Abstract
Objective
To evaluate muscle strength, balance control and gait capacity in patients with multiple sclerosis (MS) and to study the correlations between these parameters.
Patients and methods
Twenty MS patients were evaluated in terms of knee muscle strength, gait and balance parameters. These evaluations were performed using an isokinetic dynamometer (the Cybex II ® ), a Bessou gait analyzer and a Satel ® force platform, respectively. The patients’ results were compared with those of a healthy control group.
Results
Hamstring and quadriceps peak torque values were lower in the MS group than in the control group. The sway area was greater in the MS group under eyes-open and eyes-closed conditions. The MS patients displayed lower gait speed, cadence and stride length. Hamstring and quadriceps strength values were significantly correlated with posture and gait parameters.
Conclusion
The present study revealed the value of an overall evaluation of knee muscle strength, gait and posture in MS patients.
Résumé
Objectif
Mesurer les forces musculaires, les capacités d’équilibre et de marche dans une population de sclérosés en plaques et d’étudier les corrélations entre ces différents paramètres.
Patients et méthodes
Vingt patients ayant une sclérose en plaques (SEP), ont bénéficié d’une évaluation de la force musculaire des genoux, de la marche et de l’équilibre. Cette évaluation a été réalisée respectivement par l’appareil isocinétique Cybex II ® , le locomètre de Bessou et la plateforme stabilométrique SATEL ® . Les résultats de ces mesures ont été comparés à un deuxième groupe sain.
Résultats
Les pics de couple moyens des patients atteints de SEP sont inférieurs à ceux de la population saine au niveau des ischio-jambiers et des quadriceps. La surface et la longueur totale du stabilogramme étaient plus importantes dans ce groupe en condition yeux ouverts et fermés. Une réduction de la vitesse, de la longueur de l’enjambée et de la cadence a été retrouvée dans le groupe SEP. Des corrélations significatives ont été retrouvées entre les forces des quadriceps et des ischio-jambiers avec les paramètres de marche et de l’équilibre.
Conclusion
Cette étude témoigne de l’intérêt d’une évaluation globale chez les patients ayant une SEP portant sur les forces musculaires, la marche et l’équilibre.
1
English version
1.1
Introduction
Multiple sclerosis (MS) is a demyelinising, inflammatory disease of the central nervous system. It is the most frequent neurological disease in young adults. The prevalence of MS is greater in Northern Europe. There is clear female predominance, with an F/M gender ratio of 2:1. Onset occurs between the ages of 20 and 40 in 70% of cases, with a peak at 30. The progressive forms of MS (in which long-term treatment is indicated) have been classified in international consensus statements. Four subtypes are generally described: the relapsing remitting subtype (the most frequent form, characterized by successive remissions and relapses which may or may not leave sequelae), the secondary progressive subtype (in which patients with initially relapsing-remitting MS show increasing neurological decline during remissions), the primary progressive subtype (characterized by progressive worsening after the initial symptoms) and the progressive relapsing subtype (characterized by a steady decline that is nevertheless interspersed with relapses) .
Although between 10 and 40% of cases are benign , MS can lead to severe handicap. Over the course of the disease, a patient’s functional capacities may worsen to a variable extent.
Changes in balance control in MS have already been reported . This type of evaluation is based on either clinical measurements (mainly using generic scales) or posturographic measurements. A validated, MS-specific scale “A short measure of balance in MS” has been suggested .
Furthermore, gait disorders are frequent and constitute the first signs of MS in 10 to 20% of patients. After several years of disease progression, gait disorders are observed in over 50% of patients . After 18 years of disease progression, half of all patients will be unable to walk unaided .
Several studies have focused on the clinical evaluation of gait in MS . Gait speed constitutes a pertinent functional parameter for ambulatory patients . In practice, this is measured by the time needed to walk 8 or 10 m . Other tools have been used to evaluate gait capacities in MS but have not been comprehensively validated.
Few studies have focused on the quantitative analysis of motor strength in general and isokinetic measurements in particular .
The correlations between muscle strength, postural capacities and gait have rarely been studied .
Over recent years, the quantification of these parameters and the analysis of their correlations have changed the way we manage patients with central nervous system damage and gait disorders . Patient management programmes now involve a number of more analytical rehabilitation methods – principally strength training exercises and particularly those based on isokinetic paradigms .
The objective of the present study was to:
- •
measure muscle strength, balance control and gait capacity in a population of MS patients;
- •
compare the patients with a healthy population and;
- •
study the correlations between these various parameters, with a view to sharpening the focus of the rehabilitation protocols used in this disease.
1.2
Patients and methods:
1.2.1
Patients
We have recruited 20 patients (group G1) consulting the outpatient neurology clinic at Habib Bourguiba University Hospital (Sfax, Tunisia). There were no age restrictions. We included patients with relapsing remitting MS, no relapse within the previous 6 months and an expanded disability status scale (EDSS) score below 6 (as evaluated by a neurologist). The diagnosis of MS had also been made by a neurologist, according to the criteria published by Poser et al. .
Patients with cognitive disorders, severely impaired visual function, a severe psychiatric disorder or severe arthritis of the knees and/or hips or those experiencing a relapse were excluded from the study.
The EDSS scale is used worldwide to evaluate MS. It is a basic scale for evaluating neurological status and is notably used for making treatment decisions. The score ranges from 0 to 10: a score of 0 corresponds to a normal neurological examination, whereas a score of 6 or more corresponds to limited walking ability and the need to use a technical aid for walking. The spasticity scores for the quadriceps and hamstring muscles were below 3 on the modified Ashworth scale , enabling the isokinetic evaluation of these knee muscles. We used the modified Ashworth scale because it is the gold standard for spasticity evaluation and is frequently used in the literature: the score ranges from 0 (no muscle tone disorders) to 4 (one or more rigid limb segments in flexion or extension).
This comprehensive examination was completed by an evaluation of overall function using the functional independence measure (FIM) , a simple performance scale.
Patients were provided with comprehensive information on the study protocol and gave their verbal consent to participate.
1.2.2
Methods
Balance was evaluated first (i.e. before the isokinetic testing), in view of the risk of fatigue-related bias. We used a Satel ® force platform. This balance analysis technique is based on measurement of the centre of pressure’s sway in a standing subject and enables calculation of the intensity and vector of the ground reaction forces, with a recording time of 51.2 seconds and a sampling frequency of 40 Hz. The patient stood upright on the platform with bare feet and with his/her arms by the side. He/she was instructed to stand as still as possible and to look horizontally at a wall about 1.5 m in front (with no particular visual target). The evaluation was performed under static conditions with the eyes open (EO) and then closed (EC).
The following parameters were used to assess balance: the postural sway area (in mm 2 , corresponding to the surface area described by the centre of pressure during the recording) and the centre of pressure’s total path length over this time (in mm).
Gait was evaluated with a Bessou device at a spontaneously chosen speed and over a distance of ten metres. The parameters used were gait speed (in km/hour), cadence (strides per minute) and stride length (in metres). An initial practice trial was performed with a few steps, in order to familiarize the patient with the tension produced by the gait analyzer’s wires.
Quadriceps and hamstring muscle strength was evaluated with a “Cybex ® II” isokinetic device. The isokinetic dynamometer is a useful option for evaluating muscle strength , especially in cases of mild muscle impairments not evidenced by clinical muscle testing. The technique is reproducible and sensitive .
The evaluation was performed in a concentric mode and with an angular speed of 60 °s −1 . After the practice session, each patient performed a series of three-knee flexion/extension on one body side and then on the other, with a 20-second rest between the series. The peak torque in Newton-metres (N/m) was recorded.
All evaluations were performed in the morning, in order to rule out fatigue-related bias.
The data on muscle strength, gait capacity and balance control in patients (group G1) were compared with those from a control group (group G2) of 20 healthy subjects (recruited later from among the paramedical staff at Habib Bourguiba University Hospital).
We sought to match the control group with the patient group in terms of the main factors that can influence muscle strength, gait capacity and balance control, i.e. age and gender.
This one-month, cross-sectional study was performed in January, 2010.
The control group was also evaluated in the morning and in the same order (balance control, gait and then isokinetic muscle strength).
1.2.3
Statistical analysis
Data entry and analysis was performed using SPSS software (version 11.0). The results were expressed as the mean ± standard deviation. A chi-squared test was used to compare frequencies and Student’s T-test was used to compare mean values. The Spearman correlation coefficient was used to test for correlations between quantitative variables. The threshold for statistical significance was set to p < 0.05.
1.3
Results
We included 20 MS patients (group G1: 10 men and 10 women; mean age: 36.80 ± 6.01). The control population (group G2) comprised 20 healthy subjects (eight men and 12 women; mean age: 35.80 ± 5.51).
The disease characteristics and the scale scores for the MS group are summarized in Table 1 .
| Disease duration in years (mean ± standard deviation) | 8.44 ± 5.25 |
| Remittent clinical form | 100% |
| Motor symptoms | Spasticity (80%) Cerebellar ataxia (20%) |
| EDSS score (mean ± standard deviation) | 2.80 ± 0.99 |
| FIM score (mean ± standard deviation) | 120.42 ± 5.10 |
| Ashworth score (mean ± standard deviation) | 1.61 ± 0.4 |
| Ongoing treatment | Immunomodulator: interferon ß1a (60% Antispastic agent: baclofen (100%) Vitamin therapy: vitamins E, C, arginine-thiamine (100%) |
The two groups did not differ significantly in terms of gender ratio or age.
We observed significantly greater sway areas and sway path lengths in group G1 than in group G2 ( p < 0.001), under both EO and EC static conditions. These results are summarized in Table 2 .
| Group G1 n = 20 | Group G2 n = 20 | p | |
|---|---|---|---|
| Sway area (eyes open) (mm 2 ) (mean ± standard deviation) | 615.80 ± 373.59 | 174.35 ± 79.79 | < 0.001 a |
| Sway area (eyes closed) (mm 2 ) (mean ± standard deviation) | 1088 ± 503.51 | 272.15 ± 138.91 | < 0.001 a |
| Sway path (eyes open) (mm) (mean ± standard deviation) | 671.55 ± 207.01 | 431.95 ± 87.75 | < 0.001 a |
| Total length (eyes closed) (mm) (mean ± standard deviation) | 1043.4 ± 256.65 | 757.55 ± 156.05 | < 0.001 a |
An analysis of temporal and spatial gait parameters revealed lower spontaneous gait speed, stride length and cadence values in group G1, compared with group G2. The differences were all significant ( p < 0.001). These results are summarized in Table 3 .
| Group G1 n = 20 | Group G2 n = 20 | p | |
|---|---|---|---|
| Spontaneous speed (km/h) (mean ± standard deviation) | 2.84 ± 0.82 | 4.55 ± 0.82 | 0.000 a |
| Stride length (m) (mean ± standard deviation) | 0.98 ± 0.19 | 1.32 ± 0.16 | 0.000 a |
| Cadence (strides/min) (mean ± standard deviation) | 98.16 ± 12.53 | 118.37 ± 11.78 | 0.000 a |
Isokinetic assessments of the quadriceps and hamstring muscles showed that the mean peak torque values were significantly lower in group G1 than in G2, on both the stronger and weaker sides. Table 4 summarizes these results.
| Group G1 n = 20 | Group G2 n = 20 | p | |
|---|---|---|---|
| Mean peak torque for the quadriceps on the stronger side (N/m) (mean ± standard deviation) | 91.70 ± 27.11 | 182.45 ± 67.79 | 0.000 a |
| Mean peak torque for the quadriceps on the weaker side (N/m) (mean ± standard deviation) | 71.80 ± 27.60 | 157.45 ± 45.65 | 0.000 a |
| Mean peak torque for the hamstring on the stronger side (N/m) (mean ± standard deviation) | 42.60 ± 12.57 | 107.60 ± 40.93 | 0.000 a |
| Mean peak torque for the hamstring on the weaker side (N/m) (mean ± standard deviation) | 40.30 ± 13.95 | 89.70 ± 29.52 | 0.000 a |
We found statistically significant correlations between the gait speed and the mean peak torque values for the quadriceps and hamstring muscles.
We also noticed statistically significant correlations between the peak torque for the hamstrings and the sway area (more marked under EC conditions). Furthermore, the FIM score was correlated with peak torque for the quadriceps. The results concerning these correlations are presented in Table 5 .
| PT Q (stronger side) | PT Q (weaker side) | PT H (stronger side) | PT H (weaker side) | |
|---|---|---|---|---|
| Gait speed | r = 0.28 p = 0.19 | r = 0.53 p = 0.016 a | r = 0.6 p = 0.005 a | r = 0.48 p = 0.029 a |
| Sway area under static conditions, eyes open | r = 0.231 p = 0.328 | r = 0.243 p = 0.302 | r = −0.28 p = 0.08 | r r = −0.48 p = 0.029* |
| Sway area under static conditions, eyes closed | r = 0.128 p = 0.59 | r = 0.304 p = 0.193 | r = −0.58 p = 0.007 a | r = −0.6 p = 0.004 a |
| FIM score | r = 0.215 p = 0.42 | r = 0.55 p = 0.014 a | r = 0.24 p = 0.1 | r = 0.28 p = 0.08 |
1.4
Discussion
The evaluation of MS patients usually involves measurement of functional capacities (notably gait and balance control) and impairments (muscle strength, above all). Analysis of the correlations between these various parameters may enable more targeted rehabilitation protocols in MS.
The present study shows that the balance and gait disorders and quadriceps and hamstring muscle weakness in MS patients. Significant correlations between these various parameters were apparent.
In MS, many patients are often highly detrained ; this often favours a sedentary lifestyle, with muscle under-use and a muscle-sparing strategy in over 80% of cases . Fatigue can even be observed in the absence of effort: it has a central component but a variety of associated factors may also contribute: reactive psychological disorders sleep disorders, pain, comorbidity, iatrogenic problems and detraining .
In order to mitigate the impact of this fatigue, we performed the various assessments in the morning. However, we are not aware of any studies describing changes in gait, balance and muscle strength in MS patients over the day/night cycle.
In terms of balance, most clinical studies in MS patients have used generic scales, such as the Berg Balance Scale (BBS), the FIM’s transfer items or the Rivermead Mobility Index . Although an eight-item postural scale derived from the Tinetti test and the BBS has been specifically developed for and validated in MS , it does not yet seem to have been widely adopted.
As an adjunct to clinical evaluation methods, force platforms are accurate, reliable, simple-to-use and non-bulky tools for static postural assessments .
In the present study, we used the Satel ® force platform to evaluate balance under static conditions. A number of postural disorders were found in MS patients presenting essentially motor symptoms and an isolated pyramidal syndrome (80% of cases) and generalized but moderate spasticity of the legs (Ashworth score < 3). These disorders were evaluated in terms of the sway area and the centre of pressure’s total path length under EO and EC conditions.
In 2006, Cantalloube et al. also used a Satel ® force platform to evaluated balance in 21 MS patients and observed more marked postural disorders than those found in the present study. This could be explained by the fact that Cantalloube et al.’s population comprised a high proportion of patients (15 out of 21) with secondary progressive MS and the low incidence of cerebellar ataxia (only one patient had spastic symptoms). In contrast, all our patients had relapsing remitting MS and 80% presented a spastic symptoms and isolated pyramidal involvement.
Porosinska et al. studied balance in 32 MS patients and 30 control subjects by measuring the ground reaction forces on a force platform. The parameters studied were the centre of pressure’s path and speed and the sway area. Anomalies in these postural parameters were found in the MS group. The latter researchers found that these perturbations were even more marked under EC conditions and on an unstable surface.
Sosnoff et al. also used a force platform to study the effect of spasticity on balance control in 16 MS patients. The parameters studied were the sway area, the sway range in the anteroposterior and mediolateral planes and the sway speed. The MS patients presented anomalies in all these parameters, when compared with a control group. In the MS group, the patients with greater spasticity (as measured on the Ashworth scale) had poorer balance control.
In gait assessment, the measurement of gait speed is usually based on the time needed to walk 8 or 10 m. This test is simple to administer and reproduce. A 20% change in gait speed is clinically significant .
The timed 25-foot walk is now included in the MS functional composite but is also often used on its own in clinical practice .
The maximum walking distance provides an estimate of physical endurance. The distance covered in a six-minute test (or in variants such as the 2-minutes walk) has been validated in cardiovascular and respiratory diseases but not fully in MS .
Albrecht et al. have shown that spontaneous gait speed is a more reliable parameter than maximum walking distance, since the latter is more sensitive to day-to-day fluctuations.
The Bessou gait analyzer is easy to use and provides a rapid evaluation of the various temporal and spatial gait parameters (speed, cadence, cycle time, stride length, single support time and double support time, etc.). Three-dimensional gait analysis is mainly used in research and in the evaluation of new therapeutic strategies.
Our study evidenced a difference in gait parameters in MS. Stride length, gait speed and cadence were significantly lower in the MS patients. We thus confirmed the results of previous studies – most of which used the Bessou gait analyzer. Gait disorders with abnormal temporal and spatial parameters have been consistently reported. Mevellec et al. have confirmed this type of impairment in terms of spontaneous and/or maximum gait speed.
These gait anomalies are part of a gait strategy observed in the majority of central nervous system disorders.
The pyramidal damage in MS explains the motor impairment of the quadriceps and, above all, the hamstring muscles observed in the present study. Our results confirm the findings of other studies . Joubrel et al. tested the isokinetic strength of these muscles in 20 ambulatory MS patients on the Cybex II at speeds of 60° and 180 °s −1 ; they found significantly lower peak torque values in the patients than in healthy controls. This isokinetic test was found to be highly reproducible (especially at the lower speed) in MS patients. Likewise, Cantalloube et al. evaluated isokinetic muscle strength at a low speed (60 °s −1 ) in 21 MS patients and evidenced significant motor impairment of the quadriceps and hamstring muscles, compared with controls.
The present study revealed significant correlations between gait parameters and the peak torque for the quadriceps (on the weaker side) and, above all, the hamstrings (on both the weaker and stronger sides). Cantalloube et al. also found reported significant correlations between the quadriceps and hamstring peak torque values (on the weaker and stronger sides) and gait speed in 21 MS patients.
Likewise, Mevellec et al. observed correlations between motor impairment and gait speed in 27 MS patients. These correlations were strongest for the hamstring. Correlations between quadriceps impairment and gait speed were observed only in a subgroup of patients with “ataxic-spastic” damage and not in a subgroup with spastic symptoms alone (i.e. isolated pyramidal involvement). Mevellec et al. concluded that the presence of proprioceptive impairment in MS patients with “ataxic-spastic” damage could modify the correlation between gait speed and motor impairment: the correlation with the hamstring muscles was stronger and a correlation with quadriceps strength became apparent .
In hemiplegia, significant correlations between gait speed and muscle strength parameters (peak torque, in isokinetic measurements) have been evidenced by several authors .
The observed correlations between low muscle strength (mainly impairment of the hamstrings) and gait parameters suggest that a specific rehabilitation program based on strength training could effectively lead to functional improvements in MS patients. These strength training techniques seek not only to improve gait and balance but also to improve the patient’s transfer capacities and (in cases of genu recurvatum in stance) knee stability .
Recent studies have demonstrated that a rehabilitation protocol based on strength training effectively improves gait in MS patients: in Cantalloube et al.’s study of 21 MS patients , the rehabilitation protocol included conventional physiotherapy (analytical work, overall functional exercises and endurance work on an exercise bike or a treadmill). The post-training correlations between quadriceps and hamstring muscle strength were stronger than the pre-training correlations. In Robineau et al.’s study of 28 MS patients , a rehabilitation programme involving eccentric, isokinetic strengthening of the hamstrings led to an improvement in gait (as evaluated on a visual analogue scale). Aubry et al. confirmed the efficacy of this type of strength training protocol (eccentric, isokinetic, low-speed (15 °s −1 ) training of the hamstrings with visual feedback control) in MS patients. After 12 training sessions, the latter authors observed an increase in hamstring muscle strength, a higher gait quality score on a visual analogue scale, improved knee control during gait in a clinical examination and a greater maximum walking distance.
Moreover, we found positive correlations between muscle strength and balance parameters, especially for hamstring muscles under EC conditions. These correlations are unsurprising, given that balance depends on both motor and proprioceptive components.
The rehabilitation of MS patients with balance disorders should include a strength training programme (mainly for the hamstring muscles) and management of the proprioceptive component. Balance retraining in these patients appears to be necessary – even in the absence of cerebellar ataxia.
Lastly, the observed correlation between quadriceps impairment and the FIM score suggests that quadriceps strength training is necessary.
1.5
Conclusion
Our study evidenced thigh muscle weakness and gait and balance disorders in MS patients, compared with a control group.
Our MS patients had a different set of clinical symptoms (essentially spastic symptoms with an isolated pyramidal syndrome) from those described in the literature.
We also evidenced statistically significant correlations between muscle strength on one hand and gait and balance parameters and functional status on the other.
Hamstring muscle impairment appears to be related to gait and balance parameters, whereas quadriceps impairment may be more related to functional status.
Consequently, rehabilitation protocols should include an analytical strength training programme (particularly for the quadriceps and hamstring muscles), in addition to general functional retraining and proprioceptive work.
This type of rehabilitation programme might help MS patients to progress in terms of balance, gait, leg muscle strength and overall function.
Disclosure of interest
The authors declare that they have no conflicts of interest concerning this article.
2
Version française
2.1
Introduction
La sclérose en plaque (SEP) est une maladie inflammatoire démyélinisante du système nerveux central. Il s’agit de la maladie neurologique la plus fréquente du sujet jeune. Sa fréquence est plus importante en Europe du nord. Une prédominance féminine nette est notée avec un ratio de 2 sur 1. L’âge de début se situe entre 20 et 40 ans dans 70 % des cas avec un pic à 30 ans. La classification des formes évolutives de SEP sur laquelle reposent les indications des traitements de fond, a fait l’objet d’une tentative de consensus international. Il a été proposé de retenir quatre formes : la forme rémittente : la plus fréquente caractérisée par des poussées et des rémissions avec ou sans séquelles, la forme progressive secondaire caractérisée par une évolution progressive du déficit neurologique après une phase rémittente, la forme progressive primaire caractérisée par une évolution progressive d’emblée et la forme progressive à rechutes caractérisée par une évolution progressive d’emblée émaillée de poussées .
En dehors des formes bénignes (10 à 40 % des cas) , elle peut conduire à un handicap sévère. Des altérations des capacités fonctionnelles de degrés variables peuvent être observées au cours de l’évolution de la SEP.
L’évaluation de l’équilibre chez ces patient a été étudiée . Cette évaluation est basée soit sur des mesures cliniques par des échelles le plus souvent génériques, soit sur des mesures posturographiques. Une échelle spécifique et validée pour la SEP ( A short measure of balance in multiple sclerosis ) a été proposée .
Par ailleurs, les troubles de la marche sont fréquents ; ils sont révélateurs dans 10 à 20 % des cas. Après plusieurs années d’évolution, ils s’observent chez plus d’un patient sur deux . Après 18 ans d’évolution, la moitié des malades auront perdu toute autonomie de marche .
L’évaluation clinique de la marche dans la SEP a été l’objectif de plusieurs études. . La vitesse de la marche constitue un paramètre fonctionnel pertinent pour le patient déambulant . En pratique elle est mesurée par le temps pour parcourir 8 ou 10 m . D’autres outils ont été utilisés pour évaluer les capacités de marche mais leur performance dans la SEP n’a pas été testée de façon exhaustive.
Les études qui permettent des analyses quantitatives de la force motrice en particulier par la méthode d’isocinétisme ne sont pas nombreuses .
Les corrélations entre ces différents paramètres : forces musculaires, capacités posturales et de la marche ont été rarement étudiées .
En effet la quantification de ces paramètres et l’étude de leurs corrélations ont modifié ces dernières années la conception de prise en charge des patients ayant une affection du système nerveux central et présentant des troubles de la marche . Cette prise en charge comporte des méthodes de rééducation plus analytiques incluant surtout le renforcement musculaire en particulier par la méthode d’isocinétisme .
Notre objectif est de mesurer la force musculaire, les capacités d’équilibre et de marche dans une population de patients atteints de SEP en la comparant avec une population saine et d’étudier les corrélations entre ces différents paramètres afin de mieux cibler le protocole de rééducation chez ces patients.
2.2
Patients et méthodes
2.2.1
Patients
Vingt patients (groupe G1) ont été recrutés dans cette étude à partir de la consultation externe de neurologie du CHU Habib Bourguiba Sfax, Tunisie. Ont été inclus des patients (sans critère d’âge) ayant une SEP dans sa forme rémittente en dehors de toute poussée (le délai de la dernière poussée est supérieur à six mois), avec un score Expanded Disability Status Scale (EDSS) inférieur à 6 évalué par un neurologue. Le diagnostic de SEP a été posé également par un neurologue, selon les critères de Poser et al. .
Ont été exclus de l’étude les patients ayant des troubles des fonctions supérieures, une atteinte majeure de la fonction visuelle, une pathologie psychiatrique grave ou une arthrose des genoux et/ou des hanches évoluée ou en poussée.
L’échelle EDSS est l’outil universel d’évaluation des SEP. C’est l’échelle de base d’évaluation du statut neurologique, notamment pour les prises décisionnelles au niveau thérapeutique. Son score varie de 0 à 10 : le score 0 correspond à un examen neurologique normal ; à partir d’un score à 6, le périmètre de marche est limité avec nécessité d’une aide à la marche.
La spasticité était inférieure à 3 selon l’échelle d’Ashworth modifiée des muscles quadriceps et ischio-jambiers permettant l’évaluation isocinétique des muscles des genoux. Nous avons utilisé cette échelle car il s’agit du gold standard de l’évaluation de la spasticité et la plus utilisée dans la littérature : son score va de 0 correspondant à une absence de trouble du tonus à 4 correspondant à une fixation des segments de membres en flexion ou en extension.
Ce bilan a été complété par une évaluation fonctionnelle globale grâce à la mesure de l’indépendance fonctionnelle (MIF) qui est une échelle simple de réalisation.
Le protocole envisagé a été expliqué à tous les patients et réalisé après leur consentement oral.
2.2.2
Méthodes
L’évaluation de l’équilibre a été effectuée en premier, avant l’évaluation isocinétique en raison du risque de perturbation du test par la fatigue. Nous avons utilisé la plateforme de force stabilométrique (Satel ® ). C’est une technique d’investigation posturale fondée sur la mesure des oscillations du centre de pression au sol , elle permet de calculer ses positions successives exercées par le poids du sujet sur le plateau pendant une durée d’échantillonnage de 51,2 secondes à une fréquence d’acquisition de 40 Hz. Le patient a été placé sur la plateforme pieds nus. Il se tenait debout, les bras le long du corps et reçoit la consigne de rester le plus immobile possible et de fixer horizontalement le regard sur un mur sans repère particulier situé à environ 1,5 m. L’évaluation a été réalisée en condition statique en position debout yeux ouverts (YO) puis yeux fermés (YF).
Les paramètres utilisés pour juger l’équilibre étaient la surface du stabilogramme (en mm 2 ) correspondant à la surface balayée par le centre de pression plantaire pendant la durée de l’enregistrement et la longueur totale correspondant à la distance parcourue par le barycentre pendant cette durée (en mm).
L’évaluation de la marche a été réalisée par le locomètre de Bessou à une vitesse spontanée sur une distance de dix mètres. Les paramètres utilisés étaient la vitesse (en km/heure), la cadence de la marche (nombre d’enjambées par minute) et la longueur d’enjambée (en mètres). Un premier essai a été réalisé sur quelques pas afin de familiariser le patient avec la tension des fils du locomètre.
L’évaluation des forces musculaires des quadriceps et ischio-jambiers a été réalisée par l’appareil isocinétique « Cybex II ® ». L’utilisation de ces dynamomètres isocinétiques offre une alternative dans l’évaluation des forces musculaires surtout en cas de déficit musculaire discret non objectivé par le testing musculaire. Il s’agit d’une technique reproductible et sensible .
Cette évaluation a été réalisée en mode concentrique à la vitesse angulaire 60 °s −1 . Après familiarisation, Chaque patient effectue une série de trois répétitions de flexion extension du genou d’un côté puis l’autre avec des temps de repos de 20 secondes entre les séries. Le paramètre retenu était le pic de couple en Newton-mètre (N/m).
Toutes ces évaluations ont été réalisées le matin pour éliminer tout phénomène de fatigue.
Les résultats des forces musculaires et des capacités de marche et d’équilibre de ce premier groupe ont été comparés à ceux d’une population témoin de 20 sujets recrutés de façon différée du personnel paramédical de l’hôpital Habib Bourguiba Sfax – Tunisie (groupe G2). Ces témoins ont été choisis dans la perspective d’avoir deux groupes (G1 et G2) comparables selon les principaux facteurs qui pourraient influencer les résultats des forces musculaires, de la marche ainsi que des capacités posturales à savoir l’âge et le sexe.
Il s’agissait donc d’une étude transversale qui s’est déroulée en un mois (janvier 2010).
L’évaluation du groupe témoin a suivi le même ordre (équilibre puis marche puis forces musculaires isocinétiques) également le matin.
2.2.3
Analyse statistique
La saisie des données était réalisée par le logiciel SPSS 11.0. Les résultats ont été exprimés par les valeurs moyennes et leurs écarts type. Les tests utilisés étaient le test de Chi 2 pour la comparaison des fréquences et le test de Student pour la comparaison des moyennes. Le test de corrélation de Spearman a été utilisé pour la recherche de corrélation des variables quantitatives. Le seuil de signification retenu était de 5 %.
2.3
Résultats
Nous avons inclus 20 patients ayant une SEP (groupe G1) : dix hommes et dix femmes d’âge moyen de 36,80 ± 6,01 ans. La population de référence (groupe G2) comportait 20 sujets sains (huit hommes et 12 femmes) d’âge moyen de 35,80 ± 5,51 ans.
Les caractéristiques de la maladie et les scores des différentes échelles d’évaluation dans le groupe SEP sont résumés dans le Tableau 1 .
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