Summer 2006

MRI Neurography

The successful treatment of peripheral nerve disorders requires accurate diagnosis. But because peripheral nerves have a fine structure, it is difficult to get images with the required accuracy using traditional imaging methods. Recent technical advancements in MRI, however, have led to improved visualization of normal and abnormal peripheral nerves, UCSF researchers report.

Initially, the imaging of peripheral nerve disorders was limited to secondary skeletal changes on plain radiographs and to CT myelography for demonstrating nerve root avulsion in patients with severe proximal brachial plexus injuries. Standard MRI now allows the imaging of nerves, but it is difficult to differentiate the nerve tissue from the surrounding non-neural tissues, says UCSF researcher Cynthia T. Chin, M.D.

MRI neurography allows physicians to address the issues of low-signal intensity and low conspicuity of the nerves by selectively suppressing signals from non-neural structures such as fat and blood cells, Chin says. "We can highlight nervous tissue by exploiting differences in the water content and connective tissue structure of the nerve fascicles and perineurium, compared with the surrounding epineurium."

Improvements in nerve images have also come from hardware improvements such as phase array coils, which improve signal-to-noise ratios and resolution.

Examples of where this technique has proven useful are in distal sciatic nerve lesions, in persistent back or neck pain with leg or arm pain that is unexplained by a routine MR scan of the back or cervical spine and in patients with brachial plexus injuries.

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