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Grand Rounds-Posterior Fossa Exploratory Surgery for Geniculate Neuralgia

William Couldwell

May 16, 2011


- Hello, ladies and gentlemen, thank you for joining us. Final decision on the Dublin is operative grand rounds. That following session will be discussion regarding surgical management of Geniculate Neuralgia or Primary Otalgia or Neuralgia due to nervus intermedius. This is a rare and difficult disorder to diagnose. We'll discuss today, some of the technical nuances related to Exploratory Posterior Fossa surgery for transection of nervus intermedius. Thank you.

- Bill thanks again for joining us. This is a very rare disorder thanks God, geniculate neuralgia or primary otalgia or severe ear pain or ear canal pain. It's also called nervus intermedius neuralgia because originates or the pain is supposed to come more commonly from nervus intermedius, which is located between the seven and eighth cranial nerve in the cisterns of the seven, eight nerves. This is extremely rare and the diagnosis, so absolutely critical because so many different pathologists can overlap in terms of creating ear pain. However, for patients who are absolutely miserable with the pain and are often suicidal, this procedures that is technically challenging, actually can be very much satisfying. It often help happens maybe once or twice a year for me. And you know, I treat about 200 neuralgia patients who require surgery with MBDs a year. And I'm sure for you it's as rare that doing the posterior fossa exploratory surgery for severe ear pain or primary otalgia is rare and the diagnosis has to be very carefully considered. What are your pearls in terms of the diagnosis and treatment?

- So as you mentioned Aaron, it's a very difficult diagnosis to make with absolute certainty because there's a lot of overlap with the other pain syndromes. Trigeminal, and obviously glossopharyngeal. You really want to make sure you're not missing glossopharyngeal neuralgia. And I had the patient seen by otologist, and head neck specialists we do a complete radiographic workup, both CT and MRI, to look for any pathology at all that could be causing the ear pain prior to considering this. And also obviously they needed to be medically refractory. So ultimately it's an extremely rare disease that we only see a few cases compared to the, the vast number of trigeminal and unless your costs, some fringe GL neurologists we see.

- Thank you. And this is briefly the disclosures before we proceed. None of which really interferes with the presentation. So let's define Geniculate Neuralgia pretty briefly. It's an involuntary intermittent or potentially partly constant neuralgic pain deep within the ear canal. The pain may radiate to mastoid or occipital regions of of the face, But again primarily the pain is in the ear canal. The nerves that innovate the inner canal or the surrounding areas are five, nine, 10, and most importantly nervus intermedius that is responsible for tasting and lacrimation. Is this another neuralgia neurovascular conflict syndrome, such as trigeminal neuralgia and hemi facial spasm maybe. But again the verdict is out there because it is such a rare disorder and treatment options are mostly anecdotal. The series are very small and again the surgical treatment has to be very, very cautiously offered. Here is a patient's interview that would illustrate what typically Geniculate Neuralgia can be described by the patient. You can please pay attention to details of his description, as you will find out the nuances of diagnosis are absolutely the most critical factor in good outcomes in this disorder.

- Can you please tell us about your pain?

- The pain I have is very intense, worst pain in my life, 10 out of 10 on a pain scale. It would feel like I was being stabbed in the head with an ice pick or sharp object, right at the ear canal, would come and go. The pain would be intense for a few seconds, go away, come back with an a minute or two. I would have periods of remission where I wouldn't have any symptoms at all, and then for a day or two, I would feel like I was being stabbed a hundred times a day. It was terrible. And the wind from the air conditioning turning on, I could feel the light breeze from the air conditioner on my ear and that would trigger a pain episode. The point where I wouldn't try to avoid being around places where air conditioning or windows were open, just to try to prevent being around a breeze.

- Okay, can you tell us where exactly the pain was again.

- The pain was right near the ear canal. That felt like I was either being stabbed in the ear deeply or deeply through the area directly around the opening of the ear canal.

- Thank you. Now that we have listened to that patient's interview, let's talk about some additional basic information. And again, it's extremely rare. It's often misdiagnosed and again, the neurology character of being, you know, I like to call having cutaneous features and response to neuropathic medications such as taped recall is important. It is again the triggers are tactile stimulation within the ear canal, coughing, yawning, swallowing, and taking a shower as the water gets into the ear off, it creates a severe electrical shock. What has been your nuances of diagnosis in terms of this disorder of Bill?

- So I agree with you. I think you've nicely described the basic clinical features as it is. I think one of the important things is to differentiate it obviously from glossopharyngeal neuralgia because they can present primarily with ear pain as well. And to differentiate those two, I like to have on our auto laryngologist and head neck surgeons look at the patient with me and we often do the anesthetic test and the posterior pharynx to rule out glossopharyngeal neuralgia before we consider geniculate neuralgia.

- Okay. Thank you. And as you very well have mentioned, we need a CT MRI of the brain and the ear, and a very thorough ENT evaluation, a dental evaluation or other possible evaluations. Strictly exclude head and neck pathologies. If there's burning pain around the ear and ear canal, it could be part of Ramsay hunt syndrome that is herpes infection and a 10% cocaine solution into posterior pharynx, if their result causes pain relief for a couple of hours, that is consistent with diagnosis of glossopharyngeal neuralgia as glossopharyngeal neuralgia may have only ear pain as it's presenting symptom. And if that's the case during expletive surgery, you want to pay a special attention to the lower cranial nerves and proceed with surgery. as you are foreclosed referential neuralgia. At times Xylocaine solution injection into the ear canal may cause some relief and that can be consistent with diagnosis of geniculate neuralgia, but again these are not very perfect pathognomonic diagnostic features for geniculate neuralgia. The correct diagnosis is most important that neuralgic pain of shooting electrical pain upon touching the ear canal, swallowing, chewing watering to the ear or the wind going through the ear canal, it causes that shooting pain that's critical. Many conditions can cause ear and face pain. A typical facial pain, primary pathology of the ear, oral cavity, head and neck pathology. temporomandibular joint disease, probably one of the most common causes of ear pain and besides the common cause of chronic ear pain, let's put it that way. Probably acute ear pain is the infection and otitis and external, and again carcinoma of the nasal pharynx very often can present as ear pain and you don't want to miss that on time. Again what are the treatment options? Carbamazepine, and if the pain is extremely disabling and the patient comes and says, listen I have typical neuralgic pain and you can definitely verify that, and the pain is so excruciating that the patient can be suicidal at times, I think it consideration in this situation of surgical treatment would be reasonable. Any thoughts there Bill?

- No, I think that's been nicely described and we would do exactly that workup. Both trying to quell the pain with either posterior fossa injection of cocaine in that case or the intraoperative or inter ear Xylocaine as well is a good useful test.

- Thank you. And here we are. What are the surgical treatment options? Posterior fossa explanatory surgery exploring the seven, I'm sorry the five, seven and eight complex as well as nine and 10 cranial nerve complex is along the brainstem. If there is an evidence of vascular compression along any of these nerves, we go ahead and mobilize and transposition the nerve and place a Teflon patch. We will consistently proceed and section the nervus intermedius which can be technically challenging to identify between the seven and eight cranial nerves and cut the nerve and potentially consider sectioning the ninth nerve at upper rootlets of 10, if a suspicion of causal pharyngeal neuralgia is present. What are your thoughts in terms of surgical options Bill?

- Yes I mean, we would perform a lower cranial of exploration in such a case, and look for vascular compression of either seven, eight or nine, 10, 11, and a plan to go ahead and if there was vascular compression of nine and 10, we would do a microvascular decompression. And if there was no conflict at all with seven and eight, we may just leave it as the first operation. And then secondly look at nervus intermedius and section that.

- Okay so if you don't find the vascular compression at the primary first operation, would you consider finding the nervus intermedius and cutting it?

- Yeah. If it was easy to identify, we would go ahead and cut that. I think that's a reasonable option.

- Thank you. Other options that have been described in the literature includes section of the virginica ganglia or chorda tympani through a middle fossa approach, but I think those surgical options are much more invasive and really have to be very, very cautious the offer to the patient because of the morbidities that could be associated with a more extensive middle fossa exploratory surgery in addition to a posteior fossa exploratory surgery. Always the imaging is important to rule out a structural pathology, high resolution MRIs off often negative. Again the surgical exploration is very cautiously offered in terms of and the face of adequate diagnosis. So what is a surgical anatomy of nervus intermedius? There is three principle segments to this nerve described by The proximal segment is closely related to the seventh nerve, add the root exit zone of the seventh nerve along with the brain step. The intermedius segment, which is the free segment between the seven and eight cranial nerve just a little bit distal to the proximal segment is the most free piece that floats easily between the two segments, not easily in terms of finding a surgically by but its somewhat separate and then it's most accessible for the surgeon to identify. So, in other words, if you can dissect over the seven and eight cranial nerve from the nerves, the nerve is most likely between the seven and eight and along the middle segment of the cistern a portion of the seven and eight complex. And the distal segment of the nervus intermedius often is incorporated into seventh nerve and is not dissect able without morbidity. What is most important is that we have to be very careful to dissect this nerve from the eighth nerve as the long-term consequences of medical refractory vertigo can be very disabling. And therefore not much aggressive dissection should be performed. There's usually two to four fasticals for the nervus intermedius and 20% of the patients may not have a distinct nervus intermedius despite adequate inspection, even into intermedius segments. Any thoughts regarding the surgical anatomy Bill?

- Yeah, I think the key is to really make sure that you can identify it properly because it's a morbid operation. If you either end up injuring the seventh or some of the distributor components. And so we only section it if we're sure that we can identify it well and its obvious.

- Okay. Thank you. And again inter-operative monitoring eighth granular lever is important. Do you monitor anything else, bill?

- Well, we would do EMG for seven as well in a case such as this.

- Okay. So you want to make sure as you're dissecting you not going to overstimulate or injure anything else

- Correct. Also we can use it to help differentiate the nervus intermedius from the seven main branches seven.

- Okay. Thank you. And then here is an MRI of a patient with primary otalgia and as you can see, there is this loop of the vessel potentially along the root exit zone of the seventh cranial nerve. This is another image again, showing potentially a vessel in the region. And here is interestingly Bill, we found out one of our patients that we want to report is this patient had a very classic primary otalgia and had stimulation evidence of hyperactivity in functional MRI in his brain stem along the trigeminal spinal polemic tracks. And so this may be something in the future that people can look into in terms of identifying pain syndrome, specifically affecting the spinal thalamic and trigeminal thalamic tracks. Nothing that again the clinical diagnosis is more important.

- It would be nice to have an objective correlate though.

- Correct. As you can see, there's some hyperactivity you can see on the trigeminal spinal thalamic sensory tracks. And again the position of this operation is very similar to trigeminal neuralgia and lower panel nerve decompression, microvascular decompression, we're not going to go from the details right now, I would like to ask our viewers to refer to the previous presentation on geniculate neuralgia that has been recorded again by Dr. Phil Caldwell, demonstrating his neurolysis for evaluation, I'm sorry full performance of posterior fossa surgery. Here is an illustration of examining the nerve after the cerebellum has maybe correct retracted medially. And I tried to expose and identify the root exit zone, I'm sorry, root entry zone on the trigeminal nerve. And if there is a vein and not necessarily compressive, we'll leave that alone. And then next we attract our attention to the nerve seven and eight cranium left complex, where we look first above the nerve between the seven and eight nerve. And again the seven therapies more grayish in color and is anterior it's inferiorly and moves superiorly in anteriorly. The eight cranial nerve are more whitish and more posterior and both posterior origin and posteriorly sort of path the pathways more posterior. And after we look at the nerve above them, if we can't find the nervus intermedius, we try to go more inferior and usually find the testicles of the nerves intermedius and prepare them for transection. Often there is a vessel between the seventh and eighth cranial nerve complex as well, making the dissection easier. What are your nuances of technique for identifying the nervus intermedius Bill?

- So in this case, you want to look both inferiorly and superiorly and try to separate out seven and eight and see what the root entry zone of the brainstem, and then follow up between them and look in the cisterna segment to see if you can find nervus intermedius of between the two. And I think it's critically important in this case to try and really mobilize and look from fairly, but from superiorly, try to, you know, reduce the amount of manipulation of the eighth nerve as much as possible, because this is where the morbidity in with the operation is manipulating the eighth nerve trunk, when you're trying to look for seven, the nervus intermedius between seven and eight.

- Right. In other words what you're mentioning Bill is that you don't want a patient who wakes up still having horrible pain, and now can't walk anymore either. I think that that's essentially the worst of both worlds, unacceptable outcome. And here it is holding the nervus intermedius dissector and cutting that the nervus intermedius again mobilizing the arterial routes along the brainstem, along this ninth and 10th cranial nerves. And again decompressing any vessels around the seven and eight cranial nerves as well. And here is really me. I'm trying to look around it root entry zone of the fifth nerve inter-operative photo. Again looking in fairly finding their nervus intermedius with the dissector. Again this is seven and eight cranial nerve. And again, after that, the cut, the nervus cut. And we look at the root exit zone of the facial nerve and between the seventh and the eighth cranial nerve. And there's usually a vessel or a vein and artery running between the two and any additional vessels can be mobilized. Again you can see how much with adequate microsurgical techniques you can dissect the the nerve from the facial nerve and be able to look in between without causing significant morbidity. Any thoughts here Bill?

- Yeah, I think again, just like we discussed and then plenty of neuralgia case is that you need to look right at the brainstem because if you just focus on the cisterna segment you really want to look back at the brainstem, see the root entry zone of both those nerves and make sure there's no conflict at that level.

- Thank you Bill. And here it is just like you mentioned Bill, looking at the brain stem mobilizing the arteries placing Teflon patch to a shorter is no evidence of compression either at the seventh and eighth complex or the lower cranial nerves. And again, for the previous, for the exposures, please refer to the trigeminal neuralgia or hemi facial spasm as well as no most fragile neuralgia sessions for craniotomy and exposures. Let's go ahead and look at some of our videos, short videos that would again, illustrate some of the basic standards for management of all neuralgia. Here as you can see that basic exposure or posteriors foster approach, the lower end of the transfer sinus is not visible as it's not necessary to expose the posteromedial aspect of this signal sinus is exposed here is gently retracting the cerebellum and opening the rack with membranes, the bears are perfectly monitored to assure that they gentle medial attraction of the cerebral hemisphere is not interfering with the eighth cranial nerve. Here is looking at the root into his own of the fifth nerve. And again, nothing convincing is evident. Go ahead Bill, interrupt me at any time you can.

- Yeah, so we're looking for any significant conflict. You've got an artery there by seven and eight.

- And I think that's more of a vein. The artery is more superficial, but again, we look superiorly, I know you don't have the 3D view here to adequately see the instances unfortunately. And here it is sort of pulling on the nerve with a gentle, dissector you sorta go around between the two and find the fast circles of the nervus intermedius, and then hold it with your suction. Go ahead and cut it with your micro scissors. And again here is those vascular loops that you very well mentioned Bill. You have to identify them, mobilize them and carefully place the implant. Go ahead.

- There's one point that when we cut vessels, I try to cut a segment of the vessel or kind of a segment of the nerve and remove it just to avoid any potential for reenact of the nerves. So when we kind of glossopharyngeal nerve or nervus intermedius, we cut a section of the nerve.

- Okay. That's a grand new He already is between the seven and eighth cranial nerve. You can see, got to be very gentle, retracting these two vessels and create this space between them and putting the Teflon implant to mobilize the arterial loop from the lower cranial nerves. Would you have done anything different here Bill?

- No I think that's exactly what I would have done. I would have sectioned the nervus intermedius, if we can find it so easily and then decompress the vessel loop as well.

- Okay. And I think again, further placement of the Teflon implant to assure adequate mobilization. Go ahead, bill.

- Yeah. The one point that we like to do is if we can mobilize the loop such as that, we'll try to sling the loop away and we''s hard to do in this situation because you don't have a lot of working room between seven and eight and nine, 10, 11, but we'll try to mobilize the artery way and sling it away and hold it. And we'll stitch it, or sometimes fibrin glue the Teflon sling to hold the artery away.

- And you would stitch it to the dural of the peach rispoli, is that correct?

- Correct. Or the crevice depending on where you put this way.

- Okay. And you think that would potentially have a better outcome than just putting the Teflon patch as it is in this case?

- Yes. I don't know, but I prefer if I can't to leave absolutely nothing touching the root entry zone or the nerves as my primary option. If I feel I can't achieve that, then we'll do the inner physician of Teflon as you've nicely demonstrated here.

- This is another patient Bill. Again left sided approach had primarily primary otalgia and loop during this exposure, how the ninth nerve is being compressed and sort of conflicted with every pulsation of the vascular dupe. And in this situation, we looked at the seven and eight complex here and absolutely no vascular conflict was evident. We did look for any branches of nervus intermedius or its fastest holes and nothing was evident. And we do not want to place the patient at an increased risk of post operative vertigo and eighth nerve dysfunction. And so after adequate inspection around the seventh and eighth nerve at seventh and eighth complex, we went ahead and placed the Teflon patch between the ninth nerve and mobilize the nerve and ultimately cut the night nerve. And the patient did very well. And it really shows again that goes suffering. neuralgia can have very much overlaps with the, with the neuralgia and the ninth nerve has to carefully inspected. This is a branch of labyrinth you know, read that went in between the seven and eight and was decompress also. But again this vessel has to be carefully preserved. I think the results can be very much variable. The short-term results are good up to 75% of patients with primary otalgia. Unfortunately the long-term outcomes is only 30% good based on the report of Fidel Janette and others. The complications can be serious. The vertigo hearing loss and decreased taste and lacrimation again this is an operation that is nowhere comparable to microvascular decompression surgery or the fifth nerve, or the ninth and 10th nerve and for the seventh nerve for an official spasm, and therefore judicious patient selection is so critical. And Bill, any closing statements please?

- Yeah. I think you summed it up nicely Aaron. I think that this is a less gratifying operation ear pain than glossopharyngeal pain classic throat or, of course trigeminal pain. Which is usually I home run in very well selected patients. So we do this, we do this very occasionally, but only with well selected patients.

- Okay.

- Thank you very much.

- Thanks again, as always for your expertise. We really, really appreciate your time. Thank you.

- Thank you.

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