Fiber orientation distribution for detecting skull base tumor histopathology: technical note and retrospective 81-case series

OBJECTIVE Skull base tumor surgery remains challenging because these tumors are deeply seated and trapped within numerous cranial nerves and vessels. Accurate histopathological analysis of skull base tumors will strongly impact their further management. Yet, currently there is no noninvasive validated method to confirm their diagnosis. In a recent study of MRI tractography, the authors used fiber orientation distribution (FOD) and noted that this diffusion model formed a pattern that could correspond to the histopathological type of skull base tumors. The aim of this study was to propose a new imaging method for skull base tumors that can detect the diagnosis according to the FOD pattern. METHODS From an 81-case series of skull base tumors, MRI diffusion images were investigated by 3 independent observers. Diffusion patterns were classified as centrifugal, wrapped, and chaotic, corresponding to meningiomas, schwannomas, and epidermoid cysts, respectively. RESULTS The overall identification rate was 80.7%, with an excellent concordance between the 3 observers (Fleiss’s κ coefficient = 0.765, p < 0.0001). The identification rate increased along with the observers’ anatomoradiological expertise (72.8%, 77.8%, and 91.4%, for observer 1 [low expertise], 2 [average expertise], and 3 [extensive expertise], respectively) and was higher for schwannomas (88.6%), than meningiomas (72.6%) and epidermoid cysts (66.7%). CONCLUSIONS This new imaging tool could assist in complex skull base tumor identification and characterization, as well as surgical management.