Otitis externa

Otitis externa
ICD-10	H60
ICD-9	380.1 -380.2
MedlinePlus	000622

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". Inflammation of the skin of the ear canal is the essence of this disorder. If inflammation progresses to infection, the ear canal may fill with swollen tissue and drainage. Once the ear canal is blocked, hearing will be dampened (conductive hearing impairment) until the condition improves. In very severe cases, the skin infection can spread to the face (facial cellulitis) and to the major salivary gland in the cheek (parotitis). In that situation, moving the jaw and eating become painful. In its mildest forms, external otitis is so common that some ear nose and throat physicians have suggested that most people will have an episode at some point in life. In many individuals, for the reasons discussed below, the condition is recurrent and will happen several times in a lifetime.

Ordinarily, inflammation of the ear canal skin starts off with the loss of protective oils and ear wax (cerumen) along with minor injury to the skin. That injury often stem from attempts at self-cleaning or scratching using cotton swabs, hair pins or other implements small enough to fit in the ear canal. Prolonged water exposure (either swimming or exposure to extremely high humidity) is enough alone to both decrease the protective barrier of ear wax and to cause tiny breaks in the waterlogged skin, hence the name, "swimmer's ear". Since the swollen ear canal skin often is both itchy and painful, and sometimes associated with a feeling that something is stuck in the ear, a vicious cycle of self-cleaning or scratching can perpetuate the condition. Wax glands shut down the production of protective cerumen when the canal skin is inflamed, and weeks are required for the outer ear to completely return to normal production of wax and protective oils after even a short bout of moderately severe external otitis. During this recovery period, the skin is markedly more vulnerable to becoming re-infected. For these reasons, among others, some people are prone to recurrent external otitis with exposure to water.

There is a rare and serious form of external otitis called necrotizing external otitis, in which the bone of the skull surrounding the ear canal becomes infected. Although the name of this condition contains the words "external otitis" it is a very different disease than the common swimmer's ear, it is a form of osteomyelitis . Instead of being a condition that most people are subject to, necrotizing external otitis (also called malignant otitis) is a life-threatening disorder that only affects individuals with severe diabetes and major disorders of the immune system. This rare 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 external otitis. Unlike other forms of ear infections, the pain of external otitis is worsened when the outer ear is touched. 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 discharge in the ear canal is present to clog the opening, external otitis may cause temporary conductive hearing loss.

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 vacationeer 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. 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 sewerage, 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.(Kang K, Stevens SR. Pathophysiology of atopic dermatitis. Clin Dermatol 2003;21:116–121.)

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.

How The Shape and Characteristics of the External Ear Can Lead 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 surface of the ear drum is also skinlike, and is continuous with that of the ear canal. There are two distinct parts to the ear canal, the outer portion, which lines the cartilage portion of the ear canal that travels through the soft tissues of the head, and the inner portion, which lines the bony ear canal that travels through the skull. The bony ear canal can be seen on preserved specimens of the skull. The skin that is most easily inflamed 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 skin of the ear drum surface and the ear canal is much like skin anywhere on the body, it is waterproof because of layers of keratin at its surface. These surface layers are shed, but do not normally build-up in the ear canal. That's because of the way that the skin grows: migrating outward along the canal to the surface of the head and bringing any surface debris with it.

The outer ear canal skin is much thicker and more resilient to injury than the skin of the bony canal. This outer canal skin has a thick layer of subcutaneous tissue cushioning it, and contains both hairs and cerumen glands. The cerumen glands produce ear wax that is normally protective.

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.

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 supperficial 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 manuever 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 inflamation 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.

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 externa 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 clinicaly distinct from otitis externa. However, the conditions are sometimes confused - particularly when there is drainage from the ear (otorrhea). In middle-ear infections, drainage only occurs if the tympanic membrane has either a perforation or 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. In otitis media, however, there is no tenderness of the ear - no increased pain with pulling the auricle or pushing the tragus. Children with ear tubes who develop an episode of otitis media despite having open myringotomy tubes generally will develop drainage through the tubes. This is not external otitis, but otitis media.

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.( Macfadyen CA. Acuin JM. Gamble C. Topical antibiotics without steroids for chronically discharging ears with underlying eardrum perforations. [Review] [157 refs] [Journal Article. Meta-Analysis. Review] Cochrane Database of Systematic Reviews. (4):CD004618, 2005.) 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 the 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.

The use of topical solutions and suspensions in the form of ear drops is the mainstay of treatment for external otitis. These drops both physically wash collected debris from shed skin and infected drainage from the ear canal, and contain substances that either kill pathogenic germs, stop them from multiplying, or do both. The drops generally contain drying substances (astringents), acidifying agents, antibiotics and/or anti-fungal agents. Some prescription drops also contain anti-inflammatory steroids. Although there is evidence that steroids are effective at reducing the length of treatment time required, fungal otitris may be aggravated by the use of topical steroids.

When the condition has progressed to the point where the ear canal is blocked, a physician may have to begin treatment by clearing the ear under otoscopic examination and placing a thin strip of an absorbant material (ear wick) into the ear canal. In severe cases of external otitis, an otologist is needed to carefully clean out the ear canal under microscopic visualization. In such severe cases, in which drainage is abundant enough to recurrently block the ear canal, a qualified health professional may aspirate the ear as many times as twice a week for the first two or three weeks of treatment. 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 infection of external otitis generally resolves in a few days with topical washes and antibiotics, weeks are required before the ear canal skin is fully normal. The glands of the outer skin of the ear canal will not begin producing cerumen again until the skin is not only no longer infected, but no longer inflamed. Once healed completely, the ear canal is again self-cleaning. Until then, slight irritation can be enough to cause external otitis to flare again.

Effective medications include eardrops containing antibiotics to fight infection, and corticosteroids to reduce itching and inflammation. The first line is a topical preparation such as 2% acetic acid or a topical antibiotic solution containing antibiotics such as aminoglycoside, polymyxin or fluoroquinolone. It is possible to have both a bacterial and fungal ear infection, and many of the topical treatments are designed to cure both.

Ear drops used abundantly help in clearing out the shed skin and dead bacteria in the ear canal, as well as in directly fighting the infection by interfering with the growth of bacteria. If the ear canal is very swollen, a wick may be applied in the ear to allow the drops to travel to the end of the canal. Occasionally, pills may be used in addition to the topical medications. Analgesics may be used if pain is severe. Putting something warm against the ears may reduce pain.

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 acicifying 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.

Kashiwamura M. Chida E. Matsumura M. Nakamaru Y. Suda N. Terayama Y. Fukuda S. The efficacy of Burow's solution as an ear preparation for the treatment of chronic ear infections. [Clinical Trial. Journal Article] Otology & Neurotology. 25(1):9-13, 2004

Prevention

The stategies for preventing acute external otitis are similar to those for treatment.

• Dry the ear thoroughly after exposure to moisture. This can be accomplished by the use of drops containing dilute alcohol or Burow's solution. The use of dilute alochol drops is not recommended except for prevention, as the solution is painful if the skin is inflamed by an acute episode.
• Avoid swimming in polluted water.
• Avoid washing the hair or swimming if very mild symptoms of acute external otitis begin
• Although the use of earplugs when swimming and shampooing the hair may help prevent external otitis, there are important details in the use of plugs. Hard and poorly fitting ear plugs can scratch the ear canal skin and set off an episode. When earplugs are used during an acute episode, either disposable plugs are recommended, or used plugs must be cleaned and dried properly to avoid contaminating the healing ear canal with infected discharge. One simple method of fabricating soft waterproof disposable ear plugs is with cotton balls and petrolueum jelly. These jelly coated cotton balls are NOT inserted into the ear canal, but pressed into the auricle to cover the opening of the canal.

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 a physician is very important.

Complications

• Chronic otitis externa

Necrotizing External Otitis (Malignant otitis externa)

This rare form of external otitis only occurs in individuals with severe diabetes or severely compromised immune systems. Rather than being a superficial infection of the outer ear, this is an osteomyelitis of the skull base and can extend deeply into the head. Malignant otitis externa begins as a soft tissue infection of the external auditory canal, but soon goes deeper into the bone. Granulation tissue forms on the floor of the canal at the bony-cartilaginous junction. Unlike middle ear infections that involve bone, spread is not into the mastoid, but to compact bone along the middle with eventual extension to the petrous apex. There is often granulation tissue visible in the ear canal, typically at the junction of the bony and cartilaginous canals. Biopsies of affected bone show new bone formation adjacent to areas of destruction. The otic capsule exhibits significant resistance to involvement of the disease and middle ear structures are rarely involved until late in the disease course.

• Spread of infection to other areas of the body

External links

• What to do if your child has swimmer's ear, from Seattle Children's Hospital