Delineation of intermammillary relationships using magnetic resonance imaging

No study has investigated intermammillary relationships using neuroimaging modalities. This study aimed to explore them using magnetic resonance imaging (MRI).

We enrolled 72 patients who underwent conventional MRI examinations, followed by constructive interference steady-state sequence in the coronal plane. The intermammillary distances (IMDs) were measured at the uppermost level of the intermammillary gap (IMD_upp) and the lowest level (IMD_low) of the mammillary bodies (MBs).

MBs with varying morphologies were consistently delineated. The appearance of both MBs could be classified into four patterns based on the size and relative levels, with the symmetrical type being the most common. Intermammillary relationships exhibited five patterns. In 69%, the IMD_upp was discernible and measured 0.7 ± 0.4 mm, while it was not discernible in 31% due to the presence of intermammillary connection and adhesion. The age distribution did not differ between populations with and without discernible IMD_upp. The IMD_low was measured 4.4 ± 0.9 mm. Although the IMD_low was not significantly different between both sexes; it was longer in subjects in their 70s.

Intermammillary relationships show variable morphologies with gaps formed between both MBs. The IMD_low may become more evident in association with age-related increase in the width of the third ventricle and atrophy of the MBs.