Post-polio syndrome. The battle with an old foe resumes.

How many of the thousands who contracted polio during the epidemics 30 and 40 years ago will experience post-polio syndrome? What causes these delayed effects, and how quickly will they progress? None of these questions can be answered with certainty. At present, several factors appear to be at work. Patients are generally in one of two groups: The first group has deterioration in the function of muscles that were affected by the disease. This muscle weakness may be caused by a loss of motor neurons, due to aging, from an already depleted neuron pool. The remaining motor units then become stressed from overuse. The second group has problems in new muscle groups or those thought to be recovered from the disease. Problems in the second group appear to have a cause other than simple aging, possibly autoimmune, but longer follow-up is required to assess these patients. Evaluation of post-polio patients should be based on differentiating new neuromuscular disorders from exacerbations of the original disability. Although changes associated with aging cannot be halted, once post-polio syndrome is diagnosed, patients can be encouraged to follow appropriate dietary and exercise programs to maintain their present function, and they can be reassured of the relatively benign course of their problems.