Adolescent idiopathic scoliosis (AIS) is a three-dimensional spine deformation with elusive aetiopathogenesis. One appealing hypothesis points to its neurologic origin with an emphasis on a vestibular impairment. In the present study, we explored the hypothesis of a vestibular deficit accompanying AIS by assessing differences in the subjective estimation of the gravitational vertical between adolescents with idiopathic scoliosis (n = 10, age 11-16 years, Cobb's angle > 15°) and healthy age-matched controls (n = 10). Group participants actively controlled the verticality of a visual line in two visual conditions (eyes open-visual feedback and eyes closed-no visual feedback) and using three different segments (hand, head, and trunk). An electromagnetic tracking sensor (Nest of Birds, Ascension Ltd., USA, 60 Hz), attached either to a hand-held rod, the head, or the upper trunk, measured the line's deviation from the gravitational vertical that was reflected in two measures, the mean absolute and variable error. The head's medio-lateral tilt when estimating verticality with the hand was also registered. Analysis revealed that adolescents with idiopathic scoliosis made a greater error than control participants when estimating verticality with the head and eyes closed. In addition, they adopted a significantly greater head tilt when estimating the vertical by controlling the hand-held rod, regardless of the availability of vision. The error in the earth vertical was greater when the estimate was performed in the absence of vision. Results suggest a malfunction of the vestibular system and/or a sensorimotor integration impairment in patients with AIS, while vision compensates for the observed deficit in estimating the earth vertical.

One of the most appealing hypotheses around the aetiopathogenesis of adolescent idiopathic scoliosis attributes the development of the spine deformity to an imbalance in the descending vestibulospinal drive to the muscles resulting in a differential mechanical pull on the spine during the early life stages. In this study, we explored this hypothesis by examining postural and muscle responses to binaural bipolar galvanic vestibular stimulation (GVS) of randomly alternating polarity. Adolescents diagnosed with idiopathic scoliosis (n = 12) and healthy age‐matched controls (n = 12) stood quietly with feet together (stance duration 66–102 s), eyes closed and facing forward, while 10 short (2s), transmastoidal, bipolar square wave GVS pulses (0.3–2.0 mA) of randomly alternating polarity were delivered at varying time intervals. Responses depicted in the electromyographic (EMG) activity of bilateral axial and appendicular muscles, vertical reaction forces and segment kinematics were recorded and analysed. Scoliotic patients demonstrated smaller ankle muscle responses and a delayed postural shift to the right relative to controls during anode right/cathode left GVS. When GVS polarity was reversed, patients had a greater soleus short‐latency response on the left anodal side, while the rest of the muscle and postural responses were similar between groups. Vestibular stimulation also evoked greater head and upper trunk sway in scoliotic compared with healthy adolescents irrespective of stimulus polarity. Results provide new preliminary evidence for a vestibular imbalance in adolescents with idiopathic scoliosis that is compensated by somatosensory, load‐related afferent feedback from the lower limbs during the latter part of the response.