligning the fascicles, doing this end-to-end epineurial repair, or group fascicular repair, small suture, the fewest number of sutures, and then whether or not you want to reinforce it with fibrin glue, and you can get a repair that looks like that. Here's an example. This young man was stabbed by his brother, inadvertently using some sort of fishing, machete type of equipment, and the patient sustained a small laceration just above the elbow, and had a near complete finger drop. He was seen in an emergency room, was noted to have the finger drop, they thought that was muscular in nature rather than nerve. In view of that, he was sent home and then received back for wound check. Approximately 10 days later when I received a call, and at that time I decided that it most likely wasn't muscular in nature, but more to the point was probably a nerve injury. You can see my planned incision across the lateral part of the antecubital fossa. Here is my exposure. You can see the wound here from the track. I traced it down. I wanted to find the radial nerve, and then the superficial and deep branches. And you can see when I started down in that intermuscular interval, that here, one could see that hematoma along this nerve, and I was hopeful that perhaps there was just a hematoma despite the history of the sharp wound. And you can now see the nerves coming into view, the superficial and deep branches, and the clot. And again, I was somewhat optimistic, because here, again, was the site of the injury that perhaps there wasn't a transection. And then when I set out some of the clot, I first became aware of some small number of protruding fascicles, and I thought this young boy had a minor injury, and that there was a contusion. But then again, when I started removing clot, one could see that more injured fascicles were becoming apparent. And this is what it looked like with the full exposure. This is the superficial radial nerve, superficial radial nerve. And then again, matching motor fascicles of the deep radial nerve above the level of the arcade of Frohse, at the level of the antecubital fossa. So at this point, since it was still early enough, I was able to mobilize the nerves in both directions, and get a direct repair, here of the superficial radial nerve, here of those fascicles of the deep radial nerve, above the posterior interosseous nerve. I use a sleeve of a nerve tube eye valved in order to protect the repair. And then I use fibrin glue to reinforce it. Postoperatively, you can see the patient now, several months later has his wound healed, has regained excellent wrist and finger extension. A few caveats. One is this was a 12 year old male, pediatric patients do better than adults. Secondly, the radial nerve and its branches do better than many other nerves. So this result has several reasons why it's favorable. Now, in order to minimize the nerve gap, there are several tricks. One is you can mobilize the nerve by freeing up any bands and creating a straight course by even transposing the nerve when possible. And this can be done for the ulnar nerve or the radial nerve. The other trick is to flex the joint. So for example, if you flex the elbow, you can gain some additional length and you can immobilize the patient for several weeks with a partially flexed joint. And then over an additional several weeks, bring the joint out into full extension. This will allow the nerve ends to be approximate and to heal in the good tissue. This is a very useful thing to do when you think you can get a direct repair if the joint is flexed, and you are trying to avoid some degree of tension. That doesn't mean to flex it unduly, but gentle flexion is a good trick, and then you can cast them or splint them. Again, we talked about the benefits of a direct repair either in this window or the fascicular repair, but the converse would be doing an interpositional nerve graft. There we often take the sural nerve from the leg. You should know where the sural nerve lies, and the dorsal radial aspect, halfway between the Achilles tendon and the lateral malleolus. And then like a stocking scene, it follows the lesser saphenous vein. Here you can see the expected donor morbidity. When talking about the risks of the procedure, one should always talk about the small chance of neuropathic pain. We'll talk about nerve pain later. But one can harvest a lengthy segment, up to 40 centimeters of sural nerve, and then splice it into the number of cables that is necessary to do a repair like this without tension, and to fill the faces of the stumps. The sural nerve is relatively small. The radial nerve, for example, is bigger. It would take five grafts, for example, or more to fill the face of what I just showed you. Here's an example of a neurosurgical complication. A patient had a spinal accessory nerve lesion noted after an acoustic neuroma operation. Patient had a facial nerve that worked. Unfortunately, the patient had shoulder pain, and dysfunction of shoulder abduction. Scapular winging was later noted, and the patient came to me about four and a half months after the acoustic neuroma was removed. I explored, I found two ends of the spinal accessory nerve. And if you see back here, typical retrosigmoid approach right there, as opposed to your triangle of the neck. Right here, the spinal accessory nerve is deep, but still could be injured as we just saw done on the approach rather than on the craniectomy. Here's the great auricular nerve, orientation sternocleidomastoid border about 2.5 centimeters above that. That's a good landmark for finding the spinal accessory nerve. This is a nerve that's often injured during lymph node dissections by general surgeons, for example. The two ends were stapled here for the picture, but the sharp cut was noted. I was able to mobilize the stumps despite the length of time, here, several months. And by mobilizing the nerve ends, proximally and distally. Here's a branch to trapezius, the branch to the sternal mastoid is still more proximal. I was able to effect a direct repair without tension, several sutures, nino proline. And here you can see an excellent result in the patient with full abduction, good restoration of the scapular stabilizing forces, no winging, and good bulk in the muscle. This is a patient who had a radial nerve injury. Family doctor took out what was presumed to be a lipoma. It wasn't a lipoma. It ended up being a schwannoma. And when the patient had the mass removed under local anesthesia, the arm twitched. Patient had a complete wrist drop, with finger drop at the level of the mid humerus. So this is a radial nerve palsy with a wrist and finger drop. We'll talk about that later. Question comes up is now you're looking at this nerve after exploring, the nerve is in continuity. The question is, how can you tell whether or not there's any recovery? This was several months after the injury. Standard EMG didn't show any recovery. Here's proximal, here's distal. This is brachioradialis, brachioradialis in the lateral type approach to the arm. And here's a branched brachioradialis. With an EMG, standardly, one sees recovery occurring with a more advanced lesion. So you can see where the brachioradialis would be the earliest of the radial innervated muscles to recover rather than the finger extensors, which would be off the screen here to the right. So one would want to see some recovery and brachioradialis, both clinically and electrophysiologically. Here there was none. The key though is as Dr. Klein and nerve action potentials. We'll talk about that in a moment. But the point was is when we tested across this lesion in continuity, there was no nerve action potential present. Based on Dr. Klein's vast experience, both in basic science and with clinical volume, the decision then is to resect the neuroma, as you can see here. I had good tissue ends. I mobilized proximally and distally. But here the point of the slide is to show that despite the length of time, and the neuroma that was resected, even chronically, I was able to get a direct approximation of the ends in this patient, some fibrin glue. And here you can see early risk recovery, and then finger extension that then improved over time. Again, the radial nerve does well because of the short distance to the end organ, here, the forearm extensors. In contrast, this is a patient who was seen in emergency with a snowmobile injury. Here's the fibular neck. This patient had this wound. They were seen in the emergency room acutely with a foot drop. Plastic surgeons saw the patient, they were interested in the wound. They said it would heal well with secondary intention, which it was. The foot drop didn't get noted. The patient saw me about six weeks later. And then all of a sudden you can see now the ragged ends of the nerve. The peroneal nerve doesn't do well. You have to chop back on the ragged ends both sides, because now scarring has taken place. And in order to get a direct repair, I needed to do some bigger sutures here, as you can see, along with the finer ones, and then take these out to put finer ones in, in order to get a direct repair, also done with the knee inflexion. And I did all that because the peroneal nerve doesn't do well as the radial nerve does, for example. And here you can see I splinted the patient, had her in this type of position. And then gradually, after several weeks, brought her out in this hinge type brace. And here you can see as she regain some useful dorsum function. I don't believe that she would've regained that alternatively. And here is a point, my what's up my sleeve would have been a tendon transfer using posterior tibial tendon. Now, that's nerve repair. I'd like to switch gears now to neurolysis. Neurolysis is something we're all familiar with. What it is is it is the ultimate form of a nerve decompression. In this case, we're using it to refer to freeing up scar. And when do you do it? Any time a nerve which has been injured is in continuity. Now you stop at this point when after you freed up the nerve, you always do nerve action potentials based on Dr. Klein's work, and you obtain a response. So when you are able to get an NAP across a lesion, neurolysis yields good results based on Dr. Klein's extensive work. When it doesn't, so in other words when there's no nerve action potential across a lesion, and you've checked all the finer points of your technique with the electrophysiologist present, then you have to chop out the neuroma and do a repair graft. Here's what nerve action potential monitoring looks like. This is Dr. Klein's setup, where he uses three prongs for stimulating, two for recording. This is a neuroma of the upper trunk of the brachial plexus. Head is over here, C5 and C6. This is suprascapular nerve. So I'm recording here on the posterior division, and stimulating what looks like C5. And this, despite having a bad neuroma, allowed me to obtain a nerve action potential way before this could have been seen on standard EMG, which, of course, would have been testing a supraspinatus muscle, for example, which is, again, off the screen, an intermuscle. So at four months or five months, this patient had no recovery, clinically or electrophysiologically. You look at the neuroma, you can't judge a book by its cover. You use the monitoring. You see a response, despite the large neuroma, this patient recovered well over months ahead, an inch per month, with just neurolysis without resecting it. This is much better than cutting out the neuroma, and doing a graft in these circumstances. So we know that you can't judge a book by its cover. So similarly, we know that looking at a nerve's exterior does not correlate necessarily with the internal histology. Palpating nerves doesn't predict outcomes, as you can see, and many people over the years say that the neuroma doesn't feel hard. For example, some people will even work with injecting saline. The point is nerve action potential is the best technique we have nowadays to predict outcomes and to help affect appropriate treatment. So neurolysis, when there is an NAP across it after several months, is a standalone procedure, whereas if there's no nerve action potential, and you have to do some type of reconstruction. Oftentime, especially with the brachial plexus, this results in some type of graft repair. So a nerve graft is necessary when nerve stumps on either side of the gap can not be made up, they cannot be opposed well for a direct repair, unless you have tension. So this is often necessary for many types of lesions, but especially those of moderate length, or those where the stumps have retracted. Now, of course, this is for postganglionic injuries of the brachial plexus. It's not indicated in avulsions. That's important because, oftentime, if patients have a brachial plexus injury, and they haven't received a thorough workup, including a myelogram, for example, or intraoperative testing, the scarring may not be bad. You may convince yourself there's a postganglionic scar, you may resect that, put some grafts in, but in truth, there may be a lesion more proximal. In fact, with preganglionic injury, there may not be very much scar when exploring the brachial plexus, because the injury is out of your field, it's proximal to you. Now, there are many sources for autologous nerve grafting. The gold standard is sural nerve, and like I mentioned, ipsilateral can allow about 40 centimeters, sometimes you have to both legs. There are other sites as well, including sites that are in your field. So for example, with the spinal accessory nerve lesion, you can use the great auricular nerve, you could use cervical plexus. In my experience, I like to use the sural nerve. Here's a case of a patient who had a lymph node biopsy by a family doctor. Short incision, patient didn't receive imaging done of this lymph node. The lymph node wasn't in the usual location, which is up here along the accessory nerve chain. Here, this was in the course of the brachial plexus. And in fact, this like the other case of the radial nerve that I showed, wasn't a lymph node or lipoma, in that case. This was a schwannoma of the upper trunk, C5, C6. Again, suprascapular nerve, posterior division, anterior division. Shark bite where the schwannoma was resected. And that required interpositional nerve grafting from C5 and C6. Here, you can see different techniques for interpositional grafting, either doing a fascicular repair and matching the faces of individual fascicles. A simpler way, I think, is to glue the same number of nerve grafts, and then do a single repair. Results of either technique are similar. Here, you have to sew in each nerve graft. Here, if you glue each proximally and distally, you sew the glued enzyme, so you have fewer sutures and it's an easier repair. I did want to just mention briefly the concept of nerve transfers. We talked about nerve grafting. Nerve transfers has been well-known or preganglionic injury. So for example, with brachial plexus avulsion injury, you cannot do neurolysis, you cannot do nerve grafting. The only way of effecting some improvement would be taking something that is working, and expendable, and transferring it to someplace that needs it, robbing the rich to feed the poor. Now, because some new nerve transfers have been described in some very creative ways, some people now are even using nerve transfers instead of nerve grafting, in some cases of postganglionic injuries. I think this is beyond what we need to know for your oral boards. I'd like to concentrate on the preganglionic injury, because there you have no other alternative. So I think your strategy for boards would be a patient who has a pan plexal injury. So in other words, a flail arm after a severe trauma, such as a car accident that's high speed. That patient got a sufficient preoperative testing with a myelogram. The myelogram usually shows multiple pseudomeningoceles. In that case, I think the reconstruction of choice would be to explore the patient, use intraoperative monitoring of your choice, whether it's nerve action potentials. Dr. Klein's book talks about that, or different types of evoked potential, sensory or motor. These are all good at determining whether or not there's any continuity with the spinal cord. Any nerve that's connected to the spinal cord can be then used for targeting shoulder or elbow flexion. So in other words, if you found a C5 nerve stump that was postganglionic, then I would use that nerve graft using sural nerve, as we've talked about. However, if there's confirmation that that level is avulsed, then there's no other way around doing something which would be nerve transfers. And I think for your boards, what I would say is the priority would be obtaining some shoulder stability and elbow flexion. Shoulder stability decreases the subluxation of the glenohumeral joint, elbow flection, by and large, is the most useful motion because it allows people to use what might otherwise be considered a useless limb. Here, you can use several intercostal nerves, so three intercostal nerves. So what you would do is make a big inframammary incision, and cut the end near the sternal edge, and flip it over to the biceps. And at first, after a year, you would notice some twitching with deep inspiration or even laughter. And then after a year and a half, or two years, patient relearns as cortical definition becomes more apparent. And at that point, it can even become truly independent for elbow flexion, even though you're using intercostals to drive it. So that's how you would regain elbow flexion, it would be a direct repair at the level of the arm or axilla. The spinal accessory could be then taken to the suprascapular nerve. You would leave a branch or two of trapezius, so the patient does not denervate the trapezius completely. And then you can do a direct repair of the spinal accessory nerve to the suprascapular nerve. And that would allow you, hopefully, some scapular stability, and some shoulder abduction. In truth, it provides little infraspinatus or external rotation, but it does provide enough shoulder stability that makes it useful. I think that's all you really need for brachial plexus problems for your boards, for reconstruction. There are newer types of nerve transfers, including what's called the Oberlin type of transfer. There, for example, you have a C5, 6 type of policy. In other words, there's no shoulder or no elbow flexion. The Oberlin transfer is a fascicular transfer of a portion of the ulnar nerve trying to target the wrist flexor, the flexor carpi ulnaris, and putting it right into the elbow flexor muscle, right into the biceps nerve right here. You can make a small incision there, and do that safely with excellent results. People like Christophe Oberlin, Susan Mackinnon have done pioneering work in that. To be honest, I think that's beyond what you probably need for boards, but you may hear something about it during your course or during lifetime. So why do we want to know about nerve reconstruction? It's because of outcomes. We talked about favorable circumstances. The right time, in general, is the earlier the better. For your nerve lesions in continuity, it's typically best before six months. And that involves the distance to the end organ, the status of the alpha motor neuron, and the status of the end-plate. Radial nerves do better than ulnar nerves, for example. It's a long way to try to get to hand intrinsic muscles. The end-plates seem to die. Right technique? I think suffice it to say that all repairs, all surgeons are not equal, and the repairs are not done equally. It's not unusual for us to see big suture in fine nerves. The right patient, I think, patient age is important. The younger, the better. You remember that I showed you 11 or 12 year old boy at first, with the wrist drop and finger drop. The younger patients not only have shorter limbs, and shorter distances, but perhaps there are some physiological factors that may be better, we don't know. The distance is important because part of the right place is the level of injury. The more distal, the better. There is a shorter distance to where the nerve needs to go. Now, nerves regenerate an inch a month. Distance still is the biggest issue, because despite all the research we've done, in general, we're still at an inch a month or a millimeter a day of full recovery. Now, the right place type of nerve, pure nerves seem to do better than mixed nerves. What you're doing is avoiding mismatch. So perhaps that's why the spinal accessory nerve is a good nerve to repair. Specific nerves, again, we've alluded to this, this used to get asked on part one of the boards, which nerve is better than the other. The radial nerve is a good nerve. The median nerve does less well. The ulnar nerve does the least well. C5, 6 goes to shoulder and elbow, that does better than a C8, T1 which has to go all the way to the hand. In fact, with these types of reconstructions, few surgeons would even think about or contemplate a nerve reconstruction in the neck for these types of rare lesions. Interestingly, in the lower extremity, the tibial nerve does better than the peroneal nerve, that's poorly understood, but important to know about. Type of injury. Not all mechanisms of injury are the same. So a laceration, a sharp, clean injury does better than a high velocity gunshot wound. And that's thought to be due to the zone of injury. With associated soft tissue and vascular damage, it's easily understandable that the nerve zone is broader. Transection does better than avulsion, stretch does better than avulsion. I think that's intuitive based on what I've taught. So finally, I think some broad numbers that might be helpful for you in life is that when nerves recover within several months, those have the best results, better than anything you can do with surgery. So in fact, a nerve that's recovering early will tend to continue to recover, and may, in fact, recover fully. Neurolysis is the next best. When you explore somebody at the right time, several months have gone by, there's no EMG evidence of recovery, and you find, as in my case, a nerve action potential that was present, in those cases, you have a 90% chance of obtaining a good result. Nerve repairs do better than nerve grafts. Nerve grafts, nerve transfers work well about 70 to 80% of the time at obtaining what's considered a good recovery for shoulder or elbow. That doesn't mean 70 or 80% of preoperative function. And lastly, tendon or muscle transfers may restore reliable function as a salvage. And I think that's important in the patients who present late or who've had suboptimal recovery, despite an ample length of time of falling.

- Okay. Rob, thanks for this discussion. We really enjoyed it. Let's proceed to the second part of our discussion today. Thank you.

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