PINEALECTOMY AND SCOLIOSIS IN THE CHICKEN: MORPHOLOGY AND RELATIONSHIP TO MELATONIN LEVELS

Abstract

Introduction: The development of scoliosis in pinealectomised chickens was first observed by Machida¹ and since reported by others. That melatonin deficiency following pinealectomy may be a factor in causing scoliosis has been postulated. The relationship between pinealectomy, scoliosis and serum melatonin levels has been subject to experimental investigations. This study reports the incidence and type of scoliosis in pinealectomised, sham operated and unoperated chickens, and related serum melatonin levels.

Methods: Serum melatonin levels were obtained at sacrifice up to six weeks postoperatively. Radiological and histological examination of the spine was performed.

Results: The vertebral motion segment comprises a synovial joint lacking any discs. 19% of the un-operated group had a sharp angular deformity in contrast to the smooth curve seen in adolescent idiopathic scoliosis (AIS). There was a 38% incidence of scoliosis after sham operation (mostly of the angular variety) and a 75% incidence in the pinealectomy group (of which half were smooth curves similar to those in human AIS. Melatonin was not abolished by pinealectomy or sham operation but was at significantly lower levels than in the unoperated group. There was no difference in Melatonin levels between birds with the two types of curves.

Discussion: The avian spine has fundamental structural differences with the human. There is a natural incidence of short angular scoliosis that increases with posterior fossa surgery in the chicken. We confirm that scoliosis similar to AIS forms after pinealectomy but it is not directly related to diminished melatonin levels.