Abstract
Post-polio syndrome (PPS) is the commonly affected term to describe the symptoms that may develop many years after acute paralytic poliomyelitis. The etiology of PPS is still unclear. An overuse of enlarged motor units is suspected causing denervation again due to distal degeneration of axons. Metabolic and functional changes has been described in muscle fibers of partially denervated muscles. Nevertheless, submaximal aerobic training and low intensity muscular strengthening have shown positive effects on muscular strength and cardiorespiratory system in patients affected by PPS. Aquatic therapy has a positive impact on pain and muscle function. In patients with severe fatigue, it is recommended to adapt the daily exercise routine to their specific case.
Résumé
Le syndrome post-poliomyelitique ou « syndrome post-polio » (SPP) est une entité clinique définie par l’association de nouveaux symptômes qui surviennent après une longue période de stabilité chez des personnes qui ont contracté la poliomyélite antérieure aiguë. Les mécanismes de ce syndrome ne sont pas encore élucidés, un épuisement des phénomènes physiologiques de dénervation-réinnervation est suspecté. Les fibres musculaires des muscles partiellement dénervés présentent des modifications structurelles et métaboliques progressives. Cependant, les effets de la rééducation musculaire et de l’entraînement en endurance dans le SPP ont été étudiés, ils sont bénéfiques sur la fonction musculaire et cardiovasculaire avec des modalités de renforcement contre résistance modérée et en entraînement sous-maximal. La balnéothérapie apporte un bénéfice musculaire et sur la douleur. Chez les sujets en situation de fatigue intense, il est souhaitable d’adapter le rythme des activités quotidiennes.
1
English version
1.1
Introduction
Acute anterior poliomyelitis is an infectious disease affecting children and young adults caused by an Enterovirus ; there are three serotypes of Poliovirus . This affection was greatly feared and occurred during, widespread epidemics, primarily in large cities in the summer months. In the United States and Europe, the last great polio epidemics were in the 1950s . The vaccination campaigns initiated in the mid-1950s with the inactivated Poliovirus Salk vaccine, and then with the attenuated Poliovirus vaccine (Sabin) contributed largely to the eradication of polio in the western world, however, the virus is still endemic in several developing countries.
The Poliovirus targets the motoneurons of the anterior horn cells of the spinal cord or the brainstem, acute anterior poliomyelitis leads to asymmetric muscular paralysis, with varying degrees of severity, reaching its peak in 48 hours and sometimes associated to a respiratory and bulbar affection. After the acute infection, there is a slow and progressive “recovery” phase. This motor improvement is made possible by the reinnervation process of muscle fibres that have been denervated by the initial acute polio infection. The remaining brainstem and spinal cord motor neurons develop new branches, or axonal sprouts generating enlarged motor neurons. This process cannot affect all denervated fibers, explaining the residual motor sequelae. The recovery phase, optimized by physical rehabilitation, leads to a “sequelae-related impairment” with residual muscular atrophy that can vary according to the individual subject and topography. These impairments are considered stable.
The hypothesis of a secondary aggravation of the neuromuscular impairments several years after the acute infection by the Poliovirus has been suggested since Charcot . However, it is only in 1984 that the term “Post-polio syndrome (PPS)” was used during the first international conference on PPS in Warm Springs, GA (USA) .
1.2
Definition
PPS is a clinical entity affecting polio survivors with the onset of new symptoms, several years after the initial polio attack, which was followed by a period of stability. These symptoms are:
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new muscular weakness;
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fatigue;
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pain;
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onset or aggravation of muscle atrophy;
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onset or aggravation of pre-existing difficulties in accomplishing daily life activities;
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cold intolerance;
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sleep disorders;
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dysphonia or dysphagia;
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respiratory deficiency.
Since all these symptoms are not necessarily present in all cases, diagnosis criteria were suggested by Halstead in 1985 and then validated by the “European Federation of Neurological Societies” .
To validate a diagnosis of PPS, the patient needs to meet the following criteria:
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confirmed medical history of poliomyelitis;
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partial or almost complete neurological recovery after the acute period;
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a period of neurological stability that lasted for at least 15 years;
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a recent muscular weakness with a sudden onset and quick-progressing deterioration;
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at least two new symptoms among the following ones:
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excessive fatigue,
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muscle or joint pain,
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muscle atrophy,
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cold intolerance,
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no other medical explanation.
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The diagnosis of PPS is a diagnosis of exclusion with the main symptom being the onset or recent aggravation of muscular deficiency.
PPS seems to affect between 15 to 80% of polio survivors according to the various studies .
The pathophysiology of PPS is under discussion, the main hypotheses are:
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an overuse of the denervation-reinnervation process of these enlarged motor units, explaining the fast clinical deterioration;
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a defect in neuromuscular conduction along immature nerve sprouts and exhaustion of acetylcholine stores, validated by EMG findings using repetitive stimulation techniques on single fibers (jitters);
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auto-immune inflammatory processes;
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residual Poliovirus and its reactivation.
1.3
Muscular strengthening in PPS
Active motor rehabilitation by progressive muscular strengthening was one of the first solutions proposed to improve PPS symptoms. Designing a therapeutic project in Physical medicine and rehabilitation (PM&R) is still difficult due to a lingering dogma of prohibiting muscular strengthening in patients with neuromuscular diseases.
1.3.1
Clinical trials on muscular strengthening programs.
Rodriquez and Agre support the relevance of a well-conducted muscular strengthening program. First they studied the sensation of fatigue felt by the patient compared to the muscular fatigue recorded by EMG and thus showed a linear relation between these two parameters. These authors also reported a decrease in the sensation of fatigue correlated to a better post-exercise recovery by objective measurements perceived by the patient (Borg’s fatigue scale out of 20), validated by electrophysiological recordings . This same team showed the superiority of fractioned submaximal exercises versus muscular contractions up to a sensation of exhaustion . These authors published a study showing the increase in muscular strength (+61% of the initial resistance, in Kg) in isometric as well as isokinetic programs and in a significant manner with submaximal, fractioned muscular conditioning 12-week training with daily exercises. At the end of this training program, there was no detrimental effect on the sensation of fatigue. Chan et al., in a controlled, randomized study, reported the effect of a muscular strengthening protocol on the thumb muscles . The surface EMG analysis enabled the estimation of the number of activated motor units. With this technique, the authors showed an improvement of the central motor command, thanks to training. Spector et al. studied the histology and changes in the MRI signal of the muscle during a muscular strengthening program over a 10-week period. They found an improvement in muscular strength but the latter is not correlated to a modification in muscular fibres’ size (a healthy patient showed an hypertrophy). Furthermore, the biopsies do not show an alteration of the muscular system. The question is to understand how the muscular mechanisms of polio survivors adapt during muscular strengthening programs.
1.3.2
Synthesis and recommendations
Several efficacy studies report the beneficial effects on muscular strength without harmful side effects. Most of these studies are open studies without any control group or controlled, randomized studies on very small cohorts . These studies are presented in Table 1 : most of them describe a strengthening protocol with a moderate and progressive intensity in order not to go beyond the muscular fatigue threshold.
| Authors | Year | Type of study | Patients vs control group | Rehabilitation techniques | Frequency, duration | Parameters evaluated | Conclusions |
|---|---|---|---|---|---|---|---|
| Dean | 1988 | RCS | 7 vs 13 | Submaximal aerobic training on treadmill | 20 to 40 mins, 3 times/wk 8 wks | HR max , VO 2max , BP, fatigue threshold | Decrease of HR max , endurance improvement (+28%) |
| Jones | 1989 | RCS | 16 vs | Submaximal aerobic training on a bicycle w / ergometer | 13 to 30 mins, 3 times/wk 16 wks | HR max , VO 2max | Improvement of capacity (+20 W), endurance (+50%) VO 2max (+15%) and Ve max |
| Einarsson | 1991 | NCS | 12 | Exercises against intense resistance | ENZ, ISOK | Observed muscular strength gain | |
| Fillyaw | 1991 | RCS | 17 | Strengthening against moderate resistance | 2 years | ISOK | Muscular strength gain, no endurance changes |
| Peach | 1991 | Observational study | 77 | Patients classified according to observance | A little less deterioration in the most determined subjects | ||
| Kriz | 1992 | NCS | 10 vs 10 | Submaximal aerobic training on a bicycle w / ergometer and arms | 20 mins 3 d/wk 16 wks | HR max , BP, VO 2 and CO 2 production | Improvement of the cardiovascular parameters during effort without loss of muscular strength |
| Agre | 1996 | NCS | 12 | Low-intensity isotonic strengthening of the quadriceps for 12 wks | 4 times/wk 12 wks | ISOK, weight lifted, EMG | No dynamometric strength increase, improvement of the amount of weight lifted, no harmful side effects |
| Spector | 1996 | NCS | 6 | Quadriceps strengthening program | 10 wks | Muscular volume in MRI, ISOK | Gain of strength with 20% retained 5 months after stopping the training program |
| Ernstoff | 1996 | NCS | 12 | Muscular strengthening program in endurance on ergonometer bike | 60 mins 2 times/wk 22 wks | ISOK, ENZ, fibers’ size, HR max | Improvement of cardiovascular parameters, gain of strength on some muscles, no harmful side effects |
| Agre | 1997 | NCS | 12 | Static and dynamic strengthening program over 12 weeks | 12 wks | ISOK, endurance ISOM, EMG | Improved strength, no adverse side effects |
| Willen | 2001 | RCS | 25 vs 13 | Aquatic exercises of knee flexion and extension in a pool heated at 33° | 40 mins 2 d/wk 5 months | ISOK, walking speed, pain, VO 2 , HR max | Improvement of HR max during effort and pain, no improvement for strength or gait parameters |
| Klein | 2002 | NCS | 23 | Muscular strengthening program for the lower limbs vs rehabilitation in case of painful shoulders | 9 months | Scapular symptoms, ISOM | Improvement in the three groups |
| Strumse | 2003 | RCS | 88 vs 29 vs 29 | Aquatic exercises | Pain, 6MWT | Improvement for pain and gait parameters in the aquatic therapy groups | |
| Chan | 2008 | RCS | 5 vs 5 | Muscular strengthening under submaximal resistance of the thenar muscles of the thumb | 3 d/wk 12 wks | EMG, Twitch, MUNE | Improvement of the motor command in the trained group |
If the clinical conditions are not always detailed for these patients, muscular strengthening is usually applied to groups of muscles that are in good enough shape to resist gravity (manual muscular testing of at least three out of five). Isolated muscle conditioning is not recommended for deficient muscles because these muscles fatigue easily. This excessive fatigue is what we want to avoid at all costs. The positive effects of muscle conditioning were noted on muscular strength and lack of harmful side effects was also monitored on anatomical and physiological parameters (muscular biopsies with analysis of the fibres’ volume and enzymatic activity) .
However, these studies did not focus on the impact of such training programs on functional capacities and quality of life.
Halstead et al. suggested classifying the limbs of polio survivors according to muscular deficiency’s severity and its stability. Again, according to Halstead et al., the right attitude would be to personalize the muscular strengthening program according to this classification and make frequent adjustments according to the patient’s evolution and tolerance .
Thus, muscular strengthening can be indicated for PPS and allow patients to regain some muscle strength. If the subject is in a phase of progressive loss of strength, muscle conditioning is still possible but its intensity must remain moderate and it should be fractioned with periods of rest, it must be reassessed very regularly and stopped if there is pain or a worsening of muscular fatigue.
1.4
Endurance rehabilitation in PPS
In polio survivors, the energy cost for walking or completing daily life activities is quite high . The cardiovascular and respiratory tolerance to physical effort must be evaluated. Respiratory function is an essential element, 33% of patients that regained a normal respiratory function during their stability phase present an alteration of this same function in case of PPS .
1.4.1
Clinical trials on aerobic training programs
The impact of aerobic training using bike riding or fast walking exercises has been studied in the context of PPS. The goal was to improve the patients’ tolerance and fatigue during efforts. Dean et Ross reported a 15% improvement on VO 2max and VE max , endurance capacity and muscular strength. Ernstoff et al. showed a decrease in HR max of 12 beats/min in the context of a 6-month retraining program indicating that physical exercise of large muscle groups has a positive impact on the cardiovascular system. Kriz et al. examined the effects of an upper-extremity arm ergometry program over a 16-week period versus a control group. After the 16-week program, the exercise group showed significant improvement in VO 2max and VE max identical to the values expected from a healthy population. Thus, the capacities to adapt to exercise training are proportionally similar to a population of healthy subjects. It is essential to take advantage of these underused capacities furthermore, since exercise is limited by the motor impairments linked to poliomyelitis sequelae.
1.4.2
Synthesis and recommendations
Therapeutic studies describe 8- to 16-week training programs where subjects exercised two to three times a week on short periods (20 to 40 minutes). The training was always moderate respecting a threshold of 70% of the theoretical HR max ( Table 1 ). Improvements were noted on cardiovascular and respiratory parameters (HR max , VO 2 , blood pressure) . No adverse side effects were reported. However, the impact on functional abilities and quality of life were not studies, the positive impact was only observed on the short term. No harmful side effects were reported.
1.5
Aquatic physiotherapy
Aquatic physiotherapy is the treatment of choice for polo sequelae and PPS. With this therapy, it is possible to do muscular training in a controlled resistance environment but also to perform an assisted active autonomous workout on deficient muscles in an antigravity setting, thus creating the proper conditions for relieving musculoskeletal pain. Some recent studies bring positive arguments in favor of this type of physiotherapy. We will highlight here the work of Willen and Scherman who, through an evaluation of this type of training in aquatic physiotherapy, reported a significant pain decrease (15-point gain in the field of perceived pain in the NHP health questionnaire, P < 0.05). Muscular strengthening programs, mainly in a hot environment, are particularly indicated (Tenerife). Strumse et al. showed, in a multicenter study, a positive impact on strength and gait capacities .
1.6
Rehabilitation and therapeutic education
In PPS, it is essential to take fatigue into account. The most deficient muscles or the ones that are progressively evolving are subject to exhaustion. Muscle or joint pain can also be related to repeated exercise constraints. It is essential to adapt the physical therapy and propose adapted strategies that will help fight this excessive mechanical solicitation. Fatigue must be correctly assessed; patients often described it like a sensation of having to force themselves to assume simple daily activities that they were able to perform effortlessly before. Klein et al. published a randomized study comparing the impact of isolated muscular strengthening program associated to healthy life changes (to keep a stable weight, sit down at work whenever possible, energy conservation and effort planning to reduce the frequency of sit-stand transfers, make sure to rest often, use technical aids to spare movements). Only the groups with the muscular strengthening program reported a significant improvement (30% decrease) in shoulder pain. Davidson et al. reported the benefits of a multidisciplinary program including educational therapeutic care. They describe a link between PPS symptoms (pain, fatigue, anxiety and depression) and patients’ behavior (life style).
The means to adapt the activity in order not to go over the fatigue threshold are:
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walking technical aids and gait orthoses;
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environmental changes such as adapting the patients’ home environment;
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lifestyle adjustments regarding energy conservation techniques and travel modes;
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asking for human help.
This energy conservation strategy suggests that patients suffering from PPS are aware of this problem. In patients that learned earlier on to use their utmost potential to gain their autonomy, this energy conservation strategy seems sometimes difficult to accept, it can be perceived like a feeling of being powerless against the disease. This strategy is a real educational therapeutic approach for the patient; it is part of a comprehensive educational program with exercises and respecting a healthy lifestyle.
1.7
Conclusion
Various rehabilitation strategies are possible for PPS. Muscular strengthening can be beneficial on muscle groups that are not yet deficient and painless, it must be moderate and its tolerance must be regularly evaluated. Balneotherapy is certainly the best tolerated rehabilitation therapy. Endurance training also has a positive impact. In these patients experiencing increasing fatigue and for whom daily life activities are performed with difficulties, energy conservation strategies are indicated while readjusting their lifestyle and activities.
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Version française
2.1
Introduction
La poliomyélite antérieure aiguë est une maladie infectieuse de l’enfant et du jeune adulte causée par un entérovirus (le Poliovirus ). Il existe trois sérotypes de Poliovirus . Cette affection redoutée survenait au cours d’épidémies, en général pendant les périodes chaudes. Aux États-Unis et en Europe, les dernières grandes épidémies de polio ont eux lieu autour des années 1950 . Les campagnes vaccinales initiées à partir du milieu des années 1950 par virus inactivé de type Salk, puis par virus atténué (Sabin) ont permis de faire disparaître les cas d’infection dans le monde occidental, mais le virus est toujours présents dans de nombreux pays en développement, cause d’infections endémiques.
La cible cellulaire du Poliovirus est les corps cellulaires des motoneurones de la corne antérieure de la moelle ou du tronc cérébral. La poliomyélite antérieure aiguë se manifeste par une paralysie musculaire asymétrique, de sévérité variable, maximale en 48 heures qui peut s’accompagner d’une atteinte respiratoire et bulbaire. Après l’infection aiguë, s’installe une phase de « récupération » lente et progressive. Cette amélioration motrice est rendue possible par le phénomène de réinnervation des fibres musculaires initialement dénervées. Les axones épargnés par le virus sont capables de « bourgeonner », créant ainsi des unités motrices géantes. Ce phénomène ne peut cependant pas bénéficier à toutes les fibres dénervées, ce qui explique la persistance de séquelles motrices. La période de récupération est potentialisée par la rééducation motrice et aboutit à une période de « déficiences séquellaires » stabilisées, laissant une atrophie musculaire résiduelle de sévérité et de topographie variables. Ces séquelles sont considérées comme stables.
L’éventualité d’une aggravation secondaire des déficiences neuromusculaires longtemps après la survenue de l’infection aiguë par le virus de la poliomyélite (ou Poliovirus ) est décrite depuis Charcot . C’est cependant seulement en 1984 que le terme de « syndrome post-polio (SPP) » fut utilisé, lors de la première conférence internationale qui lui fut consacrée en 1984 à Warm Spring Georgia .
2.2
Définition
Le SPP est une entité clinique définie par l’association de nouveaux symptômes survenant longtemps après une poliomyélite antérieure aiguë suivie d’une période de stabilité. Ces symptômes sont :
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une nouvelle faiblesse musculaire ;
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la fatigue ;
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des douleurs ;
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l’apparition ou l’aggravation d’une atrophie ;
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l’apparition ou l’aggravation de difficultés à effectuer les activités de la vie quotidienne ;
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l’intolérance au froid ;
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des troubles du sommeil ;
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des difficultés de langage ou de déglutition ;
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une déficience respiratoire.
La totalité de ces symptômes n’étant pas présente dans toutes les situations, des critères diagnostiques ont été proposés par Halstead en 1985, validés par l’ European Federation of Neurological Societies .
Pour retenir le diagnostic de SPP, il faut réunir ces conditions :
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la confirmation d’une histoire médicale de poliomyélite ;
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la récupération neurologique partielle ou presque complète passé la période aiguë ;
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une période de stabilité neurologique d’au moins 15 ans ;
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une faiblesse musculaire récente d’apparition aiguë ou rapidement progressive ;
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au moins deux symptômes nouveaux récents parmi :
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fatigue excessive,
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douleurs musculaires ou articulaires,
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atrophie musculaire,
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intolérance au froid,
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pas d’autre explication médicale.
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Le SPP est donc avant tout un diagnostic d’élimination dont le signe principal est l’apparition ou l’aggravation récente d’une déficience musculaire.
Le SPP concernerait 15 à 80 % des sujets atteints de séquelles de poliomyélite en fonction des études .
La physiopathologie du SPP est discutée : les principales hypothèses sont :
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un épuisement du processus de dénervation réinnervation, la dénervation concernant des unités motrices géantes, on explique ainsi une traduction clinique rapide ;
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un défaut de transmission neuromusculaire par libération insuffisante d’acétyl-choline, objectivable par le décrément du potentiel d’action à l’étude électrophysiologique par stimulation répétitive en fibre unique (Jitter) ;
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des phénomènes inflammatoires auto-immuns ;
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la persistance du virus et sa réactivation.
2.3
Le renforcement musculaire dans le SPP
La rééducation motrice active sous la forme d’un renforcement musculaire progressif fut une des premières thérapies physiques proposées dans le but d’améliorer les symptômes du SPP. L’élaboration d’un projet thérapeutique en médecine physique se heurte encore malheureusement au dogme de l’interdiction de renforcer les muscles de patients atteints de maladie neuromusculaire.
2.3.1
Les essais cliniques de programmes de renforcement
Rodriquez et Agre soutiennent l’intérêt d’un renforcement musculaire bien conduit. Ils ont étudié d’abord la sensation de fatigue ressentie par le patient en comparaison avec la fatigue musculaire enregistrée en EMG et ainsi montré une relation linéaire entre ces deux paramètres. Ces auteurs ont aussi observé une diminution de la sensation de fatigue corrélée à une meilleure récupération post-effort par des mesures subjectives perçues par le patient (échelle de fatigue de Borg sur 20) confirmées par des enregistrements électrophysiologiques . Cette même équipe a montré la supériorité des exercices fractionnés sous-maximaux versus des contractions musculaires jusqu’à sensation d’épuisement . Ces auteurs ont publié un travail montrant l’augmentation de la force musculaire (+61 % de la résistance initiale, en kg) en isométrique comme en isocinétique et ce de manière significative avec un travail de renforcement musculaire sous maximal, fractionné, quotidien sur 12 semaines. Au terme de ce travail, il n’y avait pas d’effet délétère sur la sensation de fatigue. Chan et al., dans une étude randomisée contrôlée, ont étudié l’effet d’un protocole de renforcement musculaire sur les muscles du pouce . L’analyse EMG de surface permettait une estimation du nombre d’unités motrices activées, par cette technique, les auteurs montraient une amélioration de la commande motrice centrale avec l’entraînement. Spector et al. ont étudié l’histologie et les modifications du signal IRM du muscle pendant un programme de renforcement musculaire sur une durée de dix semaines. Ils retrouvent une amélioration de la force musculaire, mais celle-ci n’est pas corrélée à une modification de la taille des fibres musculaires (une hypertrophie était retrouvée chez le sujet sain). Par ailleurs, les biopsies ne montrent pas d’altération du parenchyme musculaire. Se pose donc la question des mécanismes musculaires adaptatifs lors du travail musculaire chez les patients post-polio.
2.3.2
Synthèse et recommandations
Des arguments en faveur de l’effet bénéfique au niveau de la force musculaire sans effets délétères nous sont apportés par plusieurs études d’efficacité. La plupart de ces études sont des essais ouverts, sans groupe témoin ou des essais randomisés contrôlés sur des effectifs de petite taille . Ces études sont présentées dans le tableau 1 : la plupart des études décrivent un protocole de renforcement d’intensité modérée et progressive dans le but de ne pas dépasser le seuil de fatigue musculaire.
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