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.