Otitis Externa Differential Diagnoses

Updated: Jul 11, 2016
  • Author: Ariel A Waitzman, MD, FRCSC; Chief Editor: Ravindhra G Elluru, MD, PhD  more...
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DDx

Diagnostic Considerations

Failure to recognize necrotizing (ie, malignant) otitis externa (OE) is a significant pitfall. A patient who is diabetic or immunocompromised with severe pain in the ear should have necrotizing OE excluded by an otolaryngologist.

Problems to be considered include the following:

  • Ear canal trauma
  • Ear canal carcinoma
  • Otitis media with a perforation or ventilation tube present
  • Chondritis
  • Cranial nerve palsy
  • Hearing loss
  • Wisdom tooth eruption
  • Intracranial abscess
  • Cavernous sinus thrombosis
  • Ramsay Hunt syndrome
  • Furuncle
  • Skull base osteomyelitis
  • Preauricular cyst and fistula
  • Lacerations
  • Atopic dermatitis
  • Cerumen impaction
  • Exostosis and osteoma
  • Foreign body
  • Acute (bullous) and chronic (granular) myringitis

Although malignant tumors of the ear canal are rare, they do occur and sometimes are misdiagnosed as OE. [18] If the condition does not respond to treatment as expected, an otolaryngologist should evaluate the patient.

Ramsay Hunt syndrome, more accurately known as herpes zoster oticus, is caused by varicella-zoster virus (VZV) infection. It 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 external auditory canal (EAC). Painful OE 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.

A furuncle is usually caused by staphylococcal infection of a hair follicle. This infection occurs in the lateral cartilaginous hair-bearing portion of the EAC. On otoscopic examination, a furuncle appears as a localized process, which may develop into an abscess, rather than as a diffuse inflammatory process, as is characteristic of OE.

Skull base osteomyelitis occurs most often in patients who are diabetic or immunocompromised. The usual bacterial pathogen is 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.

Computed tomography (CT) demonstrates bone erosion, and gallium scanning can be performed at points throughout treatment to monitor resolution. Treatment consists of administration of an antipseudomonal intravenous (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.

A preauricular cyst or fistula may form as the result of abnormal development of the first and second branchial arch and 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. Complete excision is indicated if these lesions become repeatedly infected. The facial nerve is at risk for injury during excision because of the close relation of the cyst or fistula to the superior branches of the nerve within the parotid gland.

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

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 to clean the ear canal with 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 resulting from sensitivity to topical antibiotic solutions is well known. Neomycin allergy occurs in as many as 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 the 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 (eg, an earring) and beginning topical steroids and antibiotics if the wound is secondarily infected. The diagnosis of metal sensitivity is confirmed by performing a skin patch test.

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 both to produce and to clear itself of cerumen. Cerumen may vary in color and consistency, and cerumen impaction may coexist with other pathologic conditions.

Debris in the EAC from cholesteatoma or tumors may be confused with cerumen; accordingly, considerable care is required when debridement of the EAC is attempted. Debridement may be accomplished by using microinstruments or by aspirating ear canal contents with a No. 5 or No. 7 Barton suction device 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.

Exostoses and osteomas, the two most common bony lesions of the EAC, differ both histologically and clinically. Exostoses tend to arise from the anterior or posterior floor of the medial EAC (or from both simultaneously), have a sessile base, and are covered with normal-appearing skin. Osteomas may arise from any region of the bony EAC, are often pedunculated, may be 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 OE.

Foreign bodies in the EAC are not infrequently encountered. In children, the appearance of these foreign bodies is variable; parts of toys or even food may be found in the EAC. In adults, fragments of cotton swabs are the most common finding. Erythema and edema surrounding the foreign body are commonly present. Depending on the patient’s ability to cooperate, the foreign body may be removed under a microscope with the aid of microinstruments. 

Hearing aid or watch batteries can sometimes end up in the ear canal accidentally, both in the pediatric and in the adult population. Time to onset of symptoms can range from a few hours to a day. Like batteries accidentally placed anywhere in the body, batteries in the ear canal represent a medical emergency. Therefore, expeditious identification and removal are absolutely necessary.

Acute myringitis is usually caused by a mycoplasmal or viral infection and has been observed in both adults and children. It is characterized by hemorrhagic bullae involving the tympanic membrane and a flulike syndrome. It is self-limiting; treatment involves pain control 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.

Differential Diagnoses