Year: 2024
Type: article
Abstract: Lateral skull base osteomyelitis (SBO), also called malignant otitis externa or necrotitizing otitis externa, is a subacute yet relentless infection of the external auditory canal and skull base most often found in elderly males and diabetics. When SBO was first described in the 1950s, the first-line therapy was surgical intervention. Over the past few decades, a transition toward culture-directed antibiotics has shifted the treatment paradigm of SBO toward primary medical management, with mortality rates now decreased to 10%–20% compared to 50% initially. Today, the treatment of SBO involves multidisciplinary coordination between otolaryngology and infectious disease. Although the introduction of quinolone antibiotics has significantly decreased mortality rate, the rate of surgical intervention has not drastically changed over time.1 Due to the rarity of this condition, there is significant variability in practice styles between individuals and institutions, and there is no consensus on the specific indications for surgical intervention. The purpose of this best practice review was to interpret the available evidence to better define contemporary indications for surgery. In the hospital setting, surgery is often requested by medical teams to obtain deeper culture data, either due to negative initial bedside cultures or concerns for antibiotic resistance. In one of the largest series to investigate the utility of surgical cultures, Go et al. reviewed the management of 40 SBO patients over a 16-year period.1 The authors found that among the 13 patients who underwent surgical intervention (two temporal bone resections, eight mastoidectomies, three local debridements), only one intraoperative culture led to a change in antibiotic therapy. The authors did not find any difference in facial nerve outcomes, total antibiotic treatment length, disease recurrence rates, or mortality rates between patients who were treated surgically or medically. The authors were unable to delineate clear indications for surgery, however, at a minimum, these data suggest that "deep" surgical cultures generally do not yield additional information that cannot be obtained from bedside ear canal samples. SBO of the lateral skull base is characterized by diffuse involvement of bony and soft tissue tracts, making traditional source control difficult to achieve. To this end, one of the major challenges in defining the role of surgery is identifying patients who would benefit. In 2015, Stevens et al. attempted to categorize 28 SBO patients into severity based on radiographic and clinical features such as fungal etiology and facial nerve paresis.2 In this series, the two patients with severe disease who underwent surgical debridement survived. The specific type of surgery performed was not described, and while anecdotal, the positive survival outcome in both surgical patients—in spite of the poor prognosis in the group overall—prompts consideration of surgery in patients with more aggressive disease. The survival benefit of surgery for clinically aggressive features has not been redemonstrated in subsequent larger studies. Facial nerve weakness is the most common adverse feature that prompts surgical intervention. In 2023, Marszał et al. performed a literature review of 23 studies and 48 patients who underwent facial nerve decompression through a variety of surgical approaches for lateral SBO (26 canal wall down mastoidectomies, four canal wall up mastoidectomies, four petrosectomies, 14 not specified). The authors found that nerve recovery was unpredictable regardless of treatment approach, and surgical intervention was not superior to medical management for improvement in posttreatment House–Brackmann scores.3 These findings are consistent with results of Go et al. in 2024.1 The majority of SBO cases can be attributed to the gram-negative Pseudomonas aueruginosa. Although fungal infection accounts for less than 10% of cases, positive fungal cultures are considered a poor prognostic factor due to fewer presenting symptoms and closer association with immunosuppression, leading to delayed diagnoses, higher rates of antibiotic failure, and increased mortality.4 Hamzany et al. compared 60 cases of SBO stratified by fungal and non-fungal causes, and found that patients with fungal disease had more severe disease characteristics, including younger age at presentation, earlier and higher rates of facial palsy, and more evidence of tissue invasion on imaging. Patients with fungal SBO in this retrospective study were more likely to undergo surgery compared to patients with bacterial etiologies (78% vs. 18%, respectively). The specific surgeries performed were not specified. Despite the greater tendency toward surgical intervention for fungal disease, both groups had comparable 5-year disease specific survival rates ranging from 83% to 90%, consistent with published values for SBO overall. The strongest justification for surgical intervention may be in the setting of recurrent disease. Singh et al. investigated the role of surgery for refractory SBO in a prospective sample of 20 patients at one tertiary care center.5 Refractory disease was defined as no clinical improvement after 6 weeks of first-line antibiotics. The first group was treated with intravenous ceftazidime and oral ciprofloxacin while the second group was treated with oral ciprofloxacin and surgical exenteration. The authors found that surgical drainage resulted in greater treatment response for refractory SBO as confirmed by posttreatment gallium scans. The surgical group also experienced greater resolution of canal edema and granulation, drainage, and nocturnal pain. A limitation of this study was that the authors did not specify the type of surgical intervention performed. Furthermore, both groups were treated with oral ciprofloxacin, confounding the benefit of surgery. Taken together, the timing, technique, and indications for surgical intervention for SBO remain difficult to generalize. Due to the rarity of this disease, single-institution experiences spanning multiple decades result in only modest small sample sizes,1, 4 and current evidence is primarily limited to case reports and small series. The specific type of surgeries performed is often underreported, contributing to the ambiguity of surgical decision-making; this piece of information is critical in order to guide management because surgery for SBO can range from simple incision and drainage to temporal bone resection with free flap reconstruction, each with a different set of risks, benefits, and surgical objectives. Prospective comparison data is lacking, however, it may not be plausible given the ethical considerations of randomized surgical trials. Therefore, larger, multi-institutional studies are needed to clarify which patients would benefit from surgical intervention. Key management principles of SBO include aggressive diabetes control, reversal of immunocompromised states, and prolonged antibiotics with anti-pseudomonal coverage. When it comes to contemporary indications for surgical intervention, failure of medical management has the strongest justification; however, the definition of "medical failure" and the type of surgeries indicated in these circumstances are not well defined. Surgical cultures do not typically yield pathogen data that leads to a change in antibiotic regime, therefore the utility of surgery solely for the purpose of obtaining deeper cultures may be limited. There may be a role for surgery in the setting of aggressive features such as facial palsy and fungal involvement, however, the benefits have not been clearly demonstrated based on currently available data. The above studies exhibit a level of evidence IV or V, with the exception of Singh et al. which demonstrates a level of evidence II.
Source: The Laryngoscope
DOI: 10.1002/lary.31703
Institution: University of Pennsylvania
Language: English
Subfield: Infectious Diseases
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
Estimated APC paid: $4,840
OpenAlex ID: W4401620950