Asymmetric Unilateral Vestibular Perception in Adolescents With Idiopathic Scoliosis

Abstract

The cause of Adolescent Idiopathic Scoliosis (AIS) remains unclear, but one proposed cause of AIS is asymmetric vestibular function and the related descending drive to the spine musculature. The objective of this study was to determine if asymmetric vestibular function is present in individuals with AIS. Ten individuals with AIS (8F, 2M) and 10 healthy age- and sex-matched controls were exposed to 10s-long virtual rotations induced by monaural or binaural electrical vestibular stimulation (EVS), and 10s-long real rotations delivered by a rotating chair. Using a forced-choice paradigm, participants indicated their perceived rotation direction (right or left) to stimuli of varying intensity. A Bayesian adaptive algorithm adjusted the stimulus intensity and direction to identify a stimulus level, which we called the direction recognition threshold, at which participants correctly identified the rotation direction 69% of the time. For unilateral vestibular stimuli (monaural EVS), the direction recognition thresholds were more asymmetric in all participants with AIS compared to control participants [(0.22–1.00 mA) vs. (0.01–0.21 mA); p < 0.001]. For bilateral vestibular stimuli, however, the direction recognition thresholds did not differ between groups for either the real or virtual rotations (multiple p > 0.05). Previous reports of semicircular canal orientation asymmetry in individuals with AIS could not explain the magnitude of the vestibular function asymmetry we observed, suggesting a functional cause to the observed vestibular asymmetry. Thus, the present results suggest that a unilateral vestibular dysfunction is linked to AIS, potentially revealing a new path for the screening and monitoring of scoliosis in adolescents.

The Effect of the Direction of Primary Lateral Spinal Curvature on Postural Stability in Children with Scoliosis

“…These results are fully consistent with the findings of Gruber et al [18]; however, numerous studies have reported not only a greater COP range in the medial-lateral and anterior-posterior directions and sway area but also a greater sway path length in children/adolescents with scoliosis [5,10,12,19,20]. The enlarged values of spatial COP displacement parameters in both directions (medial-lateral and anterior-posterior occurring at normal excursions and COP velocity, as found in the present study) may result in large body oscillations in all directions and indicate decreased spatial postural stability in scoliosis patients [21,23]. Although there is no consensus in the literature on postural instability in scoliosis patients, our results are compatible with the results of most recent studies [12][13][14][15][16][17][18][19][20][21] as well as with the findings reported in both the latest systematic review and meta-analysis [23,27], which concluded that children and adolescents with IS were characterized by worse postural stability than healthy children were.…”

“…A review of studies on postural stability in children/adolescents with scoliosis in comparison with their typically developing peers revealed that the results were not fully consistent. Notably, both earlier studies [ 8 , 9 , 10 ] as well as recent studies [ 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 ] reported significant differences in stability, while others reported a lack of differences in stability [ 22 , 23 , 24 , 25 , 26 ].…”

“…Assuming that, irrespective of the primary triggers of IS, persistent asymmetric mechanical loading relative to the spinal axis may influence scoliosis development and progression, several recent studies have focused on analyzing body weight distribution (BWD) on the basis of support (BoS) between body sides [ 4 , 5 , 6 , 7 , 8 ] and assessing postural stability in children/adolescents with scoliosis [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 ].…”

Postural control through force plate measurements in female AIS patients compared to their able-bodied peers

“…Some evidence suggests that dysfunction of the vestibular system may be a contributing factor to the development of AIS 6 . Asymmetric vestibular function and the related descending drive to the spine musculature can lead to inappropriate trunk muscle activity, spine deformation, and greater instability 7 . On the other hand, several studies on adolescent patients with idiopathic scoliosis revealed their fair postural stability compared to the control group 8 .…”

Diffusion MR imaging in the cortical spinal tract of idiopathic scoliosis

“…Asymmetric vestibular information was also suggested to be the underlying cause of the abnormal sensory integration. Monaural and binaural vestibular stimulation showed altered balance control in patients with AIS [27] and larger functional vestibular asymmetry [28]. This asymmetry can be explained by unilateral abnormalities of the vestibular organs as was demonstrated by Carry [29] and Rousie [30].…”