An Important Pitfall in Diagnosing Intracanalicular Vestibular Schwannoma

MPRAGE (A, C, and E) and CISS (B, D, and F) in 3 different patients (patient 1: A and B; patient 2: C and D; and patient 3: E and F). MPRAGE shows different degrees of enhancement in the fundus of the internal auditory canal bilaterally (left more than right) in patient 1 and on the left side in patient 2 (white arrows in A and C). However, in both patients, no analogous lesion was detected in the CISS sequence. Therefore, the enhancement was not due to the presence of a schwannoma but was most likely due to a vascular structure. In contrast, in patient 3, there was nodular enhancement in the fundus of the internal auditory canal on the right side (red arrow in E), which was accompanied by a corresponding lesion “filling defect” on the CISS sequence (red arrow in F) due to the presence of a small intracanalicular vestibular schwannoma (Koos I). Correlating findings in MPRAGE with the CISS sequence is crucial to avoiding misinterpretation of this enhancement.