Practice Essentials
Postpolio syndrome (PPS) is a neurologic disorder characterized by new and progressive muscular weakness, pain, and fatigue many years after the occurrence of acute paralytic polio. [1, 2] Halstead introduced the term "post-polio syndrome" in 1986, and he published revised criteria for diagnosing PPS in 1991, in which new muscle weakness was introduced as an obligatory criterion. [3] Functional and structural abnormalities of neuromuscular junctions are common, but not necessary, conditions for the diagnosis of PPS. The basic management principles for individuals with PPS include energy conservation and pacing one's activities.
The literature lacks consensus regarding the nomenclature applicable to the development of new health problems in persons who previously had acute paralytic poliomyelitis, with frequently used terms including, in addition to PPS, "late effects of polio" (LEoP) and "postpolio muscular atrophy." PPS is typically characterized as a sub-category of LEoP. [4]
Consensus criteria for the diagnosis of PPS were published by March of Dimes and validated by a team of international experts. [5] The criteria are as follows:
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Prior paralytic poliomyelitis with evidence of motor neuron loss, as confirmed by history of the acute paralytic illness, signs of residual weakness and atrophy of muscles on neurologic examination, and signs of denervation electromyography (EMG)
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A period of partial or complete functional recovery after acute paralytic poliomyelitis, followed by an interval (usually 15 y or more) of stable neurologic function
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Gradual or sudden onset of progressive and persistent new muscle weakness or abnormal muscle fatigability (decreased endurance), with or without generalized fatigue, muscle atrophy, or muscle or joint pain; sudden onset may follow a period of inactivity, or trauma or surgery; less commonly, symptoms attributed to PPS include new problems with breathing or swallowing.
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Symptoms persist for at least a year
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Exclusion of other neurologic, medical, and orthopedic problems as causes of symptoms
Signs and symptoms of postpolio syndrome
These include the following:
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Fatigue
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Muscle weakness
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Muscle pain
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Gait disturbance
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Respiratory problems
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Swallowing problems (dysphagia)
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Autonomic dysfunction
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Sleep apnea
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Flat-back syndrome
Workup in postpolio syndrome
A complete blood count (CBC) and cerebrospinal fluid analysis are employed to exclude conditions other than PPS. Swallowing studies should also be obtained.
Additionally, computed tomography (CT) scanning and magnetic resonance imaging (MRI) can be ordered to rule out other diagnoses, as well as structural neurologic processes (eg, stroke, multiple sclerosis, tumor). Electrodiagnostic studies [6] are another means of ruling out non-PPS neurologic or neuromuscular disorders.
In the chronically denervated muscles of patients with PPS, there are secondary myopathic features, including endomysial inflammation and rare vacuolated fibers.
Management of postpolio syndrome
The basic management principles for individuals with PPS include energy conservation and pacing one's activities. Psychological interventions, such as cognitive behavior therapy, may also be initiated to help reduce fatigue. [7, 8]
Reports on exercises are conflicting, but the key factor seems to be exercise intensity. Strengthening exercises should be nonfatiguing.
For myofascial pain, consider heat, electrical stimulation, trigger point injections, stretching exercises, biofeedback, muscle relaxation exercises, or static magnetic fields for trigger points.
For gait disturbances, assistive devices can be used, but sometimes patients refuse them because of the philosophy of "not giving in." [9] Treatment also can involve limitation of ambulation to shorter distances and the use of orthotics for joint protection.
Pathophysiology
One possible cause of postpolio syndrome (PPS) is decompensation of a chronic denervation and reinnervation process to the extent that the remaining healthy motor neurons can no longer maintain new sprouts; thus, denervation exceeds reinnervation. [10]
A second possible mechanism for PPS is motor neuronal loss due to reactivation of a persistent latent virus. In addition to muscle atrophy and denervation, foci of perivascular and interstitial inflammatory cells have been found on 50% of biopsies of patients with PPS. Activated T cells and immunoglobulin M and immunoglobulin G antibodies specific for gangliosides also have been found.
Another possibility is an infection of the polio survivor's motor neurons by an enterovirus that is different from the one responsible for the patient's polio. Others sources hypothesize that PPS is merely the loss of strength due to the usual stresses of aging and weight gain. In patients with PPS, these processes occur in muscles that already are weak, so the consequences are more noticeable compared with those of patients who have not had polio. [11]
A study by Wendebourg et al indicated that in patients with PPS, atrophy of spinal cord gray matter (SCGM) is a factor in muscle weakness. The investigators reported that “SCGM atrophy is significantly and segment‐wise associated with muscle strength in corresponding myotomes” in individuals with PPS and that the atrophy is especially pronounced at levels near the cervical and lumbar enlargements. Evidence pointed to SCGM atrophy being the result of a second disease phase rather than existing solely as a consequence of the initial infection or aging. [12]
A study by Li Hi Shing et al suggested that non-structural issues, including polypharmacy and poor sleep, play a role in the extramotor manifestations of PPS, such as apathy, verbal fluency deficits, and fatigue. The investigators’ proposal was related to a neural analysis of individuals with PPS, which found only limited degeneration of the brain’s cortical and subcortical regions and white matter. [13]
Epidemiology
Frequency
United States
The incidence of postpolio syndrome (PPS) in previous acute polio patients ranges from approximately 22-68%. The prevalence of the PPS was estimated at 28.5% of all paralytic polio cases. [14] The current prevalence is approximately 1.6 million cases. Suggestions have been made that 100% of polio survivors, if tracked for a long period, can develop some symptoms of PPS. The risk of PPS was significantly higher among patients who sustained substantial permanent impairment after polio and among females. The incidence did not vary with age at acute onset, acute severity, or level of physical activity after recovery.
International
In a Brazilian tertiary care center, study the frequency of PPS was 77.2% of the studied population. Among them, 62.8% were women and 37.2% were men. [15] Prevalence rates were reported to be 31% and 41% in Italian population in 2 different studies. [16, 17] Again, it was more common in women.
Sex
PPS is more common in women. In a survey of persons with long-term, disabling conditions—specifically, neuromuscular disease, multiple sclerosis, postpolio syndrome, or spinal cord injury—Thakral et al found that fatigue and pain were reportedly greater in women than in men. Moreover, while younger women scored higher than younger men with regard to physical functioning, the opposite was true for older individuals. [18]
Age
The strongest determinant of PPS onset was the length of the interval following the acute illness, with incidence peaking at 30-34 years after acute polio.
