Enhanced vestibular-evoked balance responses in adolescents with idiopathic scoliosis

Scoliosis is a spinal deformity characterized by lateral deviation and rotation of the vertebrae, affecting between 0.47% and 5.2% of adolescents. A proposed explanation for adolescent idiopathic scoliosis (AIS) is asymmetrical vestibular function affecting the descending control of torso muscles. To verify this hypothesis, we applied stochastic vestibular stimulation (SVS) at frequencies of up to 25 Hz, both monaurally and binaurally, to standing participants with AIS (n = 15) and to those without AIS (n = 15). We characterized potential left-right vestibulomotor asymmetry in the correlations, gain, and direction of the evoked balance responses. Contrary to our hypothesis, no asymmetry in the balance responses evoked by monaural stimuli was observed in either group. AIS participants, however, exhibited larger correlations and gains (both in the frequency and time domains, except for time-domain estimates to monaural right stimuli) between vestibular stimuli and ground reaction forces compared to control participants. This larger coupling suggests a greater association between the vestibular error and force signals in AIS participants for monaural left and binaural SVS conditions. The orientation of the vestibular-evoked balance responses, however, did not differ between groups. We conclude that adolescents with idiopathic scoliosis exhibit larger vestibular gains than control participants. This suggests an enhanced relationship between the electrical vestibular error signal and the evoked balance responses. Still, these changes do not affect the symmetry or orientation of vestibular-evoked postural responses at the tested frequencies.NEW & NOTEWORTHY We tested the hypothesis that adolescent idiopathic scoliosis (AIS) patients exhibit asymmetries in the vestibular control of balance. We observed larger vestibular-evoked balance responses in participants with AIS to stimuli targeting primary vestibular afferents unilaterally and bilaterally. These larger balance-correcting responses of vestibular origin, however, were symmetric and oriented in the expected interaural direction. Our results indicate a strengthened connection between the vestibular error signals evoked by electrical stimuli and the resulting balance responses in participants with AIS.