eMedicine Specialties > Otolaryngology and Facial Plastic Surgery > External Ear Diseases

External Ear, Infections: Differential Diagnoses & Workup

Author: Ashutosh Kacker, MD, Associate Professor of Otorhinolaryngology, Department of Otolaryngology, Weill College of Medicine of Cornell University; Consulting Staff, New York Presbyterian Hospital, New York Hospital of Queens
Contributor Information and Disclosures

Updated: Sep 17, 2009

Differential Diagnoses

Other Problems to Be Considered

Ramsay Hunt syndrome

This condition, more accurately known as herpes zoster oticus, is caused by varicella-zoster viral infection. Ramsay Hunt syndrome is characterized by facial nerve paralysis and sensorineural hearing loss, with bullous myringitis and a vesicular eruption of the concha of the pinna and the EAC. A painful otitis externa may be present as well. Treatment includes use of an antiviral agent (eg, valacyclovir) and systemic steroids. The role of facial nerve decompression remains controversial.

Furuncle

Staphylococcal infection of a hair follicle is the usual cause of a furuncle. This infection occurs in the lateral cartilaginous hair-bearing portion of the EAC. On otoscopic examination, a furuncle is a localized infection, which may develop into an abscess, rather than the diffuse inflammatory process characteristic of otitis externa.

Skull base osteomyelitis

This serious infection, also known as malignant otitis externa, occurs most often in patients who are diabetic or immunocompromised. The pathogenic bacteria are usually Pseudomonas aeruginosa. Other predisposing conditions include arteriosclerosis, immunosuppression, chemotherapy, steroid use, and other immunodeficient states. The diagnosis is strongly suggested by a history of diabetes mellitus, severe otalgia, cranial neuropathies, and characteristic EAC findings.

The EAC may be filled with friable granulation tissue, which is primarily found inferiorly. Because this presentation may be identical to that of a soft tissue malignancy, prudence dictates a tissue biopsy, even if a history of diabetes mellitus is present. Bare bone of the EAC floor may be exposed; small bony sequestra may be observed as well.

CT scanning demonstrates bone erosion, and gallium scanning can be performed at points throughout treatment to monitor resolution. Treatment consists of administration of an antipseudomonal IV antibiotic such as ceftazidime (in some cases) or oral ciprofloxacin (in less dramatic cases). Extended treatment for at least 6 weeks is most appropriate. Hyperbaric oxygen therapy may also be effective. Surgical debridement is reserved for granulation tissue and bony sequestra.

Preauricular cyst and fistula

Abnormal development of the first and second branchial arch may result in the formation of a preauricular cyst or fistula, which may manifest as persistent discharge or recurrent infection. A draining sinus may be present anterior to the tragus; when infected, the cyst distends with pus and the overlying skin is erythematous. These lesions are managed by complete surgical excision if they become repeatedly infected. The facial nerve is at risk of injury during the excision of these lesions because of the close relationship of the preauricular cyst or fistula to the superior branches of the facial nerve within the parotid gland.

First branchial cleft anomalies have a more complex embryologic origin than preauricular cysts and fistulas. These lesions may not have an obvious sinus tract on the skin and may manifest as an abscess extending deeply into the EAC, parotid, and/or neck.

Lacerations

Full-thickness auricular lacerations may be observed after blunt or sharp trauma. These injuries are managed surgically by closing both the perichondrium and the skin. In contrast, external canal lacerations may occur after attempts at cleaning the ear canal using cotton-tipped applicators. These lacerations are usually managed by microscopically placing any skin flaps in their normal position, packing the ear canal, and administering topical antibiotic drops.

Atopic dermatitis

Drug sensitivity to topical antibiotic solutions is well known. Neomycin allergy occurs in up to 5% of patients treated with the medication. Suspect drug sensitivity if worsening of symptoms associated with skin excoriation and weeping occurs in the distribution of the topical medication exposure after application of drops.

Metal sensitivity also manifests as excoriation, erythema, and edema around the exposure site (eg, a piercing hole). A common allergen is nickel, an impurity that may be present in precious metals. Atopic dermatitis is managed by removal of the allergen, such as an earring, and beginning topical steroid and antibiotics if the wound is secondarily infected. The diagnosis of metal sensitivity is confirmed by performing a skin patch test.

Cerumen impaction

Cerumen impaction is the most common abnormality found on otoscopic examination, yet only a small proportion of the general population requires regular disimpaction because the EAC has the innate ability to produce and clear itself of cerumen. Cerumen may vary in color and consistency and may exist with other pathologies. Of note, debris in the EAC from cholesteatoma or tumors may be confused with cerumen, indicating that considerable care is required when attempting debridement of the EAC. Debridement may be accomplished with microinstruments or by aspirating the ear canal contents with a No 5 or No 7 Barton suction, while under direct vision through the otoscope or microscope. Irrigation of the ear canal is another option, but use of a pressurized irrigation system entails the risk of trauma.

Exostosis and osteoma

The 2 most common bony lesions of the EAC, exostoses and osteomas, differ histologically and clinically. Exostoses tend to arise from the anterior and/or posterior floor of the medial EAC. Exostoses have a sessile base and are covered with normal-appearing skin. Both anterior and posterior exostoses may be found simultaneously.

Osteomas may arise from any region of the bony EAC and often are pedunculated. Osteomas may also be either single or multiple and are covered by normal skin. Exostosis and osteomas require surgical treatment only if they are so large that they lead to a conductive hearing loss or intractable otitis externa.

Foreign body

Foreign bodies are not infrequently encountered in the EAC. In children, parts of toys or even food may be found in the EAC, and, thus, appearance varies. In adults, fragments of cotton swabs are the most common finding. Erythema and edema surrounding the foreign body are commonly present. Using microinstruments, the foreign body may be removed under a microscope, depending on the patient's ability to cooperate.

Acute (bullous) and chronic (granular) myringitis

Acute myringitis is usually caused by a mycoplasma or viral infection and is observed in adults and children. It is characterized by hemorrhagic bullae involving the tympanic membrane and a flulike syndrome. It is self-limiting and requires pain and fever management.

Chronic myringitis is defined as deepithelization of the tympanic membrane, granulation tissue formation, and discharge. Treatment includes topical application of eardrops, a caustic solution in unresponsive cases, and mechanical removal of polypoidal granulations.

Workup

Laboratory Studies

• A formal bacterial and fungal culture, Gram stain, or KOH prep smear of the ear canal confirms the causative agent. This is typically obtained in refractory cases when empiric therapy has been unsuccessful.
• Blood work is usually unnecessary.

Imaging Studies

• Imaging studies are not required for otitis externa.
• In patients with malignant otitis media, CT scanning or MRI of the temporal bone and triple-phase bone scanning and gallium scanning are performed.

Histologic Findings

Histologic examination of the skin of the external canal shows acute inflammation with exudate.

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