Surface-coil magnetic resonance imaging of the internal auditory canal and the inner ear. Preliminary report.

Parasagittal surface-coil magnetic resonance imaging of the internal auditory canal and the inner ear was performed. We used T2-weighted fast spin-echo sequences to visualize the inner ear and the individual nerves in the internal auditory canal with high contrast in a short acquisition time. Computer-assisted quantitative measurement of the nerves was performed to estimate the cross-sectional areas and the diameters of the nerves. The average diameters of the facial nerve, the cochlear nerve, and the vestibular nerve of normal-hearing individuals were, respectively, 1.1 +/- 0.2 mm (mean +/- SD), 1.2 +/- 0.2 mm, and 1.5 +/- 0.2 mm. In the cerebellopontine angle, the average diameter of the eighth nerve was 1.8 +/- 0.2 mm. Two patients with unilateral and bilateral hearing loss were also presented. In the patient with unilateral deafness, the cochlear nerve of the diseased side was not identified and the eighth cranial nerve diameter was smaller than that of the normal side. In the patient with bilateral deafness, fibrosis of the inner ear and atrophy of the eight nerve were demonstrated in the ear with posttraumatic deafness. The present method may represent a new approach to the assessment of pathologic processes involving the inner ear and the nerves in the internal auditory canal.