Ultrasound-guided near-nerve neurography for early evaluation of nerve regeneration

For early assessment of axonal outgrowth after trauma, the nerve is surgically exposed to enable compound nerve action potential (CNAP) recordings across the lesion site. Near-nerve neurography, with needle electrodes placed transcutaneously near the nerve, could be a minimally invasive alternative if the needle placement procedure and low reproducibility are improved. We developed ultrasound-guided near-nerve neurography, which facilitates needle placement, and assessed its potential for evaluating nerve regeneration. Measurements were performed at varying times after crush lesion of the peroneal nerve of 25 rabbits. To test if ultrasound-guided near-nerve signals could be measured prior to muscle reinnervation, they were compared with recordings of compound muscle action potentials. A comparison with conventional intra-operative CNAP recordings was made by measuring nerve signal amplitude with both techniques and by assessing reproducibility. In all cases where intra-operative signals could be measured, near-nerve signals were also detected. Compound nerve activity could be recorded after 5 weeks, whereas compound muscle activity appeared after approximately 8 weeks. Reproducibility was slightly better for near-nerve than for intra-operative recordings. We conclude that ultrasound-guided near-nerve neurography is able to assess nerve regeneration well before compound muscle activity can be detected. Its accuracy and reproducibility are similar to those of conventional intra-operative recordings.

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