Frontal Sinus Dissection (Cadaver)
Main Text
Table of Contents
The frontal sinus is a critical anatomical structure that frequently presents complex pathologies requiring advanced surgical intervention. Endoscopic frontal sinus surgery is a treatment method for a variety of conditions, including medically refractory chronic rhinosinusitis,1 mucocele,2,3 and neoplasms.4 Frontal sinus dissection (FSD) techniques, classified according to the Draf system, require a comprehensive understanding of the frontal sinus anatomy and the skilled execution of delicate surgical maneuvers.5 The frontal sinus recess is a complex three-dimensional structure that is significantly influenced by several neighboring anatomical features, including the agger nasi cells, frontal cells, nasal beak, anteromedial frontal sinus floor, attachment of the most anterior middle turbinate, and the nasal septum.6 Importantly, these surrounding structures exhibit a high degree of anatomical variability between individuals, presenting a substantial challenge for the operating surgeon. Frontal sinus structures are lined with a delicate mucosal lining, which adds complexity to surgical management. This mucosal lining plays a critical role in the normal physiological functioning and healing processes of both the frontal sinus and the entire nasal cavity. The preservation of this delicate mucosa is very important, as any unnecessary damage can lead to adverse outcomes, such as scarring and stenosis, which can significantly compromise the success of surgical interventions targeting the frontal sinus region. Complications arising from improper technique or unintended injury to critical structures, including the anterior ethmoid artery (AEA) and the cribriform plate, can also lead to severe consequences, underscoring the importance of thorough surgical planning and execution. Figure 1 illustrates a frontal sinus outflow tract on the sagittal CT scan.
Figure 1. Frontal Sinus Outflow Tract on CT.
This cadaveric study aims to provide a detailed overview of the key steps involved in the dissection of the frontal sinus, including the identification of anatomical landmarks, performing of Draf I, II-A, II-B, and III procedures, and the preservation of mucosal structures.
The FSD procedure begins by transitioning to curved instruments to optimize access and maneuverability within the frontal sinus. Hyperextending the patient's head improves visualization and accessibility. Using a 45-degree endoscope, the key anatomical landmarks are identified, including the boundaries of the frontal sinus outflow tract or frontal infundibulum.
The frontal sinusotomy is classified according to the Draf system, with the Draf I procedure being the initial stage.7 This relies on a thorough anterior ethmoidectomy, removing anterior ethmoidal cells down to the skull base. The suprabullar cells and agger nasi are dissected to create working space and visualize the frontal sinus outflow tract while preserving the frontal sinus mucosa.
Following the crushing of the agger nasi, a clearer view of the frontal sinus is obtained. In the absence of navigation, transillumination can help confirm entry into the frontal sinus cavity. The Draf II sinusotomy is subdivided into two main approaches: Draf IIA and Draf IIB. The Draf IIA procedure, described as "uncapping the egg," results in complete exposure of the frontal ostium. This is achieved by removing any frontal cells occluding the frontal ostium and recess, primarily involving the removal of the superior portion of the agger nasi to facilitate access to the frontal sinus. The Draf IIA approach aims to provide unobstructed visualization and access to the frontal sinus.8 Upon completion of the Draf IIA procedure, the subsequent step involves progressing to a Draf IIB frontal sinusotomy, further expanding the surgical access to address frontal sinus pathologies comprehensively. The frontal sinusotomy is extended from the orbital roof towards the septum, necessitating the removal of the vertical lamella of the middle turbinate. Careful attention is paid to the location of the AEA, which typically runs approximately one centimeter behind the frontal outflow tract when it is below the skull base.9
The unilateral Draf IIB frontal sinus approach has limitations due to the septum and orbit. In situations where this approach does not provide sufficient width for a patent opening, extending the procedure to the contralateral side is appropriate. The Draf III procedure, which opens the frontal sinus floor from orbit to orbit, becomes the next surgical option in such cases. This procedure aims to create a wide, horseshoe-shaped cavity from orbit to orbit.10 Saucerization removes obstructing bony septations, and a superior anterior septectomy is performed to resect the perpendicular ethmoid plate. Throughout the procedure, cold dissection techniques are favored over drilling to minimize mucosal damage and preserve as much mucosa as possible. However, in some cases, opening into the contralateral frontal recess may be impossible or unnecessary. In these instances, the Draf IIC approach can be applied. This technique is an extension of the Draf IIB, involving the opening of the occluded frontal sinus through the midline without extending into the contralateral frontal recess. This approach is preferred in the presence of an interfrontal septal sinus or an eccentrically located frontal sinus septum.11
The complex and diverse nature of frontal sinus anatomy poses a significant challenge for clinicians, often making adequate visualization and access to the affected areas difficult to achieve. The proximity of the frontal sinus to vital structures, including the orbit and anterior cranial fossa, increases the risk of complications during surgery. This anatomical complexity, coupled with the predisposition of the frontal sinus to postoperative scarring and stenosis, underscores the importance of tailoring the surgical approach to the unique needs of each patient. Surgical navigation systems, which provide real-time, three-dimensional imaging, have become indispensable in addressing these challenges. It revolutionized frontal sinus surgery by enhancing precision, safety, and outcomes. They utilize advanced imaging techniques, such as computed tomography (CT) and magnetic resonance imaging (MRI), to create detailed anatomical maps. These maps guide surgeons in real-time, allowing for precise localization and navigation within the frontal sinus. This precision is crucial in avoiding critical structures and ensuring complete removal of diseased tissue.The use of surgical navigation significantly reduces the risk of iatrogenic injury to vital structures. By providing accurate spatial orientation, these systems help surgeons avoid the optic nerve, dura mater, and other critical areas. This is particularly important in the narrow and variable corridors of the frontal sinus, where even minor deviations can lead to severe complications. Clinical studies have demonstrated that surgical navigation improves surgical outcomes in frontal sinus surgery. These improvements include reduced intraoperative blood loss, shorter operative times, and lower rates of postoperative complications. Additionally, the precision offered by navigation systems decreases the likelihood of requiring revision surgeries, thereby enhancing overall patient outcomes. Surgical navigation is especially valuable in complex cases, such as those involving extensive sinus disease, tumors, or previous surgical interventions. In these scenarios, the detailed anatomical guidance provided by navigation systems is critical for thorough and safe removal of pathological tissue, minimizing the risk of residual disease and recurrence. Beyond its clinical applications, surgical navigation serves as an excellent educational tool. It allows trainees to visualize and understand the intricate anatomy of the frontal sinus, facilitating better learning and skill acquisition. This educational aspect is vital for the ongoing development of surgical expertise in otolaryngology.
To summarize, the video presented here serves as an invaluable resource for both practicing surgeons and medical students. For practicing surgeons, this resource provides a valuable reference for navigating the various stages of FSD, from the initial Draf I procedure to the more complex Draf II-A, II-B, and III techniques. The meticulous identification and preservation of crucial anatomical landmarks, such as the frontal sinus outflow tract, the agger nasi, and the vertical lamella of the middle turbinate, are essential for avoiding complications, including injury to the AEA or inadvertent penetration of the cribriform plate.
By familiarizing themselves with the step-by-step approach outlined in this text and the accompanying video, surgeons can enhance their technical proficiency and improve patient outcomes in the management of frontal sinus-related conditions. For medical students and trainees, this video offers an invaluable learning opportunity to develop a deep understanding of frontal sinus anatomy and the nuances of endoscopic dissection techniques. By using this knowledge, healthcare professionals can enhance their surgical skills, improve patient care, and contribute to the advancement of the field of endoscopic sinus surgery.
Check out the rest of the series below:
Citations
- DeConde AS, Smith TL. Outcomes after frontal sinus surgery: an evidence-based review. Otolaryngol Clin North Am. 2016;49(4). doi:10.1016/j.otc.2016.03.024.
- Trimarchi M, Bertazzoni G, Bussi M. Endoscopic treatment of frontal sinus mucoceles with lateral extension. Ind J Otolaryngol Head Neck Surg. 2013;65(2). doi:10.1007/s12070-012-0611-9.
- Peng Z, Wang Y, Fang Y, et al. Precision endonasal endoscopic surgery of the frontal recess cells and frontal sinus guided by the natural sinus drainage pathway. Front Surg. 2022;9. doi:10.3389/fsurg.2022.862178.
- Banhiran W, Casiano RR. Endoscopic sinus surgery for benign and malignant nasal and sinus neoplasm. Curr Opin Otolaryngol Head Neck Surg. 2005;13(1). doi:10.1097/00020840-200502000-00012.
- Draf W. Endonasal micro-endoscopic frontal sinus surgery: the fulda concept. Operat Tech Otolaryngol Head Neck Surg. 1991;2(4). doi:10.1016/S1043-1810(10)80087-9.
- Dassi CS, Demarco FR, Mangussi-Gomes J, Weber R, Balsalobre L, Stamm AC. The frontal sinus and frontal recess: anatomical, radiological and surgical concepts. Int Arch Otorhinolaryngol. 2020;24(3). doi:10.1055/s-0040-1713923.
- Stucker FJ, De Souza C, Kenyon GS, Lian TS, Draf W, Schick B. Rhinology and Facial Plastic Surgery.; 2009. doi:10.1007/978-3-540-74380-4.
- Eviatar E, Katzenell U, Segal S, et al. The endoscopic Draf II frontal sinusotomy: non-navigated approach. Rhinol. 2006;44(2).
- Mohammed K, Komser A, Goldberg AN. Unilateral transnasal endoscopic approach to frontal sinuses: Draf IIc. Aller Rhinol. 2013;4(2). doi:10.2500/ar.2013.4.0058.
- Dubin MG, Kuhn FA. Endoscopic modified lothrop (Draf III) with frontal sinus punches. Laryngoscope. 2005;115(9). doi:10.1097/01.mlg.0000176542.59985.9f.
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Gotlib T, Held-Ziółkowska M, Niemczyk K. Extended draf IIb procedures in the treatment of frontal sinus pathology. Clin Exp Otorhinolaryngol. 2015 Mar;8(1):34-8. doi:10.3342/ceo.2015.8.1.34.
Cite this article
Brown CS, Abi Hachem R. Frontal sinus dissection (cadaver). J Med Insight. 2024;2024(161.3). doi:10.24296/jomi/161.3.
Procedure Outline
Table of Contents
- Anterior Ethmoidectomy
- Dissect Agger Nasi
- Identify Frontal Sinus
- Remove Superior Edge of Agger Nasi
- Ensure Identification of Frontal Sinus
- Cut Down Vertical Lamella
- Enlarge Frontal Sinusotomy
- Connect Frontal Sinus and Supraorbital Ethmoid
- Drilling Frontal Sinusotomy
- Superior Anterior Septectomy
Transcription
CHAPTER 1
Alright so, we're going to start by doing the frontal sinusotomy. Basically when you’re, when you're starting your frontal sinusotomy, you got to switch to curved instruments, and so keep that in mind. The other thing you can do is hyperextend the head of the patient, so that gives you better access to the frontal sinus. So what you want to do is go into the frontal sinus outflow tract or the frontal infundibulum, and this is bordered by... Sorry, I'm using here a 45-degree by the way. I'm in the left nostril. So just for you guys to get oriented, this is the inferior turbinate right there. This is your maxillary, and then looking up this is the middle turbinate that you see kind of sitting attaching to the - sitting on the septum. And this is the middle turbinate attachment. So the frontal infundibulum is bordered anteriorly by the back wall of the agger nasi. And then posteriorly, it's bordered by the frontal suprabullar cell. The anterior wall of the suprabullar cell. Laterally, it's bordered by the orbital roof, and medially it’s bordered by the vertical attachment of the middle turbinate.
CHAPTER 2
Frontal sinusotomies are divided by Wolfgang Draf into Draf I, Draf IIA, Draf IIB, and Draf IIC. So Draf I, which is the first stage of any frontal sinusotomy, is a good anterior ethmoidectomy.
So if you do a good anterior ethmoidectomy - you have to do a good anterior ethmoidectomy before you do your frontal sinusotomy. And the other landmarks that you want to keep in mind besides the one we've mentioned is the uncinate process and its attachment, because it will dictate where the frontal sinus drains, and as Dr. Ramakrishnan mentioned, the anterior ethmoidal artery, which is right there, and it's usually - it's one centimeter behind the frontal infundibulum - back wall of the frontal infundibulum. So here - looking here you have the skull base right there, and then you have like - kind of - you see how it goes down, so you have some anterior ethmoidal cells that Dr. Jiang left for us, so we can do the dissection. You can use any instruments that you like.
But basically we want to make sure that we remove all these anterior ethmoidal cells right there. So here I'm going to use the frontal curette to kind of dissect a little bit more the cells - oh, this is very... So here... So here we’re dissecting the suprabullar cells, and then you see again, you still have one cell here, for example, that you can dissect as well. So you want to skeletonize everything to the skull base. And, here you can see better, your - the anterior ethmoidal mesentery. Alright so, and then to dissect the agger nasi... One way of doing that is basically, you put your Kerrison here and usually it, it falls down, and you can bite. And what you're biting here at the middle turbinate attachment is the agger nasi. And that will give you also space to work and to see what what you're doing so... What you want to keep in mind is that this is the - here you have the bulla, the suprabullar cells, and then the frontal sinus outflow tract is going to be actually medial to the suprabullar cells. So I'm suspecting that it's right there, and if I'm dissecting here I usually use two fingers. I don't go with my full force hands, because you know, you're close to the skull base. Just going to clean up these cells.
Agger nasi. This is the suprabullar, and then I suspect that my frontal sinus will be... If we go through here... Yeah, you should always study your scan, study especially study it before doing any frontal sinus dissection. So alright, so there it is. So this is the agger nasi. This was the suprabullar cell, and you can see where your frontal sinus is going to be right there. So it's medial to it. Then you have this - this is and now you can see it very well. Your frontal - frontal sinus is going to be here. This is the back wall of the frontal sinus, which is another landmark that you use. You got to make sure that you preserve the mucosa when you're dissecting the frontal sinus so - because the frontal sinus is very prone to scarring, so you want at least preserve that back wall mucosa and the medial one, and usually you can, you can try - you have to try and preserve preserve it circumferentially, but…
CHAPTER 3
Now we're going to basically crush the agger nasi anteriorly, and we have a better view of the frontal sinus, and you can see it here.
So another way of of knowing that you're in the frontal, if you don't have navigation is when you open up the frontal sinus, if you transilluminate it and you see that the transillumination is going to the medial canta - medial canti, it means that you are in the suprabullar or the agger nasi. But if it's transilluminating the forehead - here it's not because the, the cadaver has a darker skin coloration. So, usually the forehead should transilluminate to know that you're in the frontal sinus. Now that we uncapped, we removed the superior edge of the agger nasi; that's our Draf IIA. It's also called uncapping the egg, meaning removing the superior aspect of the agger nasi and and that gives you this frontal sinusotomy right there. You can see it. This is the anterior wall. This is the forehead. Opps, a little bit of blood. And so your next step will be to do a Draf IIB. So the Draf IIA, your boundaries are the vertical attachment of the middle turbinate medially, the orbital roof laterally, the back wall of the frontal sinus posteriorly and anteriorly it's going to be the frontal beak the nasofrontal beak. Sorry the - the vertical - the attachment of the vertical lamella also.
CHAPTER 4
Now if you want to do a Draf IIB, then basically you're extending your frontal sinusotomy from the orbital roof towards the septum. So you got to remove the vertical lamella of the middle turbinate, and so looking here at this frontal sinusotomy, the other thing that you kind of notice is the relationship of the anterior ethmoid artery, which runs - which runs posterior anterior from lateral to medial. It's always oblique in this fashion, and you can see it's usually one centimeter, almost one centimeter behind the frontal infundibulum.
So what you want basically is to enlarge this further. We can enlarge this further. But the other thing that you want is again, extend your frontal sinusotomy from the orbit to the septum, so you want to cut down the vertical or the anterior third of the vertical lamella of the middle turbinate. And so, you want that middle turbinate level be at the same level of as the back wall of the frontal sinus. So you got to remove all this. And one way of doing it is basically... Is there a lesser turn? Cutting - cutting through the vertical attachment of the middle turbinate. So what you can do is use what I was using, the lesser of curved one, and then you make your vertical cut all the way to the back wall of the frontal sinus. And then you make a cut here, and then you have this vertical lamella, and you can take out the small piece of mucosa from it and use it as a graft for your frontal sinusotomy, or you can just bite through the vertical lamella. So we’re biting through that vertical attachment, the anterior third of it, at least. You want it to go all the way back. All the way back to the back wall - to the posterior wall of the frontal sinus. Then you can clean it up. So, it looks like you have an intersinus cell here. Sort of. So you can connect that with the rest of the frontal sinusotomy.
I love the frontal sinus punch for... So see how the opening is being extended anteriorly and medially, right? Because it’s starting to - you’ve got to start going towards the septum. That’s right. But the thing is that the skull base is rounded, so you have to come somewhat anteriorly. If you just go directly, medially you’ll get into the skull base. So you’re trying to make that the half of that horseshoe shape you typically see after IIB. That’s right. So like, for example, you can see the back wall of the frontal sinus, which corresponds to the skull base and then, and so it's a horseshoe shape, meaning that as Dr. Jiang said, meaning that it bulges anteriorly and then goes goes back posteriorly. Here you have a supraorbital extension of ethmoid cell. Usually this is associated with the dehiscence of the ethmoid artery. So, the other mistake that you can do is when you have a supraorbital extension is that you think you're in the frontal, and then you start crossing over to the other side to kind of widen your frontal sinusotomy, and then you will hit the cribriform plate because you're all the way posteriorly, and I've seen that happen. We're almost done with our Draf IIB here. You guys should have the angled - the curve punches and the Kerrison. So it’s good to use that, when you can. Sometimes you have to drill, but if you don’t need to then don’t. Because drilling destroys a lot of the mucosa. It does, and it heats it up, and it stimulates osteoblast and osteoneogenesis. So, I mean, you look at this frontal sinusotomy and it's wide and big and then you see them back in clinic like a month and it's a pinhole. Alright so we'll keep doing it with cold dissection. So you want to preserve as much as you can mucosa. If the mucosa is floppy don't micronebriate it, just let it sit back here.
Again, we see our anterior ethmoidal artery. Alright so... So now I connected this frontal sinus with the supraorbital ethmoid, and basically what we're going to do is clean up.
CHAPTER 5
And then our next step would be to do the Draf III or endoscopic modified Lothrop procedure and connecting the two frontal sinuses together. And so your landmarks for this will be the middle turbinate of - the vertical lamella of the middle turbinate. Again the back wall of the frontal sinus, the septum, and the nasofrontal beak anteriorly. And, basically you can - there's three ways of doing this. You can go trans-septal into the frontal sinus. If you don't have any landmarks, sometimes you don't have any landmarks, you go trans-septal. There's also what we call supraturbinal, meaning going through this, the attachment of the vertical of the middle turbinate. And it's also called outside-in, meaning you start going from outside into the frontal sinus. Or the most popular form is you identify the frontal infundibulum, and on the side where you can identify it, and then you go from known to unknown. So you start going from this side, and you cross over through the septum to the contralateral frontal sinus. And we usually do this Draf III when you really have either very bad polyps centers, revision revision or you know like, or for skull base procedures, skull base resections. Alright so, here we started drilling our Draf III, and so what you want to do is saucerize basically, just like a mastoid. You want to drill all these bony septations that kind of occlude your vision. And your goal is going to be to create a frontal sinusotomy from orbit to orbit and from cribriform to the skin basically. You can - you can go all the way up to the skin, and so it's a horseshoe-shaped cavity as we said before. This is the cribriform. You can see the cribriform kind of peaks a little bit anteriorly from the back wall of the frontal sinus. Some people use the olfactory fiber as a landmark for their posterior dissection and so the olfactory the first olfactory fiber is going to be somewhere around here. And the safest way of drilling in a frontal is or basically kind of widening it is anteriorly because - towards the skin. One of the other things that you want to do when you're doing a Draf III is your superior anterior septectomy.
So your septectomy - your superior septectomy has to go all the way back to the frontal - to the back wall of the frontal sinusotomy. And so one easy way of doing this is just take this light frontal sinus probe, and you put it all the way up at the level of the back wall and you know that you have to take all this as a frontal. Wait how far anterior do you move? So you can go all the way anteriorly - all the way anteriorly. It’s just - it’s like mostly you have to remove, you have to do an anterior superior septectomy, and it has to go all the way posteriorly to the back wall of the frontal sinus or the cribriform basically or the - so what you're - the septectomy or basically what you're resecting here is the perpendicular plate of the ethmoid. You have to resect it all the way to the back wall of the frontal sinus, and then you don't have to go all the way down. You know, don't do a complete septectomy, just do a window kind of. So you can use your probe and that you put the probe at that at the level of the cribriform plate or the back wall of the frontal sinus here, and that kind of gives you an estimate on where you have to go. So it kind of delineates it like that. And there are multiple ways of doing your septectomy. It’s a destructive procedure. You can also save the mucosa and use it for grafting, if you can.