Objectives: Malignant otitis externa (MOE), also known as necrotizing otitis externa or lateral
skull base osteomyelitis (SBO), is an invasive and progressive infection of the external
ear and lateral skull base. We use a large national database to better understand
the epidemiology of current practice patterns of this rare clinical entity.
Materials and Methods: The Epic Cosmos database, a national HIPAA-defined limited electronic health record
(EHR) dataset, was used to analyze a retrospective cohort of patients with an encounter
including a diagnosis of malignant otitis externa between January 2010 and December
2023. Demographic information, pertinent medical history, all-cause mortality rate,
antibiotic prescribing patterns, and rates of surgical intervention were collected.
Results: A total of 80,166 encounters involving 47,387 patients were included, comprising
0.72 per 100,000 encounters and 19.58 patients per 100,000 patients. A total of 25,500
(53.8%) were female. A total of 10,653 (13.3%) encounters were for pediatric patients
and 69,401 (86.7%) encounters were for adult patients. Average age at encounter was
51.0 years (SD: 24.1), with average adult age of 57.4 years (SD 18.9) and average
pediatric age of 9.4 years (SD: 4.6). A total of 6,382 (8.0%) of the encounters were
inpatient encounters. All-cause mortality within the cohort was 5.1%. Risk factors
included type 1 diabetes mellitus (1,952, 4.1%), type 2 diabetes mellitus (13,082,
27.6%), other diabetes mellitus (3,012, 6.4%), HIV (318, 0.7%), history of malignancy
(5,485, 11.6%), and history of chemotherapy (1,514, 3.2%). The predominant antimicrobials
associated with these encounters were topical, including ciprofloxacin/dexamethasone
(17,225, 21.5%), ofloxacin (6,243, 7.8%), and acetic acid solutions (793, 1.0%). In
addition to oral ciprofloxacin (8,261, 10.3%), a wide range of other oral antibiotics
were used, including amoxicillin (3,510, 4.4%), amoxicillin-clavulanate (5,744, 7.2%),
cephalexin (1,133, 1.4%), azithromycin (1,720, 2.1%). Intravenous antibiotics such
as ampicillin-sulbactam (427, 0.5%), cefepime (2,531, 3.2%) and piperacillin-tazobactam
(2,218, 2.8%) were less commonly utilized, as were antifungal agents. The most common
antifungal medications were fluconazole (1,266, 1.6%), ketoconazole (216, 0.3%), and
voriconazole (214, 0.3%). Rates of surgical intervention were low, with a total of
533 (0.7%) encounters associated with a procedure. The most commonly performed procedure
was a biopsy of the external auditory canal (205, 0.3%), followed by complete mastoidectomy
(114, 0.1%).
Conclusion: Just over half of the cohort had classical MOE risk factors compared with the 90%
typically seen in the literature. It is unclear if there has been a change in the
profile of MOE patients or if MOE is being improperly diagnosed within EHR systems.
Additionally, 15% of encounters were associated with antibiotics that have poor coverage
against the common causative organisms, further indicating incorrect diagnosis within
the EHR or a need for more education regarding proper antibiotic management of this
recalcitrant disease. Finally, this project illustrates a potential pitfall of utilizing
the EHR for retrospective research.
