Magnetic resonance imaging of the cranial nerves in infectious, neoplastic, and demyelinating diseases, as well as other inflammatory diseases: a pictorial essay.

The cranial nerves, which represent extensions of the functional structures of the brain, traverse the head and neck. They are connected to various cranial structures and are associated with several diseases. An in-depth understanding of their complex anatomy and normal imaging appearance allows the examiner to identify and characterize abnormalities with greater precision. One important tool for evaluating the cranial nerves is contrast-enhanced magnetic resonance imaging, especially that employing three-dimensional steady-state free precession sequences, which provide high soft-tissue and spatial resolution, despite the slen-derness of the nerves. In most cases of cranial nerve abnormalities, the imaging findings are nonspecific. Therefore, to narrow the differential diagnosis, it is necessary to take a full patient history, perform a focused physical examination, and order laboratory tests. In this pictorial essay, we review, illustrate, and discuss, from a pathophysiological perspective, infectious, neoplastic, and demyelinating disorders, as well as other inflammatory disorders, affecting the cranial nerves, the aim being to provide a practical, tangible reference for radiologists to use in daily practice.