Review Question - QID 104433

The patient in this vignette most likely has necrotizing external otitis (NEO), as evidenced by the findings on otoscopic exam as well as his age and diabetic risk factors. Pseudomonas aeruginosa is the most commonly identified organism in cases of NEO.

Necrotizing (formerly known as "malignant") otitis externa is seen almost exclusively in immunocompromised persons, especially those with poorly-controlled diabetes mellitus. It should be noted that NEO is distinguidhed from otitis externa. NEO spreads from the floor of the ear canal (as can be infected in non-necrotizing otitis externa) to the nearby tissues including the bones at the base of the skull, which distinguishes the necrotizing variant. The most commonly presenting patients are the elderly with diabetes mellitus, though this condition can follow self-inflicted trauma to the external auditory canal. Patients will commonly complain of severe nocturnal otalgia and purulent otorrhea.

Handzel and Halperin report that cranial and facial nerve palsies may result from the invasion of NEO and indicate a poor prognosis. The most common cause of death from this condition results from intracranial complications.

Hollis et al. write that Pseudomonas aeruginosa is the most common cause of NEO. Treatment involves typical antipseudomonal antibiotics; however, there are increasing reports of resistance. There are also reports of fungal causes in immunosuppressed patients.

Figure A demonstrates an external ear affected with NEO. Note the erythematous, edematous appearance of the external ear with associated purulent drainage.

Incorrect Answers:
Answer 1: Haemophilus influenzae is among the most common causative organisms in acute otitis media, often affecting children. This patient has an infection of the external ear that is not commonly caused by Haemophilus influenzae.

Answer 2: Moraxella catarrhalis is also among the most common causative organisms in acute otitis media, often affecting children. This patient has an infection of the external ear that is not commonly caused by Moraxella catarrhalis.

Answer 4: Staphylococcus aureus does commonly cause otitis externa. However, it is much less commonly responsible for the necrotizing variant of otitis externa that affects immunocompromised patients such as the patient in this vignette.

Answer 5: Streptococcus pyogenes may less commonly cause otitis externa. However, it is much less commonly responsible for the necrotizing variant of otitis externa that affects immunocompromised patients such as the patient in this vignette. More often, Streptococcus pyogenes causes skin and soft tissue infections such as cellulitis or erysipelas.

Bullet Summary:
Necrotizing otitis externa is a necrotizing infection of the external ear and other surrounding structures most commonly caused by Pseudomonas aeruginosa.