The third ventricle roof: an anatomical study using constructive interference in steady-state magnetic resonance imaging

The third ventricle roof in vivo has been infrequently explored. The aim of the present study was to delineate the neurovascular structures relevant to the third ventricle roof using magnetic resonance (MR) imaging.

A total of 78 patients were enrolled in the study. Following initial examinations with conventional MR sequences, the constructive interference in steady-state (CISS) sequence was performed in coronal sections on 67 patients and in sagittal sections on 11 patients.

In the coronal sections, the fornices and internal cerebral veins were delineated in all 67 patients. The cross-sectional appearance and size of the fornices were variable, and the relationship between fornices presented as five different types. In 82% of patients, dominance of one relationship type was not found. The diameter of the internal cerebral veins (ICVs) was also variable, and the relationship between ICVs presented as four different types. In 70% of patients, dominance of one relationship type was not found. In 52% of patients, the lower layer of the third ventricle roof was identified as an inhomogeneous membranous structure. In the sagittal sections, the lower layer of the third ventricle roof was delineated as an inhomogeneous linear structure with variable slopes.

The third ventricle roof appears highly variable in morphology. Visualization of the third ventricle roof using the CISS sequence may be useful for planning safe and effective surgical maneuvers around the region.