Otitis externa: features and recommended management Debbie Shipley MRCP and Mario Jaramillo FRCS (ORL-HNS)

Transcription

1 Otitis externa: features and recommended management Debbie Shipley MRCP and Mario Jaramillo FRCS (ORL-HNS) Otitis externa is a common presentation and is usually treated in general practice. Our review describes the clinical features and current recommended management. Figure 1. Regional spread of otitis externa is an indication for the use of an oral antibiotic The term otitis externa (OE) is given to inflammation of the external auditory canal (EAC) that occasionally extends to involve the auricle. It is usually confined to the skin, associated hair follicles and glands lining the outer portion of the canal, but it can invade adjacent cartilage, bone or middle ear structures. OE can be classified in a number of different ways (see Table 1). Acute diffuse OE is the most common form occurring in everyday practice (see Figure 2). It is common in all parts of the world and presents at any age, but is more frequent in adults. In the UK, the prevalence of OE is 1.2 per cent for males and 1.3 per cent for females per year. Of these, only around 3 per cent are referred to secondary care. In a primary care study 80 per cent of patients with OE had only one recorded episode over a 12-month period with no recurrence. 1 In healthy individuals wax inhibits bacterial growth, but swabs of the EAC may grow saprophyte bacteria including staphylococci and streptococci. There is a normal migratory pattern of maturation and desquamation of the skin of the EAC; epithelial debris from the tympanic membrane and inner aspects of the canal find their way outwards to mix with wax and secretions. The debris is eventually discarded into the external auditory meatus. Factors interrupting this process may predispose to OE. Host and environmental factors OE is usually associated with local trauma (hearing aid users, cleansing attempts, manipulation with fingernails) and exposure to heat and humidity (swimmers, recent holiday). Regular swimming, showering and hair washing has also been found to predispose to OE. 1, 2 Anatomical differences in size and shape of the EAC and lesions narrowing it contribute to the 38 Prescriber 19 February

2 Duration (time limits are arbitrary) acute: <6 weeks chronic: >3 months Extension diffuse: all EAC skin affected localised (furunculosis): in the outer third of the EAC Severity simple: limited to the soft tissues of the EAC necrotising: with osteomyelitis of temporal bone Cause (reactive and infective may co-exist) reactive: including atopic eczema, psoriasis, allergic contact dermatitis and irritant dermatitis infective: bacterial, viral, fungal Table 1. Classification of otitis externa Figure 2. Acute diffuse otitis externa is the most common presentation presentation of the disease, eg osteomas, exostoses and surgical or traumatic stenoses (see Figure 3). Foreign bodies, particularly in children, may underlie OE. OE presents as a primary event or in the context of pre-existing skin disease. Eczema of the outer portions of the auditory meatus, with pruritus, triggers local trauma and build-up of skin debris, allowing conditions for organisms to multiply. The presence of eczema increases the likelihood of recurrent OE. Tympanic membrane perforation, where associated with discharge from suppurative otitis media, can cause irritation, maceration and recurrent OE. Occasionally infection develops in immunocompromised patients and leads to widespread extension and temporal bone osteomyelitis. This has been labelled malignant OE, although necrotising OE is a more descriptive term. Clinical features Isolated OE usually presents in two forms, diffuse and localised. The diffuse form affects the skin throughout the canal with aural discharge, increasing pain, pressure and hearing loss. Acute presentation usually involves one ear long-standing cases can also affect the contralateral ear. Pseudomonas spp. and Staphylococcus aureus are the most common pathogens. Fungal infections commonly appear following prolonged topical antibiotic treatment and are caused by Aspergillus or Candida. Viral OE is seen as a bullous myringitis caused by the herpes simplex virus, and influenza is the presumed cause of otitis externa haemorrhagica. The acute localised form of OE is furunculosis, caused by Staph. aureus and limited to the hair-bearing skin of the EAC at the level of the meatus. The patient presents with a red, hot ear canal, which is intensely painful and exquisitely tender to touch; the meatus is usually blocked and may show thick discharge. History and examination Details of the clinical history provide pointers towards the diagnosis: inquiries about recent swimming, exposure to local manipulation or trauma, use of drops causing sensitivity reactions or predisposing to fungal infec- 40 Prescriber 19 February

3 Figure 3. Conditions such as exostosis predispose to otitis externa tion should be made. Severe itching may indicate eczema, psoriasis or fungal infection. Pain arises locally, but ear pain can also result from adjacent infection such as otitis media, mastoiditis and tonsillitis. Physical examination is very helpful in the diagnosis of conditions localised to the EAC. Local inspection and visualisation of the ear canal are necessary, as well as examination of the tympanic membrane to exclude otitis media or tympanic membrane perforation. Erythema and skin thickening are features of eczema (see Figure 4), foul discharge of bacterial infection; thick exudate over friable skin suggests otomycosis, and vesiculation possible viral infection. Investigations In patients who are otherwise well, investigations are not usually necessary. Skin swabs for bacteriology and skin scrapings for fungal infection should be considered in patients with recurrent disease or in whom there is treatment failure. Results of bacteriological sensitivity should be interpreted with care, as the conditions of testing are for anticipated serum levels of antibiotic. Topical treatment of OE achieves much higher local concentrations of the medication. Where Staph. aureus is the infecting organism consider the possibility of MRSA. Allergic contact dermatitis is sometimes overlooked as a cause of chronic OE, and is seen particularly in patients who have received prolonged or frequent topical treatment. Topical neomycin has consistently been found to be the most important allergen. Referral for patch testing is appropriate if contact sensitivity to medication is suspected. Treatment There is no consensus for the most effective treatment for OE based on good evidence. The use of antiseptic or anti-infective and antiinflammatory preparations may be required. Caution should be taken to avoid known or potential skin sensitisers. Evidence available up until 2004 shows the use of topical aluminium acetate drops and topical steroids are likely to be beneficial in OE. Topical acetic acid use has insufficient evidence to demonstrate effectiveness. Topical anti-infective Figure 4. Topical steroid drops are indicated in eczematous otitis externa agents, antibiotics or antifungals with or without steroids are also considered likely to be beneficial. 3 Topical quinolones (ofloxacin, ciprofloxacin) have gained wide acceptance in the treatment of infective ear conditions in the last decade. They are active against Pseudomonas spp., lack ototoxicity and require less frequent application. Cochrane group reviews show the effectiveness of topical quinolones over other antibiotic drops in treatment of chronic suppurative otitis media, and that they are as effective as other anti-infective agents in OE. 2, 3 Combination preparations, such as triamcinolone-neomycin drops and neomycin-dexamethasoneacetic acid (Otomize) spray have limited randomised controlled trial evidence of resolution rates and clinical cure over other combinations in the treatment of OE. Prescriber 19 February

4 clinical suspicion of otitis externa examination of auditory canal removal of wax and debris tympanic membrane assessment impacted earwax glycerin drops tds hours reassess acute phase chronic phase localised OE diffuse OE regional extension regular aural toilet avoid irritants topical steroid oral flucloxacillin 5-7 days consider incision and drainage patent EAC aural toilet antiseptic/steroid preparation days occluded EAC ear wick insertion antibiotic/steroid drops no systemic comprise aural toilet topical and oral antibiotic systemic compromise ENT referral wick removal 48 hours reassess reassess at 48 hours Figure 5. Recommended management of otitis externa Treatment with aminoglycoside preparations in those with tympanic perforations should be undertaken with care as drugrelated ototoxicity could outweigh the risk of complications due to the infection. 4 The aim of treatment is to control pain, reduce swelling and itching, and minimise trauma to the skin of the affected EAC. Pain can be addressed with regular use of appropriate analgesia. A large proportion of mild cases respond to aural toilet followed by 7-10 days treatment with an acidifying and drying agent. Co-existing eczema is common and this responds to steroid application. Aural toilet with removal of wax and debris from the affected ear canal facilitates treatment. Impacted wax can be softened with oil or glycerin eardrops before removing. Syringing can be used but manipulation under direct vision is recommended. Where the wax proves difficult to remove, patients may require specialised microsuction by an ENT practitioner. First-line topical treatment for mild OE could include: topical acetic acid 2 per cent as an antifungal and antibacterial agent, or aluminium acetate eardrops. Where eczema is present a topical steroid is indicated, eg betamethasone sodium phosphate 0.1 per cent drops (Betnesol). Combin- 42 Prescriber 19 February

5 ation antibacterial, antifungal and steroid treatments are often prescribed for ease of administration. With clinical improvement, topical treatment should only continue for a period of two or three weeks. Prolonged treatment predisposes to drug sensitivity, antibiotic resistance and fungal infection. Prolonged continuous use of potent topical steroids is associated with skin atrophy; however, continuous use for four weeks or less is unlikely to cause such problems. In mild to moderate cases of OE oral antibiotics plus topical antiinfective agents seem to be no better than topical anti-infective agents alone. Ear wicks are used to enhance the delivery of ear medications into the swollen EAC. They are usually required in the initial stages of moderate to severe cases. Selfexpanding wicks are commercially available; ribbon gauze impregnated with a topical treatment, for example Tri-Adcortyl Otic, can also be used. Patients are reviewed within 48 hours to remove or reinsert the wick as necessary. Localised OE (furunculosis) is treated with a systemic antistaphylococcal antibiotic such as flucloxacillin orally. The only additional indication for oral antibiotic use is evidence of regional spread (see Figure 1). In severe cases, eg in patients with uncontrolled pain where there is associated otitis media or in patients who are immunocompromised or diabetic, consideration should be given to hospital admission. Necrotising OE is a life-threatening condition. Specialised microsuction, intravenous antibiotic therapy and surgical treatment are always necessary. Conclusion OE is a common condition that is usually treated in the primary care setting. The condition is multifactorial, and the majority settle within a fortnight with local measures alone. A small proportion of vulnerable patients get persistent or recurrent symptoms or present with complications. These patients should be considered for referral to a specialist service. References 1. Rowlands S, Devalla H, Smith C, et al. Otitis externa in UK general practice: a survey using the UK General Practice Research Database. Br J Gen Pract 2001;51(472): Kaushik V, Malik T, Saeed SR. Interventions for otitis externa (Protocol). The Cochrane database of systematic reviews 2004, Issue 2. Art No: CD Hajioff D. Otitis externa. Clin Evid Concise 2005;13: BNF 49. London: British Medical Association and The Royal Pharmaceutical Society of Great Britain, Further reading Kennedy CK. External otitis. In: Burns DA, Breathnach SM, Cox N, et al (eds). Rook s textbook of dermatology. 7th ed. Blackwell Sciences, Sander R. Otitis externa: a practical guide to treatment and prevention. American Family Physician 2001; 63(5): Dr Shipley is specialist registrar in dermatology at the Bristol Dermatology Centre, Bristol Royal Infirmary, and Mr Jaramillo is consultant ENT surgeon at West Wales General Hospital, Carmarthen Prescriber 19 February