Percutaneous microneurography in man does not cause pressure block of almost all axons in the impaled nerve fascicle.

Neural activity from the median nerve was recorded in 5 volunteers with a concentric needle electrode that has two recording surfaces in very close proximity at the tip. The aim of this study was to establish the probability of recording activity in the nerve from both surfaces simultaneously. We wanted to test one aspect of a recent critique of the microneurographic technique (Wall and McMahon, Pain, 21 (1985) 209-229), namely the suggestion that the recording electrode in these types of studies causes pressure block of almost all fibers in the impaled nerve fascicle. In 80% of our experiments it was possible to record neural activity at both surfaces simultaneously. These results indicate that the physiological state of the peripheral nerves during microneurographic explorations is not necessarily highly abnormal due to pressure block of nearly 100% of the nerve fibers close to the recording electrode tip. Our results thus speak against this aspect of the criticism of the microneurographic technique.