Contrast-enhanced Magnetic Resonance Imaging of the Cranial Nerves in Patients with Acoustic Schwannoma: Correlation with Surgical Findings

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Abstract
Eighteen patients with acoustic schwannoma were examined on a 1.5-T magnetic resonance imaging (MRI) unit with precontrast and postcontrast T 1 -weighted spin-echo sequences. Each abnormality was assessed in terms of the size, location, extensions and signal intensity of the lesions. If a nerve was enhanced and was involved by the tumor around the fundus of the internal auditory canal (IAC), the nerve was interpreted to be the originating nerve. The postcontrast T 1 -weighted images revealed enhanced masses of the cerebellopontine angle and/or the IAC in all cases. In 11 of the 19 operated patients with shwannomas, the site of tumor origin (or origin nerve) was confirmed by surgery. In 2 of the 11 cases (18%), surgical findings coincided with the T 1 -weighted image findings. Facial nerve enhancement on the ipsilateral side of the tumor was noted in 10 cases (53%) and the contralateral facial nerve enhancement was demonstrated in 7 (70%). The enhancement of facial nerve associated with acoustic schwannoma was not correlated to the degree of nerve compression by the tumor. These results demonstrate that it was possible, although infrequent, to predict the site of origin of acoustic schwannoma before surgery in some patients. Improvement of the imaging matrix or multiplanar reconstruction techniques with three-dimensional data acquisition may make it possible to overcome the limitations of MRI.