Abstract
Objectives
To evaluate the effects of a rehabilitation program in terms of balance, gait and muscle strength in a population of patients with myotonic dystrophy.
Patients
Twenty patients benefited, as outpatients in a hospital setting, from a rehabilitation program with clinical and instrumental evaluations. The evaluation focused on quantitative balance measurement by clinical and stabilometer tests, gait assessed by Locometre ® and extensors and flexors knee muscle strength measured in isokinetic concentric mode at 60°/s.
Results
After the rehabilitation program, we observed a significant improvement in the patients’ balance capacities measured with the Berg Balance Scale (BBS), fast gait speed and muscle strength. However, the instrumental evaluation did not report any gains for static balance and spontaneous gait speed after the training program. No correlation was found between the various improvements.
Conclusion
A rehabilitation program focused on strength, gait and balance allowed for significant improvements in some parameters of myotonic dystrophy. These results attest to the relevance of a short-term rehabilitation protocol for these patients in the framework of a multidisciplinary therapeutic care. The disparity observed in the results measured for these patients suggest the contribution of cognitive involvement in the limitations felt by patients with myotonic dystrophy in the areas of gait and balance.
Résumé
Objectifs
Évaluer les effets d’un programme de rééducation en termes d’équilibre, de locomotion et de force musculaire dans une population de patients atteints de dystrophie myotonique de Steinert.
Patients
Vingt patients ont bénéficié d’un programme de rééducation mené en milieu hospitalier et encadré par une évaluation clinique et instrumentale. L’évaluation a porté sur une mesure quantitative de l’équilibre par tests cliniques et stabilométriques, de la marche évaluée par le Locomètre ® et de la force des muscles extenseurs et fléchisseurs du genou mesurés en isocinétisme en mode concentrique à 60° par seconde.
Résultats
Après rééducation, on observe une amélioration significative des capacités d’équilibration mesurée par l’échelle de Berg, de la vitesse de marche rapide et de la force musculaire. L’évaluation instrumentale de l’équilibre statique et de la vitesse de marche spontanée ne montre pas de gain après rééducation. Aucune corrélation n’est retrouvée entre les différents gains.
Conclusion
Un programme de rééducation centré sur la force, la marche et l’équilibre a permis une amélioration significative de certains paramètres dans la dystrophie myotonique de Steinert. Ces résultats témoignent de l’intérêt d’une rééducation motrice à court terme chez ces patients dans un contexte de prise en charge multidisciplinaire. La dissociation observée dans les résultats mesurés chez ces patients suggère la contribution d’une participation cognitive aux limitations ressenties par les patients atteints de myopathie de Steinert dans le domaine de la marche et de l’équilibre.
1
English version
1.1
Introduction
Gait and balance disorders are one of the functional consequences of the impairments linked to myotonic dystrophy (Steinert disease). This affection, characterized first of all by progressive muscle atrophy, allows patients to maintain an autonomous gait for some time. However, it is also coupled to limited walking perimeter and gait speed as well as falls contributing to difficulties in social settings.
Among the deficits that promote balance disorders and falls in myotonic dystrophy, we find first of all the muscles and skeletal affections responsible for motor deficits most often distal and axial impairments and loss of extensibility of the two-joint muscles that can limit joint range of movement (ROM). Furthermore, we can find, to varying degrees, decreased visual acuity , cognitive and anxious-depressive disorders , severe fatigue , sensory-motor neuropathy , as well as cardiac arrhythmia and conduction disorders . For some of these disorders, the data have been known for years and justify that beyond a multidisciplinary therapeutic care for these patients, a meticulous evaluation of each patient’s various impairments need to be conducted before proposing a rehabilitation protocol based on clearly defined and accepted objectives.
Even though the gait and balance disorders in myotonic dystrophy are frequently reported in daily clinical practice, they have not been the focus of many studies in the literature and their therapeutic care remains poorly defined. To this day, in the only controlled study focused on this subject , a home self-training program supervised by a physiotherapist did not report any gains in muscle strength parameters for a population of patients affected by myotonic dystrophy. However, more than in other pathologies, the reality of cognitive disorders has a negative impact on rehabilitation training programs that are only supervised at a distance and the association of other disorders suggests that patients could benefit from a more elaborated therapeutic care focused on balance improvement.
The goal of this study was to evaluate in a noncontrolled, open study the impairments of patients with myotonic dystrophy and assess the efficacy of a multidisciplinary rehabilitation care focusing on balance, muscle strength and gait in an outpatient hospital setting.
1.2
Patients and method
1.2.1
Patients
The design of the study was a retrospective analysis of the medical files of 20 patients involved in a rehabilitation training program focused on balance and gait.
The diagnosis of myotonic dystrophy was established or validated by the neurological team of the Reference Center for rare neuromuscular diseases of the Salpêtrière Hospital. First of all, within the framework of the therapeutic care of these adult patients, a clinical and instrumental evaluation was systematically proposed to patients that reported gait instability with falls. Secondly, a balance and gait rehabilitation program conducted in the outpatient unit of our hospital was proposed to patients that accepted the project and its objectives. In addition, to this therapeutic care, several other evaluations were associated: occupation therapy, speech therapy as well as neuropsychological tests in order to define a more specific therapeutic care according to the specific impairments of the patients. To conduct these instrumental functional assessments, the patients needed to be able to walk without any technical aid for more than 10 m and stand still on both feet for 1 min. In this study, were included all patients with myotonic dystrophy who benefited from therapeutic rehabilitation care from 2007 to 2009. The patients excluded were individuals with cardiovascular disorders, contraindication to effort training, or subjects with cognitive disorders that would have limited their active participation in this program.
1.2.2
Evaluation methodology
1.2.2.1
Clinical evaluation
The clinical interview was based on the patient’s self-assessment of his walking perimeter and the frequency of falls during the past year.
Balance was clinically assessed using three scales. The Berg Balance Scale (BBS) consisting of 14 items that are scored on a scale of 0 to 4. Items include mobility tasks such as transfers, standing unsupported in both static and dynamic settings. The Functional Reach Test (FRT) for assessing balance measures the hand movement, arm stretched horizontally, going from a standing position to a bent forward position. The Timed Up and Go (TUG) Test is a measurement of mobility. It includes a number of tasks such as standing from a seating position, walking, turning, stopping, and sitting down which are all important tasks needed for a person to be independently mobile. For the test, the person is asked to stand up from a standard chair and walk a distance of approximately 3 m, turn around and walk back to the chair and sit down again. These three scales are commonly used in neurology daily practice and for fall prevention in elderly .
1.2.2.2
Instrumental evaluations
The objective gait and balance parameters were collected using the same evaluation method our team at previously used to assess the determinants of locomotion in patients with multiple sclerosis with a validated responsiveness to change after a specific rehabilitation program for these patients . In order to avoid any state of fatigue that could trigger biomechanical consequences, the evaluations were performed in an order corresponding to a growing cardiovascular solicitation (first balance, then gait and finally muscle strength) with a 10-minute interval between each test. The total duration of all the different tests was 75 mins, which included rest periods.
1.2.2.2.1
Balance parameters
Evaluating balance in static conditions was done using a stabilometer, a force-measuring platform (Satel, Blagnac, France), that collected the data during a task consisting in maintaining balance for 51 s. The evaluation was done successively with eyes open, eyes closed, on a hard surface then on a 4-cm thick foam surface, for a total of four different experimental settings. The stabilometer force-plate’s surface was kept as a relevant parameter of balance in all the different test settings.
1.2.2.2.2
Gait parameters
The Locometre ® (Satel) designed by Bessou et al. is made for analyzing spatiotemporal parameters during gait. This method is based on the recording of the longitudinal step length of each foot during a predefined walking perimeter. Each foot’s movement is transmitted via an inextensible thread to an optic probe. The thread is kept under tension by an electrical motor sending out a mechanical recall force that is maintained constant by a micro-computer system. After telling the patient to start, he or she has to walk over a 7-meter distance on a flat surface without any obstacles. The parameters that were kept for our study were gait speed, stride frequency and stride length. A first try-out test was performed in order for the patient to get familiar with the setting, and then two measures recordings were done under the following conditions: spontaneous gait speed and fast gait speed.
1.2.2.2.3
Evaluation of muscle strength
Isokinetic muscle strength measurement is one of the tools available for quantifying, in dynamic settings, the objective impairments of neurological pathologies; this tool has already been used for myotonic dystrophy . It has the advantage of having a high responsiveness to change greater than the one obtained with manual testing for moderate impairments (manually quoted at 4 or 5) and showed a correlation to gait parameters contrarily to isometric evaluations. The examination was conducted with the patient sitting on an isokinetic dynamometer Cybex Norm ® , after warming-up; the patient performed a series of five flexion-extension movements at the speed of 60°/s. This slow speed allowed for a better performance of the impaired muscle .
1.2.3
Rehabilitation program
It included 15 rehabilitation sessions spread out over a 6-week period. The therapeutic care was conducted by a multidisciplinary team with two or three sessions per week of physiotherapy and occupational therapy associated to, according to the cases, speech therapy or seeing a psychologist. These sessions were adapted to the fatigability and autonomy of each patient.
Rehabilitation training included stretching exercises for muscle stiffness, balance training, muscle strengthening and endurance training, each session included about 2 hours of individual rehabilitation training.
Balance training was performed both in static and dynamic conditions on a wobble force-plate and in a walking corridor with obstacles in a single task and double tasks situations (carrying a glass full of water and a counting exercise).
The muscle strengthening program focused on muscle training at knee level on an isokinetic dynamometer. The sessions included a succession of five series of 10 contractions against resistance with varying speed from 60 to 180 degrees per second.
Endurance training consisted in walking on a treadmill: a 20-minute session with an adapted speed at 60% of the maximum heart rate (210 – patient’s age).
A specific rehabilitation care for the spinal cord and upper limbs was associated to this muscle training according to the initial evaluation check-up but will not be detailed in this article.
1.3
Statistical analysis
It was based on comparing the values collected during the quantitative measures before and after rehabilitation. Data processing was done with Stat-View software and the repeated measures Anova test using P < 0.05 as a significant threshold. The data collected during the instrumental evaluation on healthy subjects (similar in age and sex) were reported for comparison value.
1.4
Results
1.4.1
Population
The population included 20 subjects, 13 men for seven women; mean age 51 years (ranges 32–69).
1.4.2
Balance
The data collected on the frequency on falls for this population reported a mean rate of 1.5 fall per month (ranges two per week to one per year).
During the initial evaluation, the clinical tests ( Table 1 ) showed a decrease in balance capacities measured by the BBS (44 versus normal value at 56), the FRT (11 cm versus normal value above 25 cm) and the TUG test (12 s versus normal value below 9 s).
| Before | After | Delta | P | F | Norms | |
|---|---|---|---|---|---|---|
| BBS | 44.35 (9.14) | 48.1 (9.76) | 3.75 (3.55) | < 0.001 | 22.28 | 56 |
| FRT (cm) | 11 (8.6) | 15.57 (10) | 4.55 (6.71) | < 0.01 | 9.18 | > 25 |
| TUG (sec) | 12.05 (7.55) | 9.52 (4.03) | 2.52 (4.88) | < 0.05 | 5.09 | < 9 |
Balanced measured on a force platform ( Table 2 ) reported a widening of the stabilogram’s surface with the eyes open at 566 (426) mm 2 , i.e. very much below the normal values in healthy subjects (mean: 91 mm 2 , CI: 39–210 mm 2 ).
| Before | After | Delta | P | F | CTL | |
|---|---|---|---|---|---|---|
| EO hard surface | 566 (426) | 525 (435) | 41 (418) | NS | 0.17 | 155 (60) |
| EC hard surface | 757 (659) | 729 (675) | 28 (432) | NS | 0.025 | 310 (115) |
| EO foam surface | 2286 (1609) | 1847 (2127) | 439 (1243) | NS | 1.84 | 325 (155) |
Recording balance measurements with the eyes closed was only possible for 13 out of the 20 subjects. The mean value for the stabilogram’s surface in these patients EC was 757 mm 2 (mean of healthy subjects: 225 mm 2 , CI: 79–638 mm 2 ).
Balance measurements on the foam surface with the eyes open was only possible in seven subjects and with the eyes closed in one subject.
After rehabilitation, there was a significant balance improvement validated by clinical tests. The mean gain was 3.75 points on the BBS, 4.55 cm on the FRT and 2.5 s on the TUG test. The number of patients that completed the instrumental tests on a hard surface with eyes closed increased from 13 to 15, on the foam surface with the eyes open from seven to 16 and the foam surface with the eyes closed from one to six. Taking into account only patients that were initially able to complete the three tests, no significant change was found for the mean values of the stabilogram’s surface in the various experimental settings.
1.4.3
Locomotion
The patients included in this study used a technical aid in eight upon 20 cases. Their walking perimeter was evaluated at a mean of 1437 m (ranges: 50–6000 m). No significant difference was found after rehabilitation.
Regarding gait parameters ( Table 3 ), we noticed a clear decrease of the spontaneous gait speed with a mean at 2.79 km/h corresponding to a concomitant decrease of the stride frequency and stride length. A decrease of fast gait speed was also reported.
| Before | After | Delta | P | F | CTL | |
|---|---|---|---|---|---|---|
| Slow speed (km/h) | 2.79 (0.75) | 2.88 (0.76) | 0.09 (0.48) | NS | 0.64 | 4.13 (0.83) |
| Stride frequency (/mn) | 98 (12) | 100 (12) | 2 (6) | NS | 1.3 | 112 (17) |
| Stride length (m) | 0.95 (19) | 0.97 (19) | 0.02 (0.1) | NS | 0.38 | 1.14 (0.18) |
| Fast speed (km/h) | 3.84 (1.02) | 4.8 (1.07) | 0.25 (0.48) | < 0.05 | 4.94 | 6.38 (1.29) |
| Stride frequency (/mn) | 110 (15) | 115 (18) | 5 (13) | NS | 3.12 | 139 (14) |
| Stride length (m) | 1.14 (0.22) | 1.14 (0.23) | 0 (0.1) | NS | 0.02 | 150 (0.18) |
After the rehabilitation program, we did not observe any improvement of the spontaneous gait speed parameters but we reported a 6% increase of the fast gait speed (going from 3.84 to 4.08 km/h, P < 0.05), with an increased stride frequency (nonsignificant) without any changes in stride length.
1.4.4
Muscle strength
The analysis of the muscle strength of the knee extensor/flexors in concentric isokinetic training in knee flexion/extension at the speed of 60°/s, (expressed in Newton metre [Nm] took into account the possibility of an asymmetric impairment. Thus, we named Qmax the quadriceps of the stronger limb and Qmin for the weakest one, HMmax the hamstrings of the stronger limb and HMmin for the weakest one.
The measures collected before rehabilitation ( Table 4 ) in these 20 subjects highlighted a decrease of the peak torque in concentric training for these patients’ quadriceps and hamstrings. The ratios HM/Q were 0.67 and 0.68 i.e. a normal value. After strength training, we observed a significant improvement of the peak torque for the quadriceps of the weaker limb (QMin: 9 ± 12 Nm, P < 0.01) and hamstrings (HMMax and HMMin: 12 ± 7 and 11 ± 10 Nm respectively, P < 0.001) without improvement to the quadriceps of the stronger limb. The ratios were respectively 0.85 and 0.86 after training.
| Before | After | Delta | p | F | CTL | |
|---|---|---|---|---|---|---|
| HMMax | 35 (16) | 47 (19) | 12 (7) | < 0.001 | 55 | 101 (28) |
| HMMin | 31 (16) | 41 (22) | 11 (10) | < 0.001 | 20.52 | 89 (27) |
| Qmax | 65 (36) | 68 (37) | 3 (8) | NS | 3 | 167 (55) |
| Qmin | 51 (30) | 60 (35) | 9 (12) | < 0.01 | 9.69 | 146 (51) |
| HM/Qmax | 0.67 (0.42) | 0.88 (0.46) | 0.21 (0.19) | < 0.01 | 10.65 | 0.67 (0.12) |
| HM/Qmin | 0.68 (0.39) | 0.86 (0.59) | 0.18 (0.31) | < 0.05 | 5.11 | 0.58 (0.09) |
1.4.5
Correlations between the different variables
The statistical analysis (Spearman’s rank correlation coefficient) did not unveil any significant correlation between the improvement of the muscle strength parameters and the clinical balance parameters on one hand or the fast gait speed on the other hand.
1.5
Discussion
We present here the first results of a study evaluating the locomotor and posture-locomotion impairments in patients with myotonic dystrophy that are at risk for falls.
Among the results of this study, we should bring up first the strong muscle deficits of the knee stabilizer muscles (quadriceps and hamstrings) associated to an instability measured with a stabilometer and a decrease in gait speed.
We found very few studies in the literature that focused on myotonic dystrophy and balance/postural evaluation and none reported the association of objective parameters of impairment and function in static and dynamic settings. In patients affected by a similar rare disease, myotonia congenita, Baumann et al. did highlight a 30 Nm decrease in peak torque of the quadriceps measured at 60°/s versus a control group, without defining the results on the antagonist muscles. The first objective correlation between deficit and functional impairment in myotonic dystrophy was established by Lindeman et al. by unveiling an influence of the quadriceps deficit (measured on an isokinetic dynamometer at 120°/s) in the decreased performances for completing timed tasks such as going down the stairs and spontaneous gait speed with respectively a coefficient of determination of 0.73 and 0.56.
More recently, Wiles et al. focused on falls in patients with myotonic dystrophy by recording nonstop over a 1-week period the gait parameters of these patients using a portable system. All the intercurrent events occurring during the dynamic activities as well as falls were computed and the results were compared to healthy controls, they revealed a higher rate of falls for these patients for a lesser activity without being able to determine the cause. These results are similar to those found in elderly individuals at risk for falls, in that case the predictive threshold measured by the BBS was at 44 out of 56, close to the mean value of our series .
The second part of the results focused on the improved impairments for patients involved in our rehabilitation protocol.
Due to the lack of knowledge regarding the pathophysiology of falls for these patients, there is no validated protocol for instability therapeutic care but some authors did look at training programs without fatigue and reported contradictory results. In fact, if several teams validated the efficacy of a submaximal muscle strengthening program , Lindeman et al. reported no gains for a muscle strengthening program of the lower limbs on a 24-week period in the only controlled, randomized study on 33 patients, for the analytical validation criterion (peak torque of the quadriceps and hamstrings in isokinetic, isometric contraction time) or the functional validation criterion (walking up the stairs test). However, none of these studies has evaluated the probable need of functional training for strengthening the action of all the structures not impaired by the disease and that are involved in balance management. Only Orngreen et al. report the usefulness of aerobic training. In fact, after 12 weeks of daily exercises on a stationary bike (ergometer), the authors highlighted, in 12 patients an improvement of cardiorespiratory endurance ( <SPAN role=presentation tabIndex=0 id=MathJax-Element-1-Frame class=MathJax style="POSITION: relative" data-mathml='VO2max’>VO2maxVO2max
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) and quality of life (Short Form 36 (SF36) questionnaire) without raising muscle enzymes. The authors however reported the lack of long-term compliance for this type of treatment.
In our study, we report a homogeneous improvement of balance management clinical tests, increased fast gait speed as well as muscle strength expect for quadriceps evaluated on the strongest limb.
The improvement reported in muscle strength test is contradictory to the results reported by Lindeman et al. in spite of close initial values measured on the quadriceps and hamstrings. The increased muscle strength in our study seems to be correlated to two factors. First, in our study, the patient takes part in rehabilitation program with the presence of a physiotherapist versus a self-rehabilitation program supervised from afar. The severity of cognitive disorders in patients with myotonic dystrophy makes it difficult to follow these patients and ensure their compliance with the treatment as it was underlined by Orngreen et al. . A repeated solicitation by the physiotherapist was necessary all along this therapeutic care program for patients that were selected based on their will to move around and to be involved in this rehabilitation program. The choice of a highly motivated population might also explain this result as well as a dynamic rehabilitation with biofeedback in real time, made possible by isokinetic tool, allowing the patient to stay motivated during the entire program looking at the results’ evolution.
The improved balance management capacity is clearly highlighted by a homogeneous result in the clinical tests and an increased feasibility of the most complex instrumental tests. According to the wide array of the results obtained with instrumental tests, the improvement of the balance management capacities does not reach a significant value and cannot be recommended as an evaluation criterion in this pathology. By contrast, it is important to note the major involvement of sensory inputs in managing balance for persons with myotonic dystrophy; this had not been reported before. After the rehabilitation program, the increase in balance management capacities with the eyes closed or on a foam surface shows clearly a decreased need for visual and proprioceptive afferents, some patients becoming able to find their balance on a foam surface which is validated as one of the most relevant test for assessing the risk of falls .
According to our results, the improvement in fast gait speed corresponds to a tendency in increased velocity without any increase in step length. It might be the consequence of the improved balance during gait; the patients describe a sensation of being more stable in dynamic conditions. The endurance training program in our protocol is probably insufficient to improve the walking perimeter which did not show any changes at the end of our therapeutic care.
For myotonic dystrophy, the biomechanical aspect of falls is still based on many different and not yet validated pathophysiological elements that some patients describe during the medical consultation. Thus, they frequently report hitting an obstacle with one foot and to a lesser degree falling down from their own height. These two clinical pictures bring up respectively a deficit of the foot flexors associated, in varying degrees, to a stiffness of the triceps surae limiting ankle dorsiflexion and a deficit in active knee locking due to impaired quadriceps. However, our study does not bring any new argument for establishing a correlation between the improvement of balance and gait disorders and gain in muscle strength, thus suggesting other hypotheses.
If these elements seem to be mostly responsible for balance disorders and falls, other biomechanical and pathophysiological hypotheses can be looked at. Most falls occur in dynamic conditions, myotonia can promote some of these episodes by having a negative impact on antagonist muscle groups involved in the key active elements for walking, creating a “locking” situation. Unfortunately, we do not have a specific tool for evaluating, in dynamic condition, myotonia on the lower limbs to back up this hypothesis.
The association of cognitive disorders, even intense fatigue, which according to Kalkman et al. affects 75% of these patients, can also have an impact on the patients’ attention and gait quality. This could explain that apart from analytical muscle strengthening and the work done on improving balance management capacities requiring multiple sensory compensatory mechanisms, the rehabilitation program proposed to our patients can contribute to improving their condition simply by having a better knowledge of their impairments and accessing a more adapted therapeutic care of the compensatory mechanisms. Some of these patients, at first during the initial phase had a difficult time acknowledging their impairments; some were even denying having any. A recent study underlined an improvement of the balance disorders after a simple evaluation outside any rehabilitation care , showing the importance of cognitive phenomena in this area. A regular multidisciplinary care of these patients seems to be the key to improving the parameters that we evaluated in this study.
Nevertheless, beyond the positive results of this study, several questions still need to be addressed. If the tests used in our protocol report a significant improvement of some parameters, their clinical relevance still needs to be validated. In fact, a clinically significant threshold for gains in muscle strength, balance and gait still has to be defined for this population. Furthermore, the functional future of these patients remains uncertain. Besides the natural progression of the disease, the transposition of the results in the patients’ daily life and maintaining the benefits of the rehabilitation program would require a controlled study including an ecological evaluation of gait and balance capacities in a home setting. Taking these neuropsychological factors into account should shed some light on the mechanisms involved in balance and gait disorders for these patients.
1.6
Conclusion
This study describes the relevance of measuring posture-locomotion deficits in patients with myotonic dystrophy and brings, for the first time, some arguments in favor of the positive impact of a rehabilitation protocol for gait and balance.
These results were only acquired for a selected population after an intensive rehabilitation program conducted within a hospital setting and the results were evaluated on the short-term.
The disparity between muscle strength gains and balance management and gait capacities shows the complex nature of this rehabilitation and brings up questions on the pathophysiology of the disorders observed in persons with myotonic dystrophy.
If these results will lead us to reassess our recommendation regarding rehabilitation for muscular dystrophy, they need to be validated by a controlled study defining clinically relevant thresholds and following these patients by monitoring the relevance of this therapeutic care as well its impact on their quality of life.
Conflicts of interest statement
The author has no conflict of interest.
Acknowledgments
We would like to thank the neurology team of the Reference Center for rare neuromuscular diseases of the Salpêtrière Hospital (especially Prof. Eymard and Dr. Laforet) for trusting us with the therapeutic care of their patients, as well as the physiotherapy team (X. Lobet, D. Delorme, P. Stephan) who helped with the design and participated in this rehabilitation program.
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