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Quantitative magnetic resonance imaging (qMRI) outcome measures such as muscle fat fraction (FF) and contractile cross-sectional area (cCSA), reflecting disease progression, and water T2, reflecting disease activity (inflammation, edema), are used in the longitudinal studies of neuromuscular diseases, including inclusion body myositis (IBM). Here, we report qMRI results from the RAPAMI study (NCT02481453), obtained at 3 Tesla in the muscle of 45 patients (rapamycine vs. placebo) at baseline and year-1. Values for FF, cCSA and water T2 values were calculated in anterior and posterior (triceps surae) leg and anterior (quadriceps) and posterior (hamstring) thigh muscle groups. Functional assessments included the six-minute walking distance (6MWD). Student's t-tests and Pearson correlation analyses were performed (P<0.05). Standardized response means (SRM) values were calculated to assess the sensitivity to change for the different MRI outcome measures. No differences in demographic data existed between rapamycine and placebo groups (P>0.20). Overall, patients (20 female, 23 male) were 66±8 years old and had symptoms for 8±5 years. There was a significant left-right difference for FF and cCSA (P<0.001) but not for water T2 (P=0.89). Values of FF and cCSA at baseline were not significantly different between both patient groups for anterior and posterior leg and thigh muscle groups (P>0.11). FF increase after one year was significantly lower in the rapamycine group for the posterior (P<0.027) but not for the anterior muscle group (P>0.08). The one-year decrease in anterior thigh cCSA was slightly significantly higher in the placebo group (P=0.045). The SRM values for FF and cCSA changes were systematically higher in the placebo group with SRM>0.8 for FF in triceps surae and quadriceps and SRM>0.8 for cCSA in hamstring, only in the rapamycine group. Water T2 was significantly elevated in leg and anterior thigh muscle compared to control values (≈39ms) and a moderately strong relation between baseline water T2 and the FF change was observed in posterior thigh (R2=0.57, overall patients). The increase in anterior thigh FF associated with a decrease in 6MWD was particularly observed in the placebo group (R2=0.30). qMRI has demonstrated that small yet significant changes can be measured between non-treated and treated IBM patients, within specific muscle groups, and correlates to function measures. [ABSTRACT FROM AUTHOR]

Introduction Les choix thérapeutiques des cliniciens reposent sur l’évaluation de l’activité des pathologies. Concernant les myopathies auto-immunes, l’évaluation repose principalement sur le testing musculaire manuel et sur le taux de créatine kinase (CK), mais elle reste très imparfaite. Si le taux d’enzymes musculaires est une mesure biologique fiable et reproductible, sa sensibilité pour mesurer l’activité de la maladie est moyenne (surtout pour les dermatomyosites). Quant à l’évaluation clinique de la force musculaire, elle manque non seulement de sensibilité mais aussi de reproductibilité. Enfin, aucune de ces mesures ne reflète le retentissement fonctionnel de ces maladies handicapantes. L’accéléromètre (porté en bracelet) offre l’opportunité de mesurer de manière objective l’activité physique des patients en condition de vie réelle et de manière objective. Dans cette étude pilote, nous avons testé l’accéléromètre portatif (bracelet) comme outil d’évaluation des myosites. Patients et méthodes Cinq patients ayant une myopathie auto-immune ont été inclus au moment du diagnostic. L’accèléromètre a été porté par ces 5 patients en continu (24 h/24 h), 14 jours/mois, au cours des 6 premiers mois suivants l’initiation du traitement. Les valeurs vectorielles d’accélération (en mg) dans les trois axes de l’espace ont permis de calculer la norme euclidienne, représentant l’activité physique globale de chaque patient (mg/j). Ces résultats ont été comparés au score du testing manuel (score sur 150), au taux de CK, et à la valeur du score de qualité de vie SF-36. Les valeurs d’accélèromètrie ont également été comparées à celles d’une population saine témoin appariée sur l’âge et sur le sexe. Résultats L’âge moyen des patients (dermatomyosite : n = 1 ; myopathie nécrosante auto-immune n = 3 ; syndrome des anti-synthétases ; n = 1) était de 47,7 ans. Le score moyen du testing musculaire était de 117/150 [104–135] avec un taux sérique moyen de CK de 3689 UI/L [1375–6366 IU/L] et un score SF36 moyen de 31,6 [19–36]. Au diagnostic (M0), l’activité physique globale moyenne était à 104,2 ± 15 mg/j soit à 52 ± 17 % de celle de la population témoin. À M6, on observait une augmentation de 40,4 % de la valeur moyenne d’activité physique alors que le score de force musculaire n’augmentait que de 17 %. À M6, les valeurs d’activité physique étaient à nouveau dans la norme. De même, à M6 tous les patients avaient un taux de CK normalisé. Mais alors que le taux de CK s’était déjà normalisé à M4, l’activité physique continuait à progresser entre M4 et M6. Entre M0 et M6, le score de qualité de vie s’est également amélioré, et de manière parallèle à l’activité physique. Ces valeurs sont positivement corrélées ( r = 0,48, p < 0,01). Conclusion Cette étude pilote montre l’intérêt d’évaluer l’activité physique quotidienne des patients par accéléromètre pour obtenir une mesure objective de l’activité des myopathies inflammatoires sans effet seuil. Une étude de plus grande ampleur devra confirmer ces données. [ABSTRACT FROM AUTHOR]

Abstract Background Greater diaphragm fatigue has been reported after hypoxic versus normoxic exercise, but whether this is due to increased ventilation and therefore work of breathing or reduced blood oxygenation per se remains unclear. Hence, we assessed the effect of different blood oxygenation level on isolated hyperpnoea-induced inspiratory and expiratory muscle fatigue. Methods Twelve healthy males performed three 15-min isocapnic hyperpnoea tests (85% of maximum voluntary ventilation with controlled breathing pattern) in normoxic, hypoxic (SpO2 = 80%) and hyperoxic (FiO2 = 0.60) conditions, in a random order. Before, immediately after and 30 min after hyperpnoea, transdiaphragmatic pressure (Pdi,tw ) was measured during cervical magnetic stimulation to assess diaphragm contractility, and gastric pressure (Pga,tw ) was measured during thoracic magnetic stimulation to assess abdominal muscle contractility. Two-way analysis of variance (time x condition) was used to compare hyperpnoea-induced respiratory muscle fatigue between conditions. Results Hypoxia enhanced hyperpnoea-induced Pdi,tw and Pga,tw reductions both immediately after hyperpnoea (Pdi,tw : normoxia -22 ± 7% vs hypoxia -34 ± 8% vs hyperoxia -21 ± 8%; Pga,tw : normoxia -17 ± 7% vs hypoxia -26 ± 10% vs hyperoxia -16 ± 11%; all P < 0.05) and after 30 min of recovery (Pdi,tw : normoxia -10 ± 7% vs hypoxia -16 ± 8% vs hyperoxia -8 ± 7%; Pga,tw : normoxia -13 ± 6% vs hypoxia -21 ± 9% vs hyperoxia -12 ± 12%; all P < 0.05). No significant difference in Pdi,tw or Pga,tw reductions was observed between normoxic and hyperoxic conditions. Also, heart rate and blood lactate concentration during hyperpnoea were higher in hypoxia compared to normoxia and hyperoxia. Conclusions These results demonstrate that hypoxia exacerbates both diaphragm and abdominal muscle fatigability. These results emphasize the potential role of respiratory muscle fatigue in exercise performance limitation under conditions coupling increased work of breathing and reduced O2 transport as during exercise in altitude or in hypoxemic patients.

Neuromuscular disorders (NMD) are characterized by progressive muscle weakness leading to dramatic impairments in functional capacities and quality of life. A new class of promising lightweight lower-limb wearable powered exoskeletons is currently emerging. However, data regarding the potential of such devices in patients with NMD are scarce. Within this work, we investigated the potential of the MyoSuit (MyoSwiss AG, Zurich, Switzerland), a lightweight wearable robotic device providing assistance for hip and knee extension against gravity using actuated cables. Four patients with NMD (2 with muscular dystrophies, 2 with inclusion body myositis) were studied. Without using the MyoSuit, 2-min walking distance (2MWD) was 128±30 m (66±17% of predicted values), number of repetitions during a 30-s sit-to-stand test (30s-STS) was 8±3, and MRC scores for knee extension and hip flexion were 3±1.1 and 3.9±0.6, respectively. Changes (n patients improved/impaired) in performance while using the MyoSuit during the following tests were as follows: 2MWD (1/3), 30-STS (1/3), TUG (0/4), 4-stairs climbing test (1/3). Regarding perceptions during the 2MWD as assessed using visual analogue scales, changes were: stability (0/4), exertion (2/2), and dyspnea (3/1). One fall occurred in one patient while wearing the device without consequences. Usability of the Myosuit as assessed using the system usability scale (/100) was 77±20, corresponding to good to excellent usability. Discomfort as assessed using the modified Nordic questionnaire (/10) was 1.0±0.5, corresponding to a low level of discomfort. The limited sample size limits the use of insightful statistics so far. Within this small group of patients, the use of the MyoSuit was associated with variable changes in performance and perceptions depending on the functional test. Further research in a larger sample is warranted to further investigate the potential of this device in patients with NMD. [ABSTRACT FROM AUTHOR]

Neuromuscular disorders (NMD) are characterized by progressive muscle weakness leading to dramatic impairments in functional capacities and quality of life. A new class of promising lightweight lower-limb wearable powered exoskeletons is currently emerging. However, data regarding the potential of such devices in patients with NMD are scarce. Within this work, we investigated the potential of the Keeogo+ (B-Temia Inc., Quebec, Canada), a lightweight wearable exoskeleton providing assistance to the knee using compact motors. Five patients with NMD (4 with inclusion body myositis, 1 with Becker muscular dystrophy) were studied. Without using the Keeogo+, 2-min walking distance (2MWD) was 126±31 m (67±17% of predicted values), number of repetitions during a 30-s sit-to-stand test (30s-STS) was 6±3, and MRC score for knee extension and hip flexion was 2.7±0.6 and 3.4±0.9, respectively. Changes (n patients improved/ impaired) in performance while using the Keeogo+ during the following tests were as follows: 2MWD (0/4), 30-STS (2/3), TUG (0/5), 4-stairs climbing test (1/3). Regarding perceptions during the 2MWD as assessed using visual analogue scales, changes were: stability (2/2), exertion (1/3), and dyspnea (4/0). No fall occurred while wearing the device. Usability of the Keeogo+ as assessed using the system usability scale (/100) was 41±23.2, corresponding to good to excellent usability. Discomfort as assessed using the modified Nordic questionnaire (/10) was 1.8±0.9, corresponding to a low level of discomfort. The limited sample size limits the use of insightful statistics. Within this small group of patients, the use of the Keeogo+ was associated with variable changes in performance and perceptions depending on the functional test. Further research in a larger sample is warranted to further investigate the potential of this device in patients with NMD. [ABSTRACT FROM AUTHOR]