Spinocerebellar fibers are involved to a lesser extent.
Neuronal cell bodies of degenerating fibers were preserved, and there was no evidence of primary demyelination. Loss of anterior horn cells is observed in some cases. Dorsal root ganglia, posterior roots and peripheral nerves are normal. One obvious feature shared by these degenerating axons is their length. Degeneration was maximal in the distal axons of these fibers.