Relationship between nerve blood flow and intercapillary distance in peripheral nerve edema.

Some human and experimental neuropathies are characterized by endoneurial edema and increased intercapillary distance (ICD). This may potentially produce chronic endoneurial ischemia. To examine the relationship between nerve blood flow (NBF) and ICD we measured NBF in rats with experimental galactose neuropathy (EGN), a model where ICD is known to be increased. Simultaneous measurements of NBF in the center and subperineurial region were made in normal and edematous tibial nerves using hydrogen-sensitive microelectrodes and hydrogen polarography. NBF was significantly reduced in rats with EGN when compared with controls. A second finding was that in half the rats with EGN there was a greater reduction in NBF in the subperineurial region, a site of maximal ICD increase. In contrast, NBF was similar in central and peripheral regions in control rats. These findings support the hypothesis that an increase in ICD produces a reduction in NBF. Further support for the hypothesis is derived from a computer model of the effect of changes in ICD on endoneurial oxygen tension. We conclude that a chronic reduction in NBF may participate in the pathogenesis of edematous neuropathies.