Abstract
Introduction
Different subclinical neurological dysfunction has been reported in adolescent idiopathic scoliosis (AIS), including poor postural control and asymmetric otolith vestibulo-ocular responses when compared with normal controls. The objective of this pilot study is to establish whether abnormal MRI morphoanatomical changes arise in the CNS (brain and vestibular system), among left-thoracic versus right-thoracic AIS when compared with normal adolescent controls, with use of advanced computerised statistical morphometry techniques.
Methods
We compared nine girls with left-thoracic AIS (mean age 14 years; mean Cobb angle 19°) with 11 matched controls, and 20 girls with right-thoracic AIS (mean age 15 years, mean Cobb angle 33·8°) with 17 matched controls. The statistical brain analysis was done with validated automatic segmentation and voxel-based morphometry (VBM). The T2W-MRI data for shape analysis of the vestibular system were obtained from 20 patients with right-thoracic AIS and 20 matched controls. A best-fit plane and a best-fit circle were calculated to approximate each semicircular canal. The shape of vestibular system was measured by: (1) the angle between each pair of best-fit planes; (2) the length; and (3) angle formed between the corresponding lines connecting the centres of each pair of circles. Statistical analysis was done with one-way ANOVA.
Results
Patients with left-thoracic AIS had significantly lower white matter density in corpus callosum, left internal capsule, and white matter underlying orbitofrontal cortex of left hemisphere, which were not observed in patients with right-thoracic AIS. In the right-thoracic AIS group, the distance between centres of lateral and superior canals (p=0·0264) and the angle with vertex at the centre of posterior canal (p=0·02) of left-side vestibular system were significantly smaller than in the control group (figure). For vestibular analysis, there were no data for left-thoracic AIS.
Conclusions
Findings from this pilot study have shown significant MRI morphoanatomical difference in CNS between patients with AIS and controls. In the brain analysis, corpus callosum (the principle commissural fibre bundle connecting left and right cerebral hemispheres, which might affect the coordination of left and right sides of the body), differed between left-thoracic and right-thoracic AIS. In the vestibular analysis, geometric morphological difference was detected on the left-side semicircular canals between right-thoracic AIS and healthy controls. These morphological changes are likely to be related to the subclinical postural, vestibular, and proprioceptive dysfunctions. Further association studies and longitudinal studies could help to further define the link between morphological and functional dysfunction, which might have important predictive and prognostic effect on curve development and progression.
