This study explored the clinical, radiological, and pathological characteristics of cerebellopontine angle (CPA) meningiomas with internal auditory canal (IAC) involvement. The pre- and postoperative MR images of 193 consecutive patients with pathologically diagnosed meningioma centered around the IAC were analyzed, focusing on changes in the IAC, maximal axial tumor volume, peritumoral brain edema, and postoperative residual tumor. Patient age, sex, tumor volume, postoperative residual tumor, and pathological subtype were compared in patients with and without IAC involvement by the tumor and among the different types of IAC involvement. The results showed that the 71 patients (36.8%) with IAC involvement had a higher ratio of peritumoral edema (chi(2) = 5.922, P = 0.015), postoperative residual tumor (chi(2) = 22.183, P < 0.001), and a predominance of the meningothelial subtype (chi(2) = 5.89, P = 0.015). Peritumoral edema was a risk factor for IAC involvement (P = 0.016, OR = 2.186). Radiologically, IAC involvement could be distinguished as intruding (31%, 22/71), filled (29.6%, 21/71), and dilated (39.4%, 28/71). Patients with intruding IAC were significantly older (54.5 +/- 9.54 years, P = 0.021) and had the lowest postoperative residual tumor values (42%, chi(2) = 7.865, P = 0.005), while those with filled IAC were more likely to be female (95%,chi(2) = 9.404, P = 0.009). Our observations provide the basis for a morphological classification of IAC involvement by CPA meningiomas and further insight into the clinical features of these tumors.