High resolution imaging of peripheral nerves — neurosonography and MRI-neurography

Abstract

Intruductiun: Technical advances in high-resolution US and MRI lead to new perspectives in visualisation of tiniest details of the human body. Our aim was to evaluate the possibilities of 15 MHz high resolution US and 3 Tesla MRI in imaging the peripheral nervous system. Material and methuds: In the first part of our study peripheral nerves of the arm of 20 fresh frozen cadaver specimen were investigated at clear defined anatomical regions using 15 Mhz SonoCT and 3 Tesla MR-Imaging technology. After histologic processing a histomorphometric and an image-morphometric investigation was performed to correlate the corresponding images: size, number, diameter and orientation of the nerve’s fascicles, and finally the relation of internal neural tissue to internal connective tissue were assessed. For exact quantification biometrical data analyses was performed. For the first time a new technique was used to visualize the brachial plexus intraoperatively: after surgical exposure of the brachial plexus a 15 MHz high resolution scanhead was placed directly onto the nerve to obtain high definition images of the intraneural fascicular architecture. In 4 cases of brachial plexopathy the use and value of this intraoperative imaging procedure of the brachial plexus is elucidated. Results: Quantitative morphometric analyses of both the obtained image and the histologic slice itself reach up to 95% correlation regarding the nerve’s content of fascicular and non-fascicular tissue. The number and diameter of fascicles measured in US and MRimages at the same anatomical levels match exactly the histologic slices taken from corresponding examination points. Intraoperative high resolution US of the brachial plexus enables imaging of its internal plexiform ultrastructure and aids in clear distinction of intrinsic and extrinsic neuropathology. In the reported cases intraoperative high resolution US functions as a navigation-tool showing pathological changes in the nerve’s fascicular ultrastructore. Conclusion: High resolution imaging techniques such as 15 Mhz SonoCT and 3 Tesla MRI allow visualisation of the intraneural fascicular ultrastructure of peripheral nerves. High resolution US and MRI facilitate the surgeon dealing with disorders of peripheral nerves to delineate the extent of intrinsic pathologic changes of peripheral nerves. Intraoperative US imaging aids as a navigation tool and leads to a clear distinction of pathologic changes in the course of the brachial plexus. Using new techniques of high resolution imaging etudbles the surgeon to reduce the extent of “cxplorative surgery” in the operative treatment of disorders of peripheral nerves to a minimum. 68. EXPRESSION OF INTERLEUKIN-6 mRNA AT THE DORSAL ROOT GANGLIA GRADUAL NERVE ELONGATION MODEL