Prediction of the origin of intracanalicular neoplasms with high-resolution MR imaging.

Correct diagnosis of intracanalicular neoplasms is important to avoid unnecessary operations or an unsuitable surgical approach. We investigated the capability of high-resolution three-dimensional MR imaging in predicting the origin of intracanalicular neoplasms. Twenty cases underwent three-dimensional Fourier-transformation (3DFT) constructive interference in steady state and contrast-enhanced 3DFT-fast low angled shot MR imaging and surgery. Seventeen cases underwent caloric test. MR diagnosis on the origin of intracanalicular neoplasms was compared with surgical results. For MR diagnosis, the origin of intracanalicular neoplasms was predicted according to the location of the tumor in the internal auditory canal (IAC) in two ways, i.e., determining (1) a single specific nerve of origin and (2) whether the tumor originated from the superior or inferior aspect of the IAC. Surgery could determine the nerve of origin in 16 cases (14 inferior and 2 superior vestibular schwannomas), but it was indeterminate in 4. Comparison between MR prediction and surgical results on a single nerve origin revealed exact agreement in five, but inconsistent in three. Regarding whether the tumor was derived from superior or inferior aspect of the IAC, agreement was found in 10 of the 16 cases (62.5%). Caloric test was abnormal in all patients examined but one with superior vestibular schwannoma. 3DFT-MR imaging was not particularly useful in predicting a precise nerve of origin of intracanalicular neoplasms. The prediction on whether the tumor originated in the superior or inferior aspect of the IAC was superior to caloric test, which might have clinical significance in treatment planning especially for hearing preservation surgery.