[Experimental study on peripheral nerve lesions--compression neuropathy].

Abstract

Compression is one of the most important causes of entrapment neuropathy. The experimental study described was performed to elucidate the pathogenesis of compression neuropathy in the sciatic nerves of 113 mongrel dogs. An apparatus, devised to compress the nerve constantly with the force of 15, 30 and 50 grams (27.6, 55.2, 92.0 mmHg), was applied to the sciatic nerve 4 cm distal to the sciatic tuberculum. The following observations were made on the 1st, 2nd, 3rd, 4th, 6th and 8th weeks. Macroscopic findings: The compressed site of the nerve was thinned and flattened. Adjacent portions both proximal and distal to the compressed site showed distinct swelling (prox. greater than dist.). Electrophysiological findings: In the 15-gram-compression group, the conductability was maintained up to the 8th week, but the motor nerve conduction velocity was reduced to approximately 60% of the control. In the 30-gram-compression group, the conductability of the compressed site was lost within one week. However, the conductability in the distal portion remained detectable. In the 50-gram-compression group, the conductability was completely lost within one week. Histological findings (H and E, Holmes and LFB stains): In the pseudoneuroma, the swelling of the individual axons was slight, but the arrangement of each axon and each funiculus was extremely sparse because of the exudate in the interstitial tissue. At the compressed site, axons were closely packed together with a concomitant decrease of interstitial tissue. In the 15-gram-compression group. Wallerian degeneration was localized in large myelinated fibers at the distal site. In the 30-gram-compression group, almost all the nerve fibers except for small ones showed degeneration. In the 50-gram-compression group, all fibers degenerated. Teased single fiber specimens: In the 15-gram-compression group, paranodal demyelination was seen from the 1st week. Up to the 8th week, such demyelination was more remarkable, and a bulbous deformity appeared at the proximal site of compression and Wallerian degeneration of the large myelinated fibers occurred at the distal site of compression. Microangiogram (India ink method): The internal microvessels decreased slightly in the 15-gram-compression group.(ABSTRACT TRUNCATED AT 400 WORDS)