[MR neurography for lesion localization in the peripheral nervous system. Why, when and how?]

Peripheral neuropathies are frequent disorders which are often challenging in the diagnostic work-up. Diagnostic difficulties first and foremost arise with regard to lesion localization and the precise definition of spatial lesion patterns. Magnetic resonance (MR) neurography as a diagnostic imaging tool directly visualizes nerve lesions thereby facilitating lesion localization not only in traumatic nerve lesions but also in the large and heterogeneous group of intrinsic, spontaneously occurring non-focal neuropathies. The major diagnostic sign for lesion detection and localization is the T2 lesion which can be evaluated with high spatial resolution at the anatomical level of nerve fascicles. Lesion detection at the fascicular level by MR neurography advances the diagnostic work-up in the peripheral nervous system (PNS), because fascicular and partial nerve lesions of spontaneously occurring intrinsic neuropathies and polyneuropathies present a classical diagnostic pitfall for traditional localization by means of physical findings and electrophysiology. With the appropriate techniques and strategies MR neurography can now cover large anatomical areas of the PNS in a single examination session.