Otitis externa

Overview
Otitis externa ("swimmer's ear") is an inflammation of the outer ear and ear canal. Along with otitis media, external otitis is one of the two human conditions commonly called "earache". It also occurs in many other species. Inflammation of the skin of the ear canal is the essence of this disorder. The inflammation can be secondary to dermatitis (eczema) only, with no microbial infection, or it can be caused by active bacterial or fungal infection. In either case, but more often with infection, the ear canal skin swells and may become painful and/or tender to touch.

Chronic otitis externa is a low-grade disease, usually non-microbial and purely on the basis of chronic dermatitis or irritation from "cleaning" the canal, often with cotton swabs. It can be thought of as chronic dermatitis of the ear canal skin and may or may not be painful. There may only be seepage, mild swelling, or itching.

In contrast to the chronic otitis externa, acute otitis externa is predominantly a microbial infection, occurs rather suddenly, rapidly worsens, and becomes very painful and alarming. The ear canal has an abundant nerve supply, so the pain is often severe enough to interfere with sleep. Wax in the ear can combine with the swelling of the canal skin and any associated pus to block the canal and dampen hearing to varying degrees, creating a temporary conductive hearing loss. In more severe or untreated cases, the infection can spread to the soft tissues of the face that surround the adjacent parotid gland and the jaw joint, making chewing painful. In its mildest forms, external otitis is so common that some ear nose and throat physicians have suggested that most people will have at least a brief episode at some point in life. While a small percentage of people seem to have an innate tendency toward chronic external otitis, most people can avoid external otitis altogether once they understand the mechanisms of the disease.

The skin of the bony ear canal is unique, in that it is not movable but is closely attached to the bone, and it is almost paper thin. For these reasons it is easily abraded or torn by even minimal physical force. Inflammation of the ear canal skin typically begins with a physical insult, most often from injury caused by attempts at self-cleaning or scratching with cotton swabs, finger nails, hair pins, keys, or other small implements. Another causative factor for acute infection is prolonged water exposure in the forms of swimming or exposure to extreme humidity, which can compromise the protective barrier function of the canal skin, allowing bacteria to flourish; hence the name, "swimmer's ear". Densely impacted wax, usually caused by enthusiastic use of cotton swabs, can put enough pressure on the ear canal skin to injure it and initiate infection. A sensation of blockage or itching can prompt attempts to clean, scratch, or open the ear canal, which potentially worsens and perpetuates the condition. The cotton fibers of a swab are abrasive to the thin, fixed canal skin. Self-manipulative measures to improve the condition often make it worse and are to be discouraged, since it is a blind exercise that can result in significant injury to the ear. Production of wax by glands in the canal may be hindered by external otitis. The exact function(s) of cerumen (earwax) is a subject that is open to speculation, since there is very little research regarding its function. Some caretakers feel strongly that earwax has a protective function with respect to infection and that a little earwax in the ear canal is a good thing.

A natural question is, "How can I clean my ears, then?" It is well established that in most people the top layer of the ear canal skin normally migrates toward the ear opening, essentially sweeping the canal on a continuing basis. In other words, a normal ear canal is self-cleaning. This self-cleaning physiologic feature fails in some patients, especially in late life, and periodic cleaning by a physician can be necessary. The most controlled and least painful means of cleaning impacted wax or dead skin from the ear canal is by using a binocular surgical microscope, which frees the examiner's hands to instrument the ear and provides the magnification and depth perception needed to avoid traumatizing the delicate canal skin and eardrum.

There is an uncommon and serious form of external otitis called malignant or necrotizing external otitis, in which the infection extends beyond the confines of the ear canal and can involve the bone of the skull. Although the name of this condition contains the words "external otitis" it tends to follow a more severe and chronic clinical course and can lead to skull base osteomyelitis. Instead of being a condition that most people are subject to, necrotizing external otitis (also called malignant otitis externa) is a life-threatening disorder that only affects older individuals with diabetes and patients with major disorders of the immune system. This uncommon complication of external otitis is discussed under Complications, below.

Symptoms
Pain is the predominant complaint and the only symptom directly related to the severity of acute external otitis. Unlike other forms of ear infections, the pain of acute external otitis is worsened when the outer ear is touched or pulled gently. Pushing the tragus (that tablike portion of the auricle that projects out just in front of the ear canal opening) so typically causes pain in this condition as to be diagnostic of external otitis on physical examination. Patients may also experience ear discharge and itchiness. When enough swelling and discharge in the ear canal is present to block the opening, external otitis may cause temporary conductive hearing loss.

Due to the fact that the ear and throat are often interconnected, irritation (whether it be in inflammation or a scratching sensation) is normal. However, excessive throat symptoms may likely point to the throat as the cause of the pain in the ear rather than the other way around.

Because the symptoms of external otitis promote many people to attempt to clean out the ear canal (or scratch it) with slim implements, and self-cleaning attempts generally lead to additional trauma of the injured skin, rapid worsening of the condition often occurs. Worsening is also common in the vacationer who continues holiday swimming despite symptoms of mild external otitis.

Causes, incidence, and risk factors
Swimming in polluted water is a common way to contract swimmer's ear, but it is also possible to contract swimmer's ear from water trapped in the ear canal after a shower, especially in a humid climate. Saturation divers have reported Otitis externa during occupational exposure. Even without exposure to water, the use of objects such as cotton swabs or other small objects to clear the ear canal is enough to cause breaks in the skin, and allow the condition to develop. Once the skin of the ear canal is inflamed, external otitis can be drastically enhanced by either scratching the ear canal with an object, or by allowing water to remain in the ear canal for any prolonged length of time.

The two factors that are required for external otitis to develop are (1) the presence of germs that can infect the skin and (2) impairments in the integrity of the skin of the ear canal that allow infection to occur. If the skin is healthy and uninjured, only exposure to a high concentration of pathogens, such as submersion in a pond contaminated by sewage, is likely to set off an episode. However, if there are chronic skin conditions that affect the ear canal skin, such as atopic dermatitis, seborrheic dermatitis, psoriasis or abnormalities of keratin production, or if there has been a break in the skin from trauma, even the normal bacteria found in the ear canal may cause infection and full-blown symptoms of external otitis.

Fungal ear canal infections, also known as otomycosis, range from inconsequential to very severe. Fungus can be saprophytic, in which there are no symptoms and the fungus simply co-exists in the ear canal in a harmless parasitic relationship with the host, in which case the only physical finding is presence of the fungus. If for any reason the fungus begins active reproduction, the ear canal can fill with dense fungal debris, causing pressure and ever-increasing pain that is unrelenting until the fungus is removed from the canal and anti-fungal medication is used. Most antibacterial ear drops also contain a steroid to hasten resolution of canal edema and pain. Unfortunately such drops make fungal infection worse. Prolonged use of them promotes growth of fungus in the ear canal. Antibacterial ear drops should be used a maximum of one week, but 5 days is usually enough. Otomycosis responds more than 95% of the time to a three day course of the same over-the-counter anti-fungal solutions used for athlete's foot.

The incidence of otitis externa is high. In the Netherlands, it has been estimated at 12-14 per 1000 population per year, and has been shown to affect more than 1% of a sample of the population in the United Kingdom over a 12 month period.

Characteristics of the external ear leading to external otitis
The outer ear canal starts at the opening on each side of the head that allows the entry of sound; the skin-lined canal extends in as far as the tympanic membrane (ear drum). The thin topmost layer of the ear canal skin is continuous with the surface of the ear drum, forming its outermost layer. There are two distinct anatomical regions of the ear canal, the outer portion, which lines the movable cartilage portion of the ear canal that is surrounded by soft tissues of the side of the head, and the inner portion, which lines the bony ear canal that is part of the skull. The bony ear canal can be seen on preserved specimens of the skull. The skin that is most easily injured, commonly giving rise to external otitis, is the delicate skin of the inner portion, the thin closely applied skin of the bony ear canal, which is perhaps the only skin of the body that ordinarily should never be touched!

The ear canal skin is specialized and is not like skin anywhere else on the body. The skin of the cartilaginous part of the ear canal contains glands that make wax (cerumen), which is believed to have protective function(s). The skin of the bony portion of the canal is almost paper thin, is firmly attached to bone, is immobile, and has no sweat glands. Like skin elsewhere on the body, the surface layer of the canal skin sheds. Accumulation of shed debris is prevented by the self-cleaning mechanism of the ear canal, with the top layer of the canal skin migrating outward along the canal to the surface of the head and bringing debris with it. The outer ear canal skin has a thick layer of subcutaneous tissue cushioning it and is thus more resistant to injury than the skin of the bony canal.

A folliculitis of one of the hairs of the outer portion of the ear canal can be the start of a bout of external otitis. Impaction of cerumen that abuts up against the delicate skin of the bony canal, or attempts to remove the impacted wax, can also be the initial event. Other inciting factors can be foreign bodies or cysts that develop in the skin near or just inside the canal opening.

The S-shape of the ear canal, the presence of hair in the outer part, and the outward migration of skin all combine to help shed water from the ear canal and keep shed skin from building up within the canal, as well as to keep water from pooling in the innermost canal. In some minor malformations of the ear canal or auricle, the size and shape of the canal may pre-dispose allowing water that enters the ear to remain, or to inhibit the normal shedding of superficial skin and cerumen from the ear canal. In such cases, the individual may have a predispostion to recurrent external otitis.

Pathogens - The Disease-Causing Germs
The bacterial pathogens at the top of the list are Pseudomonas aeruginosa and Staphylococcus aureus, followed by a great number of other gram-positive and gram-negative species. Candida albicans and Aspergillus species are the most common fungal pathogens responsible for the condition.

Diagnosis
When the physician looks in the ear, the canal appears red and swollen in well-developed cases of acute external otitis. The ear canal may also appear eczema-like, with scaly shedding of skin. Touching or moving the outer ear increases the pain, and this maneuver on physical exam is very important in establishing the clinical diagnosis. It may be difficult for the physician to see the eardrum with an otoscope at the initial examination because of narrowing of the ear canal from inflammation and the presence of drainage and debris. Sometimes the diagnosis of external otitis is presumptive and return visits are required to fully examine the ear. Culture of the drainage may identify the bacteria or fungus causing infection, but is not part of the routine diagnostic evaluation. In severe cases of external otitis, there may be swelling of the lymph node(s) directly beneath the ear.

The diagnosis may be missed in early cases because the examination of the ear, with the exception of pain with manipulation, is normal or nearly normal. In some cases of early external otitis, the most striking visual finding in the ear canal is the lack of cerumen. As a moderate or severe case of external otitis resolves, weeks may be required before the ear canal again shows a normal amount of cerumen.

Differentiating between otitis externa and otitis media
The second type of common "earache" is otitis media, and this inflammation of the tympanic membrane and middle ear space is usually clinically distinct from otitis externa. In a person with no history of chronic ear disease, acute otitis media seldom occurs in the absence of a recent viral upper respiratory infection (URI), a common cold or flu. Most earaches are caused by either acute otitis externa or by acute otitis media; it is very unusual to see both in the same ear at the same time. Importantly, persistent earache without the physical findings of ear infection can be due to more serious, even lifethreatening, conditions, and should always be investigated by an ear, nose, and throat physician (otolaryngologist). Acute otitis media and acute otitis externa are easily confused because both can cause earache and drainage from the ear (otorrhea). In middle ear infections, drainage only occurs if the tympanic membrane has a perforation or severe retraction pocket. When there is chronic suppurative otitis media, with or without cholesteatoma, the drainage in the ear canal may appear identical to drainage from external otitis. The primary distinction between acute otitis media and acute otitis externa is that otitis externa is characterized by swelling of the ear canal skin, and there is increased pain on any pushing or pulling of the ear.

Monocular otoscopy, the most common means used by family physicians and pediatricians to examine ears, has the severe limitation of providing no depth perception for the examiner. Uncertainty of the exact diagnosis can lead to unnecessarily excessive prescribing to cover treatment for both otitis media and otitis externa. Differentiating external otitis from otitis media is readily accomplished using a binocular microscope, which allows comfortable and safe cleaning of any wax or debris in the ear canal, yielding a complete view of the visble parts of the ear canal and eardrum. Most otolaryngologists (ear, nose, & throat physicians) have binocular microscopes in their offices and are trained to quickly accomplish this task, increasing the likelihood of a correct, definitive diagnosis, which can then be treated appropriately. Cleaning of an infected ear canal promotes better contact of the topical antibiotic drops and shortens recovery time. Children with surgically inserted ear tubes who fail to keep water out of their ears often develop painless drainage from resulting bacterial otitis media. This is not external otitis, but otitis media. It is painless because the opening maintained by the tube, assuming no obstructing crusts or blood clot, prevents pressure from building up within the middle ear. This problem typically clears with antibiotic drops only and does not require oral antibiotics.

Quinolone antibiotics in topical form (ear drops) have been shown to be of benefit in stopping discharge from otitis media through an open eardrum, and so some treatments for otitis externa may be of benefit to otitis media. The main pitfall of having a case of otitis media misdiagnosed as otitis externa is that a serious infection of the middle-ear may have complications and sequelae over time. Additionally, many types of topical ear drops that are safe and effective for use in the ear canal can be irritating and even damaging if allowed past the ear drum into the more delicate internal membranes of the middle-ear, prompting the warning that such topical preparations should not be used unless the tympanic membrane is known to be intact. For both reasons, caution is given against self-treatment of "earache" without proper medical evaluation.

If there is prolonged drainage of noxious substances from the middle ear through the ear drum, then the skin of the ear canal may become secondarily inflamed. In this situation, one that occurs only in individuals with severe chronic otitis media, both external otitis and otitis media are present at that same time. Prolonged care by a qualified specialist is generally required.

Treatment
The goal of treatment is to cure the infection and to return the ear canal skin to a healthy condition. When external otitis is very mild, in its initial stages, simply refraining from swimming or washing hair for a few days, and keeping all implements out of the ear, usually results in cure. For this reason, external otitis is called a self-limiting condition. However, if the infection is moderate to severe, or if the climate is humid enough that the skin of the ear remains moist, spontaneous improvement may not occur.

Topical solutions or suspensions in the form of ear drops are the mainstays of treatment for external otitis. Some contain antibiotics, either antibacterial or antifungal, and others are simply designed to mildly acidify the ear canal environment to discourage bacterial growth. Some prescription drops also contain anti-inflammatory steroids, which help to resolve swelling and itching. Although there is evidence that steroids are effective at reducing the length of treatment time required, fungal otitis externa (also called otomycosis) may be caused or aggravated by overly prolonged use of steroid-containing drops. In addition to topical antibiotics, oral anti-pseudomonal antibiotics can be used in case of severe soft tissue swelling extending into the face and neck and may hasten recovery.

Removal of debris (wax, shed skin, and pus) from the ear canal promotes direct contact of the prescribed medication with the infected skin and shortens recovery time. This is best accomplished using a binocular microscope. When canal swelling has progressed to the point where the ear canal is blocked, topical drops may not penetrate far enough into the ear canal to be effective. The physician may need to carefully insert a wick of cotton or other commercially available, pre-fashioned, absorbent material called an ear wick and then saturate that with the medication. The wick is kept saturated with medication until the canal opens enough that the drops will penetrate the canal without it. Removal of the wick does not require a health professional. Antibiotic ear drops should be dosed in a quantity that allows coating of most of the ear canal and used for no more than 4 to 7 days. The ear should be left open. Do note that it is imperative that there is visualization of an intact tympanic membrane. Use of certain medications with a ruptured tympanic membrane can cause tinnitus, vertigo, dizziness and hearing loss in some cases.

Although the acute external otitis generally resolves in a few days with topical washes and antibiotics, complete return of hearing and cerumen gland function may take a few more days. Once healed completely, the ear canal is again self-cleaning. Until it recovers fully, it may be more prone to repeat infection from further physical or chemical insult.

Effective medications include ear drops containing antibiotics to fight infection, and corticosteroids to reduce itching and inflammation. In painful cases a topical solution of antibiotics such as aminoglycoside, polymyxin or fluoroquinolone is usually prescribed. Antifungal solutions are used in the case of fungal infections. External otitis is almost always predominantly bacterial or predominantly fungal, so that only one type of medication is necessary and indicated.

The pain of acute otitis externa is often severe enough to interfere with sleep. Topical analgesic drops often prescribed by primary care providers for pain relief are almost never adequate and should not be relied upon. A brief course of oral narcotic pain medication is often necessary to maintain comfort while the antibiotic drops are working. Improvement with appropriate initial treatment (cleaning of the canal, wick insertion if necessary, and antibiotic drops in adequate amount) is fairly rapid, with pain improvement occurring within one day and resolution within 2-4 days. Heat application using a heating pad, can also aid in pain relief.

Non-prescription remedies
Provided it is not too severe, recurrent otitis externa can often be successfully treated by non-prescription means, at low cost. When symptoms recur in an individual who has had a previous diagnosis made, the use of non-prescription drops along with precautions to keep water out of the ear is generally effective. Self-treatment with non-prescription remedies is dangerous in individuals who have not been previously evaluated for the condition, because the tympanic membrane may not be intact, and because the true condition may be otitis media with drainage. Drops and water precautions may actually resolve otitis media with drainage for a period of time, while allowing an undiagnosed cholesteatoma to progress, or complications of otitis media to develop.

Effective solutions for the ear canal include acidifying and drying agents, used either singly or in combination. When the ear canal skin is inflamed from the acute otitis externa, the use of dilute acetic acid may be painful.

Burow's solution is an effective remedy against both bacterial and fungal external otitis. This is a buffered mixture of aluminum sulfate and acetic acid, and is available without prescription in the United States.

Prevention
Provided it is not too severe, recurrent otitis externa can often be successfully treated by non-prescription means, at low cost. When symptoms recur in an individual who has had a previous diagnosis made, the use of non-prescription drops along with precautions to keep water out of the ear is generally effective. Self-treatment with non-prescription remedies is dangerous in individuals who have not been previously evaluated for the condition, because the tympanic membrane may not be intact, and because the true condition may be otitis media with drainage. Drops and water precautions may actually resolve otitis media with drainage for a period of time, while allowing an undiagnosed cholesteatoma to progress, or complications of otitis media to develop.

Effective solutions for the ear canal include acidifying and drying agents, used either singly or in combination. When the ear canal skin is inflamed from the acute otitis externa, the use of dilute acetic acid may be painful.

Burow's solution is an effective remedy against both bacterial and fungal external otitis. This is a buffered mixture of aluminium sulfate and acetic acid, and is available without prescription in the United States.

Prognosis
Otitis externa responds well to treatment, but complications may occur if it is not treated. Individuals with underlying diabetes or disorders of the immune system are more likely to get complications, including malignant otitis externa. In these individuals, rapid examination by an otolaryngologist (ear, nose, and throat physician) is very important.

Complications

 * Chronic otitis externa
 * Spread of infection to other areas of the body
 * Necrotizing External Otitis

Necrotizing External Otitis (Malignant otitis externa)
This uncommon form of external otitis occurs mainly in an elderly diabetics, being somewhat more likely and more severe when the diabetes is poorly controlled. Even less commonly, it can develop due to a severely compromised immune system. Beginning as infection of the external ear canal, there is extension of infection into the bony ear canal and the soft tissues deep to the bony canal.

The hallmark of malignant otitis externa (MOE) is unrelenting pain that interferes with sleep and persists even after swelling of the external ear canal may have resolved with topical antibiotic treatment. MOE follows a more chronic course than ordinary acute otitis externa. There may be granulation involving the floor of the external ear canal, most often at the bony-cartilaginous junction. Paradoxically, the physical findings of MOE, at least in its early stages, are often much less dramatic than those of ordinary acute otitis externa. In later stages there can be soft tissue swelling around the ear, even in the absence of significant canal swelling. Unlike ordinary otitis externa, MOE requires oral or intravenous antibiotics for cure. Diabetes control is also an essential part of treatment.

When MOE goes unrecognized and untreated, the infection continues to smolder and over weeks or months can spread deeper into the head and involve the bones of the skull base, constituting skull base osteomyelitis (SBO).

The infecting organism is almost always pseudomonas aeruginosa, but it can instead be fungal (aspergillus or mucor). MOE and SBO are not amenable to surgery, but exploratory surgery may facilitate culture of unusual organism(s) that are not responding to empirically used anti-pseudomonal antibiotics.

The usual surgical finding is diffuse cellulitis without localized abscess formation. SBO can extend into the petrous apex of the temporal bone or more inferiorly into the opposite side of the skull base. As the skull base is progressively involved, the adjacent exiting cranial nerves and their branches, especially the facial nerve and the vagus nerve, may be affected, resulting in facial paralysis and hoarseness, respectively.

If both of the recurrent laryngeal nerves are paralyzed, shortness of breath may develop and necessitate tracheotomy. Profound deafness can occur, usually later in the disease course due to relative resistance of the inner ear structures. Gallium scans are sometimes used to document the extent of the infection but are not essential to disease management. Skull base osteomyelitis is a chronic disease that can require months of IV antibiotic treatment, tends to recur, and has a significant mortality rate.