Infections of the Ear: Otitis Media and Externa, Mastoiditis

Infections of the Ear: Otitis Media and Externa, Mastoiditis

Rupal S. Jain

Candace E. Hobson


Infections of the external and middle ear (otitis externa and otitis media) are common reasons for presentation to urgent care facilities or emergency departments (EDs). A foundational understanding of the anatomy of the ear and the pathophysiology of these infections is key to their successful management.

Anatomically, the ear is divided into the external, middle, and internal ear. The external ear consists of the auricle (pinna) and the external auditory canal (EAC). The auricle is the portion of the ear that protrudes from the head and is composed of cartilage covered by skin. The EAC, also known as the ear canal, is approximately 25 mm in length. The outer third of the EAC consists of an outer layer of skin with underlying skin follicles, cerumen and sebaceous glands, and cartilage. A thin layer of skin directly overlying bone comprises the medial two-thirds of the EAC. The tympanic membrane (TM) separates the external from the middle ear. The middle ear is an air-filled space containing the hearing ossicles (malleus, incus and stapes), the facial nerve, and the chorda tympani nerve. The middle ear communicates with the mastoid via the aditus ad antrum and with the nasopharynx via the eustachian tube. The inner ear consists of the cochlea and the vestibular labyrinth, the neural structures of hearing and balance.


Otitis Media

Acute otitis media (AOM) is a painful infectious process of the air-filled space of the middle ear, marked by the presence of both infected fluid and inflamed mucosa. It is a clinical diagnosis that is especially challenging owing to reliance on symptoms that are neither sensitive nor specific. Adding to the challenge, the physical examination is often limited owing to inadequate visualization of the TM secondary to obstructing cerumen, operator inexperience with otoscope, and/or lack of patient/child cooperation with examination. AOM is grossly overdiagnosed and unnecessarily treated, largely because of the aforementioned limitations, and this problem is compounded by the significant overlap of symptoms with the common cold, and patient preference for antibiotic treatment.1 Furthermore, the gold standard test for the diagnosis of otitis media is pneumatic otoscopy—a diagnostic maneuver not routinely taught to many providers.


Mastoiditis is a nonspecific term describing an inflammatory process of the mastoid. Because the middle ear and mastoid air spaces are confluent, AOM and serous otitis media typically result in some degree of mastoid inflammation. Technically, however, mastoiditis is a complication of otitis media caused by osteitis of the mastoid air cells resulting in breakdown of bony septations and coalescence of air cells. The full term for this condition, “acute coalescent mastoiditis,” is often simply referred to as “mastoiditis.”

Untreated, mastoiditis can lead to abscess formation, bone resorption, and invasive spread of the infection. Part of the diagnostic challenge is that initial findings may be subtle and variable based on the involved pathogen and patient age group. The classic postauricular symptom, tender and erythematous postauricular swelling as well as anteroinferior displacement of auricle, were present in only 10% of patients in a 2012 retrospective study.2 Accurate diagnosis relies on a combination of clinical symptoms, physical exam and otoscopic findings, and supportive evidence on computed tomography (CT) or magnetic resonance imaging (MRI).3

Otitis Externa

Acute otitis externa (AOE) affects patients of all ages with a lifetime prevalence of 10%.4,5 Otitis externa is inflammation or infection of the EAC, which may extend to involve the auricle or TM. AOE, also known as “swimmer’s ear,” is a cellulitis of the skin of the EAC. When otitis externa persists for over 3 months, it is considered chronic. Chronic otitis externa may be the result of inadequately treated AOE but is often associated with chronic dermatologic conditions. Distinguishing the nature and etiology of otitis externa is key to effective management.


Acute Otitis Media

AOM is a clinical diagnosis; therefore, laboratory and imaging tests are not routinely necessary. Symptoms of AOM may include current or recently resolved upper respiratory infection (URI) symptoms (rhinorrhea, cough), unilateral or bilateral otalgia, decreased or muffled hearing, and otorrhea. On examination, the patient may have fever, retracted or bulging TM (Figure 4.1A), erythematous (from inflammation) or a yellow/white (from effusion) hue to the TM (Figure 4.1B), reduced TM motion on pneumatic otoscopy, and TM perforation (especially if the patient presents with otorrhea). Facial paralysis, meningismus, mastoid tenderness, or toxic appearance may be late signs suggestive of spread of the infection beyond the ear. In severe cases, intracranial complications may include meningitis, intracranial abscess, lateral sinus thrombosis, and otitis hydrocephalus.

Apr 18, 2023 | Posted by in OTOLARYNGOLOGY | Comments Off on Infections of the Ear: Otitis Media and Externa, Mastoiditis

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