Post-polio syndrome
Encyclopedia
Post-polio syndrome is a condition that affects approximately 25–50% of people who have previously contracted poliomyelitis
—a viral
infection
of the nervous system
—after the initial infection. Typically the symptoms appear 15–30 years after recovery from the original paralytic
attack, at an age of 35 to 60. Symptoms include acute or increased muscular weakness, pain
in the muscle
s, and fatigue
. The same symptoms may also occur years after a nonparalytic polio (NPP) infection.
The precise mechanism that causes PPS is unknown. It shares many features with the post-viral chronic fatigue syndrome
, but unlike that disorder it tends to be progressive, and as such can cause a tangible loss of muscle strength. Treatment is primarily limited to adequate rest, conservation of available energy, and supportive measures, such as leg braces and energy-saving devices such as powered wheelchairs, analgesia (pain relief) and sleep aids.
, pain
and fatigue in limbs that were originally affected or in limbs that didn't seem to have been affected at the time of the initial polio illness. PPS is a very slowly progressing condition marked by periods of stability followed by new declines in the ability to carry out usual daily activities. Most patients become aware of their decreased capacity to carry out daily routines due to significant changes in mobility, decreasing upper limb function and lung capability. Fatigue is often the most disabling symptom; even slight exertion often produces disabling fatigue and can also intensify other symptoms. Problems breathing or swallowing, sleep-related breathing disorders, such as sleep apnea
and decreased tolerance for cold temperatures are other notable symptoms.
Increased activity during intervening healthy years between the original infection and onset of PPS can amplify the symptoms. Thus, contracting poliomyelitis at a young age can result in particularly disabling PPS symptoms.
attacks specific neurons in the brainstem and the anterior horn cell
s of the spinal cord, generally resulting in the death of a substantial fraction of the motor neuron
s controlling skeletal muscle
s. In an effort to compensate for the loss of these neurons, surviving motor neurons sprout new nerve terminals to the orphaned muscle fibers. The result is some recovery of movement and the development of enlarged motor units.
The neural fatigue theory proposes that the enlargement of the motor neuron fibres places added metabolic
stress on the nerve cell body to nourish the additional fibers. After years of use, this stress may be more than the neuron can handle, leading to the gradual deterioration of the sprouted fibers and, eventually, the neuron itself. This causes muscle weakness and paralysis. Restoration of nerve function may occur in some fibers a second time, but eventually nerve terminals malfunction and permanent weakness occurs. When these neurons no longer carry on sprouting, fatigue occurs due to the increasing metabolic demand of the nervous system. The normal aging process also may play a role. There is an ongoing denervation and reinnervation, but the reinnervation process has an upper limit where the reinnervation cannot compensate for the ongoing denervation, and loss of motor units takes place. However, what disturbs the denervation-reinnervation equilibrium and causes peripheral denervation is still unclear. With age, most people experience a decrease in the number of spinal motor neurons.Because polio survivors have already have lost a considerable number of motor neurons, further age-related loss of neurons may contribute substantially to new muscle weakness. The overuse and underuse of muscles also may contribute to muscle weakness.
Another theory is that people who've recovered from polio lose remaining healthy neurons at a faster rate than normal. However, little evidence exists to support this idea. Finally, it has been proposed that the initial polio infection causes an autoimmune reaction, in which the body's immune system
attacks normal cells as if they were foreign substances. Again, compared to neural fatigue, the evidence supporting this theory is quite limited.
. There is no laboratory test for post-polio syndrome, nor are there any other specific diagnostic criteria. Three important criteria are recognized, including: previous diagnosis of polio, long interval after recovery and the gradual onset of weakness.
In general, PPS is a diagnosis of exclusion whereby other possible causes of the symptoms are eliminated. Neurological examination
aided by other laboratory studies can help to determine what component of a neuromuscular deficit occurred with polio and what components are new and to exclude all other possible diagnoses. Objective assessment of muscle strength in PPS patients may not be easy. Changes in muscle strength are determined in specific muscle groups using various muscle scales which quantify
strength, such as the Medical Research Council
(MRC) scale. Magnetic resonance imaging
(MRI), neuroimaging
, and electrophysiological
studies, muscle biopsies, or spinal fluid analysis
may also be useful in establishing a PPS diagnosis.
can reduce energy usage. Medications for fatigue, such as amantadine
and pyridostigmine
, have not been found to be effective in the management of PPS. Muscle strength and endurance training are more important in managing the symptoms of PPS than the ability to perform long aerobic activity. Management should focus on treatments such as hydrotherapy and developing other routines that encourage strength but do not affect fatigue levels. The recent trend is towards use of intravenous immunoglobulin (IVIG)which has yielded promising, albeit modest results.
PPS increases the stress on the musculoskeletal system due to increasing muscular atrophy. A recent study showed that in a review of 539 PPS patients, 80% reported pain in muscles and joints and 87% only had fatigue. Joint instability can cause significant pain in individuals with PPS should be adequately treated with painkillers. Supervised activity programs, decreasing mechanical stress with braces and adaptive equipment is recommended.
Because PPS can fatigue facial muscles, as well as cause dysphagia
(difficulty swallowing), dysarthria
(difficulty speaking) or aphonia
(inability to produce speech), persons with PPS may become malnourished due to difficulty eating. Compensatory routines can help relieve these symptoms such as eating smaller portions at a time and sitting down whilst eating. PPS with respiratory involvement requires special management such as breathing exercises, chest percussion with a stethoscope on regular occasions for observation of the disease and management of secretions. Failure to properly assess PPS with respiratory involvement can increase the risk of missing aspiration pneumonia
(an infection of the lower respiratory tract) in an individual. Severe cases may require permanent ventilation or tracheostomy. Sleep apnoea may also occur. Other management strategies that may lead to improvement include smoking cessation
, treatment of other respiratory diseases and vaccination
against respiratory infections such as influenza
.
, and because no poliovirus is excreted in the feces, it is not considered a recurrence of the original polio. Further, there is no evidence that the poliovirus can cause a persistent infection in humans. PPS has been confused with amyotrophic lateral sclerosis
(ALS), which progressively weakens muscles. PPS patients do not have an elevated risk of ALS.
There have been no sufficient longitudinal studies on the prognosis of post-polio syndrome; however, speculations have been made by several physicians based on experience. Fatigue and mobility usually return to normal over a long period of time. The prognosis also differs depending upon different causes and factors affecting the individual. An overall mortality rate of 25% exists due to possible respiratory paralysis of persons with post-polio syndrome; otherwise, post-polio syndrome is usually non-lethal.
Post-polio syndrome is documented to occur in cases of nonparalytic polio (NPP). One review states late-onset weakness and fatigue occurs in 14% to 42% of NPP patients.
Poliomyelitis
Poliomyelitis, often called polio or infantile paralysis, is an acute viral infectious disease spread from person to person, primarily via the fecal-oral route...
—a viral
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...
infection
Infection
An infection is the colonization of a host organism by parasite species. Infecting parasites seek to use the host's resources to reproduce, often resulting in disease...
of the nervous system
Nervous system
The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous...
—after the initial infection. Typically the symptoms appear 15–30 years after recovery from the original paralytic
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...
attack, at an age of 35 to 60. Symptoms include acute or increased muscular weakness, pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
in the muscle
Muscle
Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...
s, and fatigue
Fatigue (physical)
Fatigue is a state of awareness describing a range of afflictions, usually associated with physical and/or mental weakness, though varying from a general state of lethargy to a specific work-induced burning sensation within one's muscles...
. The same symptoms may also occur years after a nonparalytic polio (NPP) infection.
The precise mechanism that causes PPS is unknown. It shares many features with the post-viral chronic fatigue syndrome
Chronic fatigue syndrome
Chronic fatigue syndrome is the most common name used to designate a significantly debilitating medical disorder or group of disorders generally defined by persistent fatigue accompanied by other specific symptoms for a minimum of six months, not due to ongoing exertion, not substantially...
, but unlike that disorder it tends to be progressive, and as such can cause a tangible loss of muscle strength. Treatment is primarily limited to adequate rest, conservation of available energy, and supportive measures, such as leg braces and energy-saving devices such as powered wheelchairs, analgesia (pain relief) and sleep aids.
Signs and symptoms
After a period of prolonged stability individuals who had been infected and recovered from polio begin to experience new signs and symptoms, characterised by muscular atrophy (decreased muscle mass), weaknessWeakness
Weakness is a symptom represented, medically, by a number of different conditions, including: lack of muscle strength, malaise, dizziness, or fatigue. The causes are many and can be divided into conditions that have true or perceived muscle weakness. True muscle weakness is a primary symptom of a...
, pain
Pain
Pain is an unpleasant sensation often caused by intense or damaging stimuli such as stubbing a toe, burning a finger, putting iodine on a cut, and bumping the "funny bone."...
and fatigue in limbs that were originally affected or in limbs that didn't seem to have been affected at the time of the initial polio illness. PPS is a very slowly progressing condition marked by periods of stability followed by new declines in the ability to carry out usual daily activities. Most patients become aware of their decreased capacity to carry out daily routines due to significant changes in mobility, decreasing upper limb function and lung capability. Fatigue is often the most disabling symptom; even slight exertion often produces disabling fatigue and can also intensify other symptoms. Problems breathing or swallowing, sleep-related breathing disorders, such as sleep apnea
Sleep apnea
Sleep apnea is a sleep disorder characterized by abnormal pauses in breathing or instances of abnormally low breathing, during sleep. Each pause in breathing, called an apnea, can last from a few seconds to minutes, and may occur 5 to 30 times or more an hour. Similarly, each abnormally low...
and decreased tolerance for cold temperatures are other notable symptoms.
Increased activity during intervening healthy years between the original infection and onset of PPS can amplify the symptoms. Thus, contracting poliomyelitis at a young age can result in particularly disabling PPS symptoms.
Mechanism
Numerous theories have been proposed to explain post-polio syndrome. Despite this, there are currently no absolutely defined causes of PPS. The most widely accepted theory of the mechanism behind the disorder is "neural fatigue". A motor unit is a nerve cell (or neuron) and the muscle fibers it activates. PoliovirusPoliovirus
Poliovirus, the causative agent of poliomyelitis, is a human enterovirus and member of the family of Picornaviridae.Poliovirus is composed of an RNA genome and a protein capsid. The genome is a single-stranded positive-sense RNA genome that is about 7500 nucleotides long. The viral particle is...
attacks specific neurons in the brainstem and the anterior horn cell
Anterior horn (spinal cord)
The anterior horn of the spinal cord is the ventral grey matter section of the spinal cord. The anterior horn contains motor neurons that affect the axial muscles while the posterior horn receives information regarding touch and sensation...
s of the spinal cord, generally resulting in the death of a substantial fraction of the motor neuron
Motor neuron
In vertebrates, the term motor neuron classically applies to neurons located in the central nervous system that project their axons outside the CNS and directly or indirectly control muscles...
s controlling skeletal muscle
Skeletal muscle
Skeletal muscle is a form of striated muscle tissue existing under control of the somatic nervous system- i.e. it is voluntarily controlled. It is one of three major muscle types, the others being cardiac and smooth muscle...
s. In an effort to compensate for the loss of these neurons, surviving motor neurons sprout new nerve terminals to the orphaned muscle fibers. The result is some recovery of movement and the development of enlarged motor units.
The neural fatigue theory proposes that the enlargement of the motor neuron fibres places added metabolic
Metabolism
Metabolism is the set of chemical reactions that happen in the cells of living organisms to sustain life. These processes allow organisms to grow and reproduce, maintain their structures, and respond to their environments. Metabolism is usually divided into two categories...
stress on the nerve cell body to nourish the additional fibers. After years of use, this stress may be more than the neuron can handle, leading to the gradual deterioration of the sprouted fibers and, eventually, the neuron itself. This causes muscle weakness and paralysis. Restoration of nerve function may occur in some fibers a second time, but eventually nerve terminals malfunction and permanent weakness occurs. When these neurons no longer carry on sprouting, fatigue occurs due to the increasing metabolic demand of the nervous system. The normal aging process also may play a role. There is an ongoing denervation and reinnervation, but the reinnervation process has an upper limit where the reinnervation cannot compensate for the ongoing denervation, and loss of motor units takes place. However, what disturbs the denervation-reinnervation equilibrium and causes peripheral denervation is still unclear. With age, most people experience a decrease in the number of spinal motor neurons.Because polio survivors have already have lost a considerable number of motor neurons, further age-related loss of neurons may contribute substantially to new muscle weakness. The overuse and underuse of muscles also may contribute to muscle weakness.
Another theory is that people who've recovered from polio lose remaining healthy neurons at a faster rate than normal. However, little evidence exists to support this idea. Finally, it has been proposed that the initial polio infection causes an autoimmune reaction, in which the body's immune system
Immune system
An immune system is a system of biological structures and processes within an organism that protects against disease by identifying and killing pathogens and tumor cells. It detects a wide variety of agents, from viruses to parasitic worms, and needs to distinguish them from the organism's own...
attacks normal cells as if they were foreign substances. Again, compared to neural fatigue, the evidence supporting this theory is quite limited.
Diagnosis
Diagnosis of post-polio syndrome can be difficult, since the symptoms are hard to separate from complications due to the original poliomyelitis infection, and from the normal infirmities of agingSenescence
Senescence or biological aging is the change in the biology of an organism as it ages after its maturity. Such changes range from those affecting its cells and their function to those affecting the whole organism...
. There is no laboratory test for post-polio syndrome, nor are there any other specific diagnostic criteria. Three important criteria are recognized, including: previous diagnosis of polio, long interval after recovery and the gradual onset of weakness.
In general, PPS is a diagnosis of exclusion whereby other possible causes of the symptoms are eliminated. Neurological examination
Neurological examination
A neurological examination is the assessment of sensory neuron and motor responses, especially reflexes, to determine whether the nervous system is impaired...
aided by other laboratory studies can help to determine what component of a neuromuscular deficit occurred with polio and what components are new and to exclude all other possible diagnoses. Objective assessment of muscle strength in PPS patients may not be easy. Changes in muscle strength are determined in specific muscle groups using various muscle scales which quantify
Quantity
Quantity is a property that can exist as a magnitude or multitude. Quantities can be compared in terms of "more" or "less" or "equal", or by assigning a numerical value in terms of a unit of measurement. Quantity is among the basic classes of things along with quality, substance, change, and relation...
strength, such as the Medical Research Council
Medical Research Council (UK)
The Medical Research Council is a publicly-funded agency responsible for co-ordinating and funding medical research in the United Kingdom. It is one of seven Research Councils in the UK and is answerable to, although politically independent from, the Department for Business, Innovation and Skills...
(MRC) scale. Magnetic resonance imaging
Magnetic resonance imaging
Magnetic resonance imaging , nuclear magnetic resonance imaging , or magnetic resonance tomography is a medical imaging technique used in radiology to visualize detailed internal structures...
(MRI), neuroimaging
Neuroimaging
Neuroimaging includes the use of various techniques to either directly or indirectly image the structure, function/pharmacology of the brain...
, and electrophysiological
Electrophysiology
Electrophysiology is the study of the electrical properties of biological cells and tissues. It involves measurements of voltage change or electric current on a wide variety of scales from single ion channel proteins to whole organs like the heart...
studies, muscle biopsies, or spinal fluid analysis
Lumbar puncture
A lumbar puncture is a diagnostic and at times therapeutic procedure that is performed in order to collect a sample of cerebrospinal fluid for biochemical, microbiological, and cytological analysis, or very rarely as a treatment to relieve increased intracranial pressure.-Indications:The...
may also be useful in establishing a PPS diagnosis.
Management
The treatment for post-polio syndrome is generally palliative and consists of rest, analgesia (pain relief) and utilisation of mechanisms to make life easier such as powered wheelchairs. There are no reversive therapies. Fatigue is usually the most disabling symptom; energy conservation can significantly reduce fatigue episodes. Such conservation can be achieved with lifestyle changes, reducing workload and daytime sleeping. Weight loss is also recommended if patients are obese. In some cases, the use of lower limb orthoticsOrthotics
Orthotics is a specialty within the medical field concerned with the design, manufacture and application of orthoses. An orthosis is an orthopedic device that supports or corrects the function of a limb or the torso...
can reduce energy usage. Medications for fatigue, such as amantadine
Amantadine
Amantadine is the organic compound known formally as 1-adamantylamine or 1-aminoadamantane. The molecule consists of adamantane backbone that has an amino group substituted at one of the four methyne positions. This pharmaceutical is sold under the name Symmetrel for use both as an antiviral and an...
and pyridostigmine
Pyridostigmine
Pyridostigmine is a parasympathomimetic and a reversible cholinesterase inhibitor. Since it is a quaternary amine, it is poorly absorbed in the gut and does not cross the blood-brain barrier, except possibly in stressful conditions.-Mode of action:...
, have not been found to be effective in the management of PPS. Muscle strength and endurance training are more important in managing the symptoms of PPS than the ability to perform long aerobic activity. Management should focus on treatments such as hydrotherapy and developing other routines that encourage strength but do not affect fatigue levels. The recent trend is towards use of intravenous immunoglobulin (IVIG)which has yielded promising, albeit modest results.
PPS increases the stress on the musculoskeletal system due to increasing muscular atrophy. A recent study showed that in a review of 539 PPS patients, 80% reported pain in muscles and joints and 87% only had fatigue. Joint instability can cause significant pain in individuals with PPS should be adequately treated with painkillers. Supervised activity programs, decreasing mechanical stress with braces and adaptive equipment is recommended.
Because PPS can fatigue facial muscles, as well as cause dysphagia
Dysphagia
Dysphagia is the medical term for the symptom of difficulty in swallowing. Although classified under "symptoms and signs" in ICD-10, the term is sometimes used as a condition in its own right. Sufferers are sometimes unaware of their dysphagia....
(difficulty swallowing), dysarthria
Dysarthria
Dysarthria is a motor speech disorder resulting from neurological injury of the motor component of the motor-speech system and is characterized by poor articulation of phonemes...
(difficulty speaking) or aphonia
Aphonia
Aphonia is the inability to speak. It is considered more severe than dysphonia. A primary cause of aphonia is bilateral disruption of the recurrent laryngeal nerve, which supplies nearly all the muscles in the larynx...
(inability to produce speech), persons with PPS may become malnourished due to difficulty eating. Compensatory routines can help relieve these symptoms such as eating smaller portions at a time and sitting down whilst eating. PPS with respiratory involvement requires special management such as breathing exercises, chest percussion with a stethoscope on regular occasions for observation of the disease and management of secretions. Failure to properly assess PPS with respiratory involvement can increase the risk of missing aspiration pneumonia
Pneumonia
Pneumonia is an inflammatory condition of the lung—especially affecting the microscopic air sacs —associated with fever, chest symptoms, and a lack of air space on a chest X-ray. Pneumonia is typically caused by an infection but there are a number of other causes...
(an infection of the lower respiratory tract) in an individual. Severe cases may require permanent ventilation or tracheostomy. Sleep apnoea may also occur. Other management strategies that may lead to improvement include smoking cessation
Smoking cessation
Smoking cessation is the process of discontinuing the practice of inhaling a smoked substance. This article focuses exclusively on cessation of tobacco smoking; however, the methods described may apply to cessation of smoking other substances that can be difficult to stop using due to the...
, treatment of other respiratory diseases and vaccination
Vaccination
Vaccination is the administration of antigenic material to stimulate the immune system of an individual to develop adaptive immunity to a disease. Vaccines can prevent or ameliorate the effects of infection by many pathogens...
against respiratory infections such as influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...
.
Prognosis
In general, PPS is not life-threatening. The major exception are patients left with severe residual respiratory difficulties, who may experience new severe respiratory impairment. Studies have shown that, compared to control populations, PPS patients lack any elevation of antibodies against the poliovirusPoliovirus
Poliovirus, the causative agent of poliomyelitis, is a human enterovirus and member of the family of Picornaviridae.Poliovirus is composed of an RNA genome and a protein capsid. The genome is a single-stranded positive-sense RNA genome that is about 7500 nucleotides long. The viral particle is...
, and because no poliovirus is excreted in the feces, it is not considered a recurrence of the original polio. Further, there is no evidence that the poliovirus can cause a persistent infection in humans. PPS has been confused with amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis , also referred to as Lou Gehrig's disease, is a form of motor neuron disease caused by the degeneration of upper and lower neurons, located in the ventral horn of the spinal cord and the cortical neurons that provide their efferent input...
(ALS), which progressively weakens muscles. PPS patients do not have an elevated risk of ALS.
There have been no sufficient longitudinal studies on the prognosis of post-polio syndrome; however, speculations have been made by several physicians based on experience. Fatigue and mobility usually return to normal over a long period of time. The prognosis also differs depending upon different causes and factors affecting the individual. An overall mortality rate of 25% exists due to possible respiratory paralysis of persons with post-polio syndrome; otherwise, post-polio syndrome is usually non-lethal.
Epidemiology
Post-polio syndrome occurs in approximately 25–50% of people who survive a poliomyelitis infection. On average, it occurs 30–35 years afterwards; however, delays of between 8–71 years have been recorded. The disease occurs sooner in persons with more severe initial infection. Other factors that increase the risk of postpolio syndrome include increasing length of time since acute poliovirus infection, presence of permanent residual impairment after recovery from the acute illness, and female sex.Post-polio syndrome is documented to occur in cases of nonparalytic polio (NPP). One review states late-onset weakness and fatigue occurs in 14% to 42% of NPP patients.
See also
- History of poliomyelitisHistory of poliomyelitisThe history of poliomyelitis infections extends into prehistory. Although major polio epidemics were unknown before the 20th century, the disease has caused paralysis and death for much of human history...
- List of polio survivors
- PoliomyelitisPoliomyelitisPoliomyelitis, often called polio or infantile paralysis, is an acute viral infectious disease spread from person to person, primarily via the fecal-oral route...
- PoliovirusPoliovirusPoliovirus, the causative agent of poliomyelitis, is a human enterovirus and member of the family of Picornaviridae.Poliovirus is composed of an RNA genome and a protein capsid. The genome is a single-stranded positive-sense RNA genome that is about 7500 nucleotides long. The viral particle is...
- Polio vaccinePolio vaccineTwo polio vaccines are used throughout the world to combat poliomyelitis . The first was developed by Jonas Salk and first tested in 1952. Announced to the world by Salk on April 12, 1955, it consists of an injected dose of inactivated poliovirus. An oral vaccine was developed by Albert Sabin...
Further reading
- Maynard, F.M., & Headley, J.H. (Eds.) (1999). Handbook on the Late Effects of Poliomyelitis for Physicians and Survivors. Saint Louis, MO: GINI (now Post-Polio Health International). Information on 90 post-polio topics; a compilation of the research and experience of over 40 experts.
- March of Dimes Birth Defects Foundation. (1999). Identifying Best Practices in Diagnosis & Care. Warm Springs, GA: March of Dimes International Conference on Post-Polio Syndrome
- Nollet F. "Perceived health and physical functioning in postpoliomyelitis syndrome". Vrije Universiteit Amsterdam, 2002.
- Nollet, F. "Post-polio syndrome". Orphanet Ecyclopaedia, 2003
- Silver, Julie K. (2001). Post-Polio Syndrome: A Guide for Polio Survivors and Their Families. New Haven: Yale University Press. (Dr. Silver is Medical Director, Spaulding-Framingham Outpatient Center; Assistant Professor, Department of Physical Medicine and Rehabilitation, Harvard Medical School.)