@incollection{bohn03_turns_2025,
author = "Kristina Bohn and Jens Seemann and Matthis Synofzik and Winfried Ilg",
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.",
booktitle = "International Society of Posture and Gait Research (ISPGR) Maastricht",
title = "{T}urns increase the impact of impaired eye movements on locomotion in cerebellar ataxia",
year = "2025",
}