Post-polio Syndrome

Post-polio syndrome (PPS) is the onset of new deterioration in function that may occur many years after recovery from acute poliomyelitis. PPS comprises various possible symptoms such as fatigue, weakness, joint and muscle pain, reduced respiratory function or dysphagia. PPS does not necessarily imply progressive deterioration, and can be helped by treatment. Management requires careful assessment and a multidisciplinary approach.

Suggested criteria for diagnosis of PPS are:¹

• Previous history of poliomyelitis.
• Stable period after recovery (usually > 15 years).
• New symptoms, such as generalised fatigue, new weakness, abnormal muscle fatigue and muscle atrophy.
• Exclusion of other cause of muscle weakness (but note that problems can be multifactorial², as discussed below).

Note:

• There is no universal definition of PPS, but most sources use one similar to the above.
• Some experts suggest that PPS may be diagnosed in those where there is no clear history of paralytic polio, but where the past history or investigations suggest that previous polio is likely.³

There is NO reactivation of the polio virus infection (patients may need reassurance about this).

The exact cause of PPS is unknown:

• There may be new muscle atrophy and weakness relating to changes in motorneurones.
• Overuse or disuse of muscles play an important role.⁴
• The cause of PPS symptoms may be multifactorial. For example, disabilities resulting from acute polio, combined with activities of daily living, can produce large stresses acting on abnormal muscles and joints. This may lead to other problems which contribute to PPS, such as:
  • Joint deformities
  • Osteoporosis
  • Scoliosis
  • Cervical spondylosis
  • Peripheral nerve entrapment (can occur with callipers, crutches etc.)

It is estimated that PPS may occur in 28-75% of patients with previous polio. The time interval is usually around 35 years, but may be 8-70 years after the acute polio episode.

Common symptoms are:⁴

• Generalised fatigue
• Joint and muscle pain
• New muscle or joint weakness
• Muscle atrophy
• Cold intolerance
• Bulbar symptoms - speech, swallowing or respiratory symptoms
• Worsening respiratory function - may present as headaches, fatigue or sleep disorder (see below under 'Respiratory and sleep problems in post-polio syndrome').

Any of these can lead to a deterioration in day-to-day functioning. A small change in clinical terms can mean a large one in its effects on daily living.

• Listen to the patient's story.
• The most important question to ask is not "can you do this activity?", e.g. climbing stairs, but "how do you do it?" This can reveal the functional change, e.g. stopping to rest half way, going upstairs by shifting on their bottom.⁵
• A patient questionnaire such as "my polio life" can be useful.⁶
• Multidisciplinary assessment may be needed, e.g. involving physiotherapist, occupational therapist, neurologist, orthopaedic/orthotic team and respiratory physician.

Bear in mind that various factors can make assessment more difficult:⁷

• Polio survivors are used to coping and adapting. Hence the importance of asking - and observing - how patients carry out each activity.
• Symptoms can vary from day to day and can be affected by recent activity, overuse or rest.
• Patients may deliberately allow for a stressful hospital visit day by resting beforehand. This can give a falsely good picture. Ask what symptoms are like "on bad days".
• Results can appear normal if patients are given long rests between tests, or if only the best result is recorded.
• Respiratory and sleep problems are easily missed (see below under 'Respiratory and sleep problems in post-polio syndrome').
• Anecdotally, patients with PPS have had their symptoms dismissed after apparently normal or near-normal results of tests, such as lung function or muscle power.

Investigations

These will depend on symptoms, but could include:

• Muscle tests - but be aware that simple tests of isometric muscle strength may be insensitive^5,8
• Respiratory investigations (see below under 'Assessment of respiratory problems')
• Sleep studies (see below under 'Assessment of respiratory problems')
• Swallowing studies, e.g. barium swallow
• Investigations to exclude other causes

Other causes of fatigue or weakness, e.g:

• Other types of neuropathy or myopathy
• Multiple sclerosis
• Amyotrophic lateral sclerosis or other anterior horn cell diseases
• Myasthenia gravis
• Systemic conditions, e.g. anaemia, chronic infection, hypothyroidism, collagen disorders, medication side-effects

Other causes of pain, e.g:

• Arthritis, bursitis, tendinitis
• Myalgias - polymyalgia rheumatica, fibromyalgia
• Neuropathies

A multidisciplinary approach is helpful.⁹ Some important aspects of management are:

• The correct balance of rest and exercise is essential:^4,10
  • Avoid overuse, as too much exercise causes increased weakness and fatigue in damaged muscles.
  • Graded exercise is beneficial - this should probably be broken up by periods of rest.
  • Non-swimming exercise in warm water often helps.
  • Many polio survivors are used to leading active lives and, to some extent, ignoring their disability. Adapting to PPS and the need for more rest may require lifestyle and employment changes.¹¹
• Orthopaedic and orthotic management of skeletal problems, e.g:
  • Simple supports for knee, ankle and cervical spine can improve function.
  • Replace damaged aids.
• Muscle pain:
  • Physical treatments, such as warmth/cold, massage, passive stretching.
  • Transcutaneous nerve stimulation.
  • Acupuncture.
• Anaesthesia requires special considerations.¹²
• Nutrition:
  • Good nutrition and weight control.
  • Some patients find that a high protein diet is helpful (e.g. the post-polio institute "hypoglycaemia diet").¹¹
• Specific treatment of other problems, e.g. dysphagia and respiratory and sleep problems (see below under 'Respiratory and sleep problems in post-polio syndrome').

Importance

• Respiratory problems in PPS are an important cause of symptoms and complications, including sleep disorders.
• They may be under-diagnosed or inadequately assessed.
• Treatment can improve both quality of life and prognosis.

Aetiology¹⁴

Respiratory problems in PPS may be due to one or more of:

• Respiratory muscle weakness.
• Bulbar impairment - this may affect control of the upper airway or the respiratory cycle. If the upper airway is affected, there may be obstructive sleep apnoea.
• Skeletal deformity - scoliosis or chest wall stiffness.
• Other pathology, e.g. COPD, asthma, obesity.
• Aspiration - if swallowing affected.

All these are likely to worsen during sleep. The pattern of respiratory impairment may be hypoventilation, obstructive sleep apnoea, or both.¹⁶

Symptoms

Respiratory failure can develop insidiously - symptoms may be subtle or unnoticed. Breathlessness may not be a symptom in patients with limited mobility. Possible symptoms are:

• Sleep disruption, eventually leading to insomnia, daytime sleepiness or fatigue.
• Morning headaches, irritability, poor concentration, anxiety or depression.
• Abnormal sleep movements, nocturnal confusion, vivid dreams.
• Breathlessness may be positional.
• Weak cough, chest infections.

Signs

May be subtle - possible signs are:

• Unexplained tachypnoea.
• Use of accessory muscles.
• Abdominal paradox - this is inward movement of the abdomen on inspiration while the upper chest expands.
  • May be best seen with patient supine during a sniff manoeuvre. When upright, can be missed as the diaphragm passively descends at the beginning of inspiration.
• Severe, untreated nocturnal hypoxaemia can cause pulmonary hypertension, giving signs such as raised JVP and ankle oedema.

Assessment of respiratory problems

• Listen to the patient's story and preferences.
• Assess:
  • Voice and cough
  • Chest deformity
  • Observe patients in realistic situations, e.g. doing repeated tests or actions, and doing everyday actions in which they may be using the necessary breathing muscles to achieve another task
• Investigations:
  • Peak flow and cough peak flow
  • Spirometry
    • Both seated AND supine spirometry are needed
    • A sensitive indicator of respiratory muscle weakness is reduction in maximal inspiratory pressure
  • Oximetry (and possibly capnography)
  • Sleep study (polysomnogram)
  • ECG and chest X-ray if appropriate
  Full sets of lung function tests and arterial blood gases may not be helpful in this scenario, unless intrinsic lung disease is suspected.

Management of respiratory problems

There are various options - choice will depend on the patient's individual situation and preferences.
Night-time mechanical ventilation is often used. This helps by resting the respiratory muscles at night, and preventing deterioration of respiratory function during sleep. It also treats the secondary sleep disorder.

Supportive measures include:

• Not smoking
• Avoiding sedatives and alcohol
• Optimal weight and nutrition
• Pneumococcal and influenza vaccination
• Postural support if needed
• Prompt treatment of chest infections
• Techniques such as assisted cough or glossopharyngeal breathing ('frog breathing')
• Chest expansion exercises

Assisted breathing options are:

• Non-invasive intermittent positive pressure ventilation (NIV or NPPV) is often useful - see box below.
• Rocking bed:
  • This helps breathing by rocking a patient consecutively head up and head down. It is surprisingly effective, especially where muscle weakness is mainly diaphragmatic
• Pneumobelt:
  • This gives intermittent abdominal pressure ventilation and is useful for daytime assistance
• Negative pressure ventilation:
  • Examples are tank ventilators (iron lung), jacket ventilators (Tunnicliffe), and cuirass ventilators. The devices are cumbersome, and mainly used where NIV is not tolerated, or to provide 'respite' from NIV
• Tracheostomy ventilation.

• Experience suggests that the functional deterioration does not necessarily progress.
• Fatigue and reduction in mobility may stabilise or progress very slowly.

Prevention of acute polio infection is discussed elsewhere (see separate article on Poliomyelitis).

Prevention of PPS is not much discussed in the literature. Given the various known contributing factors, it seems possible that PPS problems might be reduced by:

• Careful management of exercise and daily living activities to optimise muscle and joint use, and prevent overuse or disuse.
• Correct maintenance of aids and prostheses.
• Monitoring and early treatment of associated/contributing problems such as:
  • Osteoporosis.
  • Obesity.
  • Respiratory problems.

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