Hypoglossal Nerve Stimulation Surgery, Part 1: Candidacy, Technique & Device Limitations

[Matthew Hensler MD]
Sure. That's a great question because I think a lot of people hear what it is and then when they hear actually how it works, it's a little different. It's two incisions and the hypoglossal nerve stimulator implant is typically put on the right because we reserved the left if somebody would need a pacemaker and we stay away from the heart. So you go on the right and you put a processor in the chest that has a battery and there's a sensor lead that feeds off of it, down into the rib cage so that it can sense when they’re breathing. And then there's a stimulator that runs, it's a little wire that kind of comes up the neck and there is a second incision kind of under the jawline. And that's how you place the stimulator lead on the hypoglossal nerve.

So once you're done with that, at night, when they go to sleep, they take a device that kind of looks like a mouse for a computer and you turn the device on and, you can change this, but after a certain period of time, it will begin working so that every time the patient breathes- so whenever it senses that there's chest wall, expansion or movement- that will gently stimulate the base of tongue to push forward and tighten up. So it's not just working when you snore, it's not just working when you have apneas, it's doing it with every single breath, it's pushing the tongue forward. And you can turn it on and off at night. If you wake up and you need to use the restroom or something, you can turn it off and turn it back on. But that's generally how it works.
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[Gopi Shah MD]
So you described, two incisions, one in the chest and one kind of right, maybe submandibular area. Do you monitor the marg for that? Or do you just go below the gland or, is that a concern, how do you monitor?

[Matthew Hensler MD]
For sure. So it's really interesting you bring that up. I feel like in training, we're always taught two finger breadths below the mandible to avoid the marg. We avoid that nerve at all cost and the way that this was taught to implant, you end up making an incision a lot closer to the mandible. It's more like a finger breath because you kind of, you're trying to find the hyoid and you find the midline and you try to split the difference and kind of extend it back from there. So you end up being, I think, a little bit closer anatomically to the marg. I don't specifically monitor it during surgery, but you can see their mouth in view when you have them prepped out. So you're able to tell if you're getting stimulation or if you're getting close, I've never had anybody that's had marg weakness afterwards. Because I still, even though the incision is high, I still aim really low to get down on the bottom part of the submandibular gland, just so you're not close to it. And then you work your way up.

[Gopi Shah MD]
And then for the chest incision, are you below the pec and the nipple? Where is that? And are you going down to rib? Like, do you have to worry about pneumothorax? Like how does that work?

[Matthew Hensler MD]
So when I first started doing the procedure, it was three incisions and the one incision was a couple of finger breadths below the collarbone. So that was for the device. And then the sense lead was down kind of along like if you come down under their armpit and you come across just kind of like a bra line, it would sit down along the ribs there. So that was the third incision, but we really don't do that anymore because now you're placing the sense lead within that a higher incision. So it's two finger breadths below the collar bone. And you, once you've made a pocket for where the hypoglossal nerve stimulator implant is going to sit, you just kind of go through pec major and you'd bluntly divide it until you're getting down to the intercostals and you try to find the nice plane between the internal and external intercostals. In training, look, I never was dissecting down onto the ribs. So initially it was always a very like, oh my gosh, we're near the lung, it's right through there. And, you're definitely cognizant of it. It's got some really, really good safe anatomy to get to that level. And you develop a pocket between the two muscles between the intercostals and you feed the sense lead there. So as you said, pneumothorax is one of the reported risks of the procedure. I personally, knock on wood, haven't been affected by it. And again, I think it's, you're just, you're smart when you get down to that point and you're delicate as you work between the muscles to avoid that complication. And we do a chest x-ray afterwards to make sure there's no issue with pneumothorax, especially.
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[Gopi Shah MD]
Do you have any special landmarks or techniques to help you feel like your sensor is where it should be? How do you know?

[Matthew Hensler MD]
Well, when you're dissecting on the hypoglossal nerve, there are a couple little landmarks. Really the main one is, you're just looking for what we call it, the break point, where you can see these retrusive branches kind of extending up. And so we will use a nerve stimulator for that and kind of stimulate the inclusion branches and your exclusion branches. And you'll kind of tell when you'll isolate the nerve, maybe put a vessel loop around it to say, here's the branches we want to include. And then you use a little probe to stimulate them and make sure that your inclusion branches are stimulating well. And that you're not including any of the retrusor branches.