Ethmoid Artery Anatomy
Dr. Ramakrishnan explores a cadaveric ethmoid sinus to identify clinically relevant arterial anatomy for the ENT residents at Duke University Hospital.
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- Anterior and Posterior Ethmoid Arteries
- Identify Frontal Recess
- Identify Posterior Ethmoid Artery
- External Approach
So the anterior ethmoid artery - obviously, the most important reason that you talk about it or think about it is in surgical preparation, when you're doing your preoperative CT scan analysis. That's one of the things on the checklist to check for - where that artery is and is it hanging down from the skull base or not because it can be injured during your anterior ethmoidectomy, and it - in about 20% of cases, it's - it's dehiscent or hanging down below the skull base, b - so most of the time, it's going to be within your skull base. The other reason that it's important is if - again, intractable - intractable ep - epistaxis patient that you feel like the bleeding is coming from this area as opposed to posteriorly, you can do anterior ethmoid artery ligation, and then sometimes you'll have malignancies in this area where, again, you're going to need to get control of this artery to devascularize that tumor.
So David, again, has done the ethmoidectomy for the most part here. This is the frontal recess here, which I'm going to leave alone, but - oh, the other reason that the artery’s important is because that's going to be one of your boundaries for the frontal recess dissection. And so - and it's going to be the posterior boundary. And so, again, David's kind of done the dissection here already - so pretty easy to see that artery right there, but when you're doing surgery, you've done your - your sphenoidotomy back here, and you're working from posterior to anterior, and you're using your curette and up-angled instruments to take down these ethmoid cell partitions and - and identifying your orbit and making this look nice and pretty, as you start to come to this area and approaching the frontal recess, that's where you need to look for the artery. And a mentor had told me at one time: one way you can think about this artery is like the facial nerve when you're doing a parotid. And so obviously, you don't want to injure it, but you - don't be afraid of it. It's a good landmark. Identify it, and use that to help you identify that posterior border of the - of your frontal dissection.
And so there it is right there, and the - let's look at the posterior ethmoid artery real quick. Posterior ethmoid artery is rarely an issue in s - in - in just endoscopic sinus surgery. It can be - it is another artery that you're going to want to get control of if you're doing a skull base resection or a malignancy back in this area. Rarely, if you have a patient who has extremely hyperaerated sinuses, rarely, you - this artery can be dehiscent and hang down in the sinus and - and could be injured, but typically, it's going to be j - essentially, in front of the sphenoidotomy. So here's the face of the sphenoid plane right here, and right in front of that, you're g - you’re probably - this mucosa was up here. You’re prob - in order to see it, you’ll probably need to take that mucosa down, and you'll be able to see that running through the posterior ethmoid right there.
If you want, you can kind of take the lamina down and expose this more intranasally. If you have a epistaxis patient where you're trying to control this artery - that is a procedure that's been described to do this endoscopically - is essentially identify the artery here, open the lamina here, and actually cauterize the artery on the orbital side, which I've never done that before because I think it's - it's a little crazy to do because of the risk of CSF leak. And usually, the shape of that person's nose when you get them into the operating room is not good, and so this is a lot easier because there's no bleeding right now. But basically, take down this part of the lamina, and isolate that artery - and you can clip it or cauterize it as the endoscopic way.
To me the - the more effective and - and pragmatic way is with an external approach, and it's a lot quicker, a lot safer, and you can do that with either using the old school Lynch incision, you can do an upper lid bleph approach, or you can do a transcaruncular approach. I don't do this often, but I - I prefer the upper lid bleph approach, which heals very well. So here, what I've done is I've just made an incision probably a lil - in a - a little bit longer and - and higher than I normally would, but just - just cut into the upper lid.
You're going to go through the skin. You're going to go through the orbicularis and the orbital septum. You’re going to get to this medial fat pad, and you're just going to reflect the fat pad medially. And you're going to identify the medial orbital wall here, and we're going to be behind - this is the level of the lacrimal sac here. So we're going to go in behind that posterior lacrimal crest, and we're going to get underneath the periosteum. We're going to elevate that back and get the same view of the artery but from - from laterally, and you can see, you know, it's a - it's a little bit easier to expose than endoscopically. There's going to be less bleeding. And so here you can put that artery on a stretch and clip it or cauterize it, so I prefer that approach for that. And then of course, you can elevate this all the way back and find that posterior ethmoid artery, optic nerve, and - and optic canal.