The mechanics behind gait problems in patients with Dravet Syndrome

Abstract

BackgroundDravet Syndrome (DS) is a developmental and epileptic encephalopathy starting in infancy and characterised by treatment resistant epilepsy with cognitive impairment and progressive motor dysfunction. Walking becomes markedly impaired with age, but the mechanical nature of gait problems remains unclear. Research questionWhat are the kinetic strategies characterised in gait of patients with DS? MethodsThis case-control study compared 41 patients with DS aged 5.2 to 26.1 years (19 female, 22 male) to 41 typically developing (TD) peers. Three dimensional gait analysis (VICON) was performed to obtain spatiotemporal parameters, kinematics and kinetics during barefoot, level walking at self-selected walking velocity. The sagittal plane support moment was analysed using Statistical Parametric Mapping (SPM). Three DS subgroups were identified based on differences in kinetic strategies characterised by the net internal knee joint moments and trunk lean. Kinematic and kinetic time profiles of the subgroups were compared to the TD group (SPM t-test).Clinical characteristics from physical examination and parental anamnesis were compared between DS (sub)groups using non-parametric tests (Kruskal-Wallis, Wilcoxon rank-sum, Fisher's exact). ResultsSupport moments in stance were significantly increased in the DS group compared to TD and strongly related to minimum knee flexion in midstance. Persistent internal knee extension moments during stance were detected in a subgroup of 27% of the patients. A second subgroup of 34% showed forward trunk lean and attained internal knee flexion moments. The remaining 39% had neutral or backward trunk lean with internal knee flexion moments. Subgroups differed significantly in age and functional mobility. SignificanceInefficient kinetic patterns suggested that increased muscle effort was needed to control lower limb stability.Three distinct kinetic strategies that underly kinematic deviations were identified. Clinical evaluation of gait should pay attention to knee angles, trunk lean and support moments.

Quantitative Characterization of Motor Control during Gait in Dravet Syndrome Using Wearable Sensors: A Preliminary Study

“…These measures (i.e., reduced HRap, HRv, SENml and RQA parameters on the ML and V direction) can be assumed to instrumentally quantify a clinical feature of ataxic gait: a common strategy to reduce pluri-directional oscillations is to extend the base of support—i.e., widen the feet distance ( Table 3 ) [ 6 ]. This compensatory postural adjustment can be assumed to be further reinforced by two biomechanical features which are typical of DS—flat foot and valgus knee [ 6 ]—which both contribute to the increased lateral reaction forces [ 7 ].…”

“…Among DS-related gait alterations, crouch gait, a pattern typically observed in cerebral palsy and characterized by hip and knee flexion and femur anteversion, was originally identified via observational video gait analysis [ 5 ]. Quantitative gait analysis demonstrated that only a subgroup of children and young adults with DS display gait pattern with similar, but not equal, characteristics of crouch gait, termed pseudo-crouch gait [ 6 , 7 ]. The increased flexion of lower limb joints is likely related to stabilization strategies in a clinical picture often characterized by reduced muscle tone, cerebellar ataxia, and moderate hyposthenia.…”

“…The increased flexion of lower limb joints is likely related to stabilization strategies in a clinical picture often characterized by reduced muscle tone, cerebellar ataxia, and moderate hyposthenia. Instrumental gait analysis also permitted detection of higher muscular efforts and energy expenditures in the same population, with compensatory strategies to promote propulsion (i.e., forward lean of the trunk in younger subjects) [ 7 ]. A recent report [ 8 ] aimed to study foot function of people with DS using pedobarography-confirmed features of walking instability and motor development immaturity that normally disappear with growth in healthy subjects [ 9 , 10 ].…”

Altered Muscle Contributions are Required to Support the Stance Limb During Voluntary Toe-Walking

“…Frontal plane balance and mediolateral stability are fundamental aspects of any support and locomotion strategy ( Pandy et al, 2010 ). The lack of trunk markers did not allow to identify support strategies associated with upper-body control ( Wyers et al, 2021 ). The control of the contralateral limb could also play an important role in forward propulsion while maintaining stability ( Bovonsunthonchai et al, 2012 ).…”

“…Hof provided a mechanical interpretation for this concept, demonstrating that a slightly reformulated definition of the support moment was responsible for preventing the collapse of the knee due to external forces ( Hof, 2000 ). The support moment seems well-suited to investigate the required overall extensive muscular effort to maintain stance limb stability in pathological populations ( Wyers et al, 2021 ).…”