Long-term changes in the spinal cords of patients with old poliomyelitis. Signs of continuous disease activity.

In a retrospective study, we reviewed sections from the spinal cords from eight patients, aged 36 to 61 years, who had had poliomyelitis and who died of nonneurologic diseases nine months to 44 years (mean, 20.7 years) after the acute poliomyelitis infection. Five patients had stable postpoliomyelitis deficits without new symptoms, and three patients had new slowly progressive muscle weakness defined as postpoliomyelitis progressive muscular atrophy (PPMA). Representative spinal cord sections matched the patients' clinical involvement in both groups. Control tissues from ten patients with amyotrophic lateral sclerosis and five with spinocerebellar degeneration were examined simultaneously. The spinal cord segments from all patients who had had poliomyelitis showed loss or atrophy of motor neurons, severe reactive gliosis (disproportional to the neuronal loss), and a surprising mild to moderate perivascular and interparenchymal inflammation. There was no difference in these pathologic changes between the patients with stable postpoliomyelitis deficits and those with PPMA. Additional findings were axonal spheroids (dystrophic axons) and occasional chromatolytic neurons in the spinal cord of patients with PPMA. Corticospinal tracts were spared.