Lateral Semicircular Canal Asymmetry in Idiopathic Scoliosis: An Early Link between Biomechanical, Hormonal and Neurosensory Theories?

Incidence and Importance of Peripheral Vestibular Dysfunction in Adolescent Idiopathic Scoliosis

Adolescent idiopathic scoliosis (AIS) is a common form of scoliosis. As the name suggests, etiopathogenesis is not clearly defined, so treatment is still anchored in the musculoskeletal theory and correction/prevention of high Cobb angle values. This study aimed to determine whether there is any connection between developing scoliotic curvature and a positive history of motion sickness as a symptom of a peripheral vestibular dysfunction/deficit, and if vestibular rehabilitation exercises could be integrated into the treatment plan. The study was conducted over 12 months on a selected population of 159 patients to evaluate or treat scoliotic curvatures in a private clinic. The collected data were analyzed using IBM SPSS Statistics 25 and illustrated using Microsoft Office Excel/Word 2021. Patients with peripheral vestibular dysfunction had significantly higher Cobb angle values when compared to patients with a negative result in an instrumental test for peripheral vestibular dysfunction. Motion sickness was considerably more associated with peripheral vestibular dysfunction, and a positive Fukuda stepping test was associated with a positive history of motion sickness. Adolescent idiopathic scoliosis with higher Cobb angles is related to positive motion sickness history as part of peripheral vestibular dysfunction. Conservative treatment for scoliosis could incorporate sensory integration techniques, and a positive history of motion sickness could be an indicator of a higher risk of progression in adolescent idiopathic scoliosis.

Neurophysiological, balance and motion evidence in adolescent idiopathic scoliosis: A systematic review

BACKGROUND

Adolescent idiopathic scoliosis (AIS) is a spinal deformity that affects approximately 4% of the world's population. Several hypotheses regarding the etiology of AIS have been investigated. In the last decades, impaired visual-spatial perception, alterations in spatial body orientation and sensory integration deficits have been documented.

OBJECTIVE

We aimed to summarize the neurophysiological, balance, and motion evidence related to AIS published in the last fifteen years, between January 2008 and April 2023. Both observational and interventional studies were considered. Only studies using quantitative assessment methods, such as electroencephalography (EEG), electromyography (EMG), magnetic resonance imaging (MRI), somatosensory evoked potentials, force platform, or motion capture, were included.

METHODS

1250 eligible records identified from online database searching were filtered by duplicate removal, title and abstract screening, and qualitative analysis. 61 articles met the inclusion criteria (i.e., Cobb range 10°-35°, age range 10-18 years) and were summarized.

RESULTS

We found significant evidence of impaired standing balance in individuals with AIS who greatly rely on visual and proprioceptive information to stay upright. EMG studies frequently reported an increased activity on the convex side of the intrinsic spinae muscles. EEG data show increased delta and theta power, higher alpha peak frequencies, and significant suppression in the alpha and beta bands in subjects with AIS during standing tasks. MRI studies report changes in white matter structures, differences in the vestibular system, and abnormal cortical activations over motor-related areas in subjects with AIS. Bracing appears to be an effective treatment for AIS, leading to improvements in static balance and gait. Methodological issues prevent reliable conclusions about the effects of other treatment options.

CONCLUSIONS

This review underscores the importance of quantitative assessment methods to explore the etiology and pathophysiology of AIS. Further research is needed to measure the impact of physical therapy and orthotic treatments on the neurophysiological mechanisms of the disease.

Three-dimensional Analysis of the Temporal Bone Morphology in Patients with Craniofacial Microsomia

OBJECTIVE

To characterise the morphology of temporal bone in patients with craniofacial microsomia (CFM).

DESIGN

A retrospective study.

SETTING

A craniofacial centre.

PATIENTS

Ninety-four patients with unilateral craniofacial microsomia.

INTERVENTIONS

Mimics 21.0 (Materialise Inc., Belgium) was used to locate temporal bone landmarks on preoperative computed tomography data. The spatial Cartesian coordinate system was established in 3-matic 13.0 (Materialise Inc., Belgium). The coordinates of each landmark and the distances and angles between the landmarks were calculated. A classification system was used to quantify the severity of the zygomatic arch deformity.

MAIN OUTCOME MEASURE(S)

The bilateral differences in coordinates, linear and angular measurements, and the severity of temporal bone deformity (TTL δ, Psag δ, Paxiδ, and Tsag δ) among the groups were compared using the paired t-test and Kruskal-Wallis test, respectively.

RESULTS

Compared to those of the unaffected side, the landmarks of the inner ear and petrous part on the affected side showed a decrease in the Z-coordinate or an increase in the X-coordinate. A superolateral rotation tendency of the temporal bone on the affected side was found. There were no significant differences in the linear and angular measurements between the groups. The degree of zygomatic arch deformation was lower in the mild group; however, no significant difference was found between the moderate and severe groups.

CONCLUSIONS

In patients with CFM, asymmetry of the temporal bone and its inner organs (vestibulocochlear organ, facial nerve, and vessels) exists in multiple dimensions; its severity is not completely consistent with the degree of mandibular involvement.

Biomechanical changes in adolescent idiopathic scoliosis during walking: A protocol for systematic review and meta-analysis

BACKGROUND

To clarify the differences in biomechanical characteristics present in adolescent idiopathic scoliosis (AIS) patients during walking.

METHODS

Cross-sectional studies related to the biomechanical characteristics of AIS were included by searching 7 major databases and analyzed using RevMan 5.4 software.

RESULTS

There were a total of 15 trials involving 377 AIS patients. The results showed that during walking, AIS had increased pelvic coronal tilt (effect size [ES] = -1.34, 95% confidence intervals [CI] = -2.41 to -0.27, P = .01), knee and ankle sagittal mobility were reduced (ES = -5.22, 95% CI = -7.51 to -2.94, P < .001; ES = -3.58, 95% CI = -5.93 to -1.22, P = .003). The duration of electromyogram activity was prolonged in the gluteus medius (ES = 7.65, 95% CI = 5.33-9.96, P < .001), lumbar square (ES = 10.73, 95% CI = 6.97-14.49, P < .001), and erector spinae (ES = 14.35, 95% CI = 6.94-21.76, P < .001) muscles. The results of subgroup analysis showed that the step length of the concave side of the spine was reduced (ES = -0.36, 95% CI = -0.71 to -0.01, P = .04).

CONCLUSION

AIS has characteristic biomechanical changes in spatiotemporal, phase kinematics, motor mechanics, and electromyographic signatures. Further comprehensive studies are required in the future to analyze the biomechanical and electromyographic differences among different degrees and types of scoliosis, as well as the differences between the concave and convex sides of scoliosis during walking.

Vestibular Morphological Alterations in Adolescent Idiopathic Scoliosis: A Systematic Review of Observational Studies

Adolescent idiopathic scoliosis (AIS) is the most frequent pediatric spinal deformity. Its treatment still shows limited results due to the existent lack of knowledge regarding etiopathogenesis. Thus, the purpose of the study is to check the existence of vestibular morphological alterations among idiopathic scoliosis patients. To meet the objective, we performed this systematic review searching studies in PubMed Medline, SCOPUS, Web of Science, CINAHL Complete and SciELO until 15 September 2022. Articles that analyzed the morphology of the vestibular apparatus were selected, comparing subjects with AIS versus healthy subjects. Variables were selected that measured the orientation of the channels as well as the general conformation of the vestibular apparatus. One hundred and eighty-five records were retrieved in the preliminary searches, of which five studies were finally included, providing data from 154 participants (83 cases and 71 healthy controls) with a mean age 16.07 ± 2.48 years old. Two studies conclude that the superior and lateral semicircular canals are longer and thinner in patients with AIS. One study concluded that the measure between centers of superior and lateral canals and the angle whose vertex is placed the center of posterior canal were significantly shorter in subjects with AIS than in healthy controls in the left-side of vestibular apparatus. Two studies found an asymmetry in the verticality of the lateral canals on both sides in subjects with AIS, although it is not clear whether the left canal is in a more horizontal or vertical position. Patients with AIS seem to present morphological asymmetries of the vestibular apparatus, fundamentally on the left side. These anomalies seem to correlate with the location of the curve but not with its laterality or severity.

Can a structural leg length discrepancy contribute to persistent concussion symptoms? A case report

In the past several years, concussions and post-concussion syndrome (PCS) have become more commonly recognized conditions. However, with limited physiological explanation for post-concussion syndrome, there is also limited evidence supporting effective treatment. The vestibular system plays a role in postural reflexes and coordinated eye and cervical spine movements and is often disrupted in patients with prolonged concussion symptoms. This disruption has contributed to some of the most debilitating symptoms in PCS patients including dizziness, nausea, and balance deficits. Ongoing, post-concussion, vestibulo-ocular/cervical-ocular disruption due to an underlying structural leg length discrepancy as a contributing factor has not been previously described in the literature. A case of PCS with initial conservative treatment of their structural leg length discrepancy and subsequent vestibulo-ocular/cervical-ocular rehabilitation is presented.

Turning the Curve Into Straight: Phenogenetics of the Spine Morphology and Coordinate Maintenance in the Zebrafish

The vertebral column, or spine, provides mechanical support and determines body axis posture and motion. The most common malformation altering spine morphology and function is adolescent idiopathic scoliosis (AIS), a three-dimensional spinal deformity that affects approximately 4% of the population worldwide. Due to AIS genetic heterogenicity and the lack of suitable animal models for its study, the etiology of this condition remains unclear, thus limiting treatment options. We here review current advances in zebrafish phenogenetics concerning AIS-like models and highlight the recently discovered biological processes leading to spine malformations. First, we focus on gene functions and phenotypes controlling critical aspects of postembryonic aspects that prime in spine architecture development and straightening. Second, we summarize how primary cilia assembly and biomechanical stimulus transduction, cerebrospinal fluid components and flow driven by motile cilia have been implicated in the pathogenesis of AIS-like phenotypes. Third, we highlight the inflammatory responses associated with scoliosis. We finally discuss recent innovations and methodologies for morphometrically characterize and analyze the zebrafish spine. Ongoing phenotyping projects are expected to identify novel and unprecedented postembryonic gene functions controlling spine morphology and mutant models of AIS. Importantly, imaging and gene editing technologies are allowing deep phenotyping studies in the zebrafish, opening new experimental paradigms in the morphometric and three-dimensional assessment of spinal malformations. In the future, fully elucidating the phenogenetic underpinnings of AIS etiology in zebrafish and humans will undoubtedly lead to innovative pharmacological treatments against spinal deformities.

Vestibular Morphological Asymmetry Associated With Motion Sickness Susceptibility

Sensory conflicts leading to motion sickness can occur not only between but also within sensory modalities. The vestibular organs are located in both left and right inner ears, and their misalignment can be a source of self-motion related sensory conflicts. In the current study, using inner ear magnetic resonance imaging, we examined whether morphological asymmetry of the bilateral vestibular organs was associated with motion sickness susceptibility. The results showed a larger position asymmetry of bilateral vestibular organs in individuals with high rather than low susceptibility. In addition, vestibular position asymmetry was associated with reciprocal interaction (negative resting state functional connectivity) between vestibular and visuocortical regions in lowly, but not highly, susceptible individuals. In conclusion, these findings suggest that vestibular morphological asymmetry can be a source of sensory conflicts in individuals with dysfunctional reciprocal visuo-vestibular interactions, a putative neural mechanism for resolving sensory conflicts.

Idiopathic scoliosis: general characteristics and analysis of etiological theories (literature review)

Idiopathic scoliosis is a severe pathology of the musculoskeletal system that affects children and adolescents all over the world. The disease occurs in approximately 0.2-0.6% of the general population, and is the largest subgroup of spinal curvature in humans (70-90% of all known scoliosis cases). In idiopathic scoliosis, a threedimensional deformation of the vertebral column is formed, leading to the formation of a rib hump, curvature of the ribs and chest, asymmetry of the pelvis and impaired development of internal organs. The main feature of the disease is the spontaneous development of deformity during the growth of the child and the tendency to progress. Scoliosis is not only an orthopedic disease, but also a ignificant cosmetic, and, consequently, a psychological and social problem. The standard of treatment for scoliotic disease remains unchanged for a long time: observation, corset treatment and surgical correction. The prognosis for the development of pathology varies depending on the degree of deformation. The corset-therapy, hospitalization, surgery and treatment of chronic back pain have a negative impact on the psychoemotional state of children and adolescents. Despite significant advances in the methods of diagnosis of deformity, improvement of surgical treatment methods and in the study of pathogenesis, the etiological factor of pathology is still unknown. The search for the causes of idiopathic scoliosis covers almost all aspects of its possible origin: genetic, environmental, hormonal, metabolic, biochemical, neurological, and others. In recent decades, relevant theories of the development of scoliosis have been formulated, but none of the theories reveals the essence of the pathological process and has no clear justification. The greatest number of supporters is the genetic theory: genetic factors play a key role in the occurrence and development of idiopathic scoliosis. Understanding the underlying factors of the disease will enable prevention, early diagnosis, and identification of the risk groups of the patients in question.

Severity of Idiopathic Scoliosis Is Associated with Differential Methylation: An Epigenome-Wide Association Study of Monozygotic Twins with Idiopathic Scoliosis

Epigenetic mechanisms may contribute to idiopathic scoliosis (IS). We identified 8 monozygotic twin pairs with IS, 6 discordant (Cobb angle difference > 10°) and 2 concordant (Cobb angle difference ≤ 2°). Genome-wide methylation in blood was measured with the Infinium HumanMethylation EPIC Beadchip. We tested for differences in methylation and methylation variability between discordant twins and tested the association between methylation and curve severity in all twins. Differentially methylated region (DMR) analyses identified gene promoter regions. Methylation at cg12959265 (chr. 7 DPY19L1) was less variable in cases (false discovery rate (FDR) = 0.0791). We identified four probes (false discovery rate, FDR < 0.10); cg02477677 (chr. 17, RARA gene), cg12922161 (chr. 2 LOC150622 gene), cg08826461 (chr. 2), and cg16382077 (chr. 7) associated with curve severity. We identified 57 DMRs where hyper- or hypo-methylation was consistent across the region and 28 DMRs with a consistent association with curve severity. Among DMRs, 21 were correlated with bone methylation. Prioritization of regions based on methylation concordance in bone identified promoter regions for WNT10A (WNT signaling), NPY (regulator of bone and energy homeostasis), and others predicted to be relevant for bone formation/remodeling. These regions may aid in understanding the complex interplay between genetics, environment, and IS.

The orthopedic characterization of cfap298tm304 mutants validate zebrafish to faithfully model human AIS

Cerebrospinal fluid (CSF) circulation relies on the beating of motile cilia projecting in the lumen of the brain and spinal cord cavities Mutations in genes involved in cilia motility disturb cerebrospinal fluid circulation and result in scoliosis-like deformities of the spine in juvenile zebrafish. However, these defects in spine alignment have not been validated with clinical criteria used to diagnose adolescent idiopathic scoliosis (AIS). The aim of this study was to describe, using orthopaedic criteria the spinal deformities of a zebrafish mutant model of AIS targeting a gene involved in cilia polarity and motility, cfap298tm304. The zebrafish mutant line cfap298tm304, exhibiting alteration of CSF flow due to defective cilia motility, was raised to the juvenile stage. The analysis of mutant animals was based on micro-computed tomography (micro-CT), which was conducted in a QUANTUM FX CALIPER, with a 59 µm-30 mm protocol. 63% of the cfap298tm304 zebrafish analyzed presented a three-dimensional deformity of the spine, that was evolutive during the juvenile phase, more frequent in females, with a right convexity, a rotational component and involving at least one dislocation. We confirm here that cfap298tm304 scoliotic individuals display a typical AIS phenotype, with orthopedic criteria mirroring patient's diagnosis.

Etiopathogenesis of adolescent idiopathic scoliosis: Review of the literature and new epigenetic hypothesis on altered neural crest cells migration in early embryogenesis as the key event

Adolescent idiopathic scoliosis (AIS) affects 2-3% of children. Numerous hypotheses on etiologic/causal factors of AIS were investigated, but all failed to identify therapeutic targets and hence failed to offer a cure. Therefore, currently there are only two options to minimize morbidity of the patients suffering AIS: bracing and spinal surgery. From the beginning of 1960th, spinal surgery, both fusion and rod placement, became the standard of management for progressive adolescent idiopathic spine deformity. However, spinal surgery is often associated with complications. These circumstances motivate AIS scientific community to continue the search for new etiologic and causal factors of AIS. While the role of the genetic factors in AIS pathogenesis was investigated intensively and universally recognized, these studies failed to nominate mutation of a particular gene or genes combination responsible for AIS development. More recently epigenetic factors were suggested to play causal role in AIS pathogenesis. Sharing this new approach, we investigated scoliotic vertebral growth plates removed during vertebral fusion (anterior surgery) for AIS correction. In recent publications we showed that cells from the convex side of human scoliotic deformities undergo normal chondrogenic/osteogenic differentiation, while cells from the concave side acquire a neuronal phenotype. Based on these facts we hypothesized that altered neural crest cell migration in early embryogenesis can be the etiological factor of AIS. In particular, we suggested that neural crest cells failed to migrate through the anterior half of somites and became deposited in sclerotome, which in turn produced chondrogenic/osteogenic-insufficient vertebral growth plates. To test this hypothesis we conducted experiments on chicken embryos with arrest neural crest cell migration by inhibiting expression of Paired-box 3 (Pax3) gene, a known enhancer and promoter of neural crest cells migration and differentiation. The results showed that chicken embryos treated with Pax3 siRNA (microinjection into the neural tube, 44 h post-fertilization) progressively developed scoliotic deformity during maturation. Therefore, this analysis suggests that although adolescent idiopathic scoliosis manifests in children around puberty, the real onset of the disease is of epigenetic nature and takes place in early embryogenesis and involves altered neural crest cells migration. If these results confirmed and further elaborated, the hypothesis may shed new light on the etiology and pathogenesis of AIS.

Research progress on the etiology and pathogenesis of adolescent idiopathic scoliosis

Etiology of adolescent idiopathic scoliosis (AIS), a complicated three-dimensional spinal deformity with early-onset, receives continuous attention but remains unclear. To gain an insight into AIS pathogenesis, this review searched PubMed database up to June 2019, using key words or medical subject headings terms including "adolescent idiopathic scoliosis," "scoliosis," "pathogenesis," "etiology," "genetics," "mesenchymal stem cells," and their combinations, summarized existing literatures and categorized the theories or hypothesis into nine aspects. These aspects include bone marrow mesenchymal stem cell studies, genetic studies, tissue analysis, spine biomechanics measurements, neurologic analysis, hormone studies, biochemical analysis, environmental factor analysis, and lifestyle explorations. These categories could be a guidance for further etiology or treatment researches to gain inspiration.

Impact of the Vestibular System on the Formation and Progression to Idiopathic Scoliosis: A Review of Literature

The physiopathogenesis of adolescent idiopathic scoliosis remains unknown. However, a multifactorial pathogenesis is being assumed. Besides biomechanical, biochemical, and genetic factors, some studies have focused on congenital or acquired abnormalities in the vestibular organ with consecutive development of scoliosis. This study aims to analyze a possible correlation between any vestibular organ congenital or acquired pathologies and scoliosis based on the current literature. Therefore, we conducted a literature search in three databases, with search terms such as “scoliosis,” “organ of balance,” “idiopathic scoliosis,” “vestibular organ,” “spine,” and “balance.” Fifteen studies were selected and used for research. The relationship between scoliosis and vestibular organ abnormalities was recorded from all included works. Seven studies demonstrated a direct correlation between vestibular organ anatomical abnormalities and the form of the scoliotic spine. Another study confirmed the influence of the pathology of the vestibular organ on scoliosis but questioned whether it had an impact on the formation or the progression of the curvature. Others demonstrated a temporal overlap of the embryonic development of the vestibular organ and the beginning of pre-scoliotic characteristics, but their relationship remained questionable. In three studies, the correlation remained unclear, and any context has been denied. It seems unlikely that an isolated vestibular disorder can trigger structural scoliosis. However, the vestibular system pathologies may certainly occur in the multifactorial genesis of idiopathic scoliosis. Whether the correlation refers to the expression or the progression of scoliosis or may even have an influence on both remains unclear. New treatment options could be derived from these findings with a positive influence on the course of the deformity.

The link between lateral trunk flexion in Parkinson's disease and vestibular dysfunction: a clinical study

INTRODUCTION

Lateral trunk flexion (LTF) is a common postural deformity in Parkinson's disease (PD). Postural control is known to depend on visual, vestibular, and somatosensory information.

OBJECTIVES

This study aimed to investigate the relationship between vestibular dysfunction and postural abnormalities in PD patients with LTF.

METHODS

We enrolled a total of 19 PD patients with LTF (PD-LTF+) and 19 age- and sex-matched PD patients without LTF (PD-LTF-). All patients underwent vestibular tests, including spontaneous nystagmus, gaze-evoked nystagmus, ocular movements, optokinetic eye test, fast positioning maneuvers, and the bithermal caloric test.

RESULTS

Most of the PD-LTF + patients had abnormal vestibular function (11/19), while there were fewer vestibular function injuries in the control group (3/19). In PD-LTF + group, there were 5 patients (5/11, 45.5%) of peripheral vestibular dysfunction, 2 patients (2/11, 18.2%) of central vestibular damage, and 4 patients (4/11, 36.4%) of mixed injuries. The peripheral vestibular deficiencies could be either bilateral (4/9, 44.4%) or unilateral (5/9, 55.6%). The unilateral vestibular dysfunction was ipsilateral to the leaning side in 2 patients and contralateral to the leaning side in the other 3 patients.

CONCLUSION

Vestibular dysfunction may be an independent risk factor for LTF in PD patients.

Lateral semi-circular canal asymmetry in females with idiopathic scoliosis

Purpose

Adolescent idiopathic scoliosis (AIS) is a three-dimensional spinal structural deformity that occurs in otherwise normal individuals. Although curve progression and severity vary amongst individuals, AIS can lead to significant cosmetic and functional deformity. AIS etiology has been determined to be genetic, however, exact genetic and biological processes underlying this disorder remain unknown. Vestibular structure and function have potentially been related to the etiopathogenesis of AIS. Here, we aimed to characterize the anatomy of the semicircular canals (SCC) within the vestibular system through a novel approach utilizing T2-weighted magnetic resonance images (MRI).

Methods

Three dimensional, MRI-based models of the SCCs were generated from AIS subjects (n = 20) and healthy control subjects (n = 19). Linear mixed models were used to compare SCC morphological measurements in the two groups. We compared side-to-side differences in the SCC measurements between groups (group*side interaction).

Results

Side-to-side differences in the lateral SCC were different between the two groups [false discovery rate adjusted p-value: 0.0107]. Orientation of right versus left lateral SCC was significantly different in the AIS group compared to the control group [mean side-to-side difference: -4.1°, 95% CI: -6.4° to -1.7°]. Overall, among subjects in the AIS group, the left lateral SCC tended to be oriented in a more horizontal position than subjects in the control group.

Significance

Asymmetry within the SCCs of the vestibular system of individuals with AIS potentially results in abnormal efferent activity to postural muscles. Consequences of this muscular activity during periods of rapid growth, which often coincides with AIS onset and progression, warrant consideration.

Bone Mineral Density in Patients Suffering from Ménière's Disease

INTRODUCTION

Previous studies have reported an association between reduced bone mineral density and the occurrence of benign paroxysmal positional vertigo, balance impairment, and saccular dysfunction. Furthermore, the results of recent animal studies have raised the possibility that vestibular dysfunction could affect bone remodeling and bone mass. The goal of the study was to compare bone mineral density of patients suffering from definite Ménière's disease to that of a matched control group.

METHODS

We conducted a case-control cross-sectional study in a tertiary referral center. The study group included 23 patients suffering from definite Ménière's disease, and the control group was comprised of 23 patients matched in their race, gender, and age parameters in whom no vestibular pathology could be found. Dual energy X-ray absorptiometry of the femoral head was used for the assessment of bone mineral density. The T and Z scores of the femoral heads' bone mineral density were compared.

RESULTS

The average T scores were -1.53 ± 1.08 in the study and -0.39 ± 0.72 (p = 0.016) in the control groups, and the Z scores were -0.4 ± 0.63 and 0.33 ± 0.31 (p = 0.018), respectively. Seventeen patients (74%) of the study group and 9 (39%) of the control group had T scores less than -1.0, indicating osteopenia/osteoporosis (p = 0.036).

CONCLUSIONS

The results showed a significant association between Ménière's disease and reduced bone mineral density of the femoral head. Bone mineral density studies of the weight-bearing bones are warranted in Ménière's disease for the early diagnosis and treatment of osteopenia/osteoporosis on the one hand and possible benefit of this treatment for the evolution of Ménière's disease on the other hand.

Asymmetric Unilateral Vestibular Perception in Adolescents With Idiopathic Scoliosis

The cause of Adolescent Idiopathic Scoliosis (AIS) remains unclear, but one proposed cause of AIS is asymmetric vestibular function and the related descending drive to the spine musculature. The objective of this study was to determine if asymmetric vestibular function is present in individuals with AIS. Ten individuals with AIS (8F, 2M) and 10 healthy age- and sex-matched controls were exposed to 10s-long virtual rotations induced by monaural or binaural electrical vestibular stimulation (EVS), and 10s-long real rotations delivered by a rotating chair. Using a forced-choice paradigm, participants indicated their perceived rotation direction (right or left) to stimuli of varying intensity. A Bayesian adaptive algorithm adjusted the stimulus intensity and direction to identify a stimulus level, which we called the direction recognition threshold, at which participants correctly identified the rotation direction 69% of the time. For unilateral vestibular stimuli (monaural EVS), the direction recognition thresholds were more asymmetric in all participants with AIS compared to control participants [(0.22-1.00 mA) vs. (0.01-0.21 mA); p < 0.001]. For bilateral vestibular stimuli, however, the direction recognition thresholds did not differ between groups for either the real or virtual rotations (multiple p > 0.05). Previous reports of semicircular canal orientation asymmetry in individuals with AIS could not explain the magnitude of the vestibular function asymmetry we observed, suggesting a functional cause to the observed vestibular asymmetry. Thus, the present results suggest that a unilateral vestibular dysfunction is linked to AIS, potentially revealing a new path for the screening and monitoring of scoliosis in adolescents.

Postural and muscle responses to galvanic vestibular stimulation reveal a vestibular deficit in adolescents with idiopathic scoliosis

One of the most appealing hypotheses around the aetiopathogenesis of adolescent idiopathic scoliosis attributes the development of the spine deformity to an imbalance in the descending vestibulospinal drive to the muscles resulting in a differential mechanical pull on the spine during the early life stages. In this study, we explored this hypothesis by examining postural and muscle responses to binaural bipolar galvanic vestibular stimulation (GVS) of randomly alternating polarity. Adolescents diagnosed with idiopathic scoliosis (n = 12) and healthy age-matched controls (n = 12) stood quietly with feet together (stance duration 66-102 s), eyes closed and facing forward, while 10 short (2s), transmastoidal, bipolar square wave GVS pulses (0.3-2.0 mA) of randomly alternating polarity were delivered at varying time intervals. Responses depicted in the electromyographic (EMG) activity of bilateral axial and appendicular muscles, vertical reaction forces and segment kinematics were recorded and analysed. Scoliotic patients demonstrated smaller ankle muscle responses and a delayed postural shift to the right relative to controls during anode right/cathode left GVS. When GVS polarity was reversed, patients had a greater soleus short-latency response on the left anodal side, while the rest of the muscle and postural responses were similar between groups. Vestibular stimulation also evoked greater head and upper trunk sway in scoliotic compared with healthy adolescents irrespective of stimulus polarity. Results provide new preliminary evidence for a vestibular imbalance in adolescents with idiopathic scoliosis that is compensated by somatosensory, load-related afferent feedback from the lower limbs during the latter part of the response.

Considerations for Testing and Treating Children with Central Vestibular Impairments

This perspective explores common pediatric diagnoses that could present with central vestibular pathway dysfunction, leading to delays in motor development and postural control, and gaze instability. Specifically, the following diagnoses are considered: cerebral palsy, myelomeningocele, vestibular migraine, attention-deficit hyperactivity disorder, developmental coordination disorder, concussion, childhood cancer, congenital muscular torticollis, adolescent idiopathic scoliosis, and autism. Suggestions for clinical screening, vestibular function testing, and vestibular rehabilitation for children with these diagnoses are based on evidence for the efficacy of testing and interventions for children with peripheral vestibular hypofunction. More research is needed to explore peripheral and central vestibular function in children with these diagnoses. Testing and intervention methods may need to be modified to accommodate for the specific behavior and motor challenges that some children might present. Researchers should develop technology so that gaze stabilization exercises can be delivered in a fun, functional, and effective way.

Current insights into the aetiology of adolescent idiopathic scoliosis

Scoliosis occurs in about 0.2-0.6% of the general population. In the majority of cases the cause of this entity remains mostly unidentified. The search for the causes covers almost all aspects of its possible origin. We collected and systematised the contemporary theories and concepts concerning the aetiology of adolescent idiopathic scoliosis. Genetic and hereditary factors are commonly accepted as possible causes; however, the identification of the single gene responsible for the development of this condition seems impossible, which suggests multifactorial mechanism of its formation. Dysfunctions of the nervous system are recognised risks related to the development of scoliosis, but they are classified as belonging to a separate aetiological category. Scoliosis develops at the quickest rate during the child's growth spurt, which prompted the research on the role of the growth hormone in scoliosis aetiology. Melatonin is another hormone that is studied as a possible factor involved in development of this entity. In cases of progressive scoliosis, increased activity of calmodulin-a protein that regulates the levels of calcium ions-has been observed. The scientists have characterised numerous qualitative and quantitative changes in the composition of the tissue of intervertebral discs, spinal ligaments and paraspinal muscles. Some of the theories, explaining the nature of this entity, presented in this review seem to have only a purely theoretical value; their proliferation only confirms the fact that the actual nature of this condition has not been unveiled yet, and suggests its multifactorial aetiology.