MRI of the Cranial Nerves—More than Meets the Eye: Technical Considerations and Advanced Anatomy

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Magnetic resonance (MR) imaging is the method of choice to evaluate the cranial nerves. Although the skull base foramina can be seen on CT, the nerves themselves can only be visualized in detail on MR. To see the different segments of nerves I to XII, the right sequences must be used. Detailed clinical information is needed by the radiologist so that a tailored MR study can be performed. In this article, MR principles for imaging of the cranial nerves are discussed. The basic anatomy of the cranial nerves and the cranial nerve nuclei as well as their central connections are discussed and illustrated briefly. The emphasis is on less known or more advanced extra-axial anatomy, illustrated with high-resolution MR images.

Section snippets

MR technique

The MR technique must be pushed to its limits to see all 12 cranial nerves and especially some of the segments or branches of these nerves that are more difficult to depict. Imaging plane, coil and sequence choice, slice thickness and in-plane resolution, use of special techniques like parallel imaging, asymmetric k-space, fat suppression, and so forth will all influence the final image quality.5

Olfactory epithelium

The olfactory epithelium is located in the upper one fifth of the nasal cavity and covers the septal and lateral surface of this cavity, including the upper part of the superior turbinate (Fig. 6).

Transethmoidal segment

Bipolar olfactory neurons connect the olfactory epithelium with the olfactory bulbs. These neurons experience a continuous cycle of growth, degeneration, and replacement, which make them “unique” neurons. The dendrites of these olfactory neurons reach the surface of the olfactory epithelium while the

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