Modification of Brain Functional Connectivity in Adolescent Thoracic Idiopathic Scoliosis by Lower Extremities Position

Abstract

The involvement of the brain motor system in idiopathic scoliosis remains unclear. In this paper, we question whether the functional connectivity (FC) of the central motor circuitry is abnormal in adolescent idiopathic scoliosis (AIS) and whether it can be modified by flexion of the lower extremities. Functional magnetic resonance imaging (fMRI) in 18 patients with a right thoracic idiopathic curve greater than 30° (mean angle 49.4°, mean age 15.3 years, 4 males) and 22 healthy controls (mean age 18.2 years, 4 males) was explored using a 3T MR scanner. We measured their resting-state fMRI: a) with extended lower extremities; b) with semiflexion of the left lower extremity and extended right lower extremity, with hip abduction. Decreased FC between the secondary motor area (SMA) and postcentral cortex, pallidum and cuneus, postcentral gyrus and cerebellum, putamen and temporal lateral neocortex was observed in AIS. This pathological connectivity was reversed by lower extremity semiflexion. The FC between cortical and subcortical motor structures is significantly decreased in AIS. The decreased FC of the SMA, basal ganglia, cuneus (a hub structure), and cerebellum indicates the functional impairment of structures involved in regulating muscular tone. FC impairment in patients with AIS appears to be a reaction to the pathological condition. This pathological pattern flexibly reacts to changes in the positioning of the lower extremities, showing that the functional impairment of brain motor circuitry in AIS is reversible. We suggest that the reactivity of cerebral activity leading to brain activity normalization could be used for a rehabilitation program for patients with AIS.

Experimental protocol to investigate cortical, muscular and body representation alterations in adolescents with idiopathic scoliosis

“…Differences in electrocortical dynamics were found between girls with AIS and controls performing a balance task that involved alteration of ankle proprioception. Specifically, a significant suppression in the power of the alpha ( [8][9][10][11][12] Hz) and beta ( [13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30] Hz) bands emerged in the AIS group during the ankle vibration interval with eyes open and a significant increase in theta ( [4][5][6][7] Hz) band power with eyes closed [15]. Alpha oscillations are a marker of the excitability of the somatosensory cortex.…”

“…The laboratory setup will require two months (months 1-2). Data acquisition will be performed before treatment (T0) with the full-time brace (T0-months 3-7) and after 6 and 12 months (T1-months 9-13 and T2-months 15-19) full-time brace treatment and scoliosis-specific exercises (i.e., rehabilitation intervention-months [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. In parallel to subject recruitment (months 1-5) and data acquisition (months 3-7, 9-13, and [15][16][17][18][19], signal processing and interpretation (months 4-22) will be carried out to lead to the final stages of the project (months [20][21][22][23][24].…”

“…Abnormal patterns were detected in the motor network during the execution of a simple motor task which consisted in opening and closing one’s fist [ 12 ]. A decrease in functional connectivity of cortical and subcortical motor structures was found by analyzing AIS resting-state fMRIs, acquired both during extension and semi-flexion of the lower limbs [ 13 ]. Not only MRI and fMRI studies, but also EEG studies have revealed abnormal brain activity in AIS.…”

“…On the one hand, a dysfunction of postural mechanisms involving the central nervous system (CNS) and a distorted body schema have been proposed to be part of a sequence of pathological events in the development of spinal deformity in AIS [8,9]. On the other hand, CNS alterations have also been explored as a possible cause of AIS [3,[10][11][12][13][14][15].…”