Blood flow in a chronic entrapment neuropathy model in the rabbit sciatic nerve.

A model of chronic entrapment neuropathy in the rabbit sciatic nerve was developed to try to elucidate the pathogenesis of chronic nerve entrapment. A non-compressive Silastic cuff was wrapped around the nerve at the mid-thigh level in eight rabbits. A sham operation that only elevated the sciatic nerve was performed in seven control rabbits. Six months later, the blood flow in the cuffed and the control sciatic nerves was determined with intra-arterially injected microspheres. Blood flow was significantly reduced in the entrapped nerve, compared to control nerves, but only in the segment proximal to the cuff. After surgical release of the cuff, the blood flow significantly increased in the proximal segment. This suggested that decreased blood flow may occur, but not necessarily at the site of nerve entrapment. Nerve conduction velocity changes were also consistent with an entrapment neuropathy. However, there were no significant quantitative morphometric changes at the nerve entrapment site, that is, in myelin thickness/nerve diameter ratio, distribution of axon sizes, and mean nerve fiber diameter. This indicates that only a mild entrapment was created.