MR OF THE CEREBRAL OPERCULUM - TOPOGRAPHIC IDENTIFICATION AND MEASUREMENT OF INTEROPERCULAR DISTANCES IN HEALTHY INFANTS AND CHILDREN

PURPOSE: To evaluate the role of axial, coronal, and sagittal MR in id entification of surface landmarks of the cerebral operculum and to det ermine the reference values of interopercular distances of each hemisp here in healthy infants and children on MR images. METHODS: Two hundre d fourteen cerebral opercula of 35 healthy infants and 72 healthy chil dren were retrospectively evaluated from 107 routine MR brain examinat ions. The surface landmarks of the operculum and interopercular distan ces of each hemisphere, which were subjectively divided into anterior interopercular distance (anterior sylvian width) and posterior interop ercular distance (posterior sylvian width), were recorded from axial, coronal, and sagittal MR images, respectively. The mean value of anter ior interopercular distance of each hemisphere was obtained by averagi ng two linear measurements of the anterior sylvian width from lateral, sagittal, and axial planes of the same side. Likewise, the posterior interopercular distance of each side of the brain was obtained from av eraging of two measurements on lateral, sagittal, and coronal planes. RESULTS: The landmarks of the operculum were best identified by sagitt al MR, followed by axial and coronal images, The average values of lef t anterior interopercular distance, right anterior interopercular dist ance, left posterior interopercular distance, and right posterior inte ropercular distance in infants were 1.9 +/- 1.3, 1.6 +/- 1.1, 0.4 +/- 0.7, and 0.2 +/- 0.4 mm, and in children, 0.9 +/- 1.3, 1.0 +/- 1.4, 0. 03 +/- 0.23, and 0.01 +/- 0.07 mm, respectively. Infants showed signif icantly wider interopercular distances than children. Left anterior in teropercular distance was significantly wider than right in infants, b ut not in children. Male children displayed a more significant increas e in anterior interopercular distance than did female children. There was no statistic difference in measurements of anterior interopercular distance and posterior interopercular distance between female and mal e infants. CONCLUSIONS: The operculum should be evaluated with MR in t hree planes, Infants may show conspicuous sylvian fissures that should not exceed 4.5 mm (mean + 2 SD) anteriorly on axial and sagittal plan es and 1.8 mm posteriorly on sagittal and coronal planes. Healthy chil dren who have fully developed opercula should have an anterior interop ercular distance of no more than 3.5 mm and a posterior interopercular distance of 0.5 mm.