Background: Although reports in the literature have demonstrated an approximately 20% prevalence of neural axis abnormalities in patients with juvenile idiopathic scoliosis who have a curve of >20°, the prevalence of neural axis abnormalities in patients with infantile idiopathic scoliosis is not well documented. In two previous studies involving a total of only ten patients with infantile idiopathic scoliosis, five patients were noted to have a neural axis abnormality on magnetic resonance images. Methods: The records of forty-six consecutive patients who were seen between 1992 and 2000 at three spinal deformity clinics were retrospectively reviewed. The inclusion criteria included presumed idiopathic scoliosis at the time of presentation, an age of three years or less, a curve magnitude of ≥20°, normal neurological findings, no associated syndromes, and no congenital abnormalities. All patients were evaluated with a total spine magnetic resonance imaging protocol for examination of neural axis abnormalities from the skull to the coccyx. Results: Ten (21.7%) of the forty-six patients were found to have a neural axis abnormality on magnetic resonance imaging. This group included five patients with an Arnold-Chiari malformation and an associated cervicothoracic syrinx, three with syringomyelia, one with a low-lying conus, and one with a brainstem tumor. Eight of these ten patients needed neurosurgical intervention for treatment of the abnormality. Conclusions: The 21.7% prevalence of neural axis abnormalities in this group of patients with infantile idiopathic scoliosis was found to be almost identical to that reported in the literature on patients with juvenile idiopathic scoliosis. Because of the high prevalence of abnormalities and the fact that eight of the ten patients with abnormal findings on magnetic resonance images required neurosurgical intervention, a total spine magnetic resonance imaging evaluation at the time of presentation is recommended for all patients with infantile idiopathic scoliosis who have a curve measuring ≥20°.