Introduction
Post-polio syndrome (PPS) is a slowly progressive neurological condition that occurs after decades of initial polio infection, primarily affecting motor neurons. Characterised by new and persistent muscle weakness, atrophy, and fatigue among limbs, trunk, speaking, swallowing, or breathing muscles, associated with a range of symptoms, such as myalgia, and arthralgia (joint pain).1.2,3,4
Affecting 15-80% of polio survivors with high symptomatic variations among individuals,1 however, inducing significant mobility, functional and quality of life impairments to PPS individuals. This article will explore the relationship between PPS and muscle weakness in detail with you for generalised awareness.
Mechanisms and causes
Though the exact cause of post-polio muscle weakness is still not entirely understood, several factors are found contributing to its development:
Motor neuron loss and relative changes
The foremost factor of post-polio muscle weakness is motor neuron loss. During initial infection, poliovirus crosses the blood-brain barrier, triggering meninges, spinal cord, and brain inflammation leading to anterior horn (motor neuron subtype) degeneration and post-infection apoptosis. Surviving neurons have to compensate by sprouting new branches to reconnect with the affected muscles during recovery. Due to prolonged overuse, excitotoxicity, and subsequent denervation and reinnervation over time, residual motor neurons are more prone to deterioration, triggering new muscle weakness.4,5
Muscle atrophy
PPS can result in muscle atrophy, referring to the wasting of muscular tissues. Motor neuron loss and subsequent muscular denervation can induce both physiological (disuse) and neurogenic atrophy. The continuous neuromuscular protein synthesis, degradation and metabolic changes relative to motor neuron loss may also contribute to further muscle fibre damage, leading to new muscle weaknesses.5,6
Ageing
Ageing can exacerbate muscle weakness. As individuals with PPS are already experiencing sarcopenia due to post-polio muscle atrophy, muscle mass would decrease further with more pronounced motor neuron damaging signs.7
Secondary health condition
PPS could be associated with myalgia, arthralgia and comorbidities such as osteoarthritis, and osteoporosis, contributing to muscle weakness and deterioration.4,8
Physical inactivity
Individuals with poliomyelitis with existing mobility challenges would become less active due to the fear of overexertion or injury. This lack of physical activity could lead to muscle atrophy and further weakness.6
Clinical presentation and patterns
Post-polio weaknesses often resurface stepwise in the same muscles that were originally affected by polio. It commonly includes the arm, proximal leg, trunk, bulbar muscles influencing speech and swallowing, and respiratory muscles innervated by the phrenic nerve.
Details of post-polio weakness are as follows:
Muscle Group | Associated Symptoms |
Arms | - Weakness and fatigue, especially in previously affected limbs - Difficulty with fine motor tasks - Muscle atrophy (wasting) - Reduced grip strength |
Legs | - Weakness and fatigue, especially in previously affected limbs/ the thigh - Difficulty walking or standing for prolonged periods- Muscle atrophy (wasting) - Instability and increased risk of falls |
Trunk | - Weakness in muscles supporting posture and spine - Difficulty maintaining balance - Postural changes - Musculoskeletal deformities, such as scoliosis, kyphosis, degenerative spinal vertebrae, and thoracic cage deformity - Increased risk of falls |
Speech | - Weakness or fatigue in muscles involved in speech production - Slurred speech (dysarthria) - Changes in voice quality (dysphonia) - Difficulty articulating certain sounds or words |
Swallowing | - Weakness in muscles involved in swallowing (dysphagia) - Difficulty chewing and swallowing food safely - Food retention in pharynx - Increased risk of choking and aspiration - Weight loss and malnutrition |
Respiratory Muscles | - Breathing muscle weakness - Shortness of breath; respiratory insufficiency - Reduced lung capacity - Sleeping disorders - Difficulty with coughing and clearing secretions |
The degree, pattern of weakness, and rate of progression vary among individuals depending on the severity of spinal involvement during the previous acute poliomyelitis. It can still be accelerated following overexertion or concurrent illnesses in advanced cases.4,9
Diagnosis and assessment
PPS is a clinical diagnosis supported by electrophysiological findings. To diagnose muscle weakness, an extensive work-up, such as imaging studies (MRI and CT scans), electromyogram (EMG), muscle biopsy, and lumbar puncture are required to exclude possible mimics and alternative diagnoses.1,2,4
According to the March of Dimes diagnostic criteria of PPS, its universal criteria includes:4
Diagnostic Criteria of Post-polio syndrome |
Prior paralytic poliomyelitis with evidence of motor neuron loss, as confirmed by history of the acute paralytic illness, signs of residual weakness and muscle atrophy on examination, or signs of denervation on EMG. |
Period of partial or complete functional recovery after acute paralytic poliomyelitis, followed by an interval (usually 15 years or more) of stable neuromuscular function. |
Gradual, progressive and persistent new muscle weakness or abnormal muscle fatigability (decreased endurance), with or without generalised fatigue, muscle atrophy, or muscle and joint pain. Onset may at times follow trauma, surgery, or a period of inactivity. Bulbar dysfunction or respiratory weakness are less common. |
Symptoms that persist for at least a year. |
Exclusion of alternative neuromuscular, medical, and orthopaedic problems as causes of symptoms |
Clinical evaluation
Progressive muscle weakness is generally detected by gait and mobility deterioration with a number of motor ability tests. Muscle strength is typically assessed by the MRC scale, or a dynamometer during maximal isokinetic and isometric voluntary contractions. While swallowing studies are used to evaluate difficulty swallowing; pulmonary function tests (PFT), and sniff nasal inspiratory pressure (SNIP) are used to examine respiratory weaknesses in PPS.4
Functional assessment of activities of daily living (ADLs)
Functional ADL assessment is also involved in evaluating one’s ability to perform tasks like dressing, bathing, and mobility. Focusing on limitations, identifications, adaptive environments and implementing strategies will also be employed to optimise function, and maintain independence and quality of life.
Differential diagnosis
While PPS is diagnosed by exclusion, other possible causes should be thoroughly eliminated by a neuromuscular-expertised neurologist. Some conditions that might confused with PPS are:
- Amyotrophic lateral sclerosis (ALS)
- Inclusion body myositis
- Peripheral neuropathy
- Myasthenia Gravis (MG)
- Muscular dystrophy
- Radiculopathy
- Fibromyalgia
- Degenerative joint diseases (osteoarthritis)
- Anaemia
- Thyroid dysfunctions9,10
Multidisciplinary collaborative care
Multidisciplinary collaborative care team for post-polio muscle weaknesses is listed below:1
Healthcare Professional | Role and Responsibilities |
Neurologist | Diagnose and assess post-polio weakness, pain and fatigue, monitor progression, diagnostic test ordering, prescribe medications. |
Physiotherapist | Develop tailored exercise programs for strength, mobility, and flexibility improvement; provide gait training; address pain management. |
Occupational Therapist | Assess functional abilities, recommend adaptive equipment, offer strategies for activities for daily living (ADLs), and educate on energy conservation. |
Speech Therapist | Evaluate and treat speech/swallowing difficulties, provide exercises for improvement, and offer communication strategies and assistive aids. |
Respiratory Therapist | Assess respiratory function, offer pulmonary rehabilitation, prescribe/manage respiratory devices, and provide airway clearance techniques. |
Orthotist | Design, fit, and adjust mobility support orthoses for optimal outcomes. |
Psychologist | Provide emotional support, counselling, and mental health care; Address psychological challenges, coping strategies, and overall well-being. |
Under collaborative support, by combining their expertise, they aim to improve the overall well-being and functional abilities of polio survivors with PPS muscle weakness.
Treatment and management
Non-pharmacological interventions
Regarding there are currently no specific treatments for PPS, muscle weakness management is still the main focus of rehabilitation.
Physical therapy and exercise programs
Non-fatiguing physical therapy and exercise programs specifically tailored to PPS patients are fundamentals. These programs often focus on strengthening exercises to target weakened muscles, and stretching exercises for joint flexibility maintenance, and contracture prevention. Aquatic therapy, due to the buoyancy of water, can also be particularly beneficial to the PPS population to reduce the stress on joints while providing resistance for muscle strengthening and improving cardiorespiratory endurance.1,2,4,11
Assistive devices and mobility aids
Assistive devices and mobility aids such as canes, walkers, or wheelchairs may be prescribed to compensate for muscle weakness and improve mobility. These aids can help PPS individuals conserve energy, reducing the risk of falls, and allowing for greater independence.1
Orthotic interventions and bracing
Orthotic interventions and bracing are utilised to support weakened muscles and improve functional stability among PPS individuals. Ankle-foot-orthoses (AFOs) can help those with foot drop in foot alignment maintenance and prevent tripping. Knee-ankle-foot-orthoses (KAFOs) and orthotic shoes can provide additional stability for significant lower limb weakness and uneven lengths in limbs respectively.4,12
Speech and swallowing management
Speech and language therapy can address dysphagia and dysphonia, arising from bulbar weaknesses. While dysphagia can be improved through oral-motor exercises and specific swallowing techniques, dysphonia can be treated by voice therapy and tracheostomy.4,9
Respiratory management
Respiratory management is crucial in addressing breathing issues associated with post-polio weakness. Pulmonary rehabilitation and breathing exercises help to improve lung capacity and strengthen respiratory muscles. The use of non-invasive ventilation devices (such as BiPAP or CPAP) machines can assist with breathing during sleep and periods of respiratory distress.4,9
Pharmacological interventions
Myalgia and arthralgia are often associated with PPS. Pain management with the use of analgesics, muscle relaxants for cramping and anti-spasticity medications is essential to address the associated symptoms with post-polio muscle weakness and to improve functioning.1
Prognosis and long-term outlook
The degree and pattern of PPS and its muscle weaknesses vary widely among polio survivors depending on the severity and level of spinal cord involvement during acute poliomyelitis decades earlier. While some experience a slow decline in muscle function over many years, others might have a more rapid deterioration.
The long-term outlook for those with post-polio muscle weakness depends on several factors, including the severity of symptoms, overall health, and access to medical care.2
Summary
Post-polio syndrome (PPS) is a condition that potentially affects polio survivors, causing a return of symptoms such as muscle weakness, fatigue, and pain decades after the initial infection. Muscle weakness, as a hallmark feature of PPS, despite induction of mobility and daily functional challenges, varied severity, progression, and decline of muscle function can still result. While there is currently no cure, ongoing research, treatment and management are available and still on the way to address muscle weakness and optimise functioning outcomes among polio survivors with PPS.
FAQs
- Is Post-polio an autoimmune disease?
Yes, an inflammatory or autoimmune basis has been proved from the post-mortem observations of inflammatory changes in the spinal cord of PPS patients, together with the in vivo evidence.4
- What medications should be avoided in PPS?
PPS individuals should avoid drugs that would cause drowsiness or increase fatigue to prevent exacerbation in polio-related weakness and fatigue.13
- Is PPS terminal?
No, PPS is rarely life-threatening. Despite those developing breathing and swallowing complications, such as chest infections, it is generally with satisfactory life expectancy.
References
- Post-polio Syndrome - Symptoms [Internet]. National Health System. 2017 [cited 2024 Mar 4]. Available from: https://www.nhs.uk/conditions/post-polio-syndrome/symptoms/#:~:text=Increasing%20muscle%20weakness%20is%20another
- Post-Polio Syndrome: What It Is, Symptoms & Treatment [Internet]. Cleveland Clinic. [cited 2024 Mar 4]. Available from: https://my.clevelandclinic.org/health/diseases/24584-post-polio-syndrome#symptoms-and-causes
- Post-Polio Syndrome [Internet]. Harvard Health Publishing. Harvard Medical School; 2023 [cited 2024 Mar 4]. Available from: https://www.health.harvard.edu/a_to_z/post-polio-syndrome-a-to-z
- Li Hi Shing S, Chipika RH, Finegan E, Murray D, Hardiman O, Bede P. Post-polio Syndrome: More than Just a Lower Motor Neuron Disease. Frontiers in Neurology [Internet]. 2019 Jul 16 [cited 2024 Mar 4];10(773). Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6646725/
- Joyce NC, Oskarsson B, Jin LW. Muscle Biopsy Evaluation in Neuromuscular Disorders. Physical Medicine and Rehabilitation Clinics of North America [Internet]. 2012 Aug [cited 2024 Mar 5];23(3):609–31. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4590778/
- Bodine SC. Disuse-induced Muscle Wasting. The International Journal of Biochemistry & Cell Biology [Internet]. 2013 Oct [cited 2024 Mar 5];45(10):2200–8. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3856924/
- Maynard F. Sarcopenia and post-polio muscle atrophy [Internet]. Living with Polio. Post-Polio Health International ; [cited 2024 Mar 5]. Available from: https://post-polio.org/living_with_polio/sarcopenia-and-post-polio-muscle-atrophy/
- McNalley TE, Yorkston KM, Jensen MP, Truitt AR, Schomer KG, Baylor C, et al. A Review of Secondary Health Conditions in Post-Polio Syndrome:
- Prevalence and Effects of Aging. American Journal of Physical Medicine & Rehabilitation / Association of Academic Physiatrists [Internet]. 2015 Feb 1 [cited 2024 Mar 6];94(2):139–45. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4289114/
- Olunu E, Fakoya A, Oluwasanmi O, Mckenzie D, Adewole I, Aluka C, et al. Postpolio syndrome: a Review of Lived Experiences of Patients. International Journal of Applied and Basic Medical Research [Internet]. 2019 [cited 2023 Mar 7];9(3):129. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6652271/
- Nollet F. Post-polio Syndrome [Internet]. Orphanet Encyclopedia. Australia: Orphanet; 2003 Jan [cited 2024 Mar 7]. Available from: https://www.orpha.net/pdfs/data/patho/GB/uk-PP.pdf
- Physical Therapy Intervention in Post Polio Syndrome [Internet]. Physiopedia. [cited 2024 Mar 6]. Available from: https://www.physio-pedia.com/Physical_Therapy_Intervention_in_Post_Polio_Syndrome
- Genêt F, Schnitzler A, Mathieu S, Autret K, Théfenne L, Dizien O, et al. Orthotic Devices and Gait in Polio Patients. Annals of Physical and Rehabilitation Medicine [Internet]. 2010 Feb [cited 2024 Mar 7];53(1):51–9. Available from: https://www.sciencedirect.com/science/article/pii/S1877065709002814?via%3Dihub
- Perlman S. Polio Network News I Use of Medication in People with Post-Polio Syndrome. 1999;15(1). Available from: https://www.polioplace.org/sites/default/files/files/PNN15-1pg1-3.pdf