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Abstract:

BACKGROUND AND AIM: Turning movements are a highly relevant component of everyday walking behavior, since 35-45\% of steps are taken during turning. Turning movements are thought to be more challenging in terms of dynamic balance than straight walking, as they require more anticipatory postural adjustments and trunk-limb coordination strategies. In addition, certain types of degenerative cerebellar ataxias are associated with disturbances in eye movements such as nystagmus and disturbed VOR reflexes, which occur particularly during head rotation and peripheral gaze and may therefore affect turning more than straight walking. In this study, we compared the turning movements of SCA27B ataxia patients with downbeat nystagmus (DBN) to those of patients with spinocerebellar ataxia (SCA, types 1, 2, 3, 6) without nystagmus and investigated the influence of the drug 4-aminopyridine (4AP) on the reduction of DBN during turning movements. METHODS: We performed a cross-sectional analysis of motion data collected by three body-worn inertial sensors from subjects with SCA1, 2, 3, 6 (n = 359, SARA = 6.81) as well as SCA27B (n = 49, SARA = 7.0) in two conditions: a) lab-based supervised walking of a 60m corridor at preferred speed, b) lab-based turn task, i.e., subjects were instructed to walk along a T-junction of a corridor, including several 90° turns. Turning analysis included standard measures (i.e., mean and peak angular velocity (MAV, PAV), turn duration (TD), number of steps during turning (NoS)) and a measure quantifying dynamic balance during turning (lateral velocity change, LVC), which has been shown to be sensitive to ataxic-specific changes in turning and has strong correlations with self-reported balance confidence as measured by the ABC score. RESULTS: Turn analysis of the LVC revealed significantly greater impairments during lab-based 90° turning (p = 0.001, Cliff’s δ = 0.45) in SCA27B patients with DBN (n = 18) than in SCA1/2/3/6 patients without oculomotor impairment (n = 359). Small or no effects were found for the standard turn parameters (e.g., PAV (p = 0.49, δ = 0.10), TD (p = 0.30, δ = -0.15). Single-subject analysis of a 4AP-treated SCA27B patient with prominent DBN at right and left gaze directions showed both a reduction in DBN and LVC in the ON treatment phase compared to pre-treatment. The slow phase velocity was reduced by 16.1\% in right and by 51.2\% in left gaze. Accordingly, the LVC decreased by -0.46 m/s (-85.3\%) during right and by -0.51 m/s (-98.38\%) during left turns. Here, no improvements were found for the standard turn parameters. CONCLUSIONS: Ataxia-related oculomotor impairments may increase abnormalities in dynamic balance control during turning, which are not reflected in common compensatory strategies such as slowing down and taking smaller steps. The 4AP-induced reduction in DBN in SCA27B patients improves turning performance, with potentially beneficial implications for everyday walking behavior.

Authors: Bohn, Kristina; Seemann, Jens; Synofzik, Matthis Ilg, Winfried

Research Areas: Clinical Movement Control and real-life Behavior Analysis for Assistive Systems

Type of Publication: In Collection

Abstract:

Background and Aim: As in many neurological movement disorders, patients with cerebellar ataxia report an increase in gait impairment during physical activity, fatigue, and stress. This important patient-reported observation is not reflected in clinical gait analysis at present, and these particularly critical periods are not specifically examined in current motion analyses in patients' everyday lives either. The aim of this study is to investigate how short periods of physical activity (stair climbing) with corresponding increases in heart rate affect ataxia-sensitive gait measures during free walking using a multimodal approach combining wearable motion and heart rate monitoring. Methods: We evaluated gait changes in 32 individuals with degenerative cerebellar disease (SARA: 7.3±5.1; age: 45.4±14.7) and 10 age-matched healthy controls. Gait was quantified using three body-worn inertial and barometric sensors, along with an ECG chest strap, during 10 minutes of free walking. This included a fixed sequence of straight walking, climbing a flight of stairs and walking uphill one floor, and returning. Movement analysis focused on ataxia-sensitive lateral step deviation (LSD) as well as gait speed (GS) in relation to heart rate (HR). Episodes involving stairs and inclines were identified through changes in the barometric signal and excluded from the analysis. Results: Comparisons between ataxic subjects and healthy controls revealed higher effect sizes during exerted state (e.g. LSD, FWe: r = 0.52, FWf: r = 0.57) compared to rested state (e.g. LSD, FWr: r = 0.33). Lateral step deviation indicated a moderate correlation with heart rate (HR) during the fatigued phase (FWf: R=0.38). Notably, in the moderately impaired subcohort (n=17, SARA>7, determined via median split), correlation was higher (R_mod=0.51). During the exerted walking phase (FWe), gait speed (GS) showed a negative correlation with HR (GS: R=-0.36; R_mod=-0.58), whereas no correlation was observed during FWr or FWf. In contrast, healthy controls displayed no significant correlations in ataxia-sensitive measures or gait speed across conditions. Conclusions: In this study, we found a significant relationship between heart rate and quality of ataxic gait. When walking after physical exertion, subjects exhibited slower gait speeds and increased ataxia-specific spatiotemporal variability (LSD) compared to when they were rested. These findings suggest that physical exertion and fatigue may exacerbate gait symptoms, particularly in the later stages of the disease. Since fatigue is a common and critical aspect of daily life, it is essential for future therapy evaluation studies to examine patients' gait under fatigued conditions as well, in order to obtain a real-world estimate of treatment efficacy.

Authors: Seemann, Jens; Bohn, Kristina; Synofzik, Matthis Ilg, Winfried

Research Areas: Uncategorized

Type of Publication: In Collection

Abstract:

Impairments in gait– with a key component of dynamic balance– and stance– with a key component of static balance- represent the key hallmarks of ataxia; not only in clinical assessments and clinician-reported outcomes; but also in patients’ voice burden of disease severity and patient-reported outcomes. While it is obvious that both features are not independent from each other, their interplay in ataxia – in terms of underlying control mechanisms- remains unknown. Here we aimed to assess the interaction be-tween dynamic balance (gait) and static balance (stance) in response to longitudinal changes in cerebellar ataxia using wearable sensors. We assessed cross-sectional and longitudinal balance of subjects with degenerative cerebellar disease (SARA:7.5±5.14) at baseline and 1-year follow-up (n=60) by 3 body-worn inertial sensors in two conditions: (1) stance with feet together (30 seconds), (2) straight walking (2 minutes). Based on the hip sensor, sway path length was calculated as a measure of static balance during stance using both directions of sway (PLtotal), as well as exclusively anterior-posterior (PLap) and medial-lateral (PLml) direction. Gait analysis focussed on ataxic-sensitive measures of spatio-temporal variability: stride length variability (SLCV) in gait direction and lateral step deviation (LSD) as well as upper body range of motion during gait in respective directions (ROMap, ROMml). Cross-sectional analyses revealed significant correlations between PLtotal and LSD as well as ROMml (r {\textgreater}0.6), and between PLtotal and SLCV and ROMap (r{\textgreater}0.4). Matching directions of sway showed a mildly increased effect (e.g. LSD{\textbackslash}PLap:r\_total=0.61,r\_ap= 0.63). Corresponding stance and gait measures showed similar correlations to patient-reported balance confidence (ABC-score;PLtotal:0.65,LSD:0.69). Longitudinal changes in static balance were correlated with changes in dynamic bal-ance specifically in the corresponding direction (e.g. deltaLSD{\textbackslash}deltaPLml:r=0.40). We were able to identify specific influences of the static balance mechanism on gait, demonstrating the patient's relevance of static stance testing and related balance exer-cises in rehabilitation.

Authors: Bohn, Kristina; Seemann, Jens; Giese, Martin A.; Synofzik, Matthis Ilg, Winfried

Research Areas: Clinical Movement Control and real-life Behavior Analysis for Assistive Systems

Type of Publication: In Collection