Subjective Visual Vertical and Adolescent Idiopathic Scoliosis (AIS)
Dr Jean-François CATANZARITIa, Mrs Morgane LE BERREb, Mrs Monique COGETc, Mr Marc GUYOTd, Mr Olivier AGNANId, Dr Cécile DONZÉd
a SSR pédiatrique Marc Sautelet de Villeneuve d'Ascq (France), GHICL Hôpital Saint Philibert de Lomme (France), CHRU de Lille (France), b Service MPR, CHRU de Lille (France), c SSR pédiatrique Marc Sautelet de Villeneuve d'Ascq (France), d Service MPR, Hôpital Saint Philibert, GHICL, Lomme-Lille (France)
Objective: The AIS is pathology with multifactorial origin. It affects between 1-3% of the population aged 10-16 years. Many authors suggest orthostatic postural control disorders in AIS. The orthostatic postural control is the ability to organize the standing posture on the earth- vertical. The longitudinal body axis, the trunk and the spinal axis are oriented in an internal representation of the gravitational vertical. Our hypothesis is that AIS is the consequence of a re-organization of orthostatic postural control, on an erroneous internal representation of earth- vertical. Our objective is to show a disturbance of the sense of verticality in the AIS, by measuring the Subjective Visual Vertical (SVV) in AIS, particularly in dynamic visual condition.
Methods: Prospective study: a group of adolescents with AIS versus a control group of non-scoliotic adolescents. The test is a measure of the SVV (Synapsis), standing posture, in static and dynamic visual conditions (visual disturbance by optokinetic stimulation 40 ° / sec). Six measures are evaluated. Norms for static condition -2.5 ° to +2.5 °, and for dynamic condition -4 to +4 °.
Results: Preliminary results on 35 scoliotic adolescents (Groupe S : 31 girls, 14,2±1,74 years, angle 38,4±15,7°), versus 5 non scoliotic adolescents (Groupe C : 5 girls, 14,9±1,14 years). Groupe S : static VVS = 1,59±1,45°; dynamic VVS = 4,7±8,27°. 57,1% with a least 1 pathological value, 28,5% with a least 2 pathological values, particularly in dynamic visual condition. (clockwise rotation with right tilt of the VVS, average 12,39 °). Groupe C : static VVS = 0,72±0,5°; dynamic VVS = 2,17±1,5°. No subject control with pathological value.
Discussion: This preliminary study shows a disturbance in the vertical evaluation in the AIS. One possible explanation is a disturbance of the sense of verticality by impaired multisensory central integration.
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Van Nechel C, Toupet M, Bodson I (2001). The subjective visual vertical. Adv Otorhinolaryngol 58:77-87.
The authors are grateful to the Harps Association’s members, for their helpful comments.
Keywords : Adolescent idiopathic scoliosis, subjective visual vertical, pathophysiology, verticality perception