Somatosensory cortectomy induces motor cortical hyperexcitability and scoliosis: an experimental study in developing rats

Abstract Background context Dysfunctions in sensorimotor integration, reminiscent to those described in idiopathic dystonia, have been found in idiopathic scoliosis (IS) and might be involved in its pathogenesis. Studying the effects of experimental disruption of sensory cortex may shed further insi...

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Published in:The spine journal 2013-08, Vol.13 (8), p.938-946
Main Authors: Domenech, Julio, MD, PhD, Barrios, Carlos, MD, PhD, Tormos, Jose M., MD, PhD, Pascual-Leone, Álvaro, MD, PhD
Format: Article
Language:English
Subjects:
Animals
Cerebral cortex
Cortico-cortical inhibition
Disease Models, Animal
Etiology
Evoked Potentials, Motor - physiology
Evoked Potentials, Somatosensory - physiology
Experimental scoliosis
Idiopathic scoliosis
Motor Cortex - physiopathology
Orthopedics
Rats
Rats, Wistar
Scoliosis - etiology
Scoliosis - physiopathology
Somatosensory Cortex - physiopathology
Somatosensory Cortex - surgery
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Summary:Abstract Background context Dysfunctions in sensorimotor integration, reminiscent to those described in idiopathic dystonia, have been found in idiopathic scoliosis (IS) and might be involved in its pathogenesis. Studying the effects of experimental disruption of sensory cortex may shed further insight into the etiopathology of IS. Purpose To evaluate whether disruption of central sensorimotor integration through partial ablation of the somatosensory cortex leads to scoliosis in developing rats and to describe the effects of such an intervention on motor cortico-cortical inhibition and facilitation. Methods Fifty Wistar rats aged 3 weeks were used in the study. Twenty-four rats underwent craniotomy and electrocoagulation of the sensory cortex (PAR1) in the right hemisphere. A second group of 16 rats underwent a sham operation with craniotomy but no electrocoagulation. A third group of 10 rats was used as intact controls. Four weeks after surgery, motor cortical excitability was assessed with paired-pulse electrical cortical stimulation. Neurologic and behavioral examinations were completed serially, and 10 weeks after surgery, X-ray examinations were performed in anesthetized rats to assess spinal curvature. Electromyographic recordings of paravertebral muscle activity were performed in waking rats. At the end of the study, rats were sacrificed, and histologic examinations of brain tissue were performed to confirm the extent of the lesion. A grant from a Government Health Research Fund without salaries assignment financed the study. Results Almost half of the animals with somatosensory cortectomy (46%) developed scoliosis, with an average Cobb angle of 23±8°. None of the animals in the sham or control groups developed scoliosis. Despite cortical lesions, no motor or behavioral deficits were apparent in the experimental group, and cortectomized rats were neurologically indistinguishable from sham or control animals, except for the presence of scoliosis. Cortico-cortical inhibition was significantly reduced in the hemisphere of scoliotic concavity in the cortectomized group but was normal in the other groups. Conclusions These findings indicate that altered sensorimotor integration may cause scoliosis without noticeable motor impairment. Reduced cortico-cortical inhibition was observed in cortectomized rats. This finding is consistent with results in adolescents with IS and suggests that alteration of cortical hemispheric balance of sensorimotor integration
ISSN:1529-9430
1878-1632
DOI:10.1016/j.spinee.2013.03.002