Preoperative MRI analysis of patients with idiopathic scoliosis - A prospective study

Study Design. A prospective trial of preoperative MRI study in patients with "idiopathic" scoliosis. Objectives. To investigate the prevalence of neural axis malformations and the clinical relevance of MRI in the evaluation of patients with idiopathic scoliosis undergoing surgical intervention. Summary of Background Data. With the development of MRI, neural axis abnormalities such as syringomyelia or Chiari malformations are increasingly being found in patients with "idiopathic" scoliosis. The risk of neurologic complications during correction of scoliosis without prior decompression surgery for syringomyelia has been documented; however, there have been no prospective studies for identifying the risk of neurologic complications as a result of scoliosis surgery in patients with asymptomatic neural axis malformations. Methods. A total of 250 patients who were classified as having "idiopathic" scoliosis at first presentation and admitted for spinal surgery were evaluated. All patients were examined for neural axis abnormalities using MRI. The presence of neurologic symptoms and abnormal neurologic signs was also examined before and after surgical intervention. Neurologic complications during scoliosis surgery were reviewed in patients with neural axis abnormalities. Results. There were 44 (18%) patients (13 males and 31 females) who had neural axis abnormalities on MRI, including syringomyelia with Chiari malformations in 22 patients, syringomyelia with tonsillar ectopia in 2, Chiari malformations in 13, tonsillar ectopia in 6, and low conus medullaris in 1. On clinical examination, 44 (18%) patients had abnormal neurologic signs and 26 (7%) patients complained of headache or back pain. There were significant differences between patients with and without neural axis abnormalities regarding the age at first visit, gender, curve pattern, sagittal profile of thoracic spine, presence of neurologic deficit, and complaint of pain. Only 12 of 44 patients needed neurosurgical treatment for foramen magnum decompression before correction of scoliosis. Neurologic status temporarily worsened in 3 patients, including 2 patients with neurosurgical treatment and 1 patient without neurosurgical treatment; however, there were no permanent neurologic complications as a result of scoliosis surgery. All patients without neurologic deficits or complaints of pain did not receive neurosurgical treatment, while they had no permanent neurologic complications. Conclusions. Foramen magnum decompression for neural axis malformations could prevent permanent neurologic complications during scoliosis surgery. There is little risk of neurologic complications in patients with "idiopathic" scoliosis whose neurologic status is normal, even if these patients have a neural axis malformation on MRI.