Increased signal intensity of the cochlea on pre- and post-contrast enhanced 3D-FLAIR in patients with vestibular schwannoma

In the vestibular schwannoma patients, the pathophysiologic mechanism of inner ear involvement is still unclear. We investigated the status of the cochleae in patients with vestibular schwannoma by evaluating the signal intensity of cochlear fluid on pre- and post-contrast enhanced thin section three-dimensional fluid-attenuated inversion recovery (3D-FLAIR). Twenty-eight patients were retrospectively analyzed. Post-contrast images were obtained in 18 patients, and 20 patients had the records of their pure-tone audiometry. Regions of interest of both cochleae (C) and of the medulla oblongata (M) were determined on 3D-FLAIR images by referring to 3D heavily T2-weighted images on a workstation. The signal intensity ratio between C and M on the 3D-FLAIR images (CM ratio) was then evaluated. In addition, correlation between the CM ratio and the hearing level was also evaluated. The CM ratio of the affected side was significantly higher than that of the unaffected side (p < 0.001). In the affected side, post-contrast signal elevation was observed (p < 0.005). In 13 patients (26 cochleae) who underwent both gadolinium injection and the pure-tone audiometry, the post-contrast CM ratio correlated with hearing level (p < 0.05). The results of the present study suggest that alteration of cochlear fluid composition and increased permeability of the blood-labyrinthine barrier exist in the affected side in patients with vestibular schwannoma. Furthermore, although weak, positive correlation between post-contrast cochlear signal intensity on 3D-FLAIR and hearing level warrants further study to clarify the relationship between 3D-FLAIR findings and prognosis of hearing preservation surgery.