Abnormal Connection between Lateral and Posterior Semicircular Canal Revealed by a New Modeling Process

Abstract

We developed a modeling procedure using CT scans or MRI data for exploring the bony and lymphatic canals of vestibular patients. We submitted 445 patients with instability and spatial de-orientation to this procedure. Out of the 445 patients, 95 had scoliosis, some of them, because malformations were suspected also had CT-scan modeling and functional tests. We focused on a never described, abnormal connection between the lymphatic lateral and posterior canal (LPCC) with a frequency of 67/445 (15%). In the scoliosis subgroup, the frequency was 52/95 (55%). Three scoliotic patients had CT scans. For each of them, the modeling revealed that LPCC was present on the bony canals. LPCC has pathognomic signs: no rotatory vertigo but frequent instability, transport sickness head tilt on the side of the anomaly, and spatial disorientation in new environment. We evaluated the functional impact of LPCC by testing the vestibulo-ocular reflex (VOR) in horizontal and vertical planes and found reproducible abnormal responses: in the case of left LPCC, during a counterclockwise horizontal rotation or a post clockwise horizontal rotation, added to the expected horizontal nystagmus, we found an unexpected upbeat nystagmus induced by the ampullofugal displacement of the fluid in the posterior canal. As LPCC was found in CT scans and MRI modeling for a same subject, we suggest that it could be a congenital abnormal process of ossification of the canals. The responses to the vestibular tests highlighting constant unexpected nystagmus underline the potential functional consequences of LPCC on vestibular perception and scoliosis.

Is abnormal vestibulomotor responses related to idiopathic scoliosis onset or severity?

“…For instance, Shi et al [28] observed a decrease in the distance between centers of lateral and superior canals in the leftside vestibular system. Results from another study have confirmed morphological abnormalities in patients with AIS with small curve deformity [13]. Overall, these results suggest that spine deformity may occur due to malformation of the vestibular apparatus.…”

“…Consequently, during the last decades, several authors have suggested that scoliosis onset may be related to impairment of the vestibular system because of its contribution to regulation of axial muscles tone e.g. [5,[11][12][13]. Nonetheless, no study has addressed whether direct vestibular stimulation would lead to abnormal motor response in patients with AIS compared to controls.…”

Evaluation of motion sickness susceptibility by motion sickness susceptibility questionnaire in adolescents with idiopathic scoliosis: a case–control study

“…One of AIS etiological hypotheses is that the scoliotic deformation is the result of orthostatic postural control disorder, with a disturbance of internal representation of the gravitational vertical [6]. Thus, the vestibular system is the most studied sensory modality [6,[9][10][11], because it has an important role in orthostatic postural control, and measures the earth gravitational vector directly. An asymmetric disturbance of the vestibular system leads to an asymmetric activity of vestibular-spinal tract, and an asymmetric paravertebral muscle tone, which, in growing adolescent results in a scoliotic deformity [10].…”

“…Thus, the vestibular system is the most studied sensory modality [6,[9][10][11], because it has an important role in orthostatic postural control, and measures the earth gravitational vector directly. An asymmetric disturbance of the vestibular system leads to an asymmetric activity of vestibular-spinal tract, and an asymmetric paravertebral muscle tone, which, in growing adolescent results in a scoliotic deformity [10]. This is Evaluation impossible due to psychic, social or geographical problems, or inability to understand Physical examination shows measurable gibbous deformity on the forward bending test [28] confirmed by experiments in animals [11].…”

“…In favor of the first theory, investigations in AIS have shown disturbances of the different sensory modalities [5][6][7][8][9]. For example, several authors suggest asymmetrical peripheral disorder of the vestibular system in AIS [6,[9][10][11]. This abnormality could induce, via impaired activity of vestibulo-spinal tract, asymmetric paravertebral muscle tone [9,11].…”