What is sinusitis?

- [Voiceover] So, what is sinusitis? Before we can answer that question, we should talk a little bit about anatomy. So, here I've drawn a couple faces, and we're going to superimpose the sinuses on these faces. So, the largest sinuses that you have in your face are called the maxillary sinuses, and they live on the side of your nose here, right underneath your eye. If you tap on that bone right underneath your eye, your cheekbone, you're tapping on the frontal wall of the maxillary sinus. When you're looking at somebody from the front, this is what they look like, and maxillary sinuses from the side are located about right here. So, another set of sinuses lives at the top of your nasal cavity, and it's composed of multiple little air cells, multiple little bony chambers that are filled with air. These are a little bit irregular, and everybody's are a little bit different, but they kind of look about like this. There's usually two layers or so of them, and these are called the ethmoid sinuses. These are also known as the ethmoid air cells. Right behind the ethmoid air cells, and deeper back in your head, is a pair of larger sinuses called the sphenoid sinuses, and they live about right here. And another set of sinuses lives in your forehead, about like right here. It's kind of variable in shape, but kind of looks about like this, and these are called your frontal sinuses. And altogether these are known as the paranasal sinuses. The reason for that is because they're located adjacent to your nasal cavity, and the nasal cavity, as you might guess, sits right in the middle of your face, right about here. Now your paranasal sinuses and your nasal cavity are all lined by a layer of tissue called mucosa, and that mucosa is contiguous throughout your paranasal sinus and nasal system. In other words, the same mucosa lines everything, and because of this fact, sinusitis is probably more accurately termed rhinosinusitis. And in the medical literature, it's referred to in both ways. So, quickly I'd like to show a real example of this anatomy by using a CAT scan. So, I'm going to label some of the structures here on these two images of an actual patient's CAT scan. The first image is a coronal image, which means it's like we're looking at a patient's face directly on. The second one is an axial image, and that's like we're taking a slice through the patient's sinuses here and looking only at that slice. So, just like in our cartoon drawing, we have the maxillary sinuses here under your eyes. We have the ethmoid air cells. We have the nasal cavity. And on our axial image here, you can see the maxillary sinuses here and the nasal cavity here, and the nasal cavity extends all the way forward. So, you can see it going out towards the patient's nose. So, we'll go back to our cartoon. And now that we have a good grasp of the anatomy involved, we can talk about what exactly rhinosinusitis is. So, the definition of rhinosinusitis is inflammation in one or more of these cavities. Let's say, for instance, that the sphenoid sinus in this patient in this cartoon is inflamed. So, that mucosal tissue that lines that sphenoid sinus is going to become red and irritated and inflamed. And the first thing that most patients notice is going to be pain. Now, that pain can be localized to the sinus in question, but it can also produce general pain, particularly in the case of the deep sinuses, like the ethmoid air cells and the sphenoid sinuses. That may just cause headache. With maxillary sinusitis, you can actually feel the pain in that particular maxillary sinus. In fact, if you tapped on it with your finger, that could produce tenderness. And another thing that happens when you get inflammation of the mucosa is that mucosa produces mucus, as you might expect. So, going back to our sphenoid sinusitis here, we will draw in a fluid layer here of mucus that's being produced, and that mucus has to go somewhere. And all of these sinuses are connected by little holes to the nasal cavity, and the purpose of those connections is to actually allow things to drain out. So, that mucus that's produced is going to drain out into the nasal cavity. Now, there's really only two things that it can do, once it's in the nasal cavity. The first thing is to come out of your nose. So, people will notice nasal discharge. So, the other place that mucus can go is down into your throat. So, the back of your nose is connected with the back of your throat, and as that mucus leaks down into the back of your throat, it's irritating there as well, and that will cause you to cough, and when you lie down, it's particularly bad, and so the cough is often worse at night when you're trying to sleep. Now, sometimes the inflammation is bad enough that patients will get a fever. That's not always the case. You can certainly have sinusitis without having a fever, but it is one of the reported things, and it tends to happen more often in cases that are worse. And this inflammation in the mucosa can also alter the way your body smells and tastes things. Let's move this down, to give ourselves a little bit of space to write here. So, what are the causes of sinusitis? In adults, the vast majority of cases are caused by viruses. In fact, more than 98 percent of them. The remaining two percent are usually caused by bacteria, the common types of bacteria being Streptococcus pneumoniae, Haemophilus influenza, often abbreviated H. flu, and Moraxella catarrhalis. There's a small population of people that can get fungal disease. That's not as common and tends to only happen in people who are immunosuppressed. There are some predisposing factors that make it more likely that you'll get sinusitis. If you have allergic rhinitis, that could make it easier for an infection to take hold. If you're exposed to cigarette or cigar smoke, either firsthand or secondhand. And there's certain anatomic variants that make it harder for sinuses to drain. Like if the hole to one of the sinuses that leads to the nasal cavity is a little bit small, or if it's blocked by an extra large air cell, that can be a set up to get an infection. So, let's go back to a CAT scan. This one's a little bit different. This time, the patient has acute sinusitis. Here you can see in the maxillary sinus this liquid that's layering at the bottom here. You can see the fluid, and you can see sitting in the top, these little round bubbles as well. So, this is kind of a frothy fluid sitting in here. That's a definite sign of acute sinusitis. You can also see some fluid up here, in the ethmoid air cells, and a little bit of fluid sitting in the nasal cavity as well, but not a lot. You can also see some mild mucosal edema. I'll outline that for you here and here. Sometimes the mucosal edema can get so bad that it will fill up the entire cavity. This particular patient, it's not so bad. But the fact that you can see it at all, at least in the maxillary sinuses and ethmoid air cells, means that it's inflamed. So, we're going to move this picture up a little bit, and we're going to use it to illustrate some of the potential complications of sinusitis. Now, most of the time sinusitis is a self-limiting disease. The viral type will go away on its own, after a period of time, but the bacterial type tends to be a little bit more aggressive. So, you can see these structures in your face are really located in a pretty central and important area, and the complications of sinusitis are all related to spreading infection. So, there's lots of important bones here. So, if this infection was to spread into the maxillary bone, here for instance, or if it was to spread into here, that complication is called osteomyelitis, and that just means infection of the bone, and that can be a very difficult infection to treat. Let's say this infection traveled from the ethmoid air cell here, through this very thin bone, and then spread into this cavity here. Of course, that's where your brain likes to live. That's inside your skull at this point. So, now we're talking about an intracranial abscess, and, of course, that's a very major complication. That can cause all sorts of problems with the brain, if it gets up into the brain. If the infection spreads out into the soft tissues here, or here, or basically anywhere else, that is termed cellulitis. If the infection spreads this way, through the ethmoid air cells, into this cavity, that's your orbit. That's where your eyeball lives. That can be a super severe complication too. That can cause an intraorbital abscess or an orbital cellulitis. And there's all sorts of important arteries and veins that run through your head and neck, and if infection gets into them, it can cause infected clots or septic clots, and it can also travel to other parts of the body, and those are called septic emboli. Now, all of these complications are much more common in severe disease, and severe disease is usually, but not always, bacterial. So, most people will try and treat bacterial sinusitis pretty aggressively. Similarly, if your immune system isn't working properly, you can develop severe disease and are more prone to get these complications. But keep in mind that complications are rare. In fact, something on the order of 30 million people in the United States alone get sinusitis in any given year. That's a huge number, and only a tiny minority of them actually get these complications. Most of them don't need treatment at all, and those that do get treated, usually respond very well.