MR neurography and muscle MR imaging for image diagnosis of disorders affecting the peripheral nerves and musculature

Medical imaging, including MR imaging [1], is playing an increasingly important role in the diagnosis of disorders affecting the peripheral nerves and muscles [2,3]. In the past, the practical application of MR imaging of nerves has been limited by technical difficulties in obtaining good image contrast to help distinguish nerve from neighboring tissues [4-9]. By comparison, the limited capabilities of ultrasound [10] for nerve identification have seemed useful. Recently, however, advances and enhancements of MR imaging techniques have transformed the evaluation of a variety of conditions that have posed diagnostic challenges in the past. The term MR neurography is used to describe the new techniques for nerve imaging that greatly improve the reliability of identification of peripheral nerves in images and often make it possible to generate tissue-specific images of nerves analogous to angiograms. These images enable the physician to examine the peripheral nerve for anatomic abnormalities. A series of discoveries in basic MR science beginning in 1992 has led to the establishment of MR neurography as a distinct area of imaging [11,12]. The technique has now been applied in thousands of clinical cases. A series of publications cover the basic science [13-15], imaging science [16,17], and clinical application [18-23] of the technique. Large, well-controlled formal outcome trials [24,25] have established, at least in some settings, that MR neurography can be more reliable than electrodiagnostic studies in localizing peripheral nerve disorders and in guiding treatment planning. The referring physician should be aware of some of the technical aspects of MR nerve imaging. Many radiologists have limited experience with nerve imaging, and many imaging centers are not adequately equipped to carry out these studies successfully. It is important for the referring physician to have a clear idea of how a useful high-quality nerve image should appear. Awareness of some of the general technical aspects of the nerve imaging process can help the referring physician understand and address imagequality problems that can arise as this new technique is introduced in a community.