White matter changes in fetal brains with ventriculomegaly

Abstract

Introduction: Ventriculomegaly (VM) is a fetal brain malformation which may present independently (isolated form) or in association with different cerebral malformations, genetic syndromes or other pathologies (non-isolated form).

Methods: This paper aims to study the effect of ventriculomegaly on the internal tridimensional architecture of fetal brains by way of Klingler's dissection. Ventriculomegaly was diagnosed using fetal ultrasonography during pregnancy and subsequently confirmed by necropsy. Taking into consideration the diameter of the lateral ventricle (measured at the level of the atrium), the brains were divided into two groups: moderate ventriculomegaly (with atrial diameter between 13 and 15 mm) and severe ventriculomegaly (with atrial diameter above 15 mm).

Results and discussion: The results of each dissection were described and illustrated, then compared with age-matched reference brains. In the pathological brains, fascicles in direct contact with the enlarged ventricles were found to be thinner and displaced inferiorly, the opening of the uncinate fasciculus was wider, the fornix was no longer in contact with the corpus callosum and the convexity of the corpus callosum was inverted. We have studied the prevalence of neurodevelopmental delay in children born with ventriculomegaly in the literature and discovered that a normal developmental outcome was found in over 90% of the mild VM cases, approximately 75% of the moderate and 60% in severe VM, with the correlated neurological impairments ranging from attention deficits to psychiatric disorders.

Keywords: fetal brain; fiber dissection; human brain development; ventriculomegaly; white matter tracts.

Figure 1

Dissection steps adapted for severe hydrocephalus. (a1–a5) Medial to lateral dissection of the white matter. After the removal of the cortex and cingulum, the lateral ventricle was opened from the edges. (b1–b5) Lateral to medial dissection of the white matter. The dissection followed the standard protocol through the exposure of the long association tracts but continued with opening the temporal horn of the lateral ventricle followed by the occipital and frontal ones. cg, cingulum; cc, corpus callosum; f, fornix; h, hippocampus; cn, caudate nucleus; t, thalamus; ic, internal capsule; slf, superior longitudinal fasciculus; ilf, inferior longitudinal fasciculus; u, uncinate fasciculus; ifof, inferior fronto-occipital fasciculus; ec, external capsule.

Figure 2

Distribution of the cases by the anterior–posterior diameter and the width of the posterior horn.

Figure 3

White matter tracts in the 18 GW brain. Successive latero-medial (A–C) and medio-lateral (D–F) dissection steps. Outlined white matter tracts, uncinate fasciculus (cyan), internal capsule (blue), inferior fronto-occipital fasciculus (black), corpus callosum (red), fornix (gray). i, insula; sf, sylvian fissure; ht, hypothalamus; t, thalamus; m, mesencephalon; p, pons; qc, quadrigeminal colliculi; mo, medulla oblongata; cb, cerebellum.

Figure 4

White matter tracts in the first 19 GW brain (Case 3). Successive latero-medial (A–C) and medio-lateral (D–F) dissection steps. Outlined white matter tracts, uncinate fasciculus (cyan), inferior longitudinal fasciculus (magenta), internal capsule (blue), cingulum (purple), corpus callosum (red), fornix (gray), anterior commissure (orange). sf, sylvian fissure; cgs, cingulate sulcus; cn, caudate nucleus; cf, calcarine fissure; t, thalamus; m, mesencephalon; p, pons.

Figure 5

White matter tracts in the second 19 GW brain (Case 4). Successive latero-medial (A–D) and medio-lateral (E, F) dissection steps. Outlined white matter tracts, inferior longitudinal fasciculus (magenta), uncinate fasciculus (cyan), anterior commissure (orange), internal capsule (blue), corpus callosum (red), fornix (gray). Sf, sylvian fissure; t, thalamus ; m, mesencephalon; p, pons.

Figure 6

White matter tracts in the 17 GW brain. Successive latero-medial (A, B) and medio-lateral (C–F) dissection steps. Outlined white matter tracts, uncinate fasciculus (cyan), inferior longitudinal fasciculus (magenta), cingulum (purple), corpus callosum (red), fornix (gray), anterior commissure (orange). sf, sylvian fissure; t, thalamus; m, mesencephalon; p, pons; mo, medulla oblongata.

Figure 7

White matter tracts in the 21 GW brain. Successive latero-medial (A–C) and medio-lateral (D–F) dissection steps. Outlined white matter tracts, superior longitudinal fasciculus (green), inferior longitudinal fasciculus (magenta), internal capsule (blue), cingulum (purple), corpus callosum (red), fornix (gray). i, insula; sf, sylvian fissure; cgs, cingulate sulcus; cn, caudate nucleus; cf, calcarine fissure; t, thalamus; m, mesencephalon; p, pons; mo, medulla oblongata; qc, quadrigeminal colliculi; cb, cerebellum.

Figure 8

White matter tracts in the 22 GW brain. Successive latero-medial (A, B) and medio-lateral (C–F) dissection steps. Outlined white matter tracts, internal capsule (blue), uncinate fasciculus (cyan), inferior longitudinal fasciculus (magenta), inferior fronto-occipital fasciculus (black), cingulum (purple), corpus callosum (red), fornix (gray), anterior commissure (orange). i, insula; sf, sylvian fissure; cgs, cingulate sulcus; cf, calcarine fissure; t, thalamus; m, mesencephalon; p, pons; cn, caudate nucleus.