Abnormal Differential Longitudinal Growth of Spinal Cord and Vertebral Column in Adolescent Idiopathic Scoliosis: A Study with Multi-Planar Reformat Magnetic Resonance Imaging

Introduction: Tonsillar herniation, abnormal anthropometric growth and relative spinal overgrowth have been reported in AIS. Abnormal somatosensory function without obvious clinical neurological deficit was found to be associated with AIS patients with severe curve. All these observations suggest a possible neural origin of the etiopathogenesis of AIS, which can be linked to a disproportional growth between spinal column and cord.

Objectives: By using two dimensional (2D) MR imaging and reformat technique, to measure the ratio of cord length to vertebral column length in healthy adolescent girls and to compare the differences with AIS patients of different curve severity. The position of the cerebellar tonsils was also evaluated.

Methods: 2D sagittal MRI of the spine was performed in 42 adolescent girls (14 mild AIS, 14 severe AIS and 14 age-matched healthy controls). Measurements of spinal cord, vertebral column length and tonsillar position were made on reformat images and correlated with somatosensory evoked potential (SSEP) studies.

Results: No significant differences in the absolute spinal cord length were found between controls and AIS patients with different severity. However, there was significant relative segmental lengthening of the spinal column at the thoracic level in AIS patients with severe curve. The ratio of cord to vertebral column length was significantly reduced (p<0 .01) in AIS patients with severe curve. The above differences were not observed the mild and control group. There was high interobserver reliability (intraclass correlation="" 0.9) measurement. 28% (8/28) of scoliosis also found to have low-lying cerebellar tonsils abnormal SSEP respectively.

Conclusion: Cord to vertebral column ratios are significantly reduced in the AIS patients with severe curve suggesting a disproportional growth between the skeletal and the neural systems.