Brain oscillatory activity in adolescent idiopathic scoliosis

Abstract

Pathophysiology of Adolescent Idiopathic Scoliosis (AIS) is not yet completely understood. This exploratory study aims to investigate two aspects neglected in clinical practice: a defective postural central nervous system control in AIS, and alterations of body schema due to scoliosis spinal deformities. We recorded EEG data and balance data in four different standing positions in 14 adolescents with AIS and in 14 controls. A re-adaptation of the Image Marking Procedure (IMP) assessed body schema alterations on the horizontal (Body Perception Indices (BPIs)) and vertical direction (interacromial and bisiliac axes inclinations). Our results revealed no differences in balance control between groups; higher EEG alpha relative power over sensorimotor areas ipsilateral to the side of the curve and a significant increase of theta relative power localized over the central areas in adolescents with AIS. The difference in BPI shoulder and BPI waist significantly differed between the two groups. The inclinations of the perceived interacromial axes in adolescents with AIS was opposite to the real inclination. Increased theta activity and alpha lateralization observed may be a compensatory strategy to overcome sensorimotor dysfunction mirrored by altered body schema. Scoliosis onset might be preceded by sensorimotor control impairments that last during curve progression.

Figure 1

Topographic maps of relative power (%) in delta [1–4] Hz, theta [4.5–7.5] Hz, alpha [8–12] Hz, and beta [13–30] Hz bands, during OE standing and OE arms up, averaged from 14 controls (CTRL) (first row), 10 adolescents with AIS with right main curve (second row) and 4 adolescents with AIS with left main curve (third row). The fourth and the fifth rows represent p-maps derived from the Wilcoxon rank sum test (adolescents with AIS with right main curve: AIS-R vs. CTRL; adolescents with AIS with left main curve: AIS-L vs. CTRL). Statistical results were highlighted with (+) for $\text{p}<0.05$.

Figure 2

Topographic maps of relative power (%) in delta [1–4] Hz, theta [4.5–7.5] Hz, alpha [8–12] Hz, and beta [13–30] Hz bands, during CE standing and CE arms up, averaged from 14 controls (CTRL) (first row), 10 adolescents with AIS with right main curve (second row) and 4 adolescents with AIS with left main curve (third row). The fourth and the fifth rows represent p-maps derived from the Wilcoxon rank sum test (adolescents with AIS with right main curve: AIS-R vs. CTRL; adolescents with AIS with left main curve: AIS-L vs. CTRL). Statistical results were highlighted with (+) for $\text{p}<0.05$.

Figure 3

Grand-average LI in alpha band during CE arms up for controls (CTRL), adolescents with AIS with right main curve (AIS-R) and adolescents with AIS with left main curve (AIS-L). On each box, the central red line indicates the median, and the bottom and top edges of the box indicate the 25th and 75th percentiles, respectively. The whiskers extend to the most extreme data points not considered outliers, and the outliers are plotted individually using the ‘+’ symbol. Significant difference ($\text{p}<0.05$) was observed between CTRL and AIS-R.

Figure 4

Balance performances as assessed through confidence ellipse area (EA), sway path length (PL) and the root mean square of center of pressure trajectory in the anterior–posterior and medial-lateral directions (RMS-AP and RMS-ML, respectively) in: (A) standing, and (B) arms up conditions. Boxplots are filled with white for eyes open (OE) and gray for eyes closed (CE). Statistical results were highlighted with: ‘***’ for $p<0.001$, ‘**’ for $p<0.01$, ‘*’ for $p<0.05$, and ‘...’ for $p<0.10$.

Figure 5

(A) BPI delta values defined as the difference between shoulder BPI and waist BPI. A significant difference emerged between mean delta BPIs of adolescents with AIS and controls ($p<0.01$). (B,C)) On the x axis are plotted the real angles as measured with IMP while on the y axis the perceived angles as measured with IMP. To characterize curve laterality, we assigned positive values when curves’ convexity was right-oriented, and negative values when left-oriented. (B) In the adolescents with AIS 12 out of the 14 girls perceive their curve orientation as opposite to the real one. (C) For the control group, just 3 out of 14 girls perceive their curve orientation as opposite to the real one.