Common Non-infectious Diseases of the External Ear: Etiology, Anatomy, Diagnosis, Treatment

This group includes disorders that arise from causes unrelated to infection. Many of these conditions develop independently, and their etiology remains incompletely understood.

Classification

Noninfectious disorders of the external ear include:

• cerumen impaction;
• foreign bodies in external auditory canal (nonliving);
• foreign bodies in external auditory canal (living);
• external auditory canal osteoma;
• external auditory canal exostoses;
• polyp of external auditory canal;
• external auditory canal cholesteatoma.

Etiology

Cerumen impaction is more common in people with excessive cerumen production or narrow external auditory canals. It may also develop in those who regularly attempt to clean the ear canal with improvised objects, such as cotton swabs, pins, matches, knitting needles, or toothpicks, inadvertently pushing cerumen deeper into the canal.

Inanimate foreign bodies of the external auditory canal are commonly found in children, who may insert objects into their ears out of curiosity or during play. In adults, foreign bodies are more often associated with attempts at self-cleaning using improvised objects or, less commonly, psychiatric conditions.

Live foreign bodies generally enter the external auditory canal accidentally, most often during sleep or while a person is outdoors, particularly in wooded areas. Examples include cockroaches, gnats, and spiders.

The etiology of osteomas and exostoses remains incompletely understood. Both are benign bony lesions. Studies suggest that exostoses occur more frequently in professional swimmers, particularly men. This association is thought to result from chronic irritation caused by repeated water exposure.

External auditory canal polyps and cholesteatomas may develop following trauma to the ear canal or tympanic membrane, chronic middle ear infection, or repeated trauma and maceration of the canal skin. In rare cases, they may occur after traumatic removal of foreign bodies or impacted cerumen.

Anatomy

Cerumen Impaction

Ceruminous glands are located in the lateral cartilaginous portion of the external auditory canal. During chewing and speaking, movements of the temporomandibular joint alter the shape of this part of the canal. These movements help propel cerumen outward, allowing it to be cleared naturally. However, attempts to clean the ear canal with foreign objects, including cotton swabs, can push cerumen into the bony portion of the canal. Once there, it can no longer migrate outward effectively and may become impacted.

Foreign Bodies of the External Auditory Canal

In most cases, foreign bodies in the external auditory canal do not cause tissue damage. Small abrasions or hematomas occur only rarely.

Organic foreign bodies, such as beans, can absorb moisture, swell, and completely obstruct the canal, pressing firmly against the surrounding skin. Button batteries are particularly dangerous because they can cause chemical burns and damage not only the external auditory canal but also the tympanic membrane and middle ear.

Live foreign bodies, particularly insects, may injure the skin of the external auditory canal as they move within it.

Osteomas and Exostoses

Osteomas are true benign bone tumors arising from the temporal bone. They are typically unilateral and solitary and arise from a broad base near the tympanosquamous suture. With substantial growth, an osteoma may partially or completely obstruct the external auditory canal.

Exostoses are also benign bony overgrowths but are typically bilateral and multiple. They arise from broad bases around the tympanic annulus and are arranged radially within the canal.

External Auditory Canal Cholesteatoma and Polyp

External auditory canal cholesteatoma consists of an accumulation of desquamated squamous epithelium containing cholesterol-rich debris. It develops along one wall of the external auditory canal and, when extensive, may completely obstruct the lumen.

An external auditory canal polyp is an overgrowth of granulation tissue. It appears as a cushion-like, rounded, moist soft-tissue mass that produces mucous discharge and may completely obstruct the external auditory canal.

Clinical Manifestations

Cerumen impaction may cause discomfort, a sensation of aural fullness, tinnitus, and conductive hearing loss. Some patients may also experience dizziness. On examination, impacted cerumen is seen obstructing the lumen of the external auditory canal.

Inanimate foreign bodies may cause discomfort, a dull aching pain, a sensation of fluid moving within the ear, unusual sounds, and hearing loss. Foreign bodies that absorb moisture, swell, and completely obstruct the canal, as well as button batteries, tend to cause more severe pain. They may also lead to pressure necrosis and deep injury to the underlying tissues.

Live foreign bodies, particularly insects, can cause considerable distress through their movement and noise within the ear. These sensations may be painful and can quickly provoke anxiety or panic. If a foreign body remains in the canal for a prolonged period, it may traumatize the skin and lead to secondary infection, accompanied by swelling and abnormal discharge. In rare cases, foreign bodies retained for several years may become embedded in the canal and eventually become covered by overgrowing skin.

Exostoses and osteomas of the external auditory canal are usually asymptomatic and typically cause no complaints.

External auditory canal cholesteatoma typically presents with persistent itching, a foreign-body sensation, and hearing loss. If secondary infection develops, pain and abnormal discharge may also occur.

An external auditory canal polyp may cause hearing loss and scant mucous discharge.

Diagnosis

Otoscopy is generally sufficient to diagnose cerumen impaction and foreign bodies, as the characteristic findings can be directly visualized. For exostoses, osteomas, cholesteatoma, and polyps, otoscopy is supplemented by CT of the temporal bones to determine the location and extent of the pathologic process. Histologic examination is required for all neoplasms.

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Treatment

Cerumen impaction can be removed on an outpatient basis by irrigating the external auditory canal with a warm sterile nitrofural (furacilin) solution. In some cases, the impacted cerumen must first be softened with a warm 3% hydrogen peroxide solution, or additional instruments such as ear hooks may be required.

Foreign bodies can also be removed on an outpatient basis by irrigation or with specialized hooks. Irrigation should be avoided for beans and other objects that may swell when exposed to water. Forceps are generally avoided because closing the jaws may push the foreign body deeper into the canal. In some cases, alcohol-based drops may first be instilled into the canal to dehydrate organic foreign bodies or immobilize insects. Occasionally, foreign body removal must be performed in the operating room under anesthesia with microscopic visualization.

Exostoses and osteomas are treated by surgical excision with restoration of the normal anatomy of the external auditory canal. Surgery is generally indicated when these lesions obstruct the canal, cause hearing loss, or are associated with recurrent otitis externa over a prolonged period. Small lesions may be managed with observation when the tympanic membrane remains fully visible.

The mainstay of treatment for external auditory canal cholesteatoma is regular outpatient debridement by an otolaryngologist. If the condition recurs frequently or fails to respond to conservative management, surgical debridement followed by meatoplasty may be required.

External auditory canal polyps are removed surgically. Before surgery, topical drying preparations containing diluted alcohol may be used to reduce the size of the polyp.

Because external auditory canal cholesteatoma and polyps usually develop in association with an underlying condition, successful treatment also requires identification and management of the causative factor.