Transperineurial vessel constriction in an edematous neuropathy.

The hypothesis that the accumulation of endoneurial edema can exert forces sufficient to occlude transperineurial vessels was tested using light microscopy and computer-assisted morphometry in rat sciatic nerve. Experimental nerves were exposed to a concentration of 10% procaine HCl, which from previous studies has been demonstrated to routinely produce an edematous neuropathy. For each vessel, a "constriction ratio" was defined by dividing its minimum intraperineurial lumen area by the average for minimum endoneurial and epineurial lumen cross-sectional areas. Constriction ratios were 0.91 +/- 0.26 (mean +/- SD) for control vessels and 0.28 +/- 0.25 for vessels in the procaine group (p less than 0.005). In addition, a strong negative correlation was observed between the morphologic demonstration of nerve edema and the transperineurial vessel constriction ratio (r = -0.85; p less than 0.002). It is concluded that in neuropathies characterized by widespread edema and increased endoneurial fluid pressures, the concomitant constriction of transperineurial vessels could diminish nerve blood flow and facilitate nerve injury.