Study Key Points:
Posterior Basicranium (PBA), divided in 2 parts joined to the foramen magnum, presents a torque in Idiopathic scoliosis (IS) PBA torque reflects cerebellar asymmetry in IS. PBA torque induces spatial asymmetry of the vestibular system and specially, of the otolithic system, with potential consequences on vestibular function and posture in IS.
PBA asymmetry and idiopathic scoliosis Study design Are there neuro-anatomical abnormalities associated with idiopathic scoliosis (IS) Posterior Basicranium (PBA) reflects cerebellum growth and contains vestibular organs, two structures suspected to be involved in scoliosis. Objective The aim of this study was to compare posterior basicranium asymmetry (PBA) in Idiopathic scoliosis (IS) and normal subjects.
To measure the shape of PBA in 3D, we defined an intra-cranial frame of reference based on CNS and guided by embryology of the neural tube. Measurements concerned three directions of space referred to a specific intra cranial referential. Data acquisition was performed with T2 MRI (G.E. Excite 1.5T, mode Fiesta). We explored a scoliosis group of 76 women and 20 men with a mean age of 17, 2 and a control group of 26 women and 16 men, with a mean age of 27, 7.
IS revealed a significant asymmetry of PBA (Pr>|t|<.0001) in 3 directions of space compared to the control group. This asymmetry was more pronounced in antero-posterior (AP) & lateral direction, forming a torque of the posterior base shape associated with identical cerebellar torque.
IS Cerebellar and PBA asymmetries are neurodevelopmental anomalies involved in IS. The vestibular systems are embedded in the 2-parted PBA and, therefore, are in asymmetrical spatial position with potential consequences on otolithic function because this latter is devoted to gravity. In 2002, Kwak demonstrated links between patterning of the cerebellum and alterations in the development of the internal ear in experimental zebra fish (focused on semi-circular canals formation) We engaged a study on IS semi-circular canals anatomy thanks to a novel program of modelling. We will report our first results in the companion paper.
According to a report by Nachemson,idiopathic Scoliosis is now generally recognized to be caused by several conditions:
Various studies have reported links between IS and asymmetry at similar functional and anatomical levels: Chockalingam, Shimode, Kramers and Perret have reported right/left asymmetries at functional levels for gait or motor control parameters.
Geissele and Kertesz have stressed the presence of links between IS and right/left brain asymmetries. Geschwind & Galaburda have highlighted asymmetries of the temporal planum, with the left planum being more developed in 65% of examined brains. In a study by Lundstrom 60 to 75% of the examinated population has a left hemisphere larger than the right. He measured the angle formed by a line drawn from the ear to the median line. This anatomical detail has also been noted by Burke who pointed out that cause of this asymmetry is still unknown. More recently, neuroanatomical abnormalities in the pontine and hindbrain regions have been clearly implicated, in IS, in a report by Lowe in 2000. Pirttiniemi, Lahtela, Hunggare & Serlo, Delaire, Berthoz & Rousié have reported the presence of craniofacial asymmetry(CFA) in certain cases of scoliosis and /or laterocolis. These asymmetries are associated with spatial asymmetries of vestibular organs involved in postural control. CFA implicates asymmetry of each bony component of the head: vault, face and basicranium.
The basicranium is divided in three parts:
the anterior part
the middle part which is a true patella which makes the 3D movements of the two other parts possible and the posterior part in which the labyrinths are embedded. The basicranium shape reflects the underlying brain growth.
Cerebral asymmetry appears, in utero,at the beginning of the third week. At this stage, the basicranium is a pre-cartilaginous and flexible structure: the three parts of the base are separated by large and mesenchymal synchondrosis avoiding any pressure that could affect the brain growth. It is therefore obvious that no basicranium asymmetry would occur without cerebral asymmetry. The aim of this study was to compare the shape of the posterior basicranium (PBA) on IS and non-IS subjects.
This study was conducted for two reasons:
1) the PBA reflects the growth of the cerebellum, the asymmetry of which is though to be implicated in scoliosis and
2) the PBA contains vestibular organs implicated in postural disorders
Download the complete study in PDF format which talks about Posterior Basicranium asymmetry and idiopathic scolios