In vivo characterization of the vestibulo-cochlear nerve motion by MRI

The motion of the vestibulo-cochlear nerve (VCN) was quantified at the level of the cerebello-pontine angle in 28 healthy volunteers enrolled in a prospective study performed on a 3T MRI scanner. A phase contrast MRI (PCMRI) sequence was used. The VCN was divided into a cisternal part and a meatic part, both of which were measured for motion in the cranio-caudal (CC) and antero-posterior (AP) directions. Motion was cardiac-cycle-dependent in these two directions. The meatic VCN motion was delayed compared to the cisternal VCN motion. In the CC direction, the mean amplitude of the cisternal VCN motion was twice larger than the mean amplitude of the meatic VCN motion (0.37+/-0.14 mm versus 0.17+/-0.08 mm). In the AP direction, the mean amplitude of the cisternal VCN was 0.19+/-0.08 mm versus 0.16+/-0.14 mm for the meatic VCN. We used an "oscillating string" to explain the VCN motion. Reproducibility tests have shown small variations in measurements of the CC motion. PCMRI can be used to assess the VCN motion at the level of the cerebello-pontine angle.