Diffusion MR Imaging Features of Skull Base Osteomyelitis Compared with Skull Base Malignancy

BACKGROUND AND PURPOSE: SBO is a life-threatening infection that may have radiologic features similar to those of the neoplastic processes. The purpose of this study was to evaluate the DWI findings in SBO to facilitate the differential diagnosis. MATERIALS AND METHODS: The MR imaging findings of 9 patients with SBO were retrospectively evaluated and compared with MR imaging studies from 9 patients with NPC, 9 with lymphoma, and 9 with metastatic disease of the skull base. ADC measurements were performed from the ADC(ST) and the ADC(NST) in all 4 groups. RESULTS: The mean ADC(ST) values were 1.26 +/- 0.19 x 10(-3) mm(2)/s for SBO, 0.74 +/- 0.18 x 10(-3) mm(2)/s for NPC, 0.59 +/- 0.11 x 10(-3) mm(2)/s for lymphoma, and 0.99 +/- 0.34 x 10(-3) mm(2)/s for metastatic disease, respectively. The mean ADC value of SBO was significantly higher than those of NPC and lymphoma (P<.0001). There was no significant difference for the comparison of SBO and metastatic lesions. When an ADC value equal to or higher than 1.08 x 10(-3) mm(2)/s was used to rule out lymphoma and NPC, the accuracy was 96%. CONCLUSIONS: Although SBO is a relatively rare condition, its differential diagnosis from neoplastic processes of the skull base is essential to start appropriate treatment promptly. ADC values may help to distinguish patients with SBO from those with malignant lesions.