Post Polio Syndrome % Symtoms, Cause , Diagnosis, Prognosis
Post-polio syndrome can affect polio survivors many years after recovering from an initial acute attack of the poliovirus. This syndrome is characterized by new muscle pain, worsening of existing weakness, and new weakness or paralysis. The cause is unknown, and there is currently no cure. Treatment is focused on relieving the symptoms. Researchers estimate that this syndrome affects 25 to 50 percent of polio survivors in the United States.
Post-polio syndrome is not an infectious disease, and people who are experiencing it do not shed poliovirus.
What Causes It?
The cause of this condition is not known. However, research scientists believe the new weakness seen in post-polio syndrome is related to the damage of individual nerve terminals in the motor units that remain after the initial poliovirus infection.
Risk Factors for Post-Polio Syndrome
While risk factors do not cause post-polio syndrome, certain factors can increase a person's risk for developing the condition. Risk factors include:
•Increasing length of time since acute poliovirus infection
Presence of permanent disability after recovery from the original polio virus infection
The symptoms of post-polio syndrome can vary in number and severity between different people with the condition. Some patients experience only minor symptoms of post-polio syndrome, while others develop more severe symptoms.
Common post-polio syndrome symptoms can include:
•Slowly progressive muscle weakness
•Loss of muscle
•Increasing skeletal deformities such as scoliosis.
•Diagnosing Post-Polio Syndrome In order to make a diagnosis of post-poliosyndrome, the doctor will ask the patient a number of questions, perform a physical exam, and recommend certain tests looking for signs and symptoms of post-polio syndrome. Some of these tests may include:
◦Magnetic resonance imaging (MRI)
◦Computed tomography (CT)
• These tests can help diagnose post-poliosyndrome (or even another medical condition), but they do not identify survivors at greatest risk for new progression of muscle weakness. Before making a diagnosis, the doctor will also consider other medical conditions that can share similar symptoms with post-polio syndrome. Some of these conditions include:
Currently, there is no cure for post-polio syndrome. Therefore, treatment is focused on relieving the symptoms. Some treatment options for this condition include lifestyle changes and support. Research scientists continue to actively look for other post-polio treatmentoptions.
Post-Polio Syndrome and Exercise
Post-polio syndrome symptoms of pain, weakness, and fatigue can result from the overuse and misuse of muscles and joints. These same symptoms can also result from disuse of muscles and joints. This fact has caused a misunderstanding about whether to encourage or discourage exercise for polio survivors or individuals who already have post-polio syndrome. (Click Post-Polio Syndrome and Exercise for more information.)
Post-polio syndrome is a very slow, progressive condition marked by long periods of stability. The severity of post-polio syndrome will depend on the degree of the weakness and disability that remained after an individual had the original polio attack. People who had only minimal polio symptoms from the original attack and subsequently develop post-polio syndrome will most likely experience only mild symptoms. People who were originally hit hard by thepoliovirus and were left with severe weakness may develop a more severe case of post-polio syndrome with a greater loss of muscle function, difficulty in swallowing, and more periods of fatigue. (Click Post-Polio Syndrome Prognosis for more information.)
How Common Is Post-Polio Syndrome?
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 this condition affects 25 percent to 50 percent of these survivors, or possibly as many as 60 percent.
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A 41-year-old man developed an acute illness at the age of 9 months during which, following a viral illness with headache, he developed severe weakness and wasting of the limbs of the left side. After several months he began to recover, such that he was able to walk at the age of 2 years and later was able to run, although he was never very good at sports. He had stable function until the age of 18 when he began to notice greater than usual difficulty lifting heavy objects. By the age of 25 he was noticing progressive difficulty walking due to weakness of both legs, and he noticed that the right calf had become larger. The symptoms became more noticeable over the course of the next 10 years and ultimately both upper as well as both lower limbs had become noticeably weaker.
On examination there was wasting of the muscles of upper and lower limbs on the left, and massively hypertrophied gastrocnemius, soleus and tensor fascia late on the right. The calf circumference on the right exceeded that on the left by 10 cm (figure1). The right shoulder girdle, triceps, thenar eminence and small muscles of the hand were wasted and there was winging of both scapulae. The right quadriceps was also wasted. The wasted muscles were also weak but the hypertrophied right ankle plantar flexors had normal power. The tendon reflexes were absent in the lower limbs and present in the upper limbs, although the right triceps was reduced. The remainder of the examination was normal.
The patient's legs, showing massive enlargement of the right calf and wasting on the left
What is that nature of the acute illness in infancy?
What is the nature of the subsequent deterioration?
What investigations should be performed?
What is the differential diagnosis of the cause of the progressive calf hypertrophy?
An acute paralytic illness which follows symptoms of a viral infection with or without signs of meningitis is typical of poliomyelitis. Usually caused by one of the three polio viruses, it may also occur following vaccination and following infections with other enteroviruses.1 Other disorders which would cause a similar syndrome but with upper motor neurone signs would include acute vascular lesions, meningoencephalitis and acute disseminated encephalomyelitis.
A progressive functional deterioration many years after paralytic poliomyelitis is well known, although its pathogenesis is not fully understood.2 It is a diagnosis of exclusion; a careful search for alternative causes, for example, orthopaedic deformities such as osteoarthritis or worsening scoliosis, superimposed neurological disorders such as entrapment neuropathies or coincidental muscle disease or neuropathy, and general medical causes such as respiratory complications and endocrinopathies.3
Investigations revealed normal blood count and erythrocyte sedimentation rate and normal biochemistry apart from a raised creatine kinase at 330 IU/l (normal range 60–120 IU/l), which is commonly seen in cases of ongoing denervation. Electromyography showed evidence of denervation in the right APB and FDI with polyphasic motor units and complex repetitive discharges, no spontaneous activity in the left calf and large polyphasic units in the right calf consistent with chronic partial denervation. Motor and sensory conduction velocities were normal. A lumbar myelogram was normal. Magnetic resonance imaging (MRI) scan of the calves is shown in figure2.
Axial T1 weighted MRI scan (TR 588 ms, TE 15 ms) of the calves, showing gross muscle atrophy and replacement by adipose tissue on the left, and hypertrophy of the muscles on the right, with only minor adipose tissue deposition
The differential diagnosis of the progressive calf hypertrophy is given in the box.
Causes of calf muscle hypertrophy
Chronic partial denervation
hereditary motor and sensory neuropathy
spinal muscular atrophy
following paralytic poliomyelitis
Neuromyotonia and myokymia
continuous muscle fibre activity due to: chronic inflammatory demyelinating polyradiculopathy, Guillain Barre syndrome, myasthenia gravis, thymoma, thyrotoxicosis, thyroiditis