Maturation of the olfactory bulbs: MR imaging findings.

BACKGROUND AND PURPOSE The detection of time-related maturational changes of the olfactory bulb (OB) on MR imaging may help early identification of patients with abnormal OB development and anatomic-based odor-cueing anomalies. MATERIALS AND METHODS Two separate reviewers retrospectively analyzed coronal T2-weighted spin-echo MR images of the frontobasal region in 121 patients. There were 22 patients who underwent MR imaging examinations several times, accounting for a total of 156 studies. Age range was 1 day to 19.6 years. OBs were bilaterally identified in all cases and categorized according to their shape and signal intensity. RESULTS Three different anatomic patterns were identified. In pattern 1 (median age, 15 days; age range, 1-168 days), the OBs were round to oval with a continuous external T2-hypointense rim and a prominent T2-hyperintense central area. In pattern 2 (median age, 287 days; age range, 4 days-22 months), the OBs were U shaped, with thinning and concave deformation of the superior layer. A hyperintense central area on T2-weighted images was still visible. In pattern 3 (median age, 5.2 years; age range, 107 days-19.6 years), the OBs were small, round, or J shaped with a more prominent lateral part. No difference in signal intensity between the central area and the peripheral layer was identified anymore. CONCLUSIONS The OBs show time-related maturational changes on MR imaging. There is a progressive reorganization of the peripheral neuronal layers and signal intensity changes of the central area, which are completed at the end of the second year, paralleling cerebral maturational changes.