Chronic elevation of endoneurial fluid pressure is associated with low-grade fiber pathology.

The effects of chronic elevations of endoneurial fluid pressure (EFP) on mammalian nerve fibers were studied using a modified model of experimental galactose neuropathy. Fiber pathology was monitored by the sensitive method of grading the pathologic abnormalities of single teased fibers. Prominent edema was produced in rats poisoned with combined oral and parenteral galactose. EFP and fascicular size were markedly elevated and tibial nerve conduction velocity was reduced. We have demonstrated, for the first time, the presence of fiber degeneration in galactose fed rats. Possible mechanisms of nerve fiber damage include: (1) impaired capillary circulation and increased fiber separation secondary to increased EFP and edema, respectively; (2) increased endoneurial hyperosmolarity, which is known to cause changes in fiber shape; and (3) unknown metabolic derangement of axons. Because much higher rates and different types of fiber pathology are encountered in lead and hexachlorophene intoxication having comparable degrees of EFP, one cannot attribute the fiber pathology directly to the raised EFP in these latter neuropathies.