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 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.

A motor unit is a nerve cell (or neuron) and the muscle fibers it activates - for a more detailed explanation see Introduction to Neuroanatomy. 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 is 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 sub clinical 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

There is no cure for PPS and to date there are no pharmaceutical treatments that have been identified at being effective in stopping or reversing the deterioration or symptoms. Emphasis is currently on managing symptoms and the role of the physiotherapist is important to help people with PPS find suitable aids and interventions to lead independent lives.

Physiotherapy is safe and effective when carefully prescribed and monitored by experienced health professionals. Cardiopulmonary endurance as well as strengthening exercises are both effective in post polio syndrome. An intense strengthening programme using resistance or weights may be counterproductive as they can fatigue and already weaken compromised muscles. All exercise should be carefully monitored and any signs of further weakness, increased fatigue or long periods of recovery time should be an indicator to either revise the programme or stop exercise completely until recovery is evident.

Plan for Rehabilitation

Strengthening programs performed as described show increase on isokinetic strength, improved cardiorespiratory status, no decline in strength in 6-12 months, and increase in isometric strength.

Postpolio patients showed a significant improvement in their strength after isokinetic and isometric exercise sessions. It lessens fatigue, improves strength and reduces pain. The training did not adversely affect motor unit survival, and the improvement was largely attributable to an increase in voluntary motor drive.

Use of Modalities

Electrical stimulation has been used to strengthen weakened muscles or to reeducate muscles weakened through disuse, as well as to decrease pain

For myofascial pain, consider heat, electrical stimulation, trigger point injections, stretching exercises, biofeedback, muscle relaxation exercises, or static magnetic fields for trigger points. Exercise therapy and training programs in PPS patients should be carefully customized and planned by physiotherapists to avoid both overuse and disuse, and the level of physical activity should be modified to decrease pain.

Prevention

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. But 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.