What is the role of MRN in the diagnosis of foot drop?

Updated: Mar 23, 2020
  • Author: James W Pritchett, MD; Chief Editor: Vinod K Panchbhavi, MD, FACS  more...
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If a tumor or a compressive mass lesion to the peroneal nerve is being investigated, magnetic resonance neurography (MRN) may be considered. MRN has made it possible to produce high-resolution images of peripheral nerves, as well as associated intraneural and extraneural lesions.

MRN can be performed by using a standard 1.5 Tesla magnetic resonance imaging (MRI) system and special phased-array imaging surface coils. [10] Image data are acquired simultaneously from multiple receive-only surface coils. The image data from each coil in the array are combined to form a composite image with an improved signal-to-noise ratio.

Compared with standard MRI, MRN allows faster acquisition of anatomically detailed images, a smaller field of view, higher resolution, and thinner sections. By virtue of these features, MRN images are capable of showing the fascicular organization of normal peripheral nerves, thereby rendering the nerves more clearly distinguishable from other tissue (eg, tumor or blood vessels). In one study, the fascicular structure seen on MRN was found to be functional by using intraoperative electrophysiologic testing; the nonfascicular structures were nonfunctional.

Images can be processed further to allow stacking of axial sections and slicing of data in another plane of section. This is helpful in mapping the longitudinal extent of nerve involvement.

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