Intrathecal Anomalies in Presumed Infantile Idiopathic Scoliosis: When Is MRI Necessary?

STUDY DESIGN: Retrospective review. OBJECTIVE: To determine the rate of abnormal magnetic resonance imaging (MRI) findings in patients with presumed infantile idiopathic scoliosis (IIS) and the rate of neurosurgical intervention in those patients, and to develop a guideline concerning when to obtain an MRI. SUMMARY OF BACKGROUND DATA: The reported rate of intrathecal anomalies associated with presumed IIS varies in the literature (12% to 50%). Conclusions have led to conflicting recommendations concerning when an MRI is indicated. METHODS: After appropriate internal review board approval, the authors retrospectively reviewed the medical records of patients from a single institution meeting the inclusion criteria: presumed idiopathic curve with a magnitude of ≥20°, age <36 months at diagnosis, normal neurologic examination, and presentation between 2002 and 2010. The authors reviewed the MRI findings, whether neurosurgical intervention took place, and the orthopedic treatment course (observation, brace, cast, or surgery). RESULTS: A total of 56 patients were identified and reviewed; 43 had had an MRI. Seven of 43 patients were found to have an anomaly (16.2%). A fatty filum was identified in 2 patients, a syrinx in 3, Chiari I malformation in 2, and a tethered cord in 1 (this patient also had a syrinx). Two of the 7 patients required neurosurgical intervention (28%). Patients who did not have an MRI were statistically younger, had smaller Cobb angles, and required less orthopedic treatment. CONCLUSIONS: The incidence of intrathecal anomalies (16.2%) at the authors' institution was similar to previously published reports; however, the need for neurosurgical intervention was significantly lower in this study (28%). For younger patients with small curves (<30°) who do not require orthopedic treatment, MRI under sedation can be delayed or avoided. Clinical judgment should be the determinant for whether to use MRI when evaluating patients with presumed IIS.