Physical Therapy Intervention in Post Polio Syndrome

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What is Polio?

Poliomyelitis, also commonly known as polio, is a disease that mainly affects children below the age of 5. It is a highly infectious disease and spreads from person-person through the feacal-oral route or contaminated food and water. It is caused by the group C enterovirus known as Poliovirus (PV). PV mainly grows in the GI tract and can multiply and further spread to other parts of the body including nervous tissue. Upon spreading to the Central Nervous System, the virus targets motor neurons which results in its classical clinical presentation. Symptoms of Polio can manifest within a few hours or after several days, in up to 70% of infections there are no symptoms at all. Symptoms can vary but the most commonly seen are:

• Muscle weakness, most commonly in the legs but can occur in the head, neck, and diaphragm
• Fever
• Fatigue
• Headache
• Vomiting
• Neck Stiffness
• Pain in the arms and legs.

Polio is not a new disease and was in fact first reported in England, by Michael Underwood, in 1789. He described cases of children who displayed weakness and paralysis of their lower extremities. Epidemics of poliomyelitis were first observed in Scandinavia, Western Europe, and the United States towards the end of the 19^th century and steadily grew in frequency and magnitude until the late 1950s and 1960s when the poliovirus vaccine was introduced. A vaccine first developed by Jonas E. Salk, using killed or inactivated poliovirus (IPV), was made available by injection in 1955. The introduction of the trivalent Sabin oral vaccine (OPV) in 1962 was the beginning of the plan to eradicate Polio, the vaccine was affordable and easy to administer providing a cheap and readily administered vaccine. Currently, cases due to wild poliovirus have decreased by over 99% since 1988, from an estimated 350,000 cases in more than 125 endemic countries to just two endemic countries (as of October 2023).

Post Polio Syndrome

Despite the successful vaccination project a new condition has emerged known as Post-Polio Syndrome (PPS). PPS is a condition that affects polio survivors years after recovery from an initial acute attack of the poliomyelitis virus. Post-polio syndrome is mainly characterized by new weakening in muscles that were previously affected by the polio infection and in muscles that seemingly were unaffected.

The cause of PPS is unknown, but it is thought that the new weakness of post-polio syndrome may be due to the degeneration of individual nerve terminals in the motor units. The poliovirus attacks specific neurons in the brainstem and the anterior horn cells of the spinal cord. In an effort to compensate for the loss of these neurons, ones that survive create new nerve terminals to the orphaned muscle fibers. The result is some recovery of movement and enlarged motor units. Years of high use of these enlarged motor units adds stress to the neuronal cell body, which then, may not be able to maintain the metabolic demands of all the new pathways, resulting in the slow deterioration of motor units. Restoration of nerve function may occur in some fibers a second time, but eventually, nerve terminals malfunction and permanent weakness occurs. This hypothesis is consistent with post-polio syndrome's slow, stepwise, unpredictable course.

According to estimates by the National Center for Health Statistics, more than 440,000 polio survivors in the United States may be at risk for post-polio syndrome. Researchers are unable to establish a firm prevalence rate, but they estimate that the condition affects 25 percent to 50 percent of these survivors, but may be as high 60 percent.

Clinical Features

Symptoms include slowly progressive muscle weakness, unaccustomed fatigue (both generalized and muscular), and, at times, muscle atrophy. Pain from joint degeneration and increasing skeletal deformities such as scoliosis are common. Some patients experience only minor symptoms. While less common, others may develop visible muscle atrophy, or wasting.

Post-polio syndrome is rarely life-threatening. However, untreated respiratory muscle weakness can result in underventilation, and weakness in swallowing muscles can result in aspiration pneumonia.

Diagnosis

There is no definitive laboratory test for diagnosing PPS and symptoms can often mimic other neurological conditions; exclusion of these and other possible skeletal conditions is the first step in moving towards a diagnosis of PPS. Once other pathologies have been excluded the following criteria are used to confirm PPS:

1. Prior paralytic poliomyelitis with evidence of motor neuron loss, as confirmed by history of the acute paralytic illness, signs of residual weakness and atrophy of muscles on neuromuscular examination, and signs of nerve damage on electromyography (EMG). Rarely, persons have subclinical paralytic polio, described as a loss of motor neurons during acute polio but with no obvious deficit. That prior polio now needs to be confirmed with an EMG. Also, a reported history of nonparalytic polio may be inaccurate.
2. A period of partial or complete functional recovery after acute paralytic poliomyelitis, followed by an interval (usually 15 years or more) of stable neuromuscular function.
3. Gradual onset of progressive and persistent new muscle weakness or abnormal muscle fatigability (decreased endurance), with or without generalized fatigue, muscle atrophy, or muscle and joint pain. Onset may at times follow trauma, surgery, or a period of inactivity, and can appear to be sudden. Less commonly, symptoms attributed to post-polio syndrome include new problems with breathing or swallowing.
4. Symptoms that are present for at least a year

Physical Therapy Management

Physiotherapy management for post-polio syndrome (PPS) involves a multidisciplinary approach to address the various symptoms and challenges faced by individuals who have survived polio. It is essential to individualize the treatment approach based on the patient's specific needs, preferences, and response to interventions. Regular reassessment and collaboration with other healthcare professionals are crucial for optimal care.

Physiotherapy Management Considerations

• It is important to recognize the difficulty of sustaining high exercise intensities for prolonged periods, particularly in severely fatigued individuals. Training regimes must be highly individualized and exercise prescription can be based on certain individual markers such as Aerobic Threshold (AT) or Rate of Perceived Exertion (RPE).
• Efficiently evaluate muscle function which includes endurance and strength. Understanding that improvements in muscle function may be challenging in persons with PPS due possibility of hypertrophied muscle fibers.
• Training programmes must be tailored towards daily activities and functional independence. It should involve training muscle groups that may be disused or deconditioned and focusing on exercises that mimic daily tasks.
• Recognize the potential limitations of exercise modes that primarily focus on the lower extremities.
• Emphasize the importance of monitoring the actual training dose to ensure the prescribed intensities are achieved.

Physiotherapy Interventions

Exercise and Mobility

• Exercise programmes must be designed to improve strength, endurance, and flexibility through low-impact activities to reduce stress on the muscles and joints.
• Incorporate exercises that target weakened muscles with a focus on gradual progression to prevent excessive fatigue.
• Non-fatiguing strengthening exercises such as isokinetic and isometric exercises can be included in the programme.
• In addition to traditional exercises, aquatic therapy can also be beneficial due to its low-impact nature and the buoyancy of water providing support.

Manual Therapy and Modalities

• Appropriate strategies can be developed to manage musculoskeletal pain associated with PPS which may include manual therapy or heat/cold therapy. It is vital to collaborate with other healthcare providers to explore pharmacological interventions for pain management when necessary.
• Therapeutic ultrasound therapy and myofascial mobilization (Graston® technique) has been utilized for releasing stiffness and restore function to affected muscles and joints.

Patient Education

Polio survivors often ask if there is a way to prevent post-polio syndrome. Presently, no intervention has been found to stop the deterioration of surviving neurons. However physicians recommend that polio survivors get the proper amount of sleep, maintain a well-balanced diet, avoid unhealthy habits such as smoking and overeating, and follow an exercise program as discussed above. Proper lifestyle changes, the use of assistive devices, and taking certain anti-inflammatory medications may help some of the symptoms of post-polio syndrome.