Post-polio syndrome (PPS, poliomyelitis sequelae) is a group of
latent symptoms of
poliomyelitis (polio), occurring in more than 80% of polio infections. The symptoms are caused by the damaging effects of the viral
infection
An infection is the invasion of tissue (biology), tissues by pathogens, their multiplication, and the reaction of host (biology), host tissues to the infectious agent and the toxins they produce. An infectious disease, also known as a transmis ...
on the
nervous system
In biology, the nervous system is the complex system, highly complex part of an animal that coordinates its behavior, actions and sense, sensory information by transmitting action potential, signals to and from different parts of its body. Th ...
and typically occur 15 to 30 years after an initial acute
paralytic attack. Symptoms include decreasing
muscular function or acute
weakness with
pain
Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...
and
fatigue
Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself.
Fatigue (in the medical sense) is sometimes associated wit ...
. The same may also occur years after a nonparalytic polio infection.
The precise mechanism that causes PPS is unknown. It shares many features with
chronic fatigue syndrome
Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a disabling Chronic condition, chronic illness. People with ME/CFS experience profound fatigue that does not go away with rest, as well as sleep issues and problems with memory ...
, but unlike that disorder it tends to be progressive and can cause 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 management is an aspect of medicine and health care involving relief of pain (pain relief, analgesia, pain control) in various dimensions, from acute and simple to chronic and challenging. Most physicians and other health professionals ...
(pain relief), and
sleep aids.
Signs and symptoms
After a period of prolonged stability, some people who recover from polio infections begin to experience new signs and symptoms, characterised by
muscular atrophy
Muscle atrophy is the loss of skeletal muscle mass. It can be caused by sedentary lifestyle, immobility, aging, malnutrition, medications, or a wide range of injuries or diseases that impact the musculoskeletal or nervous system. Muscle atrophy le ...
,
weakness,
pain
Pain is a distressing feeling often caused by intense or damaging Stimulus (physiology), stimuli. The International Association for the Study of Pain defines pain as "an unpleasant sense, sensory and emotional experience associated with, or res ...
, and limb
fatigue
Fatigue is a state of tiredness (which is not sleepiness), exhaustion or loss of energy. It is a signs and symptoms, symptom of any of various diseases; it is not a disease in itself.
Fatigue (in the medical sense) is sometimes associated wit ...
.
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 and 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 apnoea or sleep apnœa in British English) is a sleep-related breathing disorder in which repetitive Apnea, pauses in breathing, periods of shallow breathing, or collapse of the upper airway during sleep results in poor vent ...
, and decreased tolerance for cold temperatures are other notable symptoms.
[
Increased activity during healthy years between the original infection and onset of PPS can amplify the symptoms. Thus, contracting polio at a young age can result in particularly disabling PPS symptoms.]
A possible early occurring and long-lasting sign is a slight jitter exhibited in handwriting.
Mechanism
Numerous theories have been proposed to explain post-polio syndrome. Despite this, no absolutely defined causes of PPS are known. 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. Poliovirus attacks specific neurons in the brainstem
The brainstem (or brain stem) is the posterior stalk-like part of the brain that connects the cerebrum with the spinal cord. In the human brain the brainstem is composed of the midbrain, the pons, and the medulla oblongata. The midbrain is conti ...
and the anterior horn cells of the spinal cord, generally resulting in the death of a substantial fraction of the motor neuron
A motor neuron (or motoneuron), also known as efferent neuron is a neuron whose cell body is located in the motor cortex, brainstem or the spinal cord, and whose axon (fiber) projects to the spinal cord or outside of the spinal cord to directly o ...
s controlling skeletal muscle
Skeletal muscle (commonly referred to as muscle) is one of the three types of vertebrate muscle tissue, the others being cardiac muscle and smooth muscle. They are part of the somatic nervous system, voluntary muscular system and typically are a ...
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 fibers places added ]metabolic
Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the ...
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. Denervation and reinnervation are going on, but the reinnervation process has an upper limit where the reinnervation cannot compensate for the ongoing denervation, and loss of motor units takes place. What disturbs the denervation-reinnervation equilibrium and causes peripheral denervation, though, is still unclear. With age, most people experience a decrease in the number of spinal motor neurons. Because polio survivors have already 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 have recovered from polio lose remaining healthy neurons at a faster rate than normal. Little evidence exists to support this idea. Finally, the initial polio infection is thought to cause an autoimmune reaction, in which the body's immune system
The immune system is a network of biological systems that protects an organism from diseases. It detects and responds to a wide variety of pathogens, from viruses to bacteria, as well as Tumor immunology, cancer cells, Parasitic worm, parasitic ...
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 PPS can be difficult, since the symptoms are hard to separate from complications due to the original polio infection, and from the normal infirmities of aging
Ageing (or aging in American English) is the process of becoming Old age, older until death. The term refers mainly to humans, many other animals, and fungi; whereas for example, bacteria, perennial plants and some simple animals are potentiall ...
. No laboratory test for post-polio syndrome is known, nor are any other specific diagnostic criteria. Three important criteria are recognized, including previous diagnosis of polio, long interval after recovery, and 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 that quantify strength, such as the Medical Research Council (MRC) scale. Magnetic resonance imaging
Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to generate pictures of the anatomy and the physiological processes inside the body. MRI scanners use strong magnetic fields, magnetic field gradients, and ...
, neuroimaging
Neuroimaging is the use of quantitative (computational) techniques to study the neuroanatomy, structure and function of the central nervous system, developed as an objective way of scientifically studying the healthy human brain in a non-invasive ...
, and electrophysiological studies, muscle biopsies, or spinal fluid analysis may also be useful in establishing a PPS diagnosis.
Management
PPS treatment concerns comfort (relieving pain via analgesics) and rest (via use of mechanisms to make life easier, such as a powered wheelchair) and is generally of palliative care. No reversive therapies are known. Fatigue is usually the most disabling symptom. Energy conservation can significantly reduce fatigue episodes. Such can be achieved by lifestyle changes, such as additional (daytime) sleep, reducing workload, and weight loss for obesity
Obesity is a medical condition, considered by multiple organizations to be a disease, in which excess Adipose tissue, body fat has accumulated to such an extent that it can potentially have negative effects on health. People are classifi ...
. Some require lower-limb orthotics to reduce energy usage.
Medications for fatigue, such as amantadine
Amantadine, sold under the brand name Gocovri among others, is a medication used to treat dyskinesia associated with parkinsonism and influenza caused by type A influenzavirus, though its use for the latter is no longer recommended because ...
and pyridostigmine, are ineffective in the management of PPS. Muscle strength and endurance training are more important in managing the symptoms of PPS than the ability to perform enduring aerobic activity. Management should focus on treatments such as hydrotherapy and developing other routines that encourage strength, but do not affect fatigue levels. A recent trend toward use of intravenous immunoglobulin, which had yielded promising albeit modest results, but proves insufficient to recommend as a treatment.
PPS increasingly stresses the musculoskeletal system from progressive muscular atrophy. In a review of 539 PPS patients, 80% reported pain in muscles and joints and 87% had fatigue. Joint instability can cause appreciable pain and should be adequately treated with painkillers. Directed activity, such as decreasing mechanical stress with braces and adaptive equipment, is recommended.
Because PPS can fatigue facial muscles, as well as cause dysphagia
Dysphagia is difficulty in swallowing. Although classified under " symptoms and signs" in ICD-10, in some contexts it is classified as a condition in its own right.
It may be a sensation that suggests difficulty in the passage of solids or l ...
(difficulty swallowing), dysarthria
Dysarthria is a speech sound disorder resulting from neurological injury of the motor component of the motor–speech system and is characterized by poor articulation of phonemes. It is a condition in which problems effectively occur with the ...
(difficulty speaking) or aphonia (inability to produce speech), sufferers may become malnourished from 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 exceptional therapy management, such as breathing exercises and chest percussion to expel secretions (clearing of the lungs) on a periodic basis (monitored via stethoscope). Failure to properly assess PPS with respiratory involvement can increase the risk of overlooking an aspiration pneumonia
Pneumonia is an Inflammation, inflammatory condition of the lung primarily affecting the small air sacs known as Pulmonary alveolus, alveoli. Symptoms typically include some combination of Cough#Classification, productive or dry cough, ches ...
(a life-threatening infection of the lower respiratory tract, especially so if not caught early on). Severe cases may require permanent ventilation or tracheostomy. Sleep apnoea may also occur. Other management strategies that show improvement include smoking cessation
Smoking cessation, usually called quitting smoking or stopping smoking, is the process of discontinuing tobacco smoking. Tobacco smoke contains nicotine, which is Addiction, addictive and can cause Substance dependence, dependence. As a resu ...
, treatment of other respiratory diseases, and vaccination
Vaccination is the administration of a vaccine to help the immune system develop immunity from a disease. Vaccines contain a microorganism or virus in a weakened, live or killed state, or proteins or toxins from the organism. In stimulating ...
against respiratory infections such as influenza
Influenza, commonly known as the flu, is an infectious disease caused by influenza viruses. Symptoms range from mild to severe and often include fever, runny nose, sore throat, muscle pain, headache, coughing, and fatigue. These sympto ...
.
Prognosis
In general, PPS is not life-threatening. The major exception is patients left with severe residual respiratory difficulties, who may experience new severe respiratory impairment. Compared to control populations, PPS patients lack any elevation of antibodies
An antibody (Ab) or immunoglobulin (Ig) is a large, Y-shaped protein belonging to the immunoglobulin superfamily which is used by the immune system to identify and neutralize antigens such as bacteria and viruses, including those that caus ...
against the poliovirus, and because no poliovirus is excreted in the feces, it is not considered a recurrence of the original polio. Further, no evidence has shown that the poliovirus can cause a persistent infection in humans. PPS has been confused with amyotrophic lateral sclerosis
Amyotrophic lateral sclerosis (ALS), also known as motor neuron disease (MND) or—in the United States—Lou Gehrig's disease (LGD), is a rare, Terminal illness, terminal neurodegenerative disease, neurodegenerative disorder that results i ...
(ALS), which progressively weakens muscles. PPS patients do not have an elevated risk of ALS.
No sufficient longitudinal studies have been conducted on the prognosis of PPS, but 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 patient. An overall mortality rate of 25% exists due to possible respiratory paralysis; otherwise, it is usually not lethal.
Prognosis can be abruptly changed for the worse by the use of anesthesia, such as during surgery.
Epidemiology
Old data show PPS occurs in roughly 25 to 50% of people who survive a polio infection. Newer data from countries that asked their polio survivors show 85% of respondents have symptoms of post-polio syndrome. Typically, it occurs 30–35 years afterward, but delays between 8 and 71 years have been recorded. The disease occurs sooner in those with more severe initial infections.[ Other factors that increase the risk of PPS include increasing length of time since acute poliovirus infection, presence of permanent residual impairment after recovery from the acute illness,][ and being female.] PPS is documented to occur in cases of nonparalytic polio (NPP). One review states late-onset weakness and fatigue occur in 14–42% of NPP patients.
See also
* History of polio
* List of polio survivors
References
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.)
External links
National Institute of Neurological Disorders and Stroke-Post-polio
{{DEFAULTSORT:Post-Polio Syndrome
Polio
Motor neuron diseases
Syndromes affecting the nervous system