Signal Change in the Mammillary Bodies after Perinatal Asphyxia

Abstract

BACKGROUND AND PURPOSE: Research into memory deficits associated with hypoxic-ischemic encephalopathy has typically focused on the hippocampus, but there is emerging evidence that the medial diencephalon may also be compromised. We hypothesized that mammillary body damage occurs in perinatal asphyxia, potentially resulting in mammillary body atrophy and subsequent memory impairment. MATERIALS AND METHODS: We retrospectively reviewed brain MRIs of 235 clinically confirmed full-term patients with hypoxic-ischemic encephalopathy acquired at a single center during 2004-2017. MRIs were performed within 10 days of birth (median, 6; interquartile range, 2). Two radiologists independently assessed the mammillary bodies for abnormal signal on T2-weighted and DWI sequences. Follow-up MRIs were available for 9 patients; these were examined for evidence of mammillary body and hippocampal atrophy. RESULTS: In 31 neonates (13.2%), abnormal high mammillary body signal was seen on T2-weighted sequences, 4 with mild, 25 with moderate, and 2 with severe hypoxic-ischemic encephalopathy. In addition, restricted diffusion was seen in 6 neonates who had MR imaging between days 5 and 7. For these 31 neonates, the most common MR imaging pattern (41.9%) was abnormal signal restricted to the mammillary bodies with the rest of the brain appearing normal. Follow-up MRIs were available for 9 patients: 8 acquired between 3 and 19 months and 1 acquired at 7.5 years. There was mammillary body atrophy in 8 of the 9 follow-up MRIs. CONCLUSIONS: Approximately 13% of full-term infants with hypoxic-ischemic encephalopathy showed abnormal high mammillary body signal on T2-weighted images during the acute phase, which progressed to mammillary body atrophy in all but 1 of the infants who had follow-up MR imaging. This mammillary body involvement does not appear to be related to the severity of encephalopathy, MR imaging patterns of hypoxic-ischemic encephalopathy, or pathology elsewhere in the brain.

Mammillary body atrophy and other MRI correlates of school-age outcome following neonatal hypoxic-ischemic encephalopathy

“…The MB are easy to score without additional software or post-processing and atrophy is significantly associated with neurodevelopmental outcome, hippocampal volumes and FA values, making it an easy indicator for neurodevelopmental outcome. Atrophy of the MB is already visible at three months after birth 10 . So, the MB are important to routinely assess in infants with HIE and should be added to the available scoring systems.…”

“…Recently, Molavi et al . described that 13.2% of the infants with HIE had an abnormal signal intensity on their T2-weighted MRI 10 . The strong association between subsequent atrophy of the MB and long-term problems has not been described previously in children with HIE.…”

“…The MB were scored “equivocal” if there appeared to be a higher signal intensity of the mammillary bodies on the T2-weighted image or a low signal on T1-weighted imaging but without swelling, so it was uncertain if this could be a partial volume effect. Abnormal was defined as an increased signal intensity of the mammillary bodies on the T2-weighted image, a low signal on T1-weighted imaging or diffusion restriction on DWI, in combination with swelling of the MB 10 .…”

“…Previous studies in children with HIE not treated with hypothermia, showed that smaller hippocampal volumes were associated with a lower IQ and memory problems 8 , 9 . Furthermore, it was recently hypothesized that atrophy of the mammillary bodies (MB) at three months of age might be predictive of childhood outcome 10 . Similar to the hippocampus, MB are known to be important for memory function 11 .…”

Volume reduction of caudate nucleus is associated with movement coordination deficits in patients with hippocampal atrophy due to perinatal hypoxia-ischaemia

“…Our previous reports documented the association between hippocampal atrophy following early HI and memory impairment ( Cooper et al, 2015 , Gadian et al, 2000 , Guderian et al, 2015 , Muñoz-López et al, 2017 , Vargha-Khadem et al, 2003 , Vargha-Khadem et al, 1997 ). Furthermore, our group and others have highlighted that early HI can also affect structures which are functionally connected to the hippocampus, thus compromising the wider memory network, such as the mammillary bodies and anterior thalamus ( Dzieciol et al, 2017 , Guderian et al, 2015 , Molavi et al, 2019 ).…”