The mammillothalamic tracts: Age‐related conspicuity and normative morphometry on brain magnetic resonance imaging

Abstract

The mammillothalamic tract (MTT, bundle of Vicq d'Azyr) is a white‐matter projection from each mammillary body to the anterior nucleus of the thalamus (ANT). Deep brain stimulation of the MTTs or ANTs is a treatment option for medically refractory focal epilepsy. Since the ANTs may be atrophied in epilepsy, targeting of the MTT terminations could be used as a proxy for ANT locations. However, MTT conspicuity and morphometry on MRI have not been evaluated to date. We investigated normative age‐ and sex‐related MRI morphometrics of the MTTs in healthy individuals. We retrospectively analyzed magnified axial T2‐weighted images of 80 subjects for bilateral MTT conspicuity, diameters, areas, shapes, precise locations, and symmetry. We statistically tested the effects of independent variables (sex and MTT side) on measured dependent variables using two‐way ANOVA; and performed linear regressions with age as the independent variable for each of the dependent variables. Subjects were F:M = 44:36, with mean age 45.3 years. Only one (0.63%) MTT was inconspicuous. Mean MTT diameter was 1.8 mm, area was 2.0 mm2, and distance from third ventricle was 3.1 mm. MTTs were mostly bilaterally symmetrical in shape, equally round, or ovoid. The right MTT diameter was larger than the left, and males had larger MTT areas than females. We found no statistical difference between MTT diameters and areas in young, middle‐aged, and older adults. We report normative axial MRI morphometrics of the MTTs to guide neuromodulation treatments. Future detailed analyses will determine if the MTTs atrophy in proportion to the ANTs in refractory epilepsy.

Cerebral blood flow regulates iron overload in the cerebral nuclei of hemodialysis patients with anemia

“…The reasons for the right-sided correlations are that: first, previous studies showed that the normal human brain exhibited asymmetries in brain anatomy and function. [48][49][50][51][52] Ali Abedelahi et al 52 demonstrated that normal individuals showed significant rightward asymmetry of brain volume, especially in the CA and PUT regardless of gender difference. The increased ID changes in hemodialysis patients were more obvious in the relatively larger one-sided nuclei, which was consistent with this hypothesis.…”

“…The reasons for the right-sided correlations are that: first, previous studies showed that the normal human brain exhibited asymmetries in brain anatomy and function. 48–52 Ali Abedelahi et al. 52 demonstrated that normal individuals showed significant rightward asymmetry of brain volume, especially in the CA and PUT regardless of gender difference.…”