Effets de la majoration du déficit moteur du quadriceps, induite expérimentalement, sur la locomotion des patients hémiparétiques

The main objective of this thesis was to study the effects of experimentally increasing quadriceps motor impairment on the locomotor capacity of hemiparetic stroke patients, with stiff-knee gait. The second objective was to investigate the relationship between fatigue and overactivity of the quadriceps muscle in these patients. Four studies were carried out. Study 1 was carried out to verify our methodology, and it evaluated spatiotemporal and kinematic changes which occur, in hemiparetic patients, during a gait analysis session (GA). The results suggest that at the beginning of the GA session, stroke patients exhibited phase of adaptation, characterized by a ''cautious gait'', but no fatigue was observed at the end. Thus, evaluation of the effects of experimentally increasing quadriceps motor impairment, following a fatigue protocol, on the biomechanical gait parameters of hemiparetic stroke patients can be carried out with GA. In studies 2 and 3, patients' gait was assessed before and after an experimental increase in the motor impairment of the quadriceps using two methods: pharmacological, using botulinum toxin type-A injection (BoNT -A) in the hyperactive rectus femoris (RF) (study 2) and following a fatigue protocol involving repeated contractions of the knee extensors, with an isokinetic dynamometer (study 3). Finally, in study 4, the effect of quadriceps fatigue on the characteristics of muscle spasticity was evaluated using an isokinetic dynamometer. Surprisingly, the results showed that increasing the motor impairment of one part of, or the whole quadriceps muscle, induced the same improvements in biomechanical gait parameters (spatiotemporal, kinematic and EMG), whatever the method used (after injection of BoNT-A or after fatigue). Gait velocity increased, along with peak hip and knee flexion during the swing phase, and inappropriate activity of the RF during the pre-swing and swing phases decreased. The reduction of the mechanical restriction, due to the decrease in inappropriate muscle activity appeared to be associated with a compensatory reorganization of the gait pattern in order to counteract the negative effects of the increased motor impairment of the quadriceps. In addition, although muscle fatigue reduced inappropriate activity of the RF muscle during the semi-automatic task of walking, the characteristics of the stretch reflex were not altered during passive stretching, evaluated with an isokinetic dynamometer. Disruption of the fusimotor system during the fatigue protocols may only have changed the excitability of muscle spindles in dynamic conditions (during walking). In view of all these results, it seems likely that patients' complaints of feeling more spastic and vulnerable in situations in which their quadriceps motor impairment is increased, is the result of greater neural activity of central origin and/or a "real" increase in spasticity, but which occurs in other muscles such as the ankle plantarflexors.L'objectif principal de ce travail de thèse était d'étudier les effets de la majoration du déficit moteur focal du quadriceps, sur les capacités locomotrices de patients hémiparétiques, présentant un genou raide à la marche, communément appelé stiff-knee gait. L'objectif secondaire était d'investiguer les relations entre la fatigue et l'hyperactivité musculaire du quadriceps, chez ces patients. Quatre études ont été menées. La première étude de ce travail a permis de mettre en évidence qu'au début d'une session d'AQM, le pattern de marche des patients hémiparétiques est influencé par une phase d'adaptation, caracterisée par une " marche prudente ", mais que le phénomène de fatigue n'est pas présent en fin d'examen. L'évaluation des effets de la majoration du déficit moteur du quadriceps, suite à un protocole de fatigue, sur les paramètres biomécaniques de la marche des patients hémiparétiques, peut donc être réalisée au moyen de l'AQM sans biais méthodologique. Ainsi, dans les études 2 et 3, la locomotion des patients a été évaluée avant et après une majoration du déficit moteur du quadriceps, induite expérimentalement par deux méthodes: soit pharmaco-induite par l'injection de toxine botulique de type-A (BoNT-A) dans le rectus femoris (RF) hyperactif (étude 2), soit résultante de la contraction répétée des extenseurs de genou, jusqu'à l'apparition de fatigue, par le biais d'un dynamomètre isocinétique (étude 3). Enfin dans l'étude 4, l'effet de la fatigue du quadriceps sur les caractéristiques de la spasticité a été évalué par le biais d'un dynamomètre isocinétique. De manière surprenante, les résultats montrent que la majoration du déficit moteur, d'une partie ou de toute partie du muscle quadriceps, induit des améliorations identiques sur les paramètres biomécaniques de la marche (spatiotemporels, cinématiques et EMG), quelle que soit la méthode utilisée (après injection de BoNT-A ou après fatigue). Une augmentation de la vitesse de marche, une augmentation de la flexion maximale de la hanche et du genou lors de la phase oscillante, ainsi qu'une réduction de l'activité inappropriée du RF, lors des phases pré-oscillante et oscillantes sont conjointement reportées. La réduction des freins mécaniques, liée à la baisse de l'activité musculaire inappropriée, semble être associée à une réorganisation compensatrice du pattern de marche, mise en place afin de contrer les effets néfastes de la majoration du déficit moteur du quadriceps et à l'origine de ces améliorations. De plus, alors que la fatigue musculaire réduit l'activité inappropriée du muscle RF, au cours d'une tache semi-automatique représentée par la marche, ses caractéristiques ne sont pas modifiées, au cours d'un étirement passif, évaluées par le biais d'un dynamomètre isocinétique. Au cours des protocoles de fatigue, la perturbation du système fusimoteur peut avoir modifiée l'excitabilité des fuseaux neuromusculaires, uniquement lors de sa sollicitation en condition dynamique (à la marche). Au regard de l'ensemble de ces résultats, il semble probable que, dans le contexte clinique, la plainte des patients de se sentir plus spastiques et plus vulnérables, en situation de majoration de leur déficit moteur du quadriceps, soit attribuée à une plus grande activité nerveuse d'origine centrale et/ou à une augmentation " effective " de la spasticité, mais présente au niveau d'autres muscles, comme les fléchisseurs plantaires de cheville

Return to Employment After Stroke in Young Adults: How Important Is the Speed and Energy Cost of Walking?

Background and Purpose- A quarter of individuals who experience a stroke are under the age of 65 years (defined as young adults), and up to 44% will be unable to return to work poststroke, predominantly because of walking difficulties. No research study has comprehensively analyzed walking performance in young adult's poststroke. The primary aim of this study is to investigate how a stroke in young adults affects walking performance (eg, walking speed and metabolic cost) compared with healthy age-matched controls. The secondary aim is to determine the predictive ability of walking performance parameters for return to employment poststroke. Methods- Forty-six individuals (18-40 years: n=6, 41-54 years: n=21, 55-65 years: n=19) who have had a stroke and 15 healthy age-matched able-bodied controls were recruited from 6 hospital sites in Wales, United Kingdom. Type, location, cause of stroke, and demographic factors (eg, employment status) were recorded. Temporal and spatial walking parameters were measured using 3-dimensional gait analysis. Metabolic energy expenditure and metabolic cost of walking were captured during 3 minutes of walking at self-selected speed from measurements of oxygen consumption. Results- Stroke participants walked slower (P<0.004) and less efficiently (P<0.002) than the controls. Only 23% of stroke participants returned to employment poststroke. Walking speed was the strongest predictor (sensitivity, 0.90; specificity, 0.82) for return to work (P=0.004) with a threshold of 0.93 m/s identified: individuals able to walk faster than 0.93 m/s were significantly more likely to return to work poststroke than those who walked slower than this threshold. Conclusions- This study is the first to capture walking performance parameters of young adults who have had a stroke and identifies slower and less efficient walking. Walking speed emerged as the strongest predictor for return to employment. It is recommended that walking speed be used as a simple but sensitive clinical indicator of functional performance to guide rehabilitation and inform readiness for return to work poststroke

Detecting unilateral phrenic paralysis by acoustic respiratory analysis

The consequences of phrenic nerve paralysis vary from a considerable reduction in respiratory function to an apparently normal state. Acoustic analysis of lung sound intensity (LSI) could be an indirect non-invasive measurement of respiratory muscle function, comparing activity on the two sides of the thoracic cage. Lung sounds and airflow were recorded in ten males with unilateral phrenic paralysis and ten healthy subjects (5 men/5 women), during progressive increasing airflow maneuvers. Subjects were in sitting position and two acoustic sensors were placed on their back, on the left and right sides. LSI was determined from 1.2 to 2.4 L/s between 70 and 2000 Hz. LSI was significantly greater on the normal (19.3±4.0 dB) than the affected (5.7±3.5 dB) side in all patients (p = 0.0002), differences ranging from 9.9 to 21.3 dB (13.5±3.5 dB). In the healthy subjects, the LSI was similar on both left (15.1±6.3 dB) and right (17.4±5.7 dB) sides (p = 0.2730), differences ranging from 0.4 to 4.6 dB (2.3±1.6 dB). There was a positive linear relationship between the LSI and the airflow, with clear differences between the slope of patients (about 5 dB/L/s) and healthy subjects (about 10 dB/L/s). Furthermore, the LSI from the affected side of patients was close to the background noise level, at low airflows. As the airflow increases, the LSI from the affected side did also increase, but never reached the levels seen in healthy subjects. Moreover, the difference in LSI between healthy and paralyzed sides was higher in patients with lower FEV1 (%). The acoustic analysis of LSI is a relevant non-invasive technique to assess respiratory function. This method could reinforce the reliability of the diagnosis of unilateral phrenic paralysis, as well as the monitoring of these patients.Peer ReviewedPostprint (published version

Testing Gait with Ankle-Foot Orthoses in Children with Cerebral Palsy by Using Functional Mixed-Effects Analysis of Variance

Dr Morrissey is part funded by the NIHR/HEE Senior Clinical Lecturer scheme. Tis report presents independent research part-funded by the National Institute for Health Research (NIHR) CAT SCL-2013-04-00

Orthotic management of instability of the knee related to neuromuscular and central nervous system disorders: systematic review, qualitative study, survey and costing analysis

Background Patients who have knee instability that is associated with neuromuscular disease (NMD) and central nervous system (CNS) conditions can be treated using orthoses, such as knee–ankle–foot orthoses (KAFOs). Objectives To assess existing evidence on the effectiveness of orthoses; patient perspectives; types of orthotic devices prescribed in the UK NHS; and associated costs. Methods Qualitative study of views of orthoses users – a qualitative in-depth interview study was undertaken. Data were analysed for thematic content. A coding scheme was developed and an inductive approach was used to identify themes. Systematic review – 18 databases were searched up to November 2014: MEDLINE, MEDLINE In-Process & Other Non-Indexed Citations, Cumulative Index to Nursing and Allied Health, EMBASE, PASCAL, Scopus, Science Citation Index, BIOSIS Previews, Physiotherapy Evidence Database, Recal Legacy, Cochrane Database of Systematic Reviews, Database of Abstracts of Reviews of Effects, Health Technology Assessment database, Cochrane Central Register of Controlled Trials, Conference Proceedings Citation Index: Science, Health Management Consortium, ClinicalTrials.gov, International Clinical Trials Registry Platform and National Technical Information Service. Studies of adults using an orthosis for instability of the knee related to NMD or a CNS disorder were included. Data were extracted and quality was assessed by two researchers. Narrative synthesis was undertaken. Survey and costing analysis – a web survey of orthotists, physiotherapists and rehabilitation medicine physicians was undertaken. Telephone interviews with orthotists informed a costing analysis. Results Qualitative study – a total of 24 people participated. Potential for engagement in daily activities was of vital importance to patients; the extent to which their device enabled this was the yardstick by which it was measured. Patients’ prime desired outcome was a reduction in pain, falls or trips, with improved balance and stability. Effectiveness, reliability, comfort and durability were the most valued features of orthoses. Many expressed frustration with perceived deficiencies in service provision relating to appointment and administrative systems and referral pathways. Systematic review – a total of 21 studies (478 participants) were included of people who had post-polio syndrome, inclusion body myositis, were post stroke or had spinal cord injury. The studies evaluated KAFOs (mainly carbon fibre), stance control KAFO and hip KAFOs. All of the studies were at risk of bias and, in general, were poorly reported. Survey and costing analysis – in total, 238 health-care professionals responded. A range of orthoses is prescribed for knee instability that is related to NMD or CNS conditions, approximately half being custom-made. At least 50% of respondents thought that comfort and confidence in mobility were extremely important treatment outcomes. The cost of individual KAFOs was highly variable, ranging from £73 to £3553. Conclusions Various types of orthoses are used in the NHS to manage patients with NMD/CNS conditions and knee instability, both custom-made and prefabricated, of variable cost. Evidence on the effectiveness of the orthoses is limited, especially in relation to the outcomes that are important to orthoses users. Limitations The population included was broad, limiting any in-depth consideration of specific conditions. The response rate to the survey was low, and the costing analysis was based on some assumptions that may not reflect the true costs of providing KAFOs. Future work Future work should include high-quality research on the effectiveness and cost-effectiveness of orthoses; development of a core set of outcome measures; further exploration of the views and experiences of patients; and the best models of service delivery. Study registration This study is registered as PROSPERO CRD42014010180. The qualitative study is registered as Current Controlled Trials ISRCTN65240228. Funding The National Institute for Health Research Health Technology Assessment programme

Nanooptique avec des électrons rapides : métamatériaux, formulation modale de la EMLDOS pour des systèmes plasmoniques

In the experimental part, I studied four split-ring resonators (SRRs) with sizes and shapes slightly different lithographed by a technique compatible with an EELS study. The EELS experiments allowed me to detect the first surface plasmon eigenmodes (SPs) of these SRRs in the vis-NIR spectral range. The numerical calculations also showed that the spatial distribution of SPs in the SRRs is similar to that of a plasmonic standing wave of a nanoantenna with same cross section and same length, while it is not the case for the electric field. More, compared to a nanoantenna, the coupling between the two legs of the SRR introduced a different energy spacing between the different modes taken successively, while the energy spacing between the symmetric modes in charge on the one hand and the antisymmetric modes on the other hand can still be maintained in a SRR. In the theoretical part, I introduced a new type of quasistatic eigenmodes, called geometrical eigenmodes which are independent of the energy and the nature of the underlying media, but which depend only on the geometry of the particle studied. These modes allowed me to obtain, for the first time, an universal expression of the electromagnetic local density of states (EMLDOS) for a plasmonic system and to clarify the quantities which are measured in EELS and SNOM experiments. Finally, a density of states for the geometrical eigenmodes depending only on the shape of the particle has been introduced, by analogy with the "standard" EMLDOS for the photonic eigenmodes.Dans la partie expérimentale, j'ai étudié quatre split-ring resonators (SRRs) de tailles et de formes légèrement différentes fabriqués par une technique de lithographie électronique adaptée à une étude EELS. Les expériences EELS m'ont permis de détecter les premiers modes propres plasmons de surface (SPs) de ces SRRs dans le domaine du visible et du proche infra-rouge. Les simulations numériques ont par ailleurs montré que la distribution spatiale des SPs dans les SRRs est similaire à celle d'une onde stationnaire plasmonique d'une nanoantenne de même section et de même longueur, alors que ce n'est pas le cas pour le champ électrique. De plus, par rapport à une nanoantenne, le couplage entre les deux pattes du SRR introduit un espacement en énergie différent entre les modes pris successivement, alors que la séparation en énergie entre les modes symétriques en charge d'une part et les modes antisymétriques d'autre part peut encore être maintenue dans un SRR. Dans la partie théorique, j'ai introduit un nouveau type de modes propres quasistatiques, appelés modes propres géométriques qui sont indépendants de l'énergie et de la nature des milieux mis en jeu mais qui dépendent seulement de la forme de la particule étudiée. Ces modes propres m'ont permis d'obtenir, pour la première fois, une expression universelle de la densité locale d'états électromagnétiques (EMLDOS) pour un système plasmonique et de préciser les quantités qui sont mesurées dans les expériences EELS et SNOM. Finalement, une densité d'états pour les modes propres géométriques ne dépendant que de la forme de la particule a été introduite, par analogie avec la EMLDOS "standard" pour les modes propres d'énergie