ABNORMAL CORTICAL PLATE (POLYMICROGYRIA), HETEROTOPIAS AND GRAIN DAMAGE IN MONOZYGOTIC TWINS

We report 5 cases of abnormal cortical plate (polymicrogyria or microg yric-like pattern) and heterotopias associated with hypoxic-ischemic b rain injuries in monochorionic diamniotic twin fetuses of respectively 22, 26, 28, 31, 32 weeks gestation. These fetuses belonged to a serie s of 5 pairs of patients (10 cases) presenting with the characteristic features of the twin-to-twin transfusion syndrome. Three of them (2 d onors and 1 recipient) were macerated and the brains were not availabl e for study. Two (most likely recipient twins) survived. In the remain ing 5 fetuses (3 donors and 2 recipients) with neuropathological study there were cortical plate abnormalities. In 2 cases, the dorter was d ysmorphic and consisted of focal nodular distribution or vertical stri pes of neurons. True polymicrogyria was focal in 2 cases and involved almost the entire surface of the hemispheres in another one. Heterotop ias of immature cells were found in 4 cases, either in the white matte r or in the cortex or in both sites. There was a focal laminar necrosi s only in 2 cases. The morphological pattern of the anomalies depends on the time of occurrence of the insult and on its severity. These abn ormalities, although similar to those already described in singleton f etuses, illustrate the variety of cortical dysmorphia which may be ass ociated with fetal hypoxic-ischemic injuries and emphasize the particu lar vulnerability of the brain in monozygotic twins, whether it belong s to the donor or the recipient.