Duration and Prognostic Factors of Therapy in Skull Base Osteomyelitis: A Bi-institutional Analysis

Introduction: Skull base osteomyelitis (SBO) is a rare infection comprising either the lateral (LSBO), central (CSBO), or both lateral and central (BSBO) skull base commonly associated with immunocompromised state. Traditional treatment for osteomyelitis consists of culture-directed antimicrobials (AMT) and, in some cases, surgical debridement. The recommended duration of treatment for osteomyelitis varies, with most sources recommending 6 weeks of intravenous (IV) AMT followed by variable length of oral AMT. Surgical debridement of involved bone along the skull base is limited by the close approximation to critical structures and, therefore, diseased bone often remains after debridement. Taking this into consideration, the previously recommended 6-week courses of IV AMT may not be adequate for treating SBO. The purpose of this study was to identify factors which may influence outcomes of SBO, formulate clearer recommendations on duration of AMT, and explore differences between patients with LSBO, CSBO, and BSBO.

Methods: A bi-institutional retrospective cohort study of patients with SBO at two tertiary academic medical centers was conducted. Data including age, gender, medical comorbidities, presenting symptoms, laboratory evaluation, radiographic imaging, surgical treatment, culture results, length of follow up, and type, length, and number of AMT courses was collected.

Results: 65 SBO patients were identified. The average age was 66.5 years and average length of symptoms (LOS) prior to diagnosis was 3.74 months. The most common pathogen was Pseudomonas aeruginosa (18%) followed by Staphylococcus epidermidis/coagulase negative staphylococcus (11%). 28 patients had LSBO, 10 had CSBO, and 21 had BSBO. There was no significant difference in age (p > 0.05) or incidence of diabetes (p > 0.05) between the subgroups. CSBO patients had significantly longer LOS compared to the overall (p = 0.04) and LSBO (p = 0.009) groups and required more biopsies to achieve a diagnosis compared to the overall (p = 0.03) and LSBO (p = 0.0003) groups. The BSBO group also required a significantly greater number of biopsies to achieve diagnosis versus LSBO (p = 0.0018). The average number of distinct AMT courses was 3.1. The average length of IV AMT was 6.8 weeks and average total length of AMT was 15.7 weeks. The average length of IV AMT for CSBO was significantly shorter than the overall and BSBO groups (p = 0.04 and p = 0.01 respectively). Only 9 patients received <6 weeks of IV AMT. 13 patients had positive fungal cultures. Positive fungal cultures were associated with longer total length of AMT (22.6 weeks vs 13.7 weeks, p = 0.02) and greater number of distinct courses of AMT (4.1 vs. 2.7, p = 0.01).

Conclusion: In this review which represents the largest series of SBO ever reported, the average length of IV AMT was 6.8 weeks and few patients received <6 weeks of IV AMT. The average total length of AMT was 15.7 weeks, indicating a minimum of 6 weeks of IV AMT followed by a prolonged course of oral AMT is necessary to treat most cases of SBO. Fungal involvement significantly impacts duration of AMT. Clinical guidelines are needed to better define the management of this complex disease.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
05 February 2024