Post Polio Syndrome

Post-polio syndrome is the onset of new neurological manifestations that occur in patients 10 to 40 years after recovery from acute poliomyelitis. Post-polio syndrome is characterised by fatigue, weakness, joint and muscle pain, and worsening functional abilities. Development of post-polio syndrome does not inevitably imply progressive deterioration, but management requires a multidisciplinary approach, including physiotherapy, occupational therapy and orthotic support. Accepted criteria for diagnosis of post-polio syndrome are:

• Prior history of poliomyelitis
• Stable period after recovery
• Residual disability
• New muscle weakness, and there may be new muscle atrophy

One hypothesis is that post-polio syndrome is due to slow deterioration of previously rejuvenated motor neurons (some say simply due to aging). Initial recovery leads to sprouting of many new nerve endings, and such large motor units place stress on the neuronal cell body, which in time cannot maintain the increased metabolic demands. Recovery for a second time occurs in some fibres but eventually, with denervation exceeding reinnervation, nerve terminals are destroyed, and permanent weakness occurs. This is consistent with the slow, stepwise, but unpredictable progression. Other hypotheses include reactivation of latent virus, or motor neurone infection with a different enterovirus.

• Post-polio syndrome has become more common because of the large epidemics of poliomyelitis in the 1940s and 1950s,¹ but ultimately the syndrome will become very rare.
• Estimates of the prevalence in survivors of acute polio range from approximately 20-66%.
• It has been suggested that all survivors, if tracked for long enough, can develop some symptoms of post-polio syndrome.

• The severity appears proportional to the severity of the original attack, and the degree of disability.
• Onset is approximately 30 years after the acute polio.
• Symptoms usually appear earlier in patients who have very severe residual weakness, early bulbar respiratory difficulty in the acute illness, and those who were older when they contracted acute polio.
• Symptoms tend to occur first in the weaker muscles, and include:
  • New muscle weakness, muscle atrophy, muscle pain and gait disturbance
  • Decreased muscle endurance
  • Joint pain, spinal spondylosis and scoliosis, and secondary root and peripheral nerve compression
  • Fatigue: especially in the early afternoon with remission after brief periods of rest
  • Chronic pain, depression, sleep disorders, difficulty in concentrating and memory problems
  • Respiratory problems: diminished pulmonary compliance, increased chest wall tightness, chronic alveolar hypoventilation, decreased cough and expiratory flow, and decreased clearing of secretions. Sleep apnoea may occur if residual bulbar dysfunction or severe respiratory compromise.
  • Swallowing problems
  • Autonomic dysfunction
• Signs include:
  • Progressive weakness and atrophy may be observed in muscles that were affected initially by the polio virus or in muscles that were spared.
  • Distribution tends to be asymmetrical
  • Fasciculations can sometimes be observed in atrophic muscles

Similar clinical presentations include:

• Amyotrophic lateral sclerosis
• Hypothyroid myopathy
• Multiple sclerosis
• Infectious myopathy
• Myasthenia gravis
• Weakness due to aging
• Meningoencephalitis

Diagnosis is usually based on a typical medical history, electromyography and the exclusion of other diseases presenting with similar features. Investigations are directed at excluding other possible diagnoses:

• Full blood count, renal function, electrolytes, thyroid function tests, creatinine phosphokinase, CRP, antinuclear antibodies
• Cerebrospinal fluid
• Swallowing studies
• CT scan and MRI to rule out other possible diagnoses, e.g. stroke, multiple sclerosis, tumour
• Electrodiagnostic studies in post-polio syndrome show normal sensory conductions. Motor conductions are usually normal but may be slow. In late stages, amplitude decreases significantly. Single fibre electromyography shows increased jitter and blocking.

• Effective management requires a multidisciplinary approach involving both specific management of increasing impairment and a process of enabling patients to cope with new disabilities.² Therapy includes physiotherapy, occupational therapy and speech therapy (for swallowing difficulties).
• There is no specific therapy and trials of various drugs, including prednisolone, antivirals, alpha 2 recombinant interferon, and anticholinesterases have not shown significant benefit.
• The theoretically promising benefits of nerve growth factors, using insulin-like growth factor (IGF-1) have not been realised.
• Management is focused on symptomatic and supportive treatments including non-steroidal anti-inflammatory drugs, exercise, and life-strategies for fatigue.³

• Breathing, speaking and swallowing impairment are common but not severe medical problems of post-polio patients.⁴
• More severe degrees of respiratory failure are uncommon but may require treatment with continuous positive airway pressure or even tracheotomy and permanent ventilation.

Post-polio syndrome is slowly progressive but with periods of stability which can last up to ten years.

Polio immunisation prevents the primary illness, but no further prevention exists for polio survivors.