Otitis externa (infectiosa)H60.-; H60.1 (Phlegmone des Gehörganges); H60.3(Badeotitis);

Acute or chronic microbially induced, diffuse or circumscribed inflammation of the cutis and subcutis of the external auditory canal, whereby the eardrum and auricle may also be affected. Otitis externa (OE) is one of the most common diseases in ENT practice, but is also of practical relevance for general practitioners, pediatricians and dermatologists. The different manifestations range from slight inflammation of the external auditory canal to the life-threatening clinical picture of otitis externa maligna.

Predisposing factors are soap, hairspray and hair shampoo residues in the external auditory canal; furthermore, medical exteriors (chloramphenicol or neomycin-containing ear drops); earpieces of hearing aids.

Note: The ICD-10-GM-2020 classification uses ICD H60.5 to describe "acute external otitis, non-infectious". This includes otitis externa caused by chemical substances, radiation, "eczematous" otitis externa and acute reactive otitis externa.

A distinction is made:

• Otitis externa diffusa (= inflammation of the cutis and subcutis of the auditory canal)
• Otitis externa circumscripta (= ear canal furuncle or staphylococcal infection of the hair follicles).
• Chronic OE (COE)
• the OE maligna (necroticans) (OEM) (usually triggered by Pseudomonas aeruginosa )

The external auditory canal consists of a lateral cartilaginous and medial bony part with a total length of approx. 2-3.5 cm and a diameter of 5-9 mm. While the skin of the bony auditory canal is firmly attached to the periosteum, the skin of the cartilaginous auditory canal lies on a layer of connective tissue. It contains hair follicles, sebaceous glands and apocrine ball glands, whose exudates together with exfoliated epithelia form the cerumen. The cartilaginous auditory canal has a connective tissue roof and at the bottom the connective tissue Santorini clefts, through which infections can spread to the parotid gland, infratemporal fossa and base of the skull. Sensitive care is provided via the auriculotemporal nerve, the auricular nerve, the vagi, the auricular nerve, the magnus auricular nerve and the posterior auricular nerve. The external auditory canal is physiologically colonized by bacteria, especially Staphylococcus and Corynebacterium species and streptococci (Stroman DW et al. 2001). The physiological pH value of the ear canal is 5-5.7. Bacterial growth is inhibited by the acidic environment and the hydrophobic properties of the cerumen (Neher A et al. 2008).

In acute diffuse otitis media, the auditory canal has a painful, red swelling. The pain increases when pressure is applied to the tragus.

Dry form: The dry form of diffuse otitis externa ("ear canal dermatitis") is characterised by the formation of dandruff and pruritus. In the weeping form, greasy foetal secretions are secreted from the auditory canal. A mucilaginous secretion indicates a simultaneous middle ear discharge.

The very and dreaded form of the disease, otitis externa maligna, is usually caused by Pseudomonas aeruginosa and mainly affects poorly adjusted patients with diabetes mellitus or patients with immunosuppression. This complicated form of the disease can lead to the early loss of cranial nerves (usually the facial nerve), which can spread to the bone and be potentially fatal.

Delimitation is:

• Acute non-infectious otitis externa (H60.5): caused by chemical substances, radiation, "eczematous" otitis externa (ear canal dermatitis) and acute reactive otitis externa
• Perichondritis
• Erysipelas
• Otomycosis
• shingles
• Otitis media (with perforation)
• Ear canal cholesteatoma
• Carcinoma of the auditory canal.

A transition of the inflammation to the eardrum (myringitis) and/or the outer ear(erysipelas) is possible. In case of perforation of the eardrum, ototoxic substances must be avoided.

The therapy of acute otitis externa consists of pain therapy, cleaning of the auditory canal and treatment with antiseptic and antimicrobial substances. Local antibiotic and corticosteroid preparations have proven effective, although randomized controlled trials with high numbers of patients are still pending.

External: For uncomplicated AOE, topical therapeutics (antiseptics, antibiotics, glucocorticoids and combinations of these) are recommended for their therapeutic safety, efficacy (Kaushik V et al (2010). 65-90% of patients have a clinical improvement after 7-10 days. The additive administration of topical steroids can lead to a significant reduction of redness and secretion.

Several topical antiseptics have been described for the therapy of AOE, including acetic acid, chlorhexidine, aluminium acetate, silver nitrate, N-chlortaurine. The advantage of topical antiseptics is their broad effectiveness. Many preparations contain alcohol, which has a disinfecting effect and extracts water from the tissue in high concentrations, which has a decongesting effect. The lowering of the pH-value by acidic preparations (e.g. 2% acetic acid) leads to the inhibition of bacterial growth, as most bacteria prefer a neutral pH-value. This results in faster healing compared to placebo. Acetic acid shows a comparable efficacy with antibiotics/corticoid drops after 7 days of therapy, but acetic acid preparations are significantly less effective if treatment over 2-3 weeks is necessary (Kaushik V et al. (2010)

Topical antibiotics: Topical antibiotic therapy should include the most common pathogens Pseudomonas aeruginosa and Staphylococcus aureus and should be carried out in a targeted manner, if possible, according to the antibioticogram. Recommended are ear drops with quinolone antibiotics, ciprofloxacin, aminoglycosides (neomycin and polymyxin B).

Quinolones are very effective without causing local irritation, but increased exposure may lead to resistance to this important class of antibiotics. Neomycin is effective but ototoxic and should therefore only be used if the eardrum (!) is intact (Cave: sensitization). Polymyxin alone has no activity against staphylococci and other gram-positive microorganisms. Furthermore, the antibiotics ciprofloxacin or ofloxacin can be given in topical form.

Systemic (oral) antibiotics: Despite the well-documented safety and efficacy of topical preparations, about 20-40% of patients treated for AOE primarily receive systemic antibiotic therapy. This is not necessary with uncomplicated AOE. Targeted oral antibiotic therapy (depending on the resistogram) is indicated in AOE in the presence of poorly controlled diabetes mellitus, immunosuppression or if the inflammation extends beyond the ear canal.

Topical corticosteroids: External corticosteroids are mainly used for their decongestant properties, an antibacterial and antifungal effect has been described; the evidence for monotherapy with topical corticosteroids is limited.

Topical corticoid-antibiotic combinations: In individual randomized controlled trials, there was less swelling, redness and secretion of the auditory canal compared to antibiotic-only preparations; the effect was already apparent in the first days after the start of therapy.

Antimycotic therapy: In case of proven fungal infection, the insertion of antimycotic-soaked strips (Ciclopirox, Nystatin, Clotrimazol or Miconazol) should be performed. Due to possible inner ear toxicity and reduced effect, dye solutions are no longer recommended (23). Systemic antimycotic therapy should be used for eardrum perforations, e.g. with Fluconazole or Itraconazole.

Topical local anaesthetics can also be used for pain management, but not for perforated eardrums or an inset tympanic tube. Since they can mask disease progression, a clinical control to assess the response to therapy should be performed after 48 hours.

Pain therapy: Pain relief is an essential additive component of the therapy of AOE. Since the highly sensitive periosteum of the bony auditory canal is usually involved in inflammation, severe ear pain can occur. Suitable analgesics are ibuprofen or paracetamol.

It is important to instruct the patient regarding the application of the topical agents. The patient should lie on the opposite side, apply the drops into the ear canal and then remain lying on the side for 3-5 minutes. A back and forth movement of the ear helps to transport the drops specifically to their destination. Depending on the preparation, the drops should be applied 2-5 times daily. After topical therapy, the AOE is healed in 65-90% of patients after 7-10 days, regardless of the selected therapeutic agent.

The success of the therapy should be checked after 48-72 hours. Known risk factors should be avoided in order to prevent further episodes of inflammation. The auditory canal should be kept dry and dried with a hair dryer after water infiltration (e.g. after visiting a swimming pool = bathing atotitis H60.3). If the self-cleaning of the auditory canal is disturbed, a cleaning of the auditory canal should be carried out before bathing.

The dyes that used to be popular for local antiseptic and desiccative treatment of various diseases of the external auditory canal, such as gentian violet, brilliant green, eosin or fuchsin, are no longer permitted because of their toxic properties.

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2. Kaushik V et al (2010) Interventions for acute otitis externa. Cochrane Database Syst Rev: CD004740
3. Mösges R et al (2011) A meta-analysis of the efficacy of quinolone containing otics in comparison to antibiotic-steroid combination drugs in the local treatment of otitis externa. Curr Med Res Opin 27: 2053-60
4. Neher A et al (2008) Otitis externa. HNO 56: 1067-80
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