Prenatally diagnosed neural tube defects: Ultrasound, chromosome, and autopsy or postnatal findings in 212 cases

Abstract

From January 1990 until December 1996, 212 cases of neural tube defect (NTD) were seen through the Prenatal Diagnosis Program of the University of Toronto. Of the 212 cases, 200 were karyotyped successfully and of these, 13 (6.5%) had chromosome abnormalities. When classified according to the site of the NTD, 2.3% (2/88) of anencephalics, 7.1% (1/14) of encephaloceles, and 10.2% (10/98) of meningomyeloceles had abnormal karyotypes. The absence of associated ultrasound abnormalities was not necessarily predictive of a chromosomally normal fetus; 4/167 (2.4%) of fetuses with isolated NTDs had chromosome abnormalities. Conversely, 24/33 (72%) of fetuses with additional findings on ultrasound had normal chromosomes. The diagnosis of a chromosome abnormality associated with NTD has important implications for recurrence risk and prenatal diagnosis, not only for the parents but potentially for other relatives. Based on our finding that 6.5% of prenatally detected NTDs are associated with chromosome abnormalities, we recommend karyotyping of all fetuses and/or newborns with NTD.

Chromosomal abnormalities in fetuses with ultrasonographically detected neural tube defects

“…This figure is within the range reported by other investigators, that is, Drugan et al (1989) 6%, Hume et al (1996) 2.3%, and Kennedy et al (1998) 2.3%. Our overall rate of chromosomal abnormalities in all NTDs (isolated and associated, including anencephaly) was 6.19% (12/194 cases), which confirms the findings of other groups (Kennedy et al, 1998).…”

“…The investigators suggested that karyotyping should be performed in all prenatally detected NTDs with or without associated anomalies. Kennedy et al (1998) reported 2.4% of chromosomal abnormalities in a series of 167 fetuses with isolated NTDs, 27.3% of chromosomal aberrations in NTDs with associated anomalies, and 2.3% (two of 88 cases) in 88 anencephalic fetuses. Similarly, the investigators recommended karyotyping for all fetuses with NTDs.…”

Recurrence risks for neural tube defects in siblings of patients with lipomyelomeningocele

“…A significant genetic component in the etiology of open NTDs is supported by several lines of evidence including associations with known genetic syndromes, 5,6 associations with cytogenetic abnormalities, 7,8 and a plethora of animal models. 9,10 In addition, the recurrence risk in families with one member affected with an NTD (2-5%) is 25-to 50-fold higher than the 1 in 1000 incidence of NTDs in the general population.…”

Prenatal diagnosis of mosaic ring chromosome 13 with anencephaly

“…Various reports concerning aneuploidy among prenatally detected neural tube defects have implicated an estimated aneuploidy detection rate of 5±6% ranging from 2% of the isolated neural tube defects to 24% of the multiple congenital malformation cases (Hume et al, 1996). Hence, fetal karyotyping is suggested for accurate diagnosis and recurrence risk counselling (Drugan et al, 1989;Babcook et al, 1995;Harmon et al, 1995;Seller, 1995;Hume et al, 1996;Kennedy et al, 1998). Here, we report on the prenatal diagnosis, genetic analysis and clinical manifestations of a second-trimester fetus with mosaic r(13) and anencephaly.…”