 Thank you very much for the invitation and for the next 30 minutes I'll be discussing the preoperative CT checklist for functional endoscopic sinus surgery. I want to acknowledge the following individuals for contributing to this talk. First of all, Varsha Joshi from India for some of the slides. And also I'll be heavily referencing this excellent paper by O'Brien it out, which was published in radiology, which is called title avoiding a close call with surgical complications. So in this paper, they fairly elegantly identified a preoperative checklist that's referred to as close C L O S E. In my practice, I think this is very helpful and what I've done is I've expanded this a little bit and called it closed. And the close for our checklist will be the cribiform plate, the lamina paprecia, the osteomatial unit, the anointy cell, the sphenoid sinus, the ethmoid diseases, excuse me, ethmoid sinuses, and then various diseases that can involve the perinatal sinuses. So first we'll start with the cribiform plate. We know that the cribiform plate is located in the anterior skull base, and it's a very thin bone with small perforations that allow the first nerve to provide its small little neuro fibrils to extend through the cribiform plate to innervate the nasal cavity. So when we look at the cribiform plate, it's important to understand the adjacent anatomy. So this area right here is the phobia ethmoidalis. This area laterally is called the lateral lamella. There's a small little defect here in the lateral lamella, which you will sometimes see and we'll discuss this later, which is the anterior ethmoidal artery. And then the floor of this is in the cribiform plate. And this is our crystal galley. Now, when we look at the cribiform plate, realize that there are various depths of the cribiform plate that can potentially come into play. And this has been categorized by the carous classification. So a carous one is when you have a depth of the cribiform plate, so basically the height of this from the lateral lamella is less than three millimeters. This is a type one. If it's between four and seven millimeters, it's a type two. And if it's between greater than seven millimeters, it's a type three. So I do not include the carous classification my report, but what I do do is it forces me to look at the anterior skull base, and specifically to look at the cribiform plate. So although I don't mention the carous classifications I specifically look at the anterior skull base. So here is normal on the left hand side and this is an example of a normal development variation involving the anterior skull base. Now this was just in this particular case, just a normal variant with a little bit of the gyrosis rectus extending inferiorly. Notice how the cribiform plate is intact. So in this case, this is normal gyros, but you have to realize you can have other masses that can arise in the olfactory groove in the olfactory sulcus that could potentially give you this regressive remodeling. So first of all, it forces you to look in this area. The only thing that it forces you to do is to look for any defects in the anterior skull base. So this is normal on the left hand side. But for instance, if you saw this mass here involving the right nasal cavity you may think it's polyporting because of thickening because there's disease adjacent to it. But by forcing you to look at the anterior skull base, you can see that there's a defect in the anterior skull base. And what we can see is that in this particular case, there is an encephaloscele that's extending through the anterior skull base into the nasal cavity. So certainly you do not want to send your surgeons in to resect in this case an encephaloscele. The next area when we talk about closed is the lamina perprecia. Now we're all familiar with the lamina perprecia. It's a very, very thin paper-like bone that forms the lateral wall of the ethmoid sinus and the medial wall of the orbit. Again, very, very thin bone. And it's important to look at this bone specifically to look for certain pathologies. So in this particular case, if the patient was pre-op for endoscopic sinus surgery, we would want to tell the ENT surgeons that there is a defect involving the lamina perprecia. And this is due to medial deviation. And in this case, prior fracture that has allowed for herniation of the fat and a little bit of the muscle into this defect. So this is a medial blowout fracture. And this would be part of our checklist when we evaluate the lamina perprecia. The next O that we talk about is the O for the osteomyatal unit. So let's go over the anatomy of the osteomyatal unit. So here's a normal maxillary sinus. Here's our alveolar recess. Here's our zygomatic recess. And here's our primary osteoma, the maxillary sinus. This is continuous with the ethmoidal infindibulum, which continues in superiorly. Eventually, it ends into the hiatus semulunaris, which runs from anterior to the posterior. The floor of the ethmoidal infindibulus formed by the unsinate process. Eventually, when the drainage gets right here to this hiatus semulunaris, it extends inferiorly into the middle meatus. And right above it is the middle turbinate and the middle concha. So the osteomyatal unit is formed by the primary osteoma and maxillary sinus, the ethmoidal infindibulum, the unsinate process, the middle meatus and the middle turbinate. And that is what's typically resected during a standard functional endoscopic sinus surgery. So on CT scan just to confirm. Here's the primary osteome. Here's our ethmoidal infindibulum. This is the unsinate process. This is the middle meatus. And here's our middle turbinate. So we have to evaluate the osteomyatal unit very closely in all of our studies. And we have to be aware of some of the normal variants that could potentially lead to narrowing of specifically the ethmoidal infindibulum and then potentially result in mucosal thickening. So this is an example here of multiple howler cells. What howler cells are are aerated in, I should say, formed in for orbital air cells that oftentimes track along the primary osteome and the ethmoidal infindibulum. This is the classic example of a concha bolosa. So here we have air involving both middle turbinates. This is these are concha bolosa. Occasionally we could have paradoxical rotations of the middle turbinates. So normally the middle turbinates or the inferior turbinates are typically extending outward, if you will. Here what we can see is that there's paradoxical rotation of these middle turbinates. So we want to comment here because if they are large enough. They can again push against the middle myatus or potentially have mass effect involved in the medial wall of the maxillary sinus and potentially impinge upon the ethmoidal infindibulum. And then finally, we always want to look for the integrity and the course of the normal nasal septum. So in this particular case we can see that there's a nasal septal deviation to the right and this is associated with the spur. Occasionally patients can, when they have the spur that abuts the middle turbinate, this can cause headaches. And this is sometimes referred to as sleuters headaches. And if we see this appearance in a patient that has the classic symptoms, then these can be treated by some type of nerve block or some type of anti inflammatory or a neuro, an agent that somehow blocks the plexus, the tyrogl-palatin fossa and sphenopalatin foramen. The next thing that we'll talk about are the onoity cells. So when we look at the onoity cells there are specific type of cells. So on the left hand side is the normally aerated sphenoid sinus and typically you can have some septations within the sphenoid sinus. On the right hand side, we can see a class of example of sphenoethmoidal air cells and these are referred to as the onoity air cells. Now the onoity air cells are referred to as sphenoethmoidal air cells and they are located superior lateral to the sphenoid air cells. So when we look at the sphenoid sinus, the SS here is a normal appearance of the sphenoid sinus and then just above it are other aerated air cells. And these are the posterior ethmoidal air cells and these are the onoity air cells as we see here. Notice the onoity air cells in this case are in close proximity to the optic nerves. In fact, the optic nerves are running through the superior lateral aspect of these air cells. Now during an endoscopic sinus surgery, it's important to make the surgeons aware that there are sphenoethmoidal air cells or otherwise known as the onoity air cells. Why? Because it's possible that the surgeon may confuse a sphenoid air cells with the onoity air cells and this predisposes these patients to optic nerve injuries. Another example here, this is a patient that has sphenoethmoidal air cells and when we look superiorly, we can see mucosal thickening here involving this superior air cells and this is complete opacification of an onoity air cells. And again, this can be very difficult to see. The surgeons typically comes through the sphenoethmoidal recess. They think that this is the roof of the sphenoid sinus. But in this case, there's a small onoity air cell that's completely opacified. So the next year that we'll talk about is the sphenoid sinus and the sphenoid bone. So the sphenoid bone really, it took me a while to figure this out, but the sphenoid bone has lesser and greater wings. It has a body and it has pterogoid plates. So again, when I grew up, I would always think about the sphenoid sinus in the axial plane, but we have to realize that the sphenoid sinus originally got its name by looking to this in the coronal plane. So the sphenoid bone is a wedged bone that is located between the clivus and other components of the central skull base. And when you look at the sphenoid sinus, you can almost make out that there's a wing here, a lesser wing, and there's a greater wing. So it sort of looks like a bird. On the other hand, there's a greater wing and there's a lesser wing. Here is the body of the bird or the sphenoid sinus. We have one foot here. This is the medial plate. Another foot here, which is a lateral plate. This area is a cell and here's a dorsum cell. So if you think of the sphenoid sinus as a bird, then for me, it made the sphenoid sinus seem a lot more simple. So when we look at the sphenoid sinus, this is what it looks like in the sagittal plane, and we know that the sphenoid bone has a sinus within it. So when we look at the sphenoid bone and the sphenoid sinus, here is our cell, here's the dorsal aspect, here's the anterior aspect, and there's where our pituitary gland lives. So when we look at the sphenoid sinus, it can have levels of progressive numinization. So in this particular case, this is anterior numinization of the sphenoid sinus. This is referred to as conchal numinization. It's the anterior third. Then you can have pre-cellar numinization. In this case, the numinization extends to the anterior aspect of the cell. And then you can have complete aeration of the cellar. Now this is important prior to endoscopic sinus surgery, but also if this patient did have a pituitary adenoma and the patient underwent a transfenoidal resection, it is important to comment on the level of aeration involving this sphenoid sinus, because this type of surgery would be much easier to get to the floor of the cellar. Similarly, once they got to the cellar, this would require much more packing to ensure that to prevent leaks here because this leak could go directly into that sphenoid sinus. The sphenoid sinus, once it is heavily pneumatized, it can put other neural and vascular structures at risk. This is an example of an incredibly well aerated sphenoid sinus. These arrows right here point to v2, and the hatched arrows point to this nerve right here, which are the bilateral vidian nerves. Here's an example of v2s that impinge upon the superior lateral wall of the sphenoid sinus. Excuse me, sorry about that. Here's the v2 right here that's along the lateral wall of the sphenoid sinus. This little septation right here that sometimes you see in the sphenoid bone, this little septation often tells you where the carotid artery is. So in this particular case, I messed up a little bit. This little septation goes to the carotid artery, and right here is v2 on one side and there's v2 on the opposite side. Here's an example of carotid arteries that impinge in the posterior lateral aspect of the sphenoid sinus. We have to let our surgeons be aware of this because if this was disease and they were going in to do an endoscopic resection, a functional endoscopic sinus surgery into the sphenoid sinus, they would want to make sure that they're aware of the carotid artery impinging upon the posterior lateral walls of the sphenoid sinus. And in this particular case, this patient has optic nerve, the right optic nerve is actually extending inferiorly into that sphenoid sinus. So just to reiterate the anatomy very nicely seen here, this is Vidian's canal, this is v2, this is the superior orbital fissure, this is the lesser wing of the sphenoid sinus, and here's our optic nerve on the right and an optic nerve on the left. Well, the next thing that we'll talk about when we talk about closed is that we'll talk about the ethmoid sinuses. So the ethmoid sinuses are divided into anterior, middle, and posterior ethmoid air cells. In some textbooks, they combine the anterior and the middle ethmoid air cells into the anterior ethmoidal complex and the posterior ethmoidal complex. This lateral attachment involving the bone at the very posterior aspect of either this anterior ethmoidal complex or what I more commonly refer to as a posterior aspect of the middle ethmoidal air cell, this is what's referred to as the basal lamella. So here's the basal lamella on the patient's left and this is the basal lamella on the patient's right. When we look at the sagal images, you can see the basal lamella right here very nicely identified. Now there are a couple of unique air cells that we need to be aware of. The agronasi air cell is the most anterior ethmoid air cell, and it forms the anterior boundary of the frontal recess. So the agronasi air cell is an ethmoid air cell that extends anterior to the frontal recess, and we can see here that it's aerated. Occasionally the agronasi air cell can become enlarged or opacified, and this can obstruct the frontal recess. So the frontal recess is the primary drainage of the frontal sinus, and if this becomes obstructed, then this can result in narrowing and eventually result in mucosal thickening involving the frontal sinus. When we look at the ethmoid air cells, there are different types of frontal ethmoidal air cells. The type one air cell is just a standard frontal ethmoidal air cell that extends anterior to the frontal recess, so this is a type one. If you have multiple anterior ethmoid air cells, but they're still below the level of the frontal sinus, then this is referred to as a type two. A type three ethmoid air cell is when this agronasi air cell extends superiorly into the inferior portion of the frontal recess, and the type four is when this agronasi air cell or this ethmoid air cell extends and is isolated to the frontal recess. Now I have to admit I do not comment on these in my standard reports, but just for completion's sake, this is a complete evaluation of these frontal ethmoidal air cells. The next E that we talk about when we talk about closed is the ethmoidal artery. So when we look at the anterior skull base and we talked about this earlier just to review the normal anatomy. This is the phobia ethmoidalis, it's located here. This is our ladder lateral amela. This little defect right here is the groove for the anterior ethmoidal artery. Here's our cribiform plate. This is our crystal galley. And right where my arrow is is where the olfactory groove runs, and just above it is the gyrus rectus. So this agile images identifies the the anterior ethmoidal artery as it runs in the groove involving the anterior skull base. In the anterior case, this is a normal appearance. This is an example of air rated ethmoidal air cells extending along the phobia ethmoidalis, and we can see that it's actually impinging on the groove for the anterior ethmoidal artery. This would be important of these row pacified and the surgeons were trying to resect this, they would want to make sure that this is running in close proximity to the anterior ethmoidal air cells. The last thing that we typically talk about is the D, which is the disease. So it's important to be familiar with the various tips different types of diseases that can involve the sinuses. Now I'm just going to spend a couple of minutes on this because this really is on a checklist prior to functional endoscopic sinus surgery, but I will talk about a little bit of the different diseases. In this particular case, this patient had fever and had pain involving sinus and here we have an air fluid level. So this is an air fluid level involving the right maxillary sinus. Please do not call this acute sinusitis sinusitis is a clinical diagnosis, it is not a radiological diagnosis. So in this particular case, if you see an air fluid level what you can say, as these findings are consistent with the clinical diagnosis of acute sinusitis so this is the classical appearance radiologically of acute sinusitis, but realize that this again is a clinical diagnosis. Here's an example of a completely opacified maxillary sinus, and with a leap of faith you can see that there's thickening this is what we refer to as reactive osteitis, involving the posterior wall of the right maxillary sinus compared to the side on the opposite side So this is more consistent with chronic disease again, we can suggest it's chronic sinusitis but again it is a clinical diagnosis. So finally here's an example of chronic disease it's completely opacified, we can see the reactive hyperostosis, but we can also see that this sinus is small and it shrunken. So this is a hypoplastic maxillary sinus. These are oftentimes associated with enlargement of the orbit, and sometimes inferior displacement of the inferior wall of the orbit. And this is what we refer to as silent sinus disease. Here's an example of invasive fungal sinusitis. So we look at invasive fungal sinusitis. Sometimes this can be very tricky to see, but I'm going to point out a finding to you that hopefully you won't forget, because if you have someone that's at high risk, some that's diabetic, or other types of immunocompromised sometimes these sinuses are going to be completely well aerated. But where to look at is in the fat, either the fat anterior or posterior and specifically in this case, in the retro anthral fat. Notice how the retro anthral fat is not black as it is on the opposite side there's subtle areas of increased attenuation. This is early invasive fungal sinusitis this is the bad one this is mucormicosis or invasive fragilosis. Similarly anteriorly we can see subtle evidence of extension into the canine fossa, not as obvious as posterior, but please be sure to look at this when you're evaluating patients for sinus disease. This is an example of what looks relatively aggressive but the key thing here is this is a non contrast CT. And when you have a non contrast CT and you see areas of increased attenuation, purely on a non contrast study. This is allergic fungal sinusitis this is not invasive fungal sinus sinusitis this is allergic fungal sinusitis, and this can involve multiple perinazle sinuses, it can involve the nasal cavity. It can give you this bone erosion but this really is just benign disease. This can be resected. This can be easily the surgeons say that this almost has a peanut buttery or toothpaste consistency to it, and then patients are oftentimes treated with some type of mild anti fungal or steroids. And then we also want to be aware of incidental finding so this example was a small little assioma involved in the media aspect of the right frontal sinus. So what I tried to do over the last 25 minutes or so is talk about the checklist to evaluate patients prior to functional endoscopic sinus surgery. And I use the term close CL O O SED and just to reiterate the cribiform plate, specifically to look for encephaloceles lamina propretias specifically to look for herniation of fat into the nasal cavity. We always want to evaluate the osteomyatial unit. The onoity air cells can be a fuller because they can mimic the sphenoid sinus when the surgeons are performing endoscopic sinus surgery. We always want to talk about the sphenoid sinus talk about the ethmoid area including the ethmoid air cells and the ethmoid artery. And finally, to talk about various diseases involving the perinazle sciences. Thank you very much for your attention.