Acute poliomyelitis, historically known as infantile paralysis, is a viral illness that can invade the central nervous system and cause paralysis. Post-polio syndrome (PPS) is defined as a neurologic disorder that can occur in survivors of paralytic polio after a period of functional stability (usually 15 years or more), characterized by new weakness or muscle fatigability, with or without generalized fatigue, muscle atrophy, or pain in muscles and/or joints.1
The polio virus is an RNA enterovirus that was historically reported to invade the CNS in about 5% of clinical infections, causing varying degrees of paralysis in about 2% of patients. Later studies indicate that many cases of “nonparalytic polio” did sustain a mild degree of neurological damage.2 The virus has a predilection for anterior horn cells resulting in muscle weakness and atrophy without sensory impairment. A period of neurological and functional recovery follows the acute infection. During this time reinnervation of muscle fibers through axonal sprouting and development of compensatory motor patterns occur. The neurological deterioration and functional decline of post-polio syndrome may be related to normal aging, accelerated degeneration of nerves and joints, overuse myopathy and disuse.
Epidemiology including risk factors and primary prevention
During the first half of the 20th century, polio epidemics caused widespread public concern, leading to a national campaign to develop a vaccine. Since development of the Salk and Sabin vaccines in the mid-1950s, polio has been eradicated from the US. 3 According to the World Health Organization, since 2012, only type 1 of the 3 strains of wild poliovirus has been reported. As of January, 2021, only Pakistan and Afghanistan have cases related to wild virus.4 The incidence and prevalence of post-polio syndrome is not known due to lack of accurate statistics. It is estimated that about 40% of polio survivors develop post-polio syndrome.5 Risk factors include: greater severity of acute paralytic poliomyelitis, older age at time of infection, permanent impairment with lesser degree of disability. Weight gain, change in activity level (immobility or increased activity) and joint pain have been identified as associated factors. Protection of weak muscles and unstable joints through weight control and avoidance of overuse may prevent or delay onset of post-polio syndrome.
The most widely accepted hypothesis as to the cause of new weakness, muscle fatigue and pain was proposed by Weichers and Hubbell.6 The reinnervation of denervated muscle fibers through terminal axonal sprouting during the recovery phase of acute polio results in giant motor units. Due to the slow loss of anterior horn cells with normal aging, motor units undergo continuous remodeling. Over time the numerous terminal axonal sprouts may degenerate permanently, producing additional denervation. As more motor units and terminal sprouts are lost, the ability of neighboring motor units to reinnervate the denervated muscle fibers is not sufficient to maintain the balance and permanent denervation occurs, with resultant weakness.
Disease progression including natural history, disease phases or stages, disease trajectory (clinical features and presentation over time)
Acute paralytic polio is characterized by sudden onset of paralysis with a febrile illness. Following the acute infection, recovery of strength and function occurs over a period of months to years. Initial recovery can be dramatic as anterior horn cells partially affected by the virus recover, followed by slower progression as reinnervation occurs and new motor skills are learned. The recovery phase precedes a period of neurological and functional stability usually lasting 15 years or more.
Presentation of post-polio syndrome can be insidious or acute. Acute presentation may be associated with trauma, surgery, a period of immobility or increase in activity. The most common symptoms of PPS are new weakness (with or without muscle atrophy), fatigue and pain in muscles and/or joints. Less frequent symptoms are respiratory insufficiency, dysphagia, dysarthria, and cold intolerance. Post-polio syndrome is classified as a slowly progressive neuromuscular disease but the most common clinical presentation is one of functional declines and plateaus. It is rarely fatal but can lead to death in cases of respiratory dysfunction or dysphagia.
Specific secondary or associated conditions and complications
Post-polio syndrome is often associated with musculoskeletal problems. New weakness may present as easy fatigability, change in gait, loss of function, or increased number of falls. The wide variation in degree of weakness between agonist/ antagonist muscles within a limb and between limbs can significantly alter skeletal development and normal body mechanics. These imbalances result in spine and joint deformities, accelerated degeneration, contractures and soft tissue overuse syndromes. Secondary radiculopathies and compression neuropathies are common. Respiratory muscle weakness may result in restrictive pulmonary disease or sleep apnea.
Essentials of Assessment
The patient history should document previous acute polio infection, with the extent and severity of paralysis and residual weakness. Although survivors of infantile infections will not recall the acute illness, family reports, bone and muscle atrophy and history of functional limitations can confirm the diagnosis. Historical data important in the evaluation of post-polio syndrome include: timing of onset of new weakness or atrophy; relationship of symptoms to change in activity; the presence of muscle overuse symptoms such as muscle pain, cramping, twitching or fasciculation; degree of fatigue with characterizing features and patterns; and complete description of any pain complaints. Change in functional status, frequency and nature of falls, sleep quality, and swallowing or respiratory complaints should be noted.
The neuromuscular physical examination is essential to confirm previous polio, exclude other neurologic conditions and identify associated musculoskeletal problems. A careful manual muscle test, isolating individual functionally important muscles, and documenting degree of weakness, should be performed on polio-affected muscles and those thought to be unaffected. Fasciculation during manual muscle testing or degradation of strength with repetition may help identify muscles with mild polio involvement. Stunted bone development, skeletal asymmetries, spinal deformities and joint deformities should be described. Joint evaluation should include ROM for excessive laxity, previous surgical fusion and contracture. More extensive spine or joint examination, including provocative testing, is indicated according to symptoms. Neurological examination of sensation, tone and cerebellar function may identify concurrent neurological disease or exclude the diagnosis of post-polio syndrome.
Functional mobility should be observed for muscle substitutions and compensatory strategies. Clinical gait analysis with and without orthotics and assistive devices is important for identification of mechanical stress on weak muscles and unstable or degenerative joints and fall risk.
There are no diagnostic laboratory studies for post-polio syndrome–it is a diagnosis of exclusion. Laboratory studies to exclude other potential causes of symptoms, e.g., hypothyroidism or anemia, may be indicated. Excessive muscle breakdown secondary to overuse or statin medications can result in elevated creatine kinase(CK) levels.
X-rays are often helpful in the assessment of bone and joint pain and deformities. Imaging of the central nervous system with MRI or CT may be used to exclude other neurological conditions.
Supplemental assessment tools
EMG studies are recommended if the clinical history of polio is atypical or uncertain. EMG may identify compression neuropathies, radiculopathies or other neurologic conditions such as amyotrophic lateral sclerosis (ALS), or a myopathy. Respiratory complaints should be evaluated with pulmonary function tests including supine testing. Sleep studies and swallowing evaluations may be indicated based on symptoms.
Social role and social support system
The psychological impact of functional decline on a polio survivor should not be underestimated. Symptoms of post-polio syndrome are often severe enough to alter family and social roles. Most polio survivors received extensive rehabilitation after the acute paralysis and became functionally independent, productive members of society. The need to pace or limit physical activity may affect vocational and avocational independence as well as financial stability.
Rehabilitation Management and Treatments
Available or current treatment guidelines
The common symptom of increased muscle weakness may be exacerbated by overuse or deconditioning. Based on the history and physical examination, the polio survivor may be counseled to decrease stress on specific muscles by modification of activities or use of orthoses and assistive devices, or initiate a targeted exercise program. A classification for exercise prescription was developed by the National Rehabilitation Hospital (NRH).7 Muscles are classified by severity of polio involvement and stability of strength; limbs classified according to the most severely affected muscle. Unaffected muscles, muscles with sub-clinical polio and those with clinically stable polio of at least a grade 3 strength can be exercised. Care must be taken with any polio-affected muscle, pacing activity with rest and watching for signs of overuse. Improvement in cardiovascular conditioning should be achieved through use of the strongest muscle groups. Muscles that are clinically unstable (new weakness, atrophy or painful) should initially be rested. If rest increases weakness, a very gentle, non-fatiguing exercise program can be initiated with close monitoring. Stretching programs may increase functional strength through improved body mechanics. Polio survivors with severe involvement may only tolerate ROM exercises.
Fatigue is managed through a combination of energy conservation, lifestyle modification and rest. Energy conservation may include orthotics, assistive devices and mobility aids; modifying or pacing activities and how they are performed. Lifestyle modifications include optimizing wellness principles, changing work and activity schedules to allow rest periods, and eliminating some activities. Regular rest periods or naps during the day prior to complete exhaustion and optimum sleep at night help reduce fatigue levels.
Pain associated with post-polio syndrome may be related to muscle overuse, soft tissue disorders, mechanical or degenerative joint pain, or less commonly, bone or nerve pain. Post-polio muscle pain, often described as a deep ache similar to the pain experienced with acute polio, is usually associated with overuse. It may present the same day or one to two days after increased activity and may be associated with cramps, crawling sensation, or fasciculation. Activities should be modified with the goal of preventing muscle pain. Modalities, anti-inflammatory medications and muscle relaxants can help alleviate muscle pain. Soft tissue and joint pain are related to altered body mechanics and secondary degeneration. First-line treatment is modification of activities, correcting or improving mechanics and protecting weak joints with orthotics and assistive devices. Oral medications, injections (including regenerative medicine agents), physical therapy and surgery may be appropriate, based on the diagnosis.
There are no recommended pharmaceutical treatments for post-polio syndrome. Studies have looked at medications including pyridostigmine, modafinil, amantadine, human growth hormone and prednisone. None have shown evidence of significant benefit. There is some evidence that intravenous immunoglobulin may reduce pain and increase quality of life. Evidence is inconsistent for effectiveness on muscle strength and no evidence has demonstrated beneficial effect on functional activity.8 A large multi-center international study has been underway for years, but to date there are no published randomized control trials, no treatment has been FDA-approved.
Coordination of care
An interdisciplinary team may include medical consultation from an internist, pulmonologist, otolaryngologist, or orthopedic surgeon. The rehabilitation needs over the course of life will likely include physical therapists, occupational therapists, orthotists, speech therapists and psychologists. It is often the physiatrist who must educate the other medical professionals regarding the unique aspects and concerns involved in the care of a polio survivor.
Patient & family education
Most health professionals have little knowledge of polio or post-polio and patients must be able to inform and direct aspects of their care to prevent exacerbations of post-polio symptoms. Post-Polio Health International and other organizations have developed online resources and education materials for patients, families and health care providers. Many communities have active post-polio support groups that provide information regarding local resources as well as psychological support.
Translation into practice: practice “pearls”/performance improvement in practice (PIPs)/changes in clinical practice behaviors and skills
Survivors of acute paralytic polio are each unique and require careful, detailed evaluation to determine the presence of post-polio syndrome and secondary musculoskeletal or neurological problems. The varying degrees of partial denervation of multiple muscles must be considered as rehabilitation interventions are prescribed. Surgical recommendations must address impact on mobility, change in compensatory body mechanics and risks of anesthesia.9 Many polio survivors are well-read on post-polio syndrome and expect to partner with their physicians to manage their health issues. The physician’s role is important to establish an accurate diagnosis based on exclusion of other diseases on the differential. A self-educated patient with limited medical knowledge may attribute symptoms of other conditions to post-polio syndrome.
Cutting Edge/ Emerging and Unique Concepts and Practice
Research on the use of intravenous immunoglobulin (IVIG) for post-polio syndrome has been ongoing for several years. Results have indicated some potential benefit but parameters of treatment, such as dosing and intervals, have not been well-defined. IVIG is not approved by the United States Food and Drug Administration for post-polio syndrome at this time.
Although regenerative medicine cannot provide a “cure” for post-polio syndrome, it has become a very useful tool in management of the musculoskeletal complications of aging with weak muscle, underdeveloped ligaments and unstable joints.
Gaps in the Evidence- Based Knowledge
Post-polio syndrome is considered a slowly progressive neuromuscular disease. Most prospective studies have reported a slow decline in motor function over time.10 Rehabilitation interventions can prevent or treat associated musculoskeletal disorders and minimize symptoms, but there is no evidence that post-polio syndrome can be avoided through preventive measures.
- March of Dimes. Post-polio syndrome: identifying best practices in diagnosis and care. White Plains, NY: March of Dimes Birth Defects Foundation; 2001.
- Bruno, RL. Paralytic vs. “non-paralytic polio: distinction without a difference? Am J Phys Med Rehabil. 2000;79:4-12.
- National Institute of Neurological Disorders and Stroke. Post-Polio Syndrome Fact Sheet. Available at: https://www.ninds.nih.gov/Disorders/Patient-Caregiver-Education/Fact-Sheets/Post-Polio-Syndrome-Fact-Sheet. Accessed March 22, 2021.
- Polio Global Eradication Initiative. Polio Now. Available at: https://polioeradication.org/polio-today/polio-now/ Accessed March 22, 2021.
- Trojan DA, Cashman NR. Post-poliomyelitis syndrome. Muscle Nerve. 2005;31:6-19.
- Weichers DO, Hubbell SI. Late changes in the motor unit after acute poliomyelitis. Muscle Nerve. 1981:4:524-528.
- Gawne AC, Halstead LS. Exercise in post-polio patients: A new classification. Arch Phys Med Rehabil. 1993;74:660.
- Koopman, F. S., Beelen, A., Gilhus, N. E., de Visser, M., & Nollet, F. (2015). Treatment for postpolio syndrome. The Cochrane database of systematic reviews, (5), CD007818. https://doi.org/10.1002/14651858.CD007818.pub3.
- David A. Lambert, M.D., Eleni Giannouli, M.D., Brian J. Schmidt, M.D. Postpolio Syndrome and Anesthesia. Anesthesiology. 2005; 103:638–44.
- Dalakis MC, Elder G, Hallett M, et al. A long-term follow-up study of patient with post-poliomyelitis neuromuscular symptoms. N Engl J Med. 1986;31:959-963.
Original Version of the Topic
Carol B. Vandenakker-Albanese, MD. Poliomyelitis / post-polio syndrome. 7/26/2012.
Previous Revision(s) of the Topic
Carol B. Vandenakker-Albanese, MD. Poliomyelitis / post-polio syndrome. 8/1/2017.
Carol Vandenakker-Albanese, MD
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