Abnormal Cortical Plate (Polymicrogyria), Heterotopias and Brain Damage in Monozygous Twins

Abstract

We report 5 cases of abnormal cortical plate (polymicrogyria or microgyric-like pattern) and heterotopias associated with hypoxic-ischemic brain injuries in monochorionic diamniotic twin fetuses of respectively 22, 26, 28, 31, 32 weeks gestation. These fetuses belonged to a series of 5 pairs of patients (10 cases) presenting with the characteristic features of the twin-to-twin transfusion syndrome. Three of them (2 donors and 1 recipient) were macerated and the brains were not available for study. Two (most likely recipient twins) survived. In the remaining 5 fetuses (3 donors and 2 recipients) with neuropathological study there were cortical plate abnormalities. In 2 cases, the cortex was dysmorphic and consisted of focal nodular distribution or vertical stripes of neurons. True polymicrogyria was focal in 2 cases and involved almost the entire surface of the hemispheres in another one. Heterotopias of immature cells were found in 4 cases, either in the white matter or in the cortex or in both sites. There was a focal laminar necrosis only in 2 cases. The morphological pattern of the anomalies depends on the time of occurrence of the insult and on its severity. These abnormalities, although similar to those already described in singleton fetuses, illustrate the variety of cortical dysmorphia which may be associated with fetal hypoxic-ischemic injuries and emphasize the particular vulnerability of the brain in monozygotic twins, whether it belongs to the donor or the recipient.

Causal Hypothesis for Some Congenital Anomalies

“…Where zygosity and chorionicity were reported, the cases were almost always from a MC gestation. Cerebral abnormalities such as microcephaly and cerebral atrophy (Fusi & Gordon, 1990;Ishimatsu et al, 1994), polymicrogyria (Baker et al, 1996;Bordarier & Robain, 1992;Larroche et al, 1994;Weig et al, 1995), hydranencephaly and multicystic encephalopathy (Hoyme et al, 1981;Jung et al, 1984) predominate in these reports. These cerebral impairments generally present clinically as cerebral palsy or learning disability (Durkin et al, 1976;Melnick, 1977;Pharoah & Adi, 2000.…”

Malformations of cortical development

“…The imbalance between populated layers and necrotic layer causes a distorted mechanical stimulus that leads to the formation of the multiple and small gyri [19][20][21][22] . The fact that this type of cortex appears mostly in cerebral areas belonging to medium cerebral artery territory, and the presence of PMG around porencephalic and schizencephalic borders, reinforces the idea that the polymicrogyric cortex results from anoxic-ischemic insult.…”

“…The imbalance between populated layers and necrotic layer causes a distorted mechanical stimulus that leads to the formation of the multiple and small gyri [19][20][21][22] .…”

Causal Hypothesis for Some Congenital Anomalies

“…Both mechanisms require the fetal demise of one twin. A third proposed mechanism is hemodynamic instability with episodes of acute feto-fetal transfusion causing the fetal death of one and organ damage in the other twin (Gonen, 1991;Grafe, 1993;Larroche et al, 1994). This mechanism is consonant with the fetal demise of one or both twins or with the survival of both twins.…”