Cranial Nerves III to VI

Cranial nerves III, IV, V, and VI are small structures that travel in a reproducible manner from the midbrain and pons to the cavernous sinus and then to the orbit. While there are branches that course through other foramina of the skull, the emphasis in MRI is to evaluate the brainstem, the cavernous sinus, and the pericavernous regions for pathology. This unit present a basic protocol for imaging cranial nerves III to VI. Because the nerves run from a posterior to an anterior position, coronal scanning is ideal for visualizing the nerves in cross-section. Thin sections and contrast enhancement are required to best visualize the diseases that affect these nerves. An alternate protocol is also discussed for the case when demyelinating etiologies for the cranial nerve deficits are considered.