Post Polio Syndrome Resources
(Fact Sheet)
The extent to which polio survivors will suffer from PPS depends on how seriously they were affected by the first polio attack. Patients who had only minimal symptoms from the original attack and subsequently develop PPS will most likely experience only mild PPS symptoms. People originally hit hard by the polio virus may develop a more severe case of PPS with a greater loss of muscle function, difficulty in swallowing, and more periods of fatigue.
More than 300,000 polio survivors in the United States may be at risk for PPS. Doctors are unable to establish a firm incidence rate, but they estimate that the condition affects 25 percent of these survivors.
Restoration of nerve function may occur in some fibers a second time, but eventually nerve terminals are destroyed and permanent weakness occurs. This hypothesis is consistent with PPS's slow, stepwise, unpredictable course. Through years of studies, scientists at the National Institute of Neurological Disorders and Stroke have shown that PPS is a very slowly progressing condition marked by long periods of stability.
Objective assessment of muscle strength in PPS patients may not be easy. A change in muscle strength is determined in specific muscle groups, or limbs, using various muscle scales, such as the Medical Research Council (MRC) scale or scales that quantify muscle force. Doctors use magnetic resonance imaging (MRI), neuroimaging, and electrophysiological studies, muscle biopsies, or spinal fluid analysis as tools to investigate the course of decline in muscle strength.
Once PPS is diagnosed, some patients worry that they have polio again, or even ALS. In general, PPS is not life-threatening. The only exception is in patients who experience severe respiratory impairment. Studies have proven that, compared to control populations, PPS patients lack any elevation of antibodies against the polio virus, and since PPS affects only certain muscle groups, it is not considered a recurrence of the original polio. Further, there is no evidence that the polio virus can cause a persistent infection in humans. Other studies have demonstrated that ALS, which progressively weakens muscles, does not occur more frequently in PPS patients, and PPS is not a form of ALS.
In an effort to reduce fatigue in PPS patients, scientists conducted a study using low doses of the drug pyridostigmine and found that it did reduce fatigue in some patients. Research using this drug continues. In a controlled study conducted by NIH scientists, the drug amantadine was not helpful in reducing fatigue. Scientists are also conducting more research on the use of selegiline, a drug that in an anecdotal report was thought to improve strength in PPS patients.
The future in PPS treatment may center around nerve growth factors. NINDS scientists have plans to begin a multicenter, controlled trial to test whether insulin-like growth factor (IGF-1) can enhance the ability of motor neurons to sprout new branches, maintain existing branches, and rejuvenate synapses (the space between nerve cells where signals pass from one cell to another). A preliminary study is in progress. Since PPS results from the degeneration of nerve sprouts, IGF-1 may target the heart of the problem, and may help to regenerate new sprouts. Other growth factors now under investigation have similar properties.
There is much misinformation on this subject and many doctors do not know what effect exercise has on individuals with PPS. A commonsense approach, in which patients use individual tolerance as their limit, is currently recommended. Tolerance is the level at which one starts having discomfort or fatigue. Researchers at the NIH are addressing the exercise issue, not only to determine if exercise is helpful, harmful, or ineffective, but also to define the most effective type -- isotonic, isometric, isokinetic, or repetitive.
Other investigators are searching for the polio virus, or mutated versions of it, fragments of which have been amplified from the spinal fluid. The significance of this finding is not known however, and more research is being done.
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NIH Neurological Institute
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Prepared by
Office of Communications and Public Liaison
National Institute of
Neurological Disorders and Stroke
National Institutes of Health
Bethesda, Maryland 20892-2540
NIH Publication No. 96-4030
Original Publication Date: July 1996
National Institute of Neurological Disorders and Stroke
National Institutes of Health
Bethesda, MD 20892