Association between type of skull base osteomyelitis (SBO), source, and infection spread in patients with proven SBO.

Introduction: Skull base osteomyelitis (SBO) is a challenging diagnosis with a variety of nonspecific clinical manifestations and imaging findings. This study aims to determine the association between the type of SBO and the source and infection spread in patients with histopathology/culture-proven SBO.

Materials and methods: A retrospective analysis of 55 patients with suspected SBO was conducted. Twenty-two patients (40%) were excluded because either histology resulted in neoplasia without associated infection (2[9%]) or imaging findings were negative for SBO. An additional nine patients were excluded due to negative cultures and nonspecific inflammatory changes on histology without clinical signs of sepsis. A total of 24 patients met inclusion criteria with either a positive culture (13[54.1%] or histopathologic inflammation with signs of infection (11[45.9%]).

Results: Bacterial SBO was identified in 13 patients (54.1%) and fungal SBO in two patients (8.33%). Typical SBO (TSBO) was observed in 12 patients (50%). Twelve patients (50%) had typical SBO (TSBO), and the remaining 12 (50%) presented with central or atypical SBO (ASBO). The nasopharynx was identified as the primary source of infection in one-third of ASBO cases. In this group, the infection frequently extended to the masticator space (75%, p = 0.01) and carotid space (75%, p < 0.01), with internal carotid artery thrombosis seen in half of these patients (p = 0.06). Temporomandibular joint involvement was also observed (58.3%, p = 0.2). On MRI, peri-clival soft tissue enhancement (66%, p = 0.03) and sphenoid body bone marrow edema (50%, p = 0.08) were prominent findings in ASBO cases.

Conclusion: Central or atypical SBO accounted for half of the confirmed cases in this study and was frequently associated with extensive spread to adjacent deep neck spaces and vascular complications. Characteristic MRI findings such as peri-clival soft tissue enhancement and sphenoid body marrow edema may aid early recognition. Identifying the nasopharynx as a common infection source and recognizing these imaging patterns can support earlier diagnosis and tailored treatment strategies, potentially improving patient outcomes.