The mastoid process is a dense, bony prominence of the skull located directly behind the ear, and it contains a network of small, air-filled spaces known as mastoid air cells. Chronic mastoiditis represents a long-term bacterial infection and persistent inflammation within these air cells and the surrounding bone structure. This condition is a deep-seated infection that can lead to destruction of the temporal bone. Because the mastoid bone is near the brain and major nerves, chronic mastoiditis requires definitive medical attention.
Defining Chronic Mastoiditis
Chronic mastoiditis is characterized by persistent or recurrent inflammation of the mastoid and middle ear, typically lasting for at least three months, distinguishing it from acute mastoiditis. The mastoid bone possesses a honeycomb-like structure due to its extensive system of air cells, which are lined with mucous membrane. In this chronic state, the long-standing infection causes the delicate bony partitions between these air cells to break down, a process known as coalescent osteitis.
This persistent inflammatory reaction often results in a permanent reduction of the air cell system, leading to the formation of dense, non-aerated bone, or sclerosis. The mucosal lining becomes thickened with granulation tissue, which can prevent proper drainage and aeration of the middle ear and mastoid space. This structural damage perpetuates the infection cycle, creating a reservoir of bacteria that resists typical courses of oral antibiotic treatment.
Recognizing the Signs and Symptoms
The manifestations of chronic mastoiditis develop gradually and are often less dramatic than those of the acute form, but they are persistent. A primary symptom is chronic ear discharge, medically termed otorrhea, which may last for many weeks or months. This discharge is frequently thick, purulent, and can have a foul odor due to the presence of bacterial infection and trapped debris.
Patients often experience a dull, persistent pain or tenderness localized behind the ear, which may extend to the side of the head as a low-grade headache. Unlike acute cases, the skin overlying the mastoid may not show significant redness or swelling, but it may feel firm or doughy to the touch. Progressive hearing loss is a common complaint, typically a conductive loss caused by damage to the middle ear structures and eardrum.
How the Condition Develops
The development of chronic mastoiditis nearly always follows a history of inadequately treated chronic middle ear infection, known as chronic otitis media. The underlying issue is often poor function of the eustachian tube, which connects the middle ear to the back of the nose and is responsible for regulating pressure and draining fluid. When this tube fails, a negative pressure develops in the middle ear, drawing the eardrum inward.
This chronic negative pressure can lead to the formation of a cholesteatoma, a non-cancerous skin cyst that grows behind the eardrum and into the mastoid space. The cholesteatoma is a significant factor in perpetuating the chronic state, as it traps old skin cells and debris, providing an environment for bacterial growth. This abnormal growth actively erodes the surrounding bone by secreting specialized enzymes, accelerating the destruction of the mastoid air cells.
Diagnosis and Medical Intervention
Confirming a diagnosis of chronic mastoiditis relies on clinical examination and high-resolution imaging to assess the extent of the bone disease. A high-resolution Computed Tomography (CT) scan is the preferred imaging modality, as it provides detailed views that clearly visualize the destruction of the mastoid bone septa, the presence of fluid or granulation tissue, and the extent of any cholesteatoma.
To identify the specific microbe, a sample of the persistent ear drainage is collected for a bacterial culture and sensitivity test. Initial medical management often begins with a prolonged course of targeted antibiotics, sometimes administered intravenously. However, because antibiotics struggle to penetrate the sclerotic, damaged bone and the core of a cholesteatoma, surgical intervention is frequently the definitive treatment.
The standard surgical procedure is a mastoidectomy, where the infected mastoid air cells, diseased tissue, and any cholesteatoma are carefully removed to eradicate the source of the chronic infection. Untreated chronic mastoiditis carries a risk of the infection spreading beyond the temporal bone, potentially causing facial nerve paralysis, meningitis, or a brain abscess.