High-Resolution Visualization of the Trigeminal Nerve Using 7-T Magnetic Resonance Imaging

MRI is vital for evaluating the trigeminal nerve in many disease states. However, resolution limits in existing clinical protocols using 3-T MRI may preclude definitive imaging interpretations from being made. We explore the ability of a stronger 7-T MRI magnet to image the trigeminal nerve region in higher detail.

The skull base region of 8 healthy volunteers was scanned on a Philips Achieva 7-T MRI machine. Over the region of interest, a magnetic field (B0) shim algorithm was applied to optimize B0 homogeneity, and a high dielectric-constant pad was used to improve radiofrequency field (B1) homogeneity. The following 7-T MRI sequences were acquired: T2-weighted (T2w) Turbo Spin Echo (TSE), T1-weighted (T1w) Magnetization-Prepared Rapid Gradient Echo (MPRAGE), and T2w Fluid-Attenuated Inversion Recovery (FLAIR).

The 7-T T2w TSE, T1w MPRAGE, and T2w FLAIR sequences can each visualize the trigeminal nerve in detail. In cases where the trigeminal nerve contacts another structure such as a blood vessel, the 2 can be clearly distinguished on the 7-T T2w TSE sequence. The 7-T T1w MPRAGE sequence can further highlight the cerebral arteries with bright signal intensity, facilitating the distinction between arteries and veins for cases involving vascular compression. Furthermore, the 7-T T1w MPRAGE sequence allows arteries to be traced throughout scan slices to determine their origins and identities. Finally, the 7-T T2w FLAIR sequence can successfully suppress surrounding cerebrospinal fluid signal to focus on intrinsic trigeminal nerve properties. Cerebrospinal fluid artifact in the T2w TSE sequences was uncommon and did not affect image interpretation if present.

Our optimized 7-T MRI protocol featuring T2w TSE, T1w MPRAGE, and T2w FLAIR sequences can successfully visualize the trigeminal nerve with high resolution and can be applied to evaluate the trigeminal nerve in the setting of various disease states.