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Radiofrequency Rhizotomy: Technique

January 17, 2015

Transcript

- [Doctor] Let's review technical nuances for radiofrequency rhizotomy for V3 trigeminal neuralgia. For patients who are not candidates for a microvascular decompression surgery in terms of their age, being older than 70 or medically not fit to undergo exploratory craniotomy, I consider first balloon compression rhizotomy as the first choice of percutaneous procedure. However, if the procedure is ineffective, a radiofrequency rhizotomy can be very beneficial. However, it does require the patient to be awake and could be at times uncomfortable for the patient. This patient was suffering from right-sided V3 trigeminal neuralgia. You could see the setup in the room and a lateral fluoroscopy at this position. And again, the layout of the rest of the contents in the room, you can see that the initial stab incision is made approximately two and a half centimeter lateral to the angle of the lip. The cannula is placed into the foramen standard fashion as described in our previous videos, you can see that where the clival line intersects the petrous ridge. This is the area where the trajectory of the needle is pointing at. We'll go ahead and pass the needle. You can see the patient is mildly anesthetized. Now we are entering the foramen. And oblique AP fluoroscopy parallel to the lumen of the foramen assures that we have indeed transversed the foramen. You can see the outline of the foramen here and a needle going through this, through it. So we were assured that the needle is in place. The depth stop is placed to assure that the needle is not being displaced during the rest of our manipulation. The solid stylet is removed. And the slit of the needle is turned medially to assure that the curved thermal couple enters with it's curve tip along the medial aspect of the needle. I only use the curved thermal couple and not the straight one, since the curve electrode allows a better range of mapping of the nerve as necessary. It can be a little bit challenging to get the curved thermal couple electrode into the needle. After the needle is, the electrode is in place, we go ahead with a modified anteroposterior transorbital view, and we'll adjust the depth of the electrode until the electrode is curved immediately. As the trigeminal nerve roots are located medially, and more importantly, the curved portion of the needle is just above the porus trigeminus. As you can see here is that petrous ridge curving down to become porus trigeminus. It is better actually illustrated on the left side and you can always use the left side to, again, make sure you're at the right position on the right side. This requires some adjustment in terms of the x-ray to be parallel to the petrous ridge, to assure, an adequate image is obtained. Here, you can see another x-ray in the lateral trajectory where the curve of the electrode is a few millimeter above the clival line, which is the ideal location of the curved electrode. With the electrode in position, we go ahead and map the trigeminal nerve roots. It is important to note that the patient is awoken during this time and should be co-operative to assure that the correct nerve root is being lesioned. Let's go ahead and listen to stimulation results here. The details of the stimulation are more discussed in the attached chapter. Can you feel the touch?

- Yes.

- [Doctor] Is it upper lip or lower lip?

- Lower.

- [Doctor] Is it where your pain is, dear?

- Yes.

- [Doctor] Okay, so one last time, let me confirm is the tingling on the cheek or on the lower lip?

- Lower.

- [Doctor] That's again where your pain is?

- Yes.

- [Doctor] Okay. Tell me where it goes away, okay? Did it go away? It did? Okay. Let me know when it comes on again. It came on? And again, is it lower lip?

- Yes. [Doctor] Okay. Tell me when it goes away, sweetheart. It went away. Okay. So now we have it in the right location. Let's go ahead. And we're going to put you a little bit to sleep, sweetie. Okay? Can you go ahead and do that? So you can see this patient who is suffering from right-sided V3 trigeminal neuralgia has the electrode placed actually in the right location. So we have the curved electrode only stimulating V3, the distribution of the skin in the vicinity of the lower lip. And that was confirmed twice. So we know that the electrode is in the right position. If this patient was suffering from V2 trigeminal neuralgia, I would have advanced the, first remove the electrode slightly backwards, withdrawn the electrode, and then advance the cannula slightly. And then the remapped and assured myself that actually the tip of the thermal couple electrode is at the right location. Let's go ahead and start with lesioning a stage of the procedure. I usually start at 65 degrees and lesion in there for approximately two minutes. And if that's inadequate, we can increase to 72 or 75 degrees to assure that an adequate lesion is created. Please note that if the patient is very comfortable, you can actually create the first lesion. And if it's inadequate, keep the patient relatively awake and create another lesion. And during the lesioning process, map the face with a needle to assure that adequate numbness has been created. Let's go ahead and proceed with lesioning. You can see some CSF at this time, draining through the cannula. The patient is slightly sleepy with roving eyes. That confirms that some sedation has been induced. We'll go ahead and use the generator to create the appropriate temperature within the thermal couple electrode. After about a minute or so, the patient can be awoken and re-examined. Here is again the process of lesioning. And temperatures increased. You can see from 39 to 54, 56, 62, the right side of face actually is flushed. It's more pink than the left side. And again, this confirms that we are achieving the appropriate response. So at this stage, I'll go ahead and map the face and see if we have created mild numbness in the V3 distribution as desired. I also make sure there is no anesthesia in the distribution of V1, as this can be troublesome and place the eye and the cornea at risk. Let's go ahead and listen to see if we have created the necessary mild numbness.

- [Doctor] For number two.

- They were the same.

- [Doctor #2] Which one is sharp for number one or number two?

- One.

- [Doctor #2] Number one is sharper? Which one is sharper now, number one or number two?

- Two.

- [Doctor #2] Two is sharper?

- So you can see that actually we have not reached adequate numbness. The patient does not indicate that there is any evidence of numbness, more on the right side, than compared to the left side. So let's go ahead and remap the location of electrode in this case.

- [Doctor] Do you feel it at all?

- Okay.

- [Doctor] Where do you feel it? Upper lip or lower lip?

- Lower.

- [Doctor] Do you feel it in the lower lip? Tell me when it goes away. Did it go away?

- No.

- [Doctor] How about now?

- [Doctor #2] Let me know when you feel it again, okay?

- Okay.

- [Doctor] Let me know when you feel it, sweetheart.

- Okay.

- [Doctor] Where do you feel? What's that?

- One. Oh, lower.

- [Doctor] Lower lip only? Do you feel it in the upper lip?

- No.

- [Doctor] How about around your eye?

- No.

- [Doctor] Okay, so you feel it in your lower lip. Let me know when it goes away. Did it go away?

- Yes.

- [Doctor] Okay, go ahead, to 75, Suzanne for one minute, one and a half minutes. So the patient did not have the desired effect after the first lesioning stage. We went ahead and remapped where we were along the trigeminal nerve roots to assure that the needle has not moved since we'll be stimulating with a higher temperature this time. So we went ahead and I used the higher temperature parameter to do another lesioning. And let's see the result after this stage of the operation. Which one is sharper? Number one or number two?

- Number one.

- [Doctor] It's sharper?

- Yeah.

- [Doctor] Don't give her any more anything else. Okay. Which one is sharper, sweety, number one or number two?

- Two.

- [Doctor] Which one is sharper, number one or number two?

- Number two.

- [Doctor] It's sharper? Okay. One more time. Which one is sharper, number one or number two?

- Number two.

- [Doctor] It's sharper or duller.

- Sharper.

- [Doctor] How much, how long has it passed?

- [Doctor #2] We had it the whole minute, so we turned it off.

- [Doctor] Okay. One more time, sweetie, which one is sharper, number one or number two?

- Number one.

- [Doctor] It's sharper? Which one is sharper, number one or number two?

- Number one.

- [Doctor] Okay, one more time. Which one is sharper, number one or number two?

- Number two.

- [Doctor] So you can see that during the lesioning process, the patient was awake. Initially the desired effect was not apparent, but as time went along, the desired numbness on the right side in the V3 distribution was achieved. This patient had an excellent control of her pain after the operation. And this really concludes the technical nuances for a radio-frequency rhizotomy and often the operator's patience with it. The patient is important to assure that a desirable result has been achieved. Thank you.

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