Characteristics of Axonal Neuropathies

The vast majority of neurotoxic agents that affect the PNS preferentially cause axonal injury rather than Schwann cell injury. Axonal injury is usually manifested as axonal degeneration, a pathologic process characterized by complete dissolution of the axon. If the degeneration involves a myelinated axon, then the myelin sheath enveloping the degenerating axon also breaks down. This myelin breakdown, which occurs in the context of axonal degeneration, is not considered demyelination, since demyelination refers to loss of the myelin sheath from an intact axon. 

Detailed studies of the PNS in animal models of toxic neuropathy reveal that in most instances the axonal degeneration initially involves only the distal end of the 

Among the best studied of these morphologic abnormalities associated with toxic neuropathies are the large masses of neurolilaments that accumulate locally within axons during intoxication with 2,5-hexanedione (2,5-HD) and related y-diketones, as well as with acrylamide, p, 3-iminodipropionitrile (IDPN), and carbon disulfide. 

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