UBC Theses and Dissertations
Vestibular perception in adolescents with Idiopathic Scoliosis Woo, Emma Jean
Adolescent Idiopathic Scoliosis (AIS) is a three-dimensional spinal deformity. One of the proposed causes of AIS is asymmetric vestibular function and the related descending drive to the spine musculature. Indeed, unilateral labyrinthectomy in tadpoles results in a spinal curvature similar to scoliosis. The objective of this study was to determine if asymmetric vestibular function is present in individuals with AIS. Ten individuals with AIS (8 females, 2 males) and ten healthy controls (8 females, 2 males) were exposed to 10s virtual rotations induced by monaural or binaural electrical vestibular stimulation (EVS), and 10s real rotations delivered by sitting atop a rotary chair. Using a forced-choice paradigm, participants indicated their perceived rotation direction (right or left). A Bayesian adaptive algorithm adjusted the stimulus intensity and direction to identify a stimulus level, which we called the vestibular recognition threshold, at which participants correctly identified the rotation direction 69% of the time. For unilateral vestibular stimuli (monaural EVS), the recognition thresholds were more asymmetric in all participants with AIS compared to control participants (1.16 vs 0.06 mA; p < 0.001) but the recognition thresholds for bilateral vestibular stimuli did not differ between groups for both real and virtual rotations (multiple p > 0.05). No correlation was observed between the degree/side of the spine curvature and vestibular asymmetry in persons with AIS (p = 0.30). Our results demonstrate an asymmetry in vestibular function in individuals with AIS. Previous reports of semicircular canal orientation asymmetry in individuals with AIS could not explain this vestibular function asymmetry, suggesting a functional cause of the observed vestibular asymmetry. Vestibular function related to bilateral stimuli was well compensated, showing similar recognition thresholds across both groups of participants. The present results indicate that vestibular dysfunction is linked to AIS, potentially revealing a new path for the screening and monitoring of scoliosis in adolescents.
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