Sense of verticality in girls with right thoracic adolescent idiopathic scoliosis (AIS): Evaluation of bottom up and top down mechanisms

• Published in: Annals of physical and rehabilitation medicine Vol. 60; p. e80
• Main Authors: Catanzariti, Jean-Francois, Le Berre, Morgane, Darchicourt, Delphine, Guyot, Marc-Alexandre, Chevutshi, Alain, Thévenon, André
• Format: Journal Article
• Language: English
• Published: Elsevier Masson SAS 01-09-2017
• Subjects: Adolescent idiopathic scoliosis; Postural control; Self-image; Verticality perception; Verticality perception; Self-image; Postural control; Adolescent idiopathic scoliosis
• ISSN: 1877-0657; 1877-0665
• DOI: 10.1016/j.rehab.2017.07.219

AIS is the most frequent spinal deformity in adolescence, but its etiology remains unknown. We hypothesized that AIS is secondary to perturbation of sense of verticality. Orthostatic postural control is organized, in part, from the vertical gravity, by two mechanisms: bottom up (central integrating of multisensorial inputs) and top down (cognitive process, as notion of self-image representation). We studied sense of verticality in SIA by subjective visual vertical (SVV), postural vertical (VP) and self-image representation, with reference to the vertical gravity.
We conducted two prospective multicentre case–control studies. Study 1 aimed at the evaluation of static and dynamic SVV and VP, in two groups. Thirty girls (14.2±1.7 years) with right thoracic AIS (3.97±12.9°), matched to 30 controls (13.9±1.8 years). Study 2 aimed at the evaluation of perception of form trunk with pictorial scale in three groups. Thirty-one girls (13.5±1.3 years) with minor right thoracic AIS, 32 girls (14±0.9 years) with major right thoracic AIS, 30 control girls (13.6±1.3 years). A weighted score is established: higher score reveal worse perception of trunk form.
Study 1 found no significant difference in SVV and VP was shifted to the right in right thoracic AIS group: 2.1±2.2° vs. score control group=0.08°±1.4° (P<0.001). Study 2 found a stronger perception of their form trunk, in vertical standing (2.2±1.4) in patients with major AIS, versus minor AIS (1.2±1.1; P=0.008) and versus controls (1.2±1.2; P=0.006).
Our studies show disturbance of sense of verticality in AIS, with somaesthesic graviception disorder. The loss of concordance between central internal representation of verticality and earth-vertical could lead to a perturbation of longitudinal body axis, by impaired postural adjustment of the trunk. AIS could be the result of a reorientation of longitudinal body axis, consequently of spinal axis, in accordance with an erroneous representation of verticality. This model modifies the management of scoliosis AIS.