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AJNR - American Journal of Neuroradiology

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American Journal of Neuroradiology 26:973-980, April 2005
© 2005 American Society of Neuroradiology

PERIPHERAL NERVES

Imaging of Intraneural Edema by Using Gadolinium-Enhanced MR Imaging: Experimental Compression Injury

Shigeru Kobayashi^a,b, Adam Meir^a, Hisatoshi Baba^b, Kenzo Uchida^b and Katsuhiko Hayakawa^c

^a Physiology Laboratory of Oxford University, Oxford, United Kingdom
^b Department of Orthopedics and Rehabilitation Medicine, Fukui University School of Medicine, Fukui, Japan
^c Department of Radiology and Orthopedics, Aiko Orthopedic Hospital, Aichi, Japan

Address reprints requests and correspondence to Shigeru Kobayashi, MD., PhD., Department of Orthopedics and Rehabilitation Medicine, Fukui University School of Medicine, Shimoaizuki 23, Matsuoka, Fukui, 910-1193, Japan

BACKGROUND AND PURPOSE: Compressive and entrapment neuropathies are diseases frequently observed on routine clinical examination. A definitive diagnosis based on clinical symptoms and neurologic findings alone is difficult in many cases, however, and electrophysiologic measurement is used as a supplementary diagnostic method. In this study, we examined to use protein tracers (Evans blue albumin or horseradish peroxidase) and gadolinium-enhanced MR imaging to determine the changes of blood-nerve barrier permeability in compressive neuropathies.

METHODS: In dogs, the median nerve was compressed for 1 hour by using five kinds of clips with various strengths (7.5–90-g force). After clip removal, the combined tracers of Evans blue albumin and gadolinium or horseradish peroxidase was administered intravenously as a tracer. After the animals were euthenized, we compared gadolinium-enhanced MR images with Evans blue albumin distribution in the nerve under fluorescence microscopy. The horseradish peroxidase–injected specimens were observed by transmission electron microscopy.

RESULTS: On enhanced MR imaging, intraneural enhancement was caused by 60- and 90-g-force compression after 1 hour. Marked extravasation of protein tracers in the nerve occurred where there was compression by 60- and 90-g-force compression, and capillaries in the nerve showed the opening of tight junction and an increase of vesicular transport under the electron microscopy. This situation indicated breakdown of the blood-nerve barrier, with consequent edema formation and was seen as enhancement on MR imaging.

CONCLUSION: Gadolinium-enhanced MR imaging can detect morphologic and functional changes of blood-nerve barrier in the nerve induced by mechanical compression.

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