External otitis can be classified into two types:

Localized external otitis, manifested by furunculosis of the external auditory canal
Diffuse external otitis, characterized by diffuse inflammation of the skin or subcutaneous tissue of the external auditory canal

Etiology

Furunculosis of the external auditory canal is a localized purulent inflammation of the hair follicles or sebaceous glands in the canal's skin. It is more common in individuals with diabetes or weakened immunity. The primary pathogen is Staphylococcus aureus.

Diffuse external otitis is a widespread inflammation of the external auditory canal. It is often triggered by water entering the ear, prolonged discharge from chronic suppurative otitis media, or trauma to the skin of the canal, especially when local immunity is compromised. Individuals with diabetes or allergic constitutions are prone to recurrent episodes. Common pathogens include Staphylococcus aureus, Streptococcus hemolyticus, Pseudomonas aeruginosa, and Proteus species.

Clinical manifestations

Furunculosis of the external auditory canal

Early symptoms include severe ear pain, which worsens with jaw movement or chewing and may radiate to the same side of the head. Patients often experience general malaise, and body temperature may be slightly elevated.

When the furuncle obstructs the canal, symptoms such as tinnitus and ear fullness may occur.
On examination, pain is elicited on pulling the auricle or pressing the tragus. A furuncle can be seen on the cartilage portion of the external auditory canal skin.

Once the abscess matures and ruptures, thick pus, sometimes mixed with blood, drains from the ear, leading to pain relief.

Furuncles on the posterior wall of the canal may cause redness and swelling in the postauricular groove and mastoid region, which can be mistaken for mastoiditis.

Diffuse external otitis

In the acute phase, symptoms include ear pain, burning sensation, and a small amount of discharge. Examination reveals pain on pulling the auricle or pressing the tragus, diffuse redness and swelling of the canal skin, narrowing of the canal, and secretions accumulating on the canal wall. Regional lymph nodes around the ear may be swollen and tender.
In the chronic phase, symptoms include pruritus, mild discharge, and thickened, cracked, or scaly skin in the canal. Secretions may accumulate, and in severe cases, canal stenosis may develop.

Necrotizing external otitis

This is a severe form of diffuse external otitis, often referred to as malignant external otitis, though it is not a malignancy.

It frequently leads to external auditory canal osteomyelitis and progressive necrosis, potentially involving the temporal and cranial bones, causing complications such as multiple cranial nerve palsies, with facial nerve paralysis being the most common.

Symptoms include severe stabbing pain, ear discharge, and a prolonged disease course.

It predominantly affects older individuals and those with diabetes. The primary pathogen is Pseudomonas aeruginosa.

In severe cases, the infection may extend to the infratemporal fossa or subarachnoid space, leading to meningitis, brain abscess, encephalomalacia, and death.

Treatment

Infection should be controlled with antibiotics. Sedatives and analgesics can be administered. In the early stages, local heat application or shortwave diathermy may be beneficial.

For non-suppurative cases, 1 - 3% phenol-glycerin or 10% ichthyol-glycerin ear drops can be applied. Alternatively, soaked gauze strips in these solutions can be placed on the affected area, changing dressings twice daily.

For mature furuncles, incision and drainage may be required. The external auditory canal can be cleaned with 3% hydrogen peroxide to remove pus and secretions.

For chronic cases, a combination of antibiotics and corticosteroids in the form of ointments, pastes, or creams can be applied. Excessively thick coating should be avoided.

Underlying infections, such as chronic suppurative otitis media, should be properly treated. Debridement of granulation tissue should be performed, and systemic diseases such as diabetes should be addressed.

For suspected necrotizing external otitis, bacterial cultures and antibiotic sensitivity testing should be conducted as early as possible. Appropriate antibiotics can be administered promptly to correct systemic conditions.