Endoneurial blood supply to peripheral nerves is not uniform.

Peripheral nerves are not uniformly susceptible to the effects of ischemia in human and experimental ischemic neuropathies. Since endoneurial blood flow is directly proportional to the number of endoneurial capillaries, we studied endoneurial capillary density at multiple levels of the peripheral nerves of normal rats. Capillary density was lowest in the sciatic and proximal tibial nerves and significantly higher in dorsal and ventral roots and distal tibial and plantar nerves. Endoneurial capillary density corresponds to the hierarchy of susceptibility to ischemic nerve damage in human and experimental ischemic neuropathies. These findings suggest that susceptibility of peripheral nerves to ischemia is determined, at least in part, by the density of endoneurial capillaries.