Dynamics of lower limb & standing balance recovery early post-stroke : measurement, mechanisms and treatment
Stroke is one of the main causes of serious adult disability in Europe. Approximately 80% of people after a stroke suffer from motor impairments, typically affecting unilateral motor control of the face, arm, and leg; this condition is referred to as hemiplegia. These impairments cause poor execution of balance control with a resultant elevated risk of falls. Therefore, improving balance control is a cornerstone of stroke rehabilitation when aiming to improve activities of daily life and enable home discharge. Most patients show spontaneous motor recovery of the hemiplegic leg in the initial weeks post-stroke, measured with, for example, the Fugl-Meyer (FM-LE) and the Motricity Index lower extremity subscale (MI-LE). Unfortunately, how these unilateral motor improvements contribute to recovery in balance control during complex tasks as standing has not been thoroughly investigated. To this end, it is crucial to acknowledge that task improvements may be compensatory by relying on the less-affected limb, as typically observed in this population. Improving our knowledge of behavioural recovery mechanisms after stroke requires well-designed longitudinal studies with instrumented measurements. For example, center of pressure (COP) movements may serve as a biomechanical measure of individual limb contributions to standing balance, called the dynamic control asymmetry (DCA). These measures may overcome limitations of traditional clinical outcomes, such as the Berg Balance Scale, which cannot distinguish re-emergence of more “normal” movement patterns – a process called behavioural restitution – from compensatory strategies. Hence, kinematics and kinetics applied serially in time are the only way to capture quality of movement (QoM) during tasks, and changes therein due to motor recovery or an intervention. This thesis describes the design of an observational study, the TARGEt-1 trial, which unravels the finer-grained changes in balance performance early post-stroke. We chose a quiet standing task with relatively low functional demands to start measurements as early as 3 weeks post-stroke and relate subsequent performance changes to ongoing motor recovery (FM-LE and MI-LE) at 5-, 8-, and 12-weeks post-stroke follow-up. In total, 60 first-ever stroke survivors participated in TARGEt-1, of which 48 were tested on sufficient occasions to be included in the analyses. Consistent with the literature, we found significant FM-LE and MI-LE improvements post-stroke, which were most pronounced in the first 5-8 weeks. During the same period, patients exhibited improvements in their postural stability while standing. However, when observed within subjects, reductions in intralimb motor impairments were not significantly associated with improved postural stability, or with changes in DCA and weight-bearing asymmetry (WBA). In fact, DCA and WBA were quite invariant for change and remained significantly different from normative symmetry scores. Hence, QoM did not normalize, and behavioural restitution of motor functions in the hemiplegic limb appears to hardly contribute to balance improvements. Rather, early balance improvements post-stroke seem to reflect optimizing compensations with the less-affected limb. The innate ability of the brain to undergo plastic changes raises the question of how to capitalize on an enhanced state of brain plasticity early post-stroke. Clinical evidence emphasizes the amount of task practice to improve daily activities. Likewise, a literature review with meta-analyses (15 studies, 915 subjects) described in this thesis found that starting higher training intensities within the first month post-stroke – the critical period for motor recovery – is safe and likely important for promoting walking independence. This may involve the use of therapeutic robots that enable training in patients when otherwise not feasible. A subsequent pilot rehabilitation study, the TARGEt-2 trial, involved 19 stroke patients. Here, we hypothesized that restorative effects of additional training with a wearable exoskeleton – a bilateral robotic orthosis that steers the lower limb in symmetric patterns – are enhanced if delivered within the first 5 weeks post-stroke, when compared with a delayed delivery 8 weeks post-stroke. However, our findings suggest that robotic exercises were generally ineffective in enhancing FM-LE scores beyond spontaneous recovery. Therefore, we were unable to reduce compensations with the less-affected leg, even if robotic training was applied during the critical recovery period. In this thesis, we suggest that current robotic designs that focus on “correcting” kinematics to mimic trajectories as seen in healthy controls are inadequate. After all, the enforced symmetric gait patterns hardly allow adaptions in which patients develop compensatory movements to optimally cope with existing deficits. Although our results suggest that even “well-recovered” patients may rely on behavioural compensation with the less-affected limb to recover balance, this needs further investigation, including more difficult balance tasks. Only then can we judge whether a patient’s preferred asymmetry is actually beneficial in improving activities and preventing falls, and whether these adaptions should be encouraged early during rehabilitation to enable home discharge.
Antwerpen : Universiteit Antwerpen, Faculteit Geneeskunde en Gezondheidswetenschappen , 2023
243 p.
Supervisor: Truijen, S. [Supervisor]
Supervisor: Saeys, W. [Supervisor]
Supervisor: Kwakkel, G. [Supervisor]
Supervisor: Yperzeele, L. [Supervisor]
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Creation 21.12.2023
Last edited 23.12.2023
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