Parotid Dissection (Cadaver)
Dr. Esclamado instructs a cadaver lab at Duke University Hospital to assist resident training on a standard parotid dissection. The approach should be adjusted depending on tumor malignancy, as Dr. Esclamado explains.
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- Malignant Tumor
- Benign Tumor
- Raising the Flap
- Dissect Great Auricular Nerve
- Dissect Above Band of Dense Connective Tissue
- Identification of Tragal Pointer
- Expose Tragal Pointer
- Identify Digastric Tendon
- Cut Through Parotid Fascia
- Identify Artery
- Identify Facial Nerve
- Dissect Superficially Along Facial Nerve
- Follow Superficial Temporal Vessels
- Identify Lower Division
- Deep Lobe
- Mobilize the Nerve
- Control Superficial Temporal Vessels
- Find Terminal Branch of External Carotid
- Dissect Parotid from Posterior Border of Mandible
- Free Deep Lobe from the Styloid
The first thing to think about is your incision. You basically have four things to think about. One is cosmesis. You can do an incision in a crease here. I try to do a little “gull-wing” - just you want to have a straight line that shortens. And then around the - the ear, I like to make a point, so as that contracts, you don't get pulling up of the ear like that. Now if you really want to hide the incision, you can do it as a facelift, which you can go way back here and into the hairline and then elevate a real broad flap like that - shave the hair a little bit. That's - this works if you have a posterior lesion here. Tumor’s up there. Your exposure’s going to be a little bit worse, but it's a nice way to do it, particularly in women who have - wear their hair long; you can shave a little hair and the - the scar is basically imperceptible. The other option is taking it down into a crease like this, and the - the decision of how far to go depends on whether or not you're going to incorporate a neck dissection. So if you’re going to do a neck, you may want to take it down in here. If you’re going to do a parotid, you can even just limit the incision in a crease. You’re pretty limited there. So that's the first thing.
The next thing is your plane of dissection and raising your flap. If you - if your tumor is - so you got to point here - if your tumor is on this - is on the capsule or near the capsule of the gland and it's malignant, I like to raise the fat, the plane, above this mass. So if you do that, you're going to want to see the bottom of the hair follicles in your flap. If it's benign and the tumor’s deep in the gland, I prefer to save this mass. I don't know whether that helps with the postoperative Frey’s or anything like that, but it also gives you a little bit of thickness.
The - the other topographical anatomies you got to be aware of are the great auricular nerve. It runs behind the EJ and about halfway between the mastoid tip and angle of the mandible. If - if you can and you don't have a tail or parotid lesion, you can dissect the nerve up and save the posterior branch, which will preserve some sensation. If you just dissect it all the way up, you're going to leave a little bit - you’re going to leave a little bit of parotid here as you preserve the nerve, but that's okay as long as the tumor’s not nearby.
The hardest place in elevating this flap is right here because there's a - there’s a dense connective tissue band there that - that you don’t really - you can't see the plane, but the - the key is - is just to stay on top of it. I think I’m beneath - this is that connected tissue band here. You can barely see it, but I think I'm on top of the - this mass here - below this mass here. Okay so - so there’s fat, and I’m deep to mass. Okay, then you can take it right to the front end of the gland. Just want to raise this back a little bit - just so you can identify the EJ, and - and this is going to get you your exposure. There.
So the next move is to separate the parotid fascia from the perichondrium of the external auditory cartil - the cartilaginous canal, and when you dissect, that's a - usually - a very easy plane to get into. It's a - it's a kind of a wispy plane, and if you're in it, it will spread pretty easily. You can see that there is a plane here.
Okay. So now you want to just expose it to the level of the tragal pointer. Okay, that's your first landmark. Your three landmarks are your tragal pointer - you see that nice areolar plane there? That's where you want to be, okay? So there’s your tragus right there, and just cut down through there, Kevin. Let’s see - you don’t want to get too deep. Okay, so you got to expose that whole tragal pointer, which is - you can see it there. It comes into a point, okay? That's the tip of it. So the - the location of the facial nerve is 1 cm anterior and inferior to the tragal pointer unless there's a tumor pushing it up from below - a deep lobe tumor - or it’s being distorted by the tumor. That’s usually where it is. The key is there - it is in the parotid gland, okay?
So to get there, you've got to cut the fascia of the parotid. The other way to do it is to follow the tympanomastoid suture line that - in the books, they say that is the most consistent landmark that you can follow - the tympanomastoid suture line down into the stylomastoid foramen. I don't like to do that personally because I just feel like it's too deep. The nerve is going to cross the parotid fascia, so you won't even have to get into the parotid. You can just dig down there and get to it, but it’s a - tends to be a deep hole down there. So I - that's - I - I don't know who does it - if the other - my esteemed colleagues do it that way, but I don't like to do it unless forced.
So the next point here is you got to find the - the digastric tendon, right? So this looks like a CM to me and some wonderful tissue planes. That's probably EJ there - going to cut it. So you got to elevate this off. There's digastric there, okay? Then you can just follow this digastric, and there’s only one thing that crosses the digastric, which is the common facial vein, anteriorly. And once you got the digastric, you can now do this dissection here very easily until you get all of this removed. Okay. And when you get to level of the digastric and the tragal pointer, which is here, you can feel the tympanomastoid suture, which is right there. Okay, then what you have to do is - now you know that the nerve is going to be about here, right? About a centimeter anterior inferior - and it's going to be at the level of the digastric in the parotid.
So the next move here is actually to go through the parotid fascia and just make sure that you can see everything, and I'll probably cut the nerve here but… Okay, so this just - oh see I just - did you see that fascia I just cut? It's all parotid fascia that's going to... Okay. So, it should be about right here, and all this is fascia, which you cut. Now there’s usually an artery that lives above that. I'm - I’m not sure what that artery is called. Does anyone know the name of it? I think it's right there. And that'll be a bother. It's always there. Okay. And that should - this should take you right to the nerve. I don't know if that's it or not. Okay, it’s either that, or it’s the artery.
So there's a structure here. In the cadaver, it's hard to tell whether it’s her artery or nerve, but - see that? It's kind of right where it should be. You can follow it forward a little bit to see if it is it. Okay. Looks like that's it. Okay, so that's probably the facial nerve there. Is there anything below there? No. Here’s the artery above it, okay? So this is probably lower division here. The pes, yeah.
So now, the tendency here is - is to just - once you see that, is to start cutting everything above it, but remember - it's a lateral dissection, so you want to make all your cuts inferiorly or superiorly. I've had most trouble with superior with the upper division and that forehead branch. That's hard because you have all these superficial temporal vessels that usually are deep to it, but there are - sometimes, there’s branches above it, so the best thing to do is instead of - I try to - tend to follow the superior most aspect. If this is your nerve, instead of dissecting this way - it's going up - I try to stay on that side of it - that way, so I can see it going superiorly, okay?
You can open all that up. Let’s see. I think the branch is going this way. You can see your - your superficial temporal vessels there, and then you would follow it the other way also.
So I’m going to take that. So there's the lower division there. You can see it right there. See, I'm just taking everything. So the other thing to remember is - and this is important - is that the lower division - particularly the marginal mandibular nerve - its relationship to the retromandibular vein and the posterior facial vein; it's always superficial to it, okay? So you - you got to look for that, and that - that nerve will go over the top, and you can see - I think this is - this is a vein here, and the nerves are going deep to this. You got to actually follow those nerves. Those ves - those nerves then divide these vessels above it. Okay. Let me just take it here. Hope I don't cut it here. Let’s see. So there's - this is probably platysma branch going down. This is probably the marginal branch going up, okay?
So then when you get to this point, I’m just going to do this for expediency's sake. I'm going to take all of these. There’s a big vessel there. I'm just going to go ahead and take this, okay? Because I want to get to the deep lobe. The dissection of the peripheral branches is pretty straightforward. So now - if you hold that out - the deep lobe anatomy is important, and you know, as I told Helen the other day, is whenever you're doing a parotid, you need to be prepared to do a total, okay? Depending on the pathology.
So, the first thing you do is you basically mobilize - mobilize the nerve, okay? Off. Just mobilize the nerve off all the soft tissue.
Then, you've got to control the superficial temporal vessels up here. You got to find the terminal branch of external carotid. It's best to find it low. I think it comes between - it's right here. Okay now, the - the point here is that the terminal branch of external carotid and the posterior facial - the retromandibular vein, again, go deep to the nerve. So, if you're doing a deep low parotid tumor or a parapharyngeal space tumor, you don't have to identify the facial nerve if you’re deep to those structures, okay? It's safe, but - and that's - that’s one way to look at it - superficial versus deep lobe - because deep lobe tumors are going to be deep to those vessels.
So you can dissect it out. You just got to follow all of the - and just detach all of the parotid from the posterior border of the mandible, here, and... There's the stylomandibular ligament and all of that stuff, but your deep - your deep part of your resection is your styloid, which is here, okay? And as you come across the front, the vessels you often forget about are the internal maxillary artery and vein, so you've got to find those, control them, take the artery here above and below, take the IMA, and then you can free up all the deep lobe off the styloid until you get to the parapharyngeal fat - and you just slide it under your nerves, okay?