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. 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.Introduction
Methods
The main challenge in management of adolescent idiopathic scoliosis (AIS) is to predict which curve will progress so that appropriate treatment can be given. We previously reported that low bone mineral density (BMD) was one of the adverse prognostic factors for AIS. With advancement in imaging technology, quantitative ultrasound (QUS) becomes a useful method to assess bone density and bone quality. The objective of this study was to assess the role of QUS as a radiation-free method to predict curve progression in AIS. 294 girls with AIS were recruited at ages 11–16 years and followed up until skeletal maturity. 269 age-matched healthy girls were recruited as controls. They provided the normal reference for calculation of Z score for QUS parameters. QUS measurements, including BUA (broadband ultrasound attenuation), VOS (velocity of sound) and SI (stiffness index) of the calcaneum, BMD of femoral neck, menarche history, ages, and Cobb angle of the major curve were recorded at baseline as independent variables. The predictive outcome was curve progression defined as an increase of Cobb angle of 6° or more. Logistic regression model and the ROC curve were used for statistical analysis.Introduction
Methods
Observation of sub-clinical neurological abnormalities has led to the proposal of a neuro-developmental etiologic model for AIS. Our research group have demonstrated longer latency in somatosensory–evoked potential (SSEP) and impaired balance control in AIS subjects. A previous pilot study compared the regional brain volume between right thoracic AIS subjects and normal controls. Significant regional brain differences were found relating to corpus callosum, premotor cortex, proprioceptive and visual centers. Most of these regions involved the brain unilaterally, indicating there might be abnormal asymmetrical development in the brain in right thoracic AIS. In this pilot study, we investigated whether similar changes are present in left thoracic AIS patients who differ from matched control subjects. Nine AIS female patients with atypical left thoracic AIS (mean age 14.8, mean Cobb angle 19°) and 11 matched controls as well as 20 right thoracic AIS (mean Cobb angle 33.8°) and 17 matched controls, underwent three-dimensional isotropic magnetization prepared rapid acquisition gradient echo (3D_MPRAGE) magnetic resonance (MR) imaging of the brain. Fully automatic morphometric analysis was used to analyse the MR images; it included brain-tissue classification into grey matter (GM), white matter (WM) and cerebrospinal fluid (CSF). and non-linear registration to a template brain. Tissue densities were compared between AIS subjects and controls. There was no significant difference between AIS subjects and normal controls when comparing absolute and relative (i.e. brain-size adjusted) volumes of grey and white matter. Using voxel-based morphometry, significant group differences (controls >
left AIS) were found in the density of WM in the genu of the corpus callosum, the left internal capsule (anterior arm) and WM underlying the orbitofrontal cortex of the left hemisphere. The above differences were not observed in the right AIS group. This first controlled study of regional tissue density showed that corpus callosum, which is the major commissural fiber tract, was different in the atypical left thoracic scoliosis while significant regional brain changes have not yet been found in those with typical right thoracic scoliosis. Further investigation is warranted to see whether the above discrepancy is related to laterality of the scoliotic curves and infratentorial neuroanatomical abnormalities. A larger sample and a longitudinal study is required to establish whether the brain abnormalities are predictive of curve progression.
