Welcome to Module three, Disorders of the Middle Ear. In this module, we're going to identify pathologies of the tympanic membrane, we're going to discuss types of otitis media, we're going to explain the role of the eustachian tube, and then we're going to describe various abnormalities that can occur with the ossicular chain. A hole in the eardrum can come from a variety of causes, the first one is trauma and this can even include a Q-tip, in addition to pushing wax farther in your ear, a Q-tip can cause a hole or damage to the eardrum. You may have heard the old adage that says, "Don't put anything smaller than your elbow in your ear", and now you have an idea about why. Problems with the tympanic membrane can also come from inside the ear, such as an infection or an acute otitis media that bursts or perforates the eardrum. And lastly, holes in the drum can also come from pressure equalization tubes, and that's a procedure we're gonna cover in a few more slides where, a tube is placed in the tympanic membrane. Any problem with the tympanic membrane such as the ones I just mentioned, results in a conductive hearing loss. Depending on the cause of the hole in the eardrum, there are a variety of treatments. If it's a small hole, it may close on its own and indeed the vast majority of problematic holes in the eardrum close on their own. Sometimes a surgery is required. This is typically when the hole is large or when there's an accompanying infection, in that case, someone who's experienced in fixing the tympanic membrane performs something called a tympanoblasty. As you've probably gathered by now, the term ear infection is not very specific. It can refer to an infection of the outer ear, or to the middle ear. The term otitis media, is a non-specific term for inflammatory pathology of the middle ear and we're going to talk a little bit more about this to explain it better. When there is fluid in the middle ear and this fluid is infected and has an abrupt onset, we call that an acute otitis media. This is typically what we discuss or what we're referring to, when we talk about a middle ear infection. When the infections are recurrent, we call it recurrent acute otitis media, and when that fluid doesn't go at all but stays for a long time, we describe that as chronic or, chronic suppurative otitis media. Often, there can be fluid that builds up in the middle ear that's not infected. This serous fluid, when it collects in the middle ear can be called otitis media with effusion, and when it's chronic, we call it chronic otitis media with a effusion. The differentiation between all of these medical terms is typically made after a physical examination of the ear and eardrum. By looking through the ear canal and the tympanic membrane, we can tell if the fluid in the middle ear is infected, or if it is serous. In most cases, the underlying problem can be traced to eustachian tube dysfunction. The eustachian tube connects the middle ear to the back of the nose or the nasal pharynx. It's one of the primary ways that the ear nose and throat are all connected. The eustachian tube has three primary functions. The first one is equilibration of pressure between the middle and external ear. The second is clearance of middle ear secretions, and the third is the protection from sound pressure as it moves through the auditory pathway. The eustachian tube is composed partially of cartilage, that's the portion closest to the nose, and partially of bone. The eustachian tube opens with swallowing or yawning, and it activates with movement of the palette. You may have had problems with your eustachian tube on a plane and this is one reason, why chewing gum can often help you pop your ears. In children, the eustachian tube is in a more horizontal position, as you can see on the slide. As individuals grow or with development, the length and the angle of this eustachian tube changes over time, such that in adults, it's in a much more vertical angle. This is one of the reasons why children are much more prone to ear infections than in adults, and it really explains why many people often say that children might, "grow out of having ear infections". In fact, they don't grow out of having infections, but as their eustachian tube matures, the new configuration makes it much less prone to develop infections. Let's talk about fluid that's built up in the middle ear that's not infected. This is called serous otitis media, or otitis media with effusion, and this is a non-purulent or non-infection collection, of fluid in the middle ear. When people have fluid behind their ear drum they typically complain of ear pressure or fullness, and often of hearing loss or blocked hearing. The way this is diagnosed is with a physical exam, by looking through the ear canal and seeing a normal tympanic membrane with fluid on the other side. This fluid is not infected and that's able to be seen visually. This is often due to chronic eustachian tube dysfunction as mentioned, and the treatment of this can be observation, in the case that the otitis media with effusion is acute, but in the cases that it's chronic, such as lasting more than three months, that might be an indication for placement of a pressure equalization tube. This pressure equalization tube is placed in the tympanic membrane, and its primary purpose is to help equilibration of pressure between the middle and the outer ear, or to essentially circumvent the eustachian tube while it's experiencing dysfunction. That's why pressure equalization tubes or tubes, are more common in children because during that portion of development that the eustachian tube is more horizontal, tubes can help with equalization. When the fluid in the middle ear is infected, we call that acute otitis media. That's what we typically refer to as an ear infection. Obviously, the symptoms associated with that are ear pain and fever. Because that fluid is pressing on the tympanic membrane, the physical exam of the ear and the tympanic membrane show that the ear drum is red and erythematous and bulging, it really looks quite painful even when you're just looking at it. The tympanic membrane can't vibrate, because of the fluid that's on the other side, and typically people feel fullness and hearing loss. This is very common in children for the exact reasons of eustachian tube dysfunction that we just went over in the prior slide. There's a lot known about acute otitis media including the microbiology or the actual bacteria that are known to cause this infection. One of the most common bacteria as Streptococcus pneumoniae, and you may have heard about this as a strep infection. You can actually get that in the ear. Haemophilus influenza and Moraxella catarrhalis are two other common bacteria that are known to cause acute otitis media. The treatment for this is antibiotics, typically those taken orally. In situations where there's recurrent infections or other complications, a surgery, such as to place a pressure equalization tube or to deal with other consequences of the infection, may be necessary. In rare cases, an acute otitis media can spread to the surrounding bone, and this is a serious problem that's called a cute mastoiditis, this typically follows otitis media, although the phenomenon itself is not that common. It's important for us to discuss, because it can be very serious. In general, when there's an acute otitis media, that's very bad, it can spread to the surrounding bone. It can do that by direct extension because it's physically connected or by going into the bloodstream through the veins that all connect this area. Once the bone has been involved, it can become infected itself. Pieces of the bone can fall apart and across, and an abscess cavity can develop. The mastoid bone is localized behind the ear, and so the symptoms that result from this can be a redness or swelling and pain behind the ear. The ear itself can be bulging or sticking out. Hearing loss, pain, and fever are also very common. But in this situation, more serious complications can also occur, such as nerve paralysis or even spread to the surrounding structures because the ear is so very close to very many important things such as the brain or even the fluid surrounding the brain. All of those things are at risk when there is an acute mastoiditis. If this happens, it's an emergency, and it's necessary to go maybe even immediately to the operating room or at least get immediate antibiotics, often intravenously. Let's move on to discuss something that's not an infection. We're going to discuss a cholesteatoma. This is a term that refers to a benign neoplasm or a benign growth that's essentially a skin filled cyst. We're going to go over this in detail. There are two types. The first one is acquired, and that means that it develops over time. If you remember back a few modules ago, we went through the composition of the tympanic membrane that had had three layers, and there was a middle fibrous layer that provided strength or support to the tympanic membrane. Well, there's one part of the eardrum that doesn't have this fibrous layer. In situations of chronic use station tube dysfunction, this weaker portion of the tympanic membrane can get retracted. This retraction pocket can slowly filled with slough skin and other portions of the cyst, and can cause damage to both the eardrum and the ossicles or bones of hearing which are right behind the ear drum. This is the way that a cholesteatoma can cause damage to the ear. It can cause it both from pressure as well as from enzymatic destruction that occurs within the cyst. The symptoms are typically ones that we're very familiar with us far, such as fullness or pressure in the ear, sometimes some pain, and hearing loss. That's why it's very important when you have these symptoms to have someone look inside the ear. An experienced individuals such as myself can see a cholesteatoma, and that's primarily how it's diagnosed when it's acquired. There's another type of cholesteatoma, and this is not acquired. In fact, it's congenital. Meaning, someone is born with it. It involves abnormal migration of cells during development, such that squamous epithelium or skin which we normally have in the outer portion of the ear canal get trapped in the middle ear, and over time these skin cells multiply and thereby create a benign skin filled cysts on the other side of the tympanic membrane. This can be fairly hard to diagnose, because the eardrum itself is intact. One of physician looks inside the ear, they would see a white mass on the other side of an intact tympanic membrane, and this in itself is what gives us the clue that there might be a congenital cholesteatoma. The treatment for both acquired or congenital cholesteatoma is surgery, and the name of that surgery is a tympanomastoidectomy. At the time of surgery, we remove the cyst, reconstruct the eardrum, and also reconstruct any of the bones of hearing that may have been damaged with a prosthesis. So, let's talk about one last pathology of the middle ear. This is one that's uniquely related to the bones of hearing, and the name of this pathology is called otosclerosis. So, in this, the third bone of hearing, the stapes is affected. What happens is the foot plate or the base of the stapes gets fixed at the oval window where the connection between the stapes and the inner ear. So, essentially, sound is not transmitted. If you recall a few slides ago, we went through the auditory pathway, which requires vibration of the bones of hearing, and this pathology fixes the third bone of hearing, so it no longer vibrates. It typically happens in onset between 20 and 40 years old, and a family history is fairly common. People who have this problem often know someone in their family who may have had surgery to fix this problem. On the physical exam, it's very suspicious, and that's what helps us figure out what's going on. When we look in the ear, we see the eardrum looks normal. There's no fluid in the middle ear, there's no cholesteatoma. So, what could be causing this? Well, we're able to tell from the audio gram, that the pathology may be related to the third bone of hearing or the stapes. When this occurs, there are a couple options for treatment, which include getting a hearing aid or potentially even a surgery where we replace that third bone of hearing with one that works. So, in summary, we went through a bunch of different disorders of the middle ear, and we found out that they can be traumatic, infectious, or even hereditary, and typically, all result in conductive hearing loss. We've reviewed the function of these station tube, which has three functions: equilibration of pressure, clearance of secretions, and protection from sound pressure, and we talked about how eustachian tube dysfunction typically underlies a lot of middle ear pathology. Lastly, we discussed that middle ear pathology is something that is often amenable to surgical treatment, and this is something that it's very useful to get checked out by a physician. Thank you very much.
