Diffusion-Weighted Imaging Does Not Differentiate Between Bacterial and Fungal Skull Base Osteomyelitis

Area of Science:

• Radiology
• Infectious Diseases
• Oncology

Background:

• Apparent diffusion coefficient (ADC) values are used in magnetic resonance imaging (MRI) to distinguish between infections and neoplasms.
• Skull base osteomyelitis (SBO) is a challenging condition requiring accurate diagnosis and pathogen identification.

Purpose of the Study:

• To evaluate if ADC values derived from diffusion-weighted imaging (DWI) can differentiate between fungal and bacterial SBO.
• To analyze the microbiological spectrum of SBO patients.

Main Methods:

• Retrospective observational study of 142 SBO patients (January 2010 - May 2023).
• Comparison of ADC values between bacterial and fungal SBO using Chi-square or Fisher's exact test.
• Microbiological analysis of isolated pathogens.

Main Results:

• The most common pathogens identified were Pseudomonas (42.2%), Aspergillus (30.98%), and S. aureus (23.94%).
• Average ADC values for affected soft tissues (1.13 ± 0.26 × 10^-3 mm²/s) were lower than normal soft tissues (1.34 ± 0.31 × 10^-3 mm²/s).
• No statistically significant difference in ADC values was found between bacterial and fungal SBO (p = 0.142).

Conclusions:

• While Pseudomonas was the most frequent pathogen, over half of SBO cases involved other organisms, highlighting the need for early, deeper biopsies.
• Diffusion-weighted imaging (DWI) does not reliably differentiate between bacterial and fungal SBO.
• Emphasis on obtaining deeper tissue biopsies for accurate microbiological diagnosis in SBO is critical.