Differential Diagnosis of Cerebellopontine Angle Lesions: Key MRI and CT Features in a 159-Patient Retrospective Cohort

Objective: To assess the diagnostic value of routinely evaluated magnetic resonance imaging (MRI) and computed tomography (CT) features for differentiating cerebellopontine angle (CPA) and internal auditory canal (IAC) region lesions in a retrospective clinical cohort. Methods:We conducted a retrospective review of 159 patients with CPA or IAC lesions.MRI was available for all patients; contrast-enhanced MRI and evaluable apparent diffusion coefficient (ADC) maps were available for 145 and 156 patients, respectively.CT was available in 83 patients (52.2%).Comparisons focused on vestibular schwannoma, meningioma, arachnoid cyst, and epidermoid cyst, and modality-dependent findings were calculated from evaluable examinations.Results: The median age was 53 years (range <1-93 years); 90 patients (56.6%) were women.The most common diagnosis was arachnoid cyst (29.6%), followed by vestibular schwannoma (28.3%), meningioma (20.8%), metastasis or suspected metastasis (6.3%), and epidermoid cyst (4.4%).IAC enlargement was most frequent in vestibular schwannoma cases (73.3%;P <0.001).A broad dural base was present in 29 of 33 meningiomas (87.9%), and the dural tail sign was present in 8 of 30 contrast-evaluable meningiomas (26.7%;P <0.001).Among CT-evaluable examinations, calcification was present in 8 of 20 meningiomas (40.0%;P <0.001) and bone remodeling/scalloping was present in 13 of 19 arachnoid cysts (68.4%;P <0.001).ADC values differed among the selected groups (P <0.001) based on evaluable maps from 44 schwannomas, 31 meningiomas, 47 arachnoid cysts, and 7 epidermoid cysts.Conclusion: IAC enlargement, dural morphology, CT-detected calcification and osseous remodeling, and ADC were useful in differentiating common CPA/IAC lesions.Modality-dependent findings should be reported using the number of evaluable examinations.