First-Trimester Sonographic Diagnosis of Holoprosencephaly

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1 Article First-Trimester Sonographic Diagnosis of Holoprosencephaly Value of the Butterfly Sign Waldo Sepulveda, MD, Victor Dezerega, MD, Cecilia Be, MSc Objective. To study the value of choroid plexus dysmorphology as a screening tool for the firsttrimester sonographic diagnosis of holoprosencephaly in a high-risk population. Methods. A total of 378 consecutive pregnancies undergoing chorionic villus sampling between 11 and 14 weeks gestation were scanned before the procedure, following the recommendations of the Fetal Medicine Foundation (London, England). A cross-sectional view of the fetal brain, including the visualization of both choroid plexuses (the butterfly sign), was obtained in all cases. Results. There were 3 cases in which the butterfly sign was not identified. In these cases, the first-trimester diagnosis of holoprosencephaly was confirmed by the presence of a single monoventricular cavity and fused thalami. Two of these fetuses had features of facial dysmorphism at the time of presentation and 2 had extracranial anomalies, including a cystic hygroma in 1 and a small omphalocele and polydactyly in another. Chromosomal analysis showed trisomy 13 in 2 cases and a ring chromosome 13 in the other. Conclusions. This series suggests that failure to identify the butterfly sign is a warning sign of holoprosencephaly in the first trimester. Systematic identification of the butterfly sign at the time of sonographic assessment of nuchal translucency provides a valuable tool for the early screening of holoprosencephaly. Key words: brain anomalies; choroid plexus; first trimester; holoprosencephaly; prenatal sonography. Abbreviations CVS, chorionic villus sampling Received January 27, 2004, from the Fetal Medicine Center, Department of Obstetrics and Gynecology (W.S., V.D.), and Cytogenetics Laboratory (C.B.), Clinica Las Condes, Santiago, Chile. Revision requested February 5, Revised manuscript accepted for publication February 10, This work was supported by the Sociedad Profesional de Medicina Fetal "Fetalmed" Limitada, Chile. Address correspondence and reprint requests to Waldo Sepulveda, MD, Fetal Medicine Center, Clinica Las Condes, Casilla 208, Santiago 20, Chile. waldosep@hotmail.com. Holoprosencephaly is a severe brain anomaly characterized by different degrees of fusion of the lateral ventricles resulting from failure of the prosencephalon to cleave during early embryogenesis. 1 This condition is invariably associated with a wide range of midfacial defects ranging from a single incisor to cyclopia. 2 Prenatal diagnosis of holoprosencephaly is usually made in the second trimester by the sonographic demonstration of fused lateral ventricles, no visible midline structures, and fusion of the thalami. 3 Recently, first-trimester sonographic screening for chromosomal abnormalities by measuring the nuchal translucency thickness at 11 to 14 weeks gestation 4,5 has been increasingly incorporated into routine clinical practice. An important advantage of this examination is the possibility of an early examination of the fetal anatomy for major structural defects by the American Institute of Ultrasound in Medicine J Ultrasound Med 2004; 23: /04/$3.50

2 First-Trimester Sonographic Diagnosis of Holoprosencephaly The aim of this study was to determine the value of a focused examination of the fetal brain for assessing the morphologic characteristics of the choroid plexuses as a screening tool for the early diagnosis of holoprosencephaly in a highrisk population. Materials and Methods This was a retrospective analysis of 378 consecutive first-trimester pregnancies undergoing chorionic villus sampling (CVS) in our institution by 1 of 2 fetal medicine specialists (W.S. and V.D.). In all cases, sonography was performed before the procedure, following the recommendations of the Fetal Medicine Foundation (London, England). These included measurements of the crown-rump length and nuchal translucency thickness, and assessment of the fetal anatomy looking for major structural defects. 4,5 Evaluation of the brain included a cross-sectional view of the fetal head, which in normal circumstances shows 2 paired echogenic structures filling most of the lateral ventricles, corresponding to the choroid plexuses. Because the choroid plexus is narrow in its medial portion and prominent at both the frontal and caudal ends, the apposition of both choroid plexuses in the midline at this particular gestational age produces a characteristic Figure 1. Cross-sectional view of the fetal brain at 11 weeks 5 days menstrual age showing the characteristic butterfly appearance of the choroid plexuses. appearance resembling a butterfly (Figure 1). This feature is not present in first-trimester fetuses with holoprosencephaly, however, because that condition is associated with severe distortion of the lateral ventricles and choroid plexuses. After informed consent was obtained, CVS was performed transabdominally under continuous sonographic guidance using the freehand technique. The fetal karyotype was obtained from short- and long-term cultures of chorionic villi with the use of standard cytogenetic techniques. Whenever possible, a second-trimester follow-up scan was performed to confirm the first-trimester sonographic findings. Results During the study period, 378 women considered at risk for chromosomal defects underwent first-trimester CVS at a median gestational age of 12 weeks (range, weeks). Three fetuses had a diagnosis of holoprosencephaly at gestational ages ranging from 12 weeks 4 days to 13 weeks 5 days. In none of the cases was it possible to identify the butterfly sign (Figures 2 and 3). Focused examination of the fetal brain in these cases showed the characteristic intracranial sonographic findings associated with holoprosencephaly, including a monoventricular cavity with an absent midline and fused thalami. Table 1 shows the most relevant clinical and sonographic findings in these cases. Nuchal translucency thickness was normal in 2 fetuses and abnormally increased in the other (cystic hygroma). Associated facial anomalies were found at the time of presentation in 2 cases, and extracranial anomalies were found in 2, 1 with a cystic hygroma and 1 with a small omphalocele and polydactyly. Prenatal karyotyping revealed trisomy 13 in 2 cases and a ring chromosome 13 in the other. Both pregnancies associated with trisomy 13 were terminated abroad. The other pregnancy miscarried at 23 weeks. Second-trimester sonography in this case revealed holoprosencephaly, microcephaly, abnormal facial features, an abnormal 4-chamber view of the heart, talipes, and intrauterine growth restriction. In all the remaining 375 cases, the butterfly sign was identified, and none of the fetuses proved to have holoprosencephaly. 762 J Ultrasound Med 23: , 2004

3 Sepulveda et al Discussion This study confirms previous reports that the prenatal sonographic diagnosis of holoprosencephaly is feasible in the first trimester Moreover, we have documented the value of systematic visualization of the cross section of the fetal brain in the early detection of this condition. As part of our routine examination of the fetal anatomy in fetuses at 11 to 14 weeks gestation, the butterfly sign was consistently looked for in our study. Indeed, 2 cases of holoprosencephaly in our series were detected in women originally requesting nuchal translucency screening. In the other, the diagnosis was incidentally made during sonographic evaluation of the fetal anatomy before CVS. In recent years, there has been an increasing interest in the early diagnosis of fetal anomalies. Among them, early prenatal diagnosis of holoprosencephaly is a desirable clinical goal because this condition is associated with several chromosomal defects, mainly trisomy 13, trisomy 18, and triploidy. 1 Even in fetuses with a normal karyotype, the detection of holoprosencephaly is important because this major brain anomaly is associated with an almost uniformly lethal outcome or, in the few survivors, with profound neurodevelopmental delay. Several authors have studied the association between holoprosencephaly and chromosomal abnormalities, particularly trisomy 13. In a large series of 38 fetuses with holoprosencephaly undergoing second- and third-trimester karyotyping, 11 (29%) had an abnormal karyotype, 8 with trisomy 13 and 3 with other chromosomal defects. 11 In another study of 30 fetuses with holoprosencephaly, 11 (37%) had chromosomal abnormalities, 8 of which involved chromosome Conversely, of 46 cases of trisomy 13 diagnosed as part of a large multicentric firsttrimester sonographic screening study involving 100,311 singleton pregnancies with live fetuses, 11 (24%) had holoprosencephaly at the time of nuchal translucency measurement. 12 Later on in pregnancy, when a thorough examination of the fetal brain is more plausible, detection of holoprosencephaly in fetuses with trisomy 13 is higher. Indeed, a series of 15 fetuses with trisomy 13 scanned at 16 to 22 weeks gestation showed that 7 (47%) had holoprosencephaly. 13 In another series involving 33 fetuses with trisomy 13 scanned in the second and third trimesters, 13 Figure 2. Case 2: cross-sectional view of the fetal brain in a fetus with trisomy 13 at 12 weeks 4 days showing the absence of the butterfly sign. (39%) had holoprosencephaly. 14 In our series, 3 cases of holoprosencephaly were detected in the first trimester, and all were associated with abnormalities of chromosome 13: trisomy 13 in 2 and a ring chromosome 13 in the other. A limited anatomic survey of the fetal brain in the first trimester can be achieved in a high percentage of cases. According to a previous study, the cranium, thalamus, choroid plexus, and lat- Figure 3. Case 3: holoprosencephaly in a fetus with a ring chromosome 13 at 13 weeks 5 days. Note the absence of the butterfly sign. J Ultrasound Med 23: ,

4 First-Trimester Sonographic Diagnosis of Holoprosencephaly Table 1. First-Trimester Sonographic Diagnosis of Holoprosencephaly Case MA, y GA, wk/d Reason for Referral NT, mm Sonographic Findings Karyotype /4 Consanguinity, 2.2 Holoprosencephaly, 47,XY,+13 advanced MA facial dysmorphism, small omphalocele, polydactyly /4 Suspected brain 1.6 Holoprosencephaly, 47,XY,+13 anomaly facial dysmorphism /5 Routine 5.8 Holoprosencephaly, 46,XX,+r(13) cystic hygroma GA indicates gestational age; MA, maternal age; and NT, nuchal translucency. eral ventricles can be visualized sonographically in 90% of cases at 11 weeks and in virtually all cases between 12 and 14 weeks. 15 The choroid plexuses of the lateral ventricles are very prominent organs during this developmental period. They can be easily identified by sonography, which can provide an important landmark for normalcy of the fetal brain at this early gestational age. Our study revealed that failure to identify the normal anatomic characteristics of the choroid plexuses and absence of the butterfly sign in the first trimester were diagnostic of holoprosencephaly in all cases. However, the inability to identify the normal morphologic characteristics of the choroid plexuses could be a prominent feature in other pathologic conditions, such as the acrania/anencephaly sequence, posterior fossa cysts (Dandy-Walker malformation), and large cephaloceles. Although the prenatal diagnosis of holoprosencephaly in the first trimester has been reported by several authors, 7 10 to our knowledge, no reports on the systematic evaluation of the choroid plexuses for the screening of holoprosencephaly have been described thus far. In a low-risk population, the first-trimester diagnosis of holoprosencephaly may be elusive if a systematic review of the fetal brain is not performed. Hernadi and Torocsik 16 and D Ottavio et al 17 were unable to detect the single cases of holoprosencephaly in their series of 3991 and 3490 low-risk women, respectively, screened sonographically in the first trimester. However, in 2 other series involving a total of 4485 low-risk pregnancies undergoing first-trimester sonographic screening for nuchal translucency measurements, all 3 cases of holoprosencephaly were diagnosed in the first trimester. 18,19 Although no specific method for achieving this diagnosis was reported by the authors, the latter 2 groups followed the recommendation of the Fetal Medicine Foundation, 4,5 as we did. Therefore, these preliminary data suggest that the routine sonographic evaluation of the butterfly sign at the time of nuchal translucency thickness measurement may be useful for the early prenatal diagnosis of holoprosencephaly, both in high- and low-risk populations. References 1. Peebles DM. Holoprosencephaly. Prenat Diagn 1998; 18: Blaas HGK, Eriksson AG, Salvesen KA, et al. Brains and faces in holoprosencephaly: pre- and postnatal description of 30 cases. Ultrasound Obstet Gynecol 2002; 19: McGahan JP, Pilu G, Nyberg DA. Cerebral malformations. In: Nyberg DA, McGahan JP, Pretorius DH, Pilu G (eds). Diagnostic Imaging of Fetal Anomalies. Philadelphia, PA: Lippincott Williams & Wilkins; 2003: Snijders RJ, Noble P, Sebire N, Souka A, Nicolaides KH. UK multicentre project on assessment of risk of trisomy 21 by maternal age and fetal nuchal-translucency thickness at weeks gestation. Fetal Medicine Foundation First Trimester Screening Group. Lancet 1998; 352: Nicolaides KH, Sebire NJ, Snijders RJM (eds). The Week Scan. The Diagnosis of Fetal Abnormalities. Carnforth, England: Parthenon Publishing; Souka AP, Nicolaides KH. Diagnosis of fetal abnormalities at the week scan. Ultrasound Obstet Gynecol 1997; 10: Nelson LH, King M. Early diagnosis of holoprosencephaly. J Ultrasound Med 1992; 11: J Ultrasound Med 23: , 2004

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