Vestibular Function in Adolescent Idiopathic Scoliosis
• (a - Orthpaedic Research and Education Foundation - Resident Research Grant)
Objective: The etiology of adolescent idiopathic scoliosis (AIS) is still unclear. The purpose of this study is to determine a relationship between vestibular function and scoliosis by studying human subjects in a state-of-the-art comprehensive vestibular-balance assessment.
Methods and Materials: Patients with AIS and matched controls were recruited in a prospective observerblinded control trial according to inclusion criteria outlined by the Scoliosis Research Society and excluded with prior vestibular-balance disorders, claustrophobia, hearing loss, or abnormal reflexes. All patients underwent a two-phase study - (1) a comprehensive scoliosis evaluation and radiographs, and (2) a comprehensive vestibular-balance assessment. Vestibular measures include vertical axis rotation chair evaluation (VAR at 0.08 Hz, 0.32 Hz, and 0.64 Hz chair speed), eccentric vertical axis rotation (EcVAR), computerized oculomotor testing (OM), dynamic posturography (CPD), spinal reflex testing (Fukuda Test), and rotation chair testing for vestibular-visual interaction (VFX and VVOR) and VORTEQ testing for high -frequency motor tracking to test for both peripheral and central brainstem function. Statistical analysis was performed with Fisher's exact test, multivariate regression, ANOVA, and correlation coefficients.
Results: Forty patients were enrolled, 27 with AIS and 13 as controls. Peripheral vestibular and ear ossicle function was normal in both groups. A significant difference was detected for rotation chair testing at 0.32 Hz and 0.64 Hz between scoliosis and control patients (p=0.015 and 0.027, respectively. Figures 1 & 2). There were no differences in oculomotor function (p>0.4), computerized dynamic posturography (CDP), and rotation chair vestibular-visual interaction (VFX, p=0.24, and VVOR, p=0.27). The largest differences were for EcVAR testing of phase and asymmetry (p<0 .001, p<0.01, respectively, Figure 3), however, EcVAR gain showed no difference. These studies were also consistent with well-established adult normative data. When compared orthopaedic variables, as Cobb Angle increased, so did the central vestibular dysfunction (p Curves in low-thoracic and lumbar regions demonstrated greatest abnormalities for testing. The majority of right curves left-sided rotation asymmetry. There differences function respect to Risser sign maturity>0.05).
Conclusion: A central vestibular deficit is present in scoliosis patients. Central vestibular function is worse with larger curves, and the dysfunction is opposite to the curve. Curves with location in the mid-thoracic region demonstrated less central deficit than low-thoracic and lumbar scoliosis curves. The data supports a central vestibular dysfunction in patients with scoliosis.
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