Lumbar and sacral proximal motor roots revealed severe loss of most myelinated axons seen at low power as pallor in the motor roots compared to the sensory roots . The loss of axons is evident at higher power. Trichrome stains demonstrate these changes a bit more dramatically at both low and high magnification. Myelin ovoids were abundant. The sensory roots and dorsal root ganglia were intact. There was extensive infiltration of motor roots by macrophages, and macrophages were identified within residual Schwann cell tubes (arrows) (HAM-56 and reticulin double-labeling). There were no giant cells, and CMV immunohistochemistry was negative. Spinal cord sections revealed prominent anterior horn cell central chromatolysis with minimal neuronal degeneration, no gliosis (GFAP), and no inflammation. Immunohistochemical stains for IgG, IgM, and C5b-9 were negative in the spinal cord and roots. No B or T cells were identified in the spinal cord or nerve roots with cell markers. Paraffin-embedded sections of the sural nerve were normal, and sections of the sciatic nerve revealed occasional myelin ovoids and axonal swellings and the motor roots showed axonal loss and swellings. (serial Bielschowsky: root, sciatic, sural).
Gross brain sections revealed a small left frontoparietal subdural hematoma, a left temporoparietal hemorrhage with softening, Durét brainstem hemorrhages, and bilateral uncal and cerebellar herniation. Microscopic studies did not reveal arteriovenous malformations, amyloid angiopathy, or tumor. There was mild to moderate atherosclerosis of the intracranial arteries. Macrophages were present in the region of intracerebral hemorrhage. In addition, the general autopsy revealed an occult Duke's B moderately differentiated adenocarcinoma of the colon.