Restricted neural plasticity in vestibulospinal pathways after unilateral labyrinthectomy as the origin for scoliotic deformations

• Published in: The Journal of neuroscience 2013-04, Vol.33 (16), p.6845-6856
• Main Authors: Lambert, François M, Malinvaud, David, Gratacap, Maxime, Straka, Hans, Vidal, Pierre-Paul
• Format: Article
• Language: English
• Subjects: Animals; Anura; Disease Models, Animal; Evoked Potentials; Evoked Potentials - physiology; Female; Fluoresceins; Fluoresceins - metabolism; Functional Laterality; Functional Laterality - physiology; In Vitro Techniques; Larva; Life Sciences; Male; Muscular Diseases; Muscular Diseases - etiology; Neural Pathways; Neurodegenerative Diseases; Neurodegenerative Diseases - etiology; Neuronal Plasticity; Neuronal Plasticity - physiology; Scoliosis; Scoliosis - etiology; Sensation Disorders; Sensation Disorders - etiology; Spinal Cord; Spinal Cord - physiology; Statistics, Nonparametric; Time Factors; Vestibule, Labyrinth; Vestibule, Labyrinth - injuries; Vestibule, Labyrinth - physiology; Vestibulocochlear Nerve Diseases; Vestibulocochlear Nerve Diseases - complications; Xenopus
• ISSN: 0270-6474; 1529-2401; 1529-2401
• DOI: 10.1523/jneurosci.4842-12.2013

Adolescent idiopathic scoliosis in humans is often associated with vestibulomotor deficits. Compatible with a vestibular origin, scoliotic deformations were provoked in adult Xenopus frogs by unilateral labyrinthectomy (UL) at larval stages. The aquatic ecophysiology and absence of body-weight-supporting limb proprioceptive signals in amphibian tadpoles as a potential sensory substitute after UL might be the cause for a persistent asymmetric descending vestibulospinal activity. Therefore, peripheral vestibular lesions in larval Xenopus were used to reveal the morphophysiological alterations at the cellular and network levels. As a result, spinal motor nerves that were modulated by the previously intact side before UL remained permanently silent during natural vestibular stimulation after the lesion. In addition, retrograde tracing of descending pathways revealed a loss of vestibular neurons on the ipsilesional side with crossed vestibulospinal projections. This loss facilitated a general mass imbalance in descending premotor activity and a permanent asymmetric motor drive to the axial musculature. Therefore, we propose that the persistent asymmetric contraction of trunk muscles exerts a constant, uncompensated differential mechanical pull on bilateral skeletal elements that enforces a distortion of the soft cartilaginous skeletal elements and bone shapes. This ultimately provokes severe scoliotic deformations during ontogenetic development similar to the human syndrome.