In utero MR imaging in fetuses at high risk of lissencephaly.

OBJECTIVE: Lissencephaly is a rare disorder of cortical developmental, which usually carries increased risk of recurrence in future pregnancies. In this prospective observational study, we wished to test the hypothesis that sulcation patterns can be used to diagnose lissencephaly successfully on in utero MR (iuMR) imaging in the third-trimester but not in the late second-trimester fetus.
METHODS: Pregnant females were recruited into this study if they had an increased risk of fetal lissencephaly based on a fetus or child with lissencephaly in an earlier pregnancy. All females were offered serial iuMR examinations at one centre and are reported whether they had at least two examinations. The overall recurrence rate of lissencephaly was recorded along with the sulcation patterns of non-affected fetuses.
RESULTS: 19 females were recruited with 23 pregnancies. In 3/23 (13%) fetuses, lissencephaly was diagnosed on iuMR and not detected on ultrasonography. In two cases, the diagnosis of lissencephaly was made on second-trimester iuMR imaging-with certainty in one and described as "possible" in the other. Confident diagnoses of lissencephaly were made by 28-week gestation in all three cases. Four fetuses, ultimately shown not to have lissencephaly, were judged to have minor sulcation delay on second-trimester imaging but became gestational age appropriate in the third trimester.
CONCLUSION: iuMR imaging can identify fetal lissencephaly between 20 and 24 weeks, but false positives should be expected, particularly in the second trimester, and follow-up imaging later in pregnancy may be required. Advances in knowledge: It is possible to detect fetal lissencephaly between 20- and 24-week gestational age; but, it is considerably easier in the third trimester. As a result, if a fetus has an increased risk of lissencephaly on the basis of family history, it may be necessary to do serial iuMR studies to confirm normality (or abnormality) of the fetal brain.