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| | {{Infobox disease| |
| | Name = Post-polio syndrome | |
| | Image = PPS.jpeg| |
| | Caption = Science fiction writer [[Arthur C. Clarke]] developed post-polio syndrome in 1988 after initially contracting polio in 1962. | |
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| '''For patient information, click [[Post-polio syndrome (patient information)|here]]''' | | '''For patient information, click [[Post-polio syndrome (patient information)|here]]''' |
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| {{CMG}} | | {{CMG}} |
| {{SI}} | | {{Post-polio syndrome}} |
| ==Overview==
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| '''Post-polio syndrome''' ('''PPS''') is a condition that affects survivors of [[poliomyelitis]], a [[virus|viral]] [[infection]] of the [[nervous system]], after recovery from an initial paralytic attack of the virus. Typically the symptoms appear 20-40 years after the original infection, at an age of 35 to 60. Symptoms include new or increased [[muscular weakness]], [[Pain and nociception|pain]] in the [[muscle]]s, and [[fatigue (physical)|fatigue]].<ref name=Cashman_2005>{{cite journal |author=Trojan D, Cashman N |title=Post-poliomyelitis syndrome |journal=Muscle Nerve |volume=31 |issue=1 |pages=6-19 |year=2005 |pmid = 15599928}}</ref>
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| The precise mechanism that causes post-polio syndrome is unknown. It shares many features in common with [[myalgic encephalomyelitis]], a form of [[chronic fatigue syndrome]] that is apparently caused by viral infections, but unlike those disorders it tends to be progressive, and can cause tangible loss of muscle strength.
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| Treatment generally is limited to supportive measures, primarily [[leg braces]] and energy-saving devices such as powered wheelchairs, plus pain relievers, sleep aids, etc.
| | ==[[Post-polio syndrome overview|Overview]]== |
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| ==Diagnosis== | | ==[[Post-polio syndrome historical perspective|Historical Perspective]]== |
| Diagnosis of post-polio syndrome can be difficult, since the symptoms are hard to separate from the original symptoms of polio and from the normal infirmities of [[Senescence|aging]]. There is no laboratory test for post-polio syndrome, nor is there any other specific diagnostic, and diagnosis is usually a "diagnosis of exclusion" whereby other possible causes of the symptoms are eliminated.<ref name=Silver_2003>{{cite book | author = Silver JK, Gawne AC | title = Postpolio Syndrome | publisher = Hanley & Belfus | location = Philadelphia | year = 2003 | isbn = 1560536063 }}</ref>
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| PPS may be difficult to diagnose in some because it is hard to determine what component of a neuromuscular deficit is old and what is new: Neurological examination aided by other laboratory studies can help 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 sing various muscle scales which [[quantitative|quantify]] strength, such as the Medical Research Council (MRC) scale. [[Magnetic resonance imaging]] (MRI), [[neuroimaging]], and [[electrophysiology|electrophysiological]] studies, muscle [[biopsies]], or [[Lumbar puncture|spinal fluid analysis]] may also be used in establishing a PPS diagnosis.<ref name=Silver_2003 />
| | ==[[Post-polio syndrome classification|Classification]]== |
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| In general, PPS is not life-threatening. The only exception is in patients left with severe residual respiratory difficulties, who may experience new severe respiratory impairment. Studies have proven that, compared to control populations, PPS patients lack any elevation of [[antibodies]] against the [[poliovirus]], 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 can be confused with [[Amyotrophic lateral sclerosis]] (ALS), which progressively weakens muscles. PPS patients do not have an elevated risk of ALS.
| | ==[[Post-polio syndrome pathophysiology|Pathophysiology]]== |
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| ==Symptoms== | | ==[[Post-polio syndrome causes|Causes]]== |
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| Symptoms include new or increased [[muscular weakness]], [[Pain and nociception|pain]] in the [[muscle]]s, and [[fatigue (physical)|fatigue]].<ref name=Cashman_2005>{{cite journal |author=Trojan D, Cashman N |title=Post-poliomyelitis syndrome |journal=Muscle Nerve |volume=31 |issue=1 |pages=6-19 |year=2005 |pmid = 15599928}}</ref> [[Fatigue (medical)|Fatigue]] is often the most disabling symptom, as often even slight exertion can produce disabling fatigue and also increase other symptoms.<ref name=Jubelt_2000>{{cite journal |author=Jubelt B, Agre JC |title=Characteristics and management of postpolio syndrome |journal=JAMA |volume=284 |issue=4 |pages=412-4 |year=2000 |pmid=10904484}}</ref>
| | ==[[Post-polio syndrome differential diagnosis|Differentiating Post-polio syndrome from other Diseases]]== |
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| Some post-polio patients report having [[memory]] problems, or various other [[cognition|cognitive]] difficulties that are difficult to distinguish from normal aging. Some physicians have suspected that post-polio patients have an increased sensitivity to [[anesthetic]]s, but rigorous work on the subject remains to be done. Weight gain is also a frequently noted symptom, though it is hard to tell if this is due to the disorder directly or due to the decreased level of physical activity that usually accompanies the disorder.
| | ==[[Post-polio syndrome epidemiology and demographics|Epidemiology and Demographics]]== |
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| == Causes == | | ==[[Post-polio syndrome risk factors|Risk Factors]]== |
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| Several theories have been proposed to explain post-polio symptoms. One theory of the mechanism behind the disorder is that it is due to "neural fatigue" from overworked [[neuron]]s. The original polio infection generally results in the death of a substantial fraction of the [[motor neuron]]s controlling [[skeletal muscle]]s, and the theory is that the remaining neurons are thus overworked and eventually wear out.
| | ==[[Post-polio syndrome natural history, complications and prognosis|Natural History, Complications and Prognosis]]== |
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| Another theory holds that the original viral infection damages portions of the lower [[brain]], possibly including the [[thalamus]] and [[hypothalamus]]. This somehow upsets the hormones that control muscle metabolism, and the result is a [[metabolic disorder]] similar to [[mitochondrial disease|mitochondrial disorder]] that causes muscle pain and injury (via [[rhabdomyolysis]]) and also causes the fatigue. Some also believe that the original polio caused the [[atrophy]]ing of some muscles and as the person ages the weakness caused by loss of muscle mass due to aging is accelerated due to the person starting off with less muscle. Another possibility is that post-polio symptoms are due to some combination of mechanisms.
| | ==Diagnosis== |
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| ===Neural fatigue=== | |
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| The most widely accepted theory is the "neural fatigue" one. [[Motor neuron]] fibers were originally damaged by the polio virus and were subsequently over-stressed because too few surviving neurons activated too many muscles. Eventually these neurons become fatigued and die, leading to the slowly advancing loss of muscle function that is typical of post-polio. This scenario may be accelerated by the fall-off in production of [[nerve growth factor]] (NGF) that occurs with [[menopause]]/[[andropause]].
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| ===Mitochondrial disruption===
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| This theory assumes that the major symptoms of PPS are a result of some interference with the action of [[mitochondria]] in the muscles and possibly the nerves. Failure of the mitochondria to produce sufficient energy would result in the muscle pain typical of PPS, and would, over time, cause muscle death ([[rhabdomyolysis]]) due to exerting the muscle beyond its ability to recover. The cause of this interference with mitochondrial action is presumably a change in the body's [[hormone]] balance, as mediated by the [[hypothalamus]] and other lower [[brain]] areas that control hormones (and which were, presumably, damaged by the original polio virus infection). As with the ''neural fatigue'' theory, menopause/andropause accelerates the process, though this time by most likely disrupting the [[Notch signaling|NOTCH pathway]] that controls cell differentiation and damage repair.
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| One significant argument in favor of the mitochondrial disruption theory is that it explains the fatigue and [[cognitive]] difficulties ("brain fog") symptoms that usually accompany post-polio better than the neural fatigue theory does.
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| ===Reticular activating system damage===
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| Damage to the [[reticular activating system]] and related areas such as the [[thalamus]] can also produce most of the fatigue, "brain fog", and [[dysautonomia]] symptoms of post-polio, and may be able to cause hormonal changes that result in progressive muscle weakness. [[Post-mortem examination]]s of polio patients have shown damage to these areas, and some PPS patients show lesions in these areas when examined by MRI. Many authorities believe that these areas are damaged by the initial polio infection, either as a direct result of the polio virus, or due to an [[autoimmune]] reaction following the polio infection.
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| One problem with this theory, though, is that it doesn't easily explain the delayed onset of PPS. It may be that this theory needs to be combined with one of the others to explain delayed onset.
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| ===Mechanical overwork===
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| The stresses placed on nerves, muscles, and joints in a polio survivor are in many cases several times those experienced by other people. Problems with [[gait (human)|gait]], in particular, can greatly over-stress joints and the surviving muscles, and the polio survivor is also likely to compensate for weakened arms by jerking more when lifting/pulling something. Over time (and again with menopause/andropause), this results in fatigue and damage.
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| ===Reactivated polio===
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| An early theory stated that PPS is caused by reactivation of latent polio virus in the body, similar to the way that [[shingles]] is a reactivation of the [[chicken pox]] virus. This theory has been discredited by laboratory studies that show no active polio virus in the body.
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| == Treatment ==
| | [[Post-polio syndrome history and symptoms|History and Symptoms]] | [[Post-polio syndrome physical examination|Physical Examination]] | [[Post-polio syndrome laboratory findings|Laboratory Findings]] | [[Post-polio syndrome MRI|MRI]] | [[Post-polio syndrome imaging findings|Other Imaging Findings]] | [[Post-polio syndrome other diagnostic studies|Other Diagnostic Studies]] |
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| Treatment for post-polio is primarily [[palliative]], as no reliable therapy to reverse symptoms is known. Palliative treatment includes: | | ==Treatment== |
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| Very often fatigue is the most disabling symptom of PPS, and many of those with the disease have discovered that by carefully managing energy expenditure they can prevent or reduce the worst fatigue episodes. Further, for many this "energy management" approach appears to reduce pain. Though most authorities agree that rest is an important component of post-polio treatment, there is significant disagreement as to how much rest is necessary. Some hold that the best approach is to expend the absolute minimum amount of energy necessary to enjoy a reasonable lifestyle, while others feel that there is some threshold below which energy conservation is not helpful and may in fact be harmful (due to the general effects caused by lack of exercise).
| | [[Post-polio syndrome medical therapy|Medical Therapy]] | [[Post-polio syndrome surgery|Surgery]] | [[Post-polio syndrome prevention|Prevention]] | [[Post-polio syndrome cost-effectiveness of therapy|Cost-Effectiveness of Therapy]] | [[Post-polio syndrome future or investigational therapies|Future or Investigational Therapies]] |
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| [[Leg braces]] and other [[orthosis|orthotics]] can reduce the stress on joints and, in some cases, muscles, and so may slow the progression of joint and muscle damage related to PPS. However, some authorities feel that many PPS patients rely on such items too much and for too long when they should be graduating to a wheelchair. [[Wheelchair]]s (particularly powered wheelchairs) and "scooters" (small battery-powered vehicles) are useful both to conserve energy and to reduce the stress on weakened joints and muscles. Non-powered wheelchairs, however, are not generally recommended since they place too much stress on arm muscles and joints and may take too much energy to operate. In some cases even the scooters are not recommended since operating the "tiller" of the typical scooter can be tiring to arm muscles. A [[standing frame]] can be used in conjunction with the wheelchair to provide alternative positioning and prevent secondary complications.
| | ==Case Studies== |
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| Post-polio syndrome often causes significant levels of pain, sometimes in specific muscles or joints, and sometimes body-wide. Various forms of [[narcotic]] and non-narcotic [[Analgesic|pain-reliever]]s, [[muscle relaxant]]s, [[tranquilizer]]s, and sleep medications may help to deal with the pain and related sleep problems. In some cases surgery can be used to repair joint deformities, or to fuse joints (as in the back or ankle) that have become too weak. | | [[Post-polio syndrome case study one|Case #1]] |
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| Very few non-palliative treatments for post-polio syndrome have shown any promise, and none have been subjected to any sort of rigorous clinical testing. There are, however, a few treatments that have developed some "following" in the PPS community:
| | ==Further Reading== |
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| The [[amino acid]], [[Carnitine|L-carnitine]] has several functions in the body, one of the most important being the transport of [[fatty acid]]s into the mitochondria. Researchers in Australia have had some success using doses of several grams per day.
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| [[Coenzyme Q10]]is a general [[antioxidant]], but it also plays a critical role in the function of the mitochondria, transporting electrons between the "complexes" that participate in the energy conversion cycle. A shortage of CoQ10 can cause the fatigue and muscle pain much like that experienced with PPS. Some PPS patients have reported significant improvements in their symptoms when taking several hundred milligrams of CoQ10 per day.
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| The [[pentose]] sugar <small>D</small>-[[ribose]] is the "R" in [[RNA]] and a critical component of [[DNA]], RNA, and [[enzyme]]s. It is also a component of [[Adenosine triphosphate|ATP]], the energy-transporting molecule produced by the mitochondria. A shortage of <small>D</small>-ribose can produce fatigue and muscle pain. Some PPS patients have reported significant improvement in pain and fatigue symptoms when taking on the order of 20 grams/day of <small>D</small>-ribose.
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| ==References==
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| {{Reflist}}
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| ===Further reading===
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| * {{cite book | last = Bruno | first = Richard L. | title = The Polio Paradox | publisher = Warner Books | location = New York | year = 2002 | isbn = 0446529079 }} | | * {{cite book | last = Bruno | first = Richard L. | title = The Polio Paradox | publisher = Warner Books | location = New York | year = 2002 | isbn = 0446529079 }} |
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| * 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.) | | * 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.) |
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| ==External links== | | ==External Links== |
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| * [http://www.ninds.nih.gov/disorders/post_polio/post_polio.htm National Institute of Neurological Disorders and Stroke] | | * [http://www.ninds.nih.gov/disorders/post_polio/post_polio.htm National Institute of Neurological Disorders and Stroke] |
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| * [http://www.post-polio.org Post-Polio Health International] | | * [http://www.post-polio.org Post-Polio Health International] |
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| * [http://www.disabledservices.net/ Post Polio and Equipment]
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| * [http://www.poliocanada.com/ Polio Canada]
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| {{Viral diseases}} | | {{Viral diseases}} |
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| {{SIB}}
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| [[Category:Poliomyelitis]] | | [[Category:Poliomyelitis]] |
| [[Category:Motor neuron disease]] | | [[Category:Motor neuron disease]] |
| [[Category:Infectious disease]]
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