Post-Polio Syndrome Update
Guest Editor: Neil R. Cashman, MD
Polio Experts Grapple with the Complexities of Post-Polio Syndrome
Post-polio syndrome (PPS) is a term that encompasses a range of symptoms experienced by survivors of polio years after their original infection. Defining the exact parameters of the condition has proven to be problematic given the subjective nature of many PPS symptoms, such as pain, fatigue and new weakness. In addition, arriving at a definitive diagnosis of the condition can be difficult even for polio specialists, because many PPS symptoms overlap with those of other common disorders, including fibromyalgia and osteoarthritis.
Pathophysiology Holds Clues to Post-Polio Syndrome Therapy
Recent insights into the pathophysiology of post-polio syndrome (PPS) may hold clues to effective treatment modalities, two leading investigators reported at a roundtable meeting of the Post-Polio Task Force held last April in Boston.
Differential Diagnosis of Post-Polio Syndrome Requires Knowledge, Skill and Persistence
Diagnosing post-polio syndrome (PPS) is a challenging process. There are no pathognomonic tests for the condition, and a definitive diagnosis can be achieved only through exclusion of other conditions that may be responsible for causing PPS-like symptoms, such as pain, new weakness and fatigue. A successful exclusionary diagnosis of PPS depends on the knowledge, skill and persistence of the examining physician.
Strategies Help Manage Post-Polio Symptoms
Even though no specific treatment is currently available for post-polio syndrome (PPS), strategies are available to help improve symptoms such as weakness, pain, respiratory dysfunction, dysphagia and fatigue. A variety of techniques were outlined.
Quality of Life Improves with Post-Polio Self-Care
Promotion of the concept of self-care can help to optimize wellness in patients with post-polio syndrome (PPS), according to Joan L. Headley, Executive Director of Post-Polio Health International (formerly International Polio Network), Saint Louis, Missouri.
Polio Experts Grapple with the Complexities of Post-Polio Syndrome
Post-polio syndrome (PPS) is a term that encompasses a range of symptoms experienced by survivors of polio years after their original infection. Defining the exact parameters of the condition has proven to be problematic given the subjective nature of many PPS symptoms, such as pain, fatigue and new weakness. In addition, arriving at a definitive diagnosis of the condition can be difficult even for polio specialists, because many PPS symptoms overlap with those of other common disorders, including fibromyalgia and osteoarthritis.
To help clarify these issues, Lauro Halstead, MD, Director of the Post-Polio Program at the National Rehabilitation Hospital in Washington, DC, and Burk Jubelt, MD, Professor and Chairman of the Department of Neurology at the State University of New York Health Sciences Center in Syracuse, New York, led a roundtable discussion concerning the epidemiology, definition and diagnosis of PPS.
Definitive Data Lacking
A 1987 National Center for Health Statistics survey found that there are 640,000 survivors of paralytic polio in the United States, and that roughly half have reported new manifestations of the disorder. A 1991 survey by Windebank et al showed that 64% of survivors of paralytic polio experienced new manifestations and 44% had weakness. The results of a 1987 survey by Speier et al indicated a lower prevalence of post-polio symptoms – 42% of respondents reported new problems, including pain, decreased endurance and increased weakness – while a 1992 study by Ramlow et al found that 28% of paralytic polio survivors suffered from new neuromuscular symptoms. Thus, based upon symptoms, about half of acute paralytic poliomyelitis (APP) survivors go on to develop PPS. However, Dr. Jubelt noted, objective criteria need to be applied to more accurately determine the incidence of PPS. Uncontrolled, retrospective studies using objective criteria have estimated that 20%-40% of APP survivors will develop PPS. “Obviously, we need better epidemiological data,” he said.
Towards a Definition of PPS
PPS may be defined as a cluster of symptoms experienced by individuals who had paralytic polio years earlier, Dr. Halstead said. Typically, these symptoms occur 30 to 50 years after the initial illness, and include new weakness, fatigue and pain in the muscles and/or joints. Less common symptoms can include muscle atrophy, breathing and swallowing difficulties, and intolerance to cold.
According to Dr. Halstead, it is useful to categorize PPS symptoms into two groups:
- those that are caused by a progressive deterioration of motor neurons (e.g., new weakness, fatigue and muscle atrophy); and
- those that are secondary to musculoskeletal changes (e.g., muscle and joint pain from osteoarthritis, tendinitis, ligament strains and joint deformities); the musculoskeletal changes may be a result of years of abnormal wear and tear and/or new weakness. “I believe that new weakness is the hallmark symptom of PPS,” Dr. Halstead said. ” When new weakness appears in muscles previously affected by polio and/or muscles thought to be unaffected originally, it may or may not be accompanied by other symptoms. This is a crucial point to recognize – a patient can have PPS even if new weakness is the only symptom.”
However, “weakness” is a notoriously difficult symptom to pin down, roundtable participants noted, and they expressed concern that some patients may be confusing “weakness” with “decreased endurance.” To cloud the picture even further, there is evidence that some patients may experience subjective feelings of increased weakness in response to muscle pain, cramps, and soreness. Several investigators (Dalakas et al, 1986; Stâlberg and Grimby, 1995; Agre et al, 1995) have shown a slow (1%-2% per year) decline in muscle strength in post-polio patients based on objective criteria; however, noted some roundtable participants, two 1996 studies of polio survivors by Windebank et al and Ivanyi et al failed to find a progressive decline in muscle strength, even in those patients who reported this symptom. In the study by Windebank et al, which involved 50 subjects, muscle strength tests, functional analyses and electrophysiologic tests detected no evidence of progression over a 5-year period. Similarly, Ivanyi et al examined 56 polio survivors – 43 complaining of new progressive muscle weakness and 13 without new neuromuscular complaints – and found that there were no significant differences in reduction of muscle strength between the two groups after a mean period of 2.1 years.
Dr. Jubelt pointed out that lack of adequate control in the studies for modification of the patients’ daily activities could help to explain some of the discrepancies in reported prevalence of new weakness. “When you make positive changes in a patient’s daily activities, such as providing them with assistive devices, you reduce the stress on already overburdened muscles and motor neurons, which in turn reduces the progression of weakness in these patients. I think something similar could have happened in the two studies in question – even though the researchers attempted to conduct completely ‘controlled’ trials, they inevitably influenced the study participants’ daily activities and, subsequently, effected long-term changes in the participants’ health.”
Roundtable participant Neil Cashman, MD concurred with Dr. Jubelt’s assessment that progressive new weakness does occur in this patient population. ” We have all seen this manifestation in our patients. The question is not whether increasing weakness exists as a symptom of PPS, but rather, when patients complain of weakness, is it actually due to increasing weakness or is it due to another cause, such as increased joint pain or decreased endurance? I believe that it is an endurance problem in most patients.”
Diagnostic Criteria for PPS
Despite the difficulties in defining and identifying PPS symptoms such as “weakness” and “decreased endurance,” roundtable members agreed on some general diagnostic criteria for PPS (see Table, below). Ultimately, Dr. Halstead noted, the diagnosis of PPS is one of exclusion.