UNILATERAL CLOSURE OF THE NEUROCENTRAL JUNCTION AS A CAUSE OF ADOLESCENT IDIOPATHIC SCOLIOSIS

Abstract

Introduction: Although there are several known causes of scoliosis, most are of unknown cause and develop during adolescence, making adolescent idiopathic scoliosis (AIS) the most common form. It has long been hypothesised that unilateral closure of the neurocentral junction accompanied by continued growth on the opposite side could lead to vertebral rotation and subsequent lateral curvature. However, autopsy studies of neurocentral junction closure in children has revealed that these joints close at approximately six years of age consequently excluding this hypothesis as a cause of AIS. In contrast, a recent MRI study has suggested that in some children at least, the NCJ does not close until much later in development around the time of puberty thereby resurrecting this hypothesis as a potential cause of AIS. This study was designed to investigate closure time and pattern of closure of the NCJ in normal patients to determine whether further examination of this hypothesis might be warranted.

Methods and results: The morphology of the NCJs in 20 patients between the ages of 3 and 15 were observed in MR images taken for purposes other than spinal anomaly. The structure of individual NCJs were observed and reconstructed in 3-dimensions. The age at which NCJs became closed was determined and pattern of closure of a typical NCJ was created using the reconstructed images. The pattern of closure of the NCJs along the vertebral column was also determined and any differences between right and left sides at the same level was also noted.

The results showed that there was a sequence of closure along the vertebral column for the NCJs with those in the cervical and lumbar regions being the first to close and those at the approximate level of T8 being the last to close. While the NCJs in the cervical and lumbar regions close at 5–6 years of age, those in the thoracic region, that are the last to close, do so at approximately 12 years of age. No significant difference between the stage of closure of the left and right sides was seen at any level.

Conclusion: The results of this study have shown that the closure of the NCJs in those vertebrae that form at approximately the most common level for the apical vertebra associated with AIS (midthoracic) does not occur until the time of puberty. This contrasts sharply with previously held views on the age of closure. Although no significant difference in closure between left and right sides was seen among these particular patients it does not exclude unilateral closure as a cause of AIS at least in some patients. These results suggest that examination of this hypothesis should be resurrected and that further study is well warranted. MR examination of young patients with small, initial curves could be well worthwhile.