The tuber cinereum as a circumventricular organ: an anatomical study using magnetic resonance imaging

The tuber cinereum (TC) comprises the hypothalamic gray matter that forms the anterior portion of the third ventricle floor. However, since it has been rarely documented in previous neuroimaging investigations, the aim of the current study was to explore the morphology of the TC using magnetic resonance imaging (MRI). Ninety-two patients were enrolled in this study. Following initial examination with conventional MRI sequences, a contrast study using intravenous gadolinium injection was performed in thin-sliced sections. The TC, which was commonly defined as a linear, enhancing structure on the midsagittal section, was identified in all 92 cases. In 83% of cases, the third ventricle floor had a gentle inflection at the junctional site between the median eminence and TC. The angle formed between the line parallel to the TC and the horizontal line showed considerable variability, which ranged from 0.5A degrees to 56A degrees. Furthermore, a non-enhancing segment of variable length was identified in the posterior-most TC. In 11% of cases, the midline TC was enhanced over the whole length. Since the most part of the midline TC was enhanced with intravenous gadolinium injection, it may function as a circumventricular organ. The TC should be evaluated with contrast sagittal MRI prior to performing surgery with management of the anterior third ventricle floor.