Ventriculus terminalis of the conus medullaris: MR findings in children

To determine the appearance of the ventriculus terminalis of the conus medullaris and the frequency with which it is seen on MR. Four hundred eighteen normal spine MR examinations were reviewed. Eleven (2.6%) of 418 children, all younger than 5 years of age, demonstrated an ovoid, nonenhancing, smooth dilation of the central canal within the conus medullaris. Averaged volume of the oblate spheroid was 0.18 cm3. Fluid within the cavity behaved as cerebrospinal fluid on all pulse sequences, and there was no abnormal signal in the cord tissue surrounding the cavity. Asymptomatic localized dilatation of the ventriculus terminalis is a normal developmental phenomenon that can be seen on MR.