Introduction

At the Zorab Symposium in Oxford, 2006, we showed that semicircular canal (SCC) anomalies occurring with posterior basicranium asymmetry affect the oculovestibular system in human beings. As a consequence, we proposed the hypothesis of a descending direct vestibulospinal and cognitive top-down effect on some scoliosis. We will show that some SCC anomalies detected with MRI modelling are malformations frequently found in scoliosis.

Introduction

The Proprio-oculo-vestibular system is involved in scoliosis. In Congress ZORAB, Oxford 2006, we showed correlations between morphological semicircular canals (SCC) anomalies and vestibular dysfunctions associated with oculomotor anomalies. We will describe a set of specific anomalies in adolescent idiopathic scoliosis (AIS) in favour of an altered perception of space.

The assessment of vestibular function throws new light on scoliosis. Vestibular morphological anomalies are frequent in scoliosis. This communication has two aims:

to correlate the dysfunctions of the semi-circular canal system with morphological anomalies.

These anomalies are demonstrated by graphic modelling from MRI images (see abstract of Dr. Rousié). The examination of the proprio-oculo-labyrinthine system is done by Videonystagmography (VNG) and Videooculography (VOG). We able to test both horizontal and vertical canal function to give a 3D vestibular assessment. We use these tests to measure primitive vestibular dissymmetry (PVD). We compare the 3D endolymphatic morphology with the 3D vestibular function.

Results: The study comprises more than 100 cases. Inclusion criteria: scoliosis and cranio-facial asymmetry (CFA); Exclusion criteria: previous history of vestibular pathology or head injury.

In the horizontal plane the correlations are: with caloric test over 80%; with kinetic test around 70%;

In the vertical plane the correlation is around 70%. The figures will be detailed in the communication.

The difference between the results obtained with the caloric test and the kinetic tests is in connection with the phenomena of central compensation. On the vestibular level there is a close connection between the scoliosis, the vestibular morphological anomalies and the vestibular examination.

Clinical application: We proceed systematically to a vestibular assessment, even in absence of vestibular complaints or disequilibrium. We have found in certain cases where there has been a poor response to treatment or a defect of compliance, there has been an anomaly of vestibular function. After vestibular rehabilitation we observe an improvement of the effectiveness and acceptance of the treatment. We analyse the proprio-oculo-labyrinthin system by VNG, VOG, fundus (asymmetry of static ocular torsion) and the vestibulo-spinal system by posturography. The main anomalies concern vertical semi-circular canals function, otolithic system and vertical ocular smooth pursuit. The vestibular rehabilitation rebuilds a coherence between these three systems. This is possible in the child of more than six years. For us the vestibular assessment and vestibular rehabilitation are the first step of the management of the treatment.

The vestibular assessment and vestibular rehabilitation are necessary because of the close connections between the anomalies of the proprio-oculo-labyrinthin and the scoliosis.

Introduction: Several authors observed links between AIS and asymmetries as in function and anatomy, especially in the brain. Others described high frequency of AIS in patients suffering from craniofacial asymmetry (CFA). CFA involves asymmetry of Basicranium separating the face from the brain. Because of neurodevelopmental factors, CFA reflects brain growth. So, Posterior Basicranium (PB) asymmetry involves cerebellum asymmetry and spatial asymmetry of vestibular organs. In a previous study we highlighted that CFA was associated with functional anomalies: difficulty of fixation caused by ocular torsion, off balance caused by vestibular dysfunction, postural disorders.

Purpose: To explore AIS on different levels: PB, Eyes and Vestibular System.

Patients:

Control group (CG):32 subjects, 26W. & 6M., fr. 8 to 51.

Methods: We used MRI (EXCITE G.E.) 1.5T, head coil, Volumic T2-weighted sequence.

Step1: 3D Basicranium measurements in both groups with Brainvisa processing: (http://brainvisa.info/)

Discussion: Normal subjects revealed weak asymmetry and dorsoventral rotation of P.B & cerebellum

AIS showed a pathognomic increase of these Human traits. Inside AIS subgroups, TL & G3 revealed highest levels of asymmetry and rotation.

We will discuss, thanks to AIS homozygosis twins in mirror, genetic origins for these specific P.B. & Cerebellum asymmetries.

Modelling of semi-circular canals revealed significative malformations in AIS compared to normal group. Again, T.L. and G3 revealed highest scores of canals anomalies. We highlighted a specific malformation in AIS: abnormal connexion between lateral & posterior canal.

We will demonstrate, thanks to same AIS twins, genetic origins of this malformation and propose a genetic hypothesis to link the different results.

Conclusion: These specific anomalies could be considered as preventive factors of AIS. Work supported by Cotrel Fondation.