Clinical Relevance of Preoperative MRI in Adolescent Idiopathic Scoliosis: Is Hydromyelia a Predictive Factor of Intraoperative Electrophysiological Monitoring Alterations?

Study Design: This was a prospective cohort study. Objectives: The main objectives of this study were to evaluate the prevalence and clinical relevance of neuroaxial anomalies in adolescent idiopathic scoliosis (AIS) patients as well as to evaluate different clinical and radiologic variables as potential predictors of the presence of a magnetic resonance imaging (MRI) abnormality. Summary of Background Data: The usefulness of preoperative magnetic resonance imaging in AIS is still debated in the literature as well as the clinical relevance of the neuroaxial anomalies detected. Materials and Methods: We performed an analysis on 88 patients affected by AIS with normal neurological examination undergoing a posterior arthrodesis intervention. Patients were stratified according to the presence and type of neuroaxial abnormalities and were compared by age, sex, Risser grading, Lenke curve type, coronal and sagittal curve parameters, presence of alterations at intraoperative neuromonitoring, and "pain" and "function" scores at the SRS-22 test. Results: Neuroaxial abnormalities were reported in 23 patients (26.14%): 14 hydromyelias, 7 syringomyelias, 1 case of Chiari I syndrome, and 1 case of spinal ependymoma. Age, sex, Risser grading, curve type, and coronal and sagittal curve parameters did not differ between normal patients and patients with any neuroaxial abnormality. Alterations of motor-evoked potential/somatosensory-evoked potential monitoring during surgery were reported in 23 patients; the difference in their incidence between normal (20%) and hydromyelia (64%) patients was significant (P<0.01). In evaluating the subareas of the SRS-22 test, we found that the "function" scores differed significantly by comparing normal (21.5 +/- 1.6) and hydromyelia (20.4 +/- 1.8) patients (P<0.05). Conclusions: The prevalence of neuroaxial abnormalities in AIS patients is relatively high, but we could not identify any definitive clinical or radiologic predictor of their presence. Hydromyelia was correlated with intraoperative motor-evoked potential/somatosensory-evoked potential electrophysiological alterations.