DOI: 10.1002/pd.4598
ORIGINAL ARTICLE
Abnormal sonographic appearance of posterior brain at 11–14weeks and fetal outcome P. Volpe1*, B. Muto1, U. Passamonti2, G. Rembouskos1, V. De Robertis1, G. Campobasso1, A. Tempesta1, G. Volpe3 and T. Fanelli1 1
Fetal Medicine Unit, Di Venere and Sarcone Hospitals, Bari, Italy Fetal Medicine Unit, Galliera Hospital, Genoa, Italy 3 Department of Obstetrics and Gynecology, University of Bari, Bari, Italy *Correspondence to: Paolo Volpe. E-mail: [email protected] 2
ABSTRACT Objective The aim of this retrospective study was to describe the sonographic appearance of the posterior brain anatomy in normal fetuses at 11 to 14 weeks of pregnancy and to determine the fetal outcome when one of the posterior brain anatomical space is not recognized. Methods Two groups of patients were included in the study: a control group of consecutive 311 healthy fetuses with a normal sonogram and a study group of 21 fetuses with absence of one of the three posterior brain spaces. In each fetus, images of the mid-sagittal view of the fetal face and brain at 11 to 14 weeks of gestation were obtained. Results In all fetuses with absence of one of the three posterior brain spaces, a severe anomaly, including open spina bifida, cephalocele, Dandy–Walker complex, and chromosomal aberrations, was associated.
Conclusion Our study indicates that the sonographic finding characterized by the absence of one of the three posterior brain spaces seems to facilitate not only the detection of open spina bifida, as previously reported, but also of other neural tube defects, such as cephalocele, and is an important risk factor for cystic posterior brain anomalies, and/or chromosomal abnormalities. Thus it seems a poor prognostic finding for major fetal abnormalities. © 2015 John Wiley & Sons, Ltd.
Funding sources: None Conflicts of interest: None declared
INTRODUCTION
METHODS
Recent publications show improvement in the detection of fetal abnormalities in the first trimester during pregnancy.1–4 According to the recent literature, evaluation of the posterior fossa anatomy and its measurement might improve the detection rate of several posterior fossa anomalies including Chiari II malformation.5–11 At 11 to 14 weeks of gestation it is possible to visualize and measure three spaces in the posterior brain. These posterior brain spaces are: the brain stem (BS), the fourth ventricle, or intracranial translucency (IT), and the cisterna magna. Such anatomical spaces are commonly evaluated in the mid-sagittal view of the fetal face assessed at 11 to 14 weeks by ultrasound as part of the nuchal translucency (NT) measurement. Anomalies of the posterior brain spaces, including their measurement, have been proposed as markers of posterior fossa anomalies.6–14 The aim of this study was to describe the sonographic appearance of the posterior cranial fossa anatomy in normal fetuses at 11 to 14 weeks of pregnancy and to determine the fetal outcome when one of the aforementioned anatomical spaces is not recognized.
This was a retrospective study of a pregnant population undergoing first trimester scan in two referral centers for prenatal diagnosis, including both patients at low risk and patients referred because of an increased risk for chromosomal and anatomic defects. Two groups of patients were included: a control group of consecutive 311 healthy fetuses with a normal sonogram and a study group of 21 fetuses with absence of one of the three posterior brain spaces. In each fetus, images of the mid-sagittal view of the fetal face and brain at 11 to 14 weeks of gestation, following the recommendations of the Fetal Medicine Foundation, were obtained. In all cases, crown– rump length (CRL) and NT thickness were measured, and the nasal bone, ductus venosus, and tricuspid valve flow were assessed; a detailed examination of the fetal anatomy for the detection of major defects was also performed. Maternal biochemistry (free b-human chorionic gonadotrophin and pregnancy-associated plasma protein A) was also available. All examinations were performed trans-abdominally, using a Voluson E8 (GE Medical Systems, Zipf, Austria) with RAB 4 to 8 MHz and RM6C matrix 1 to 7 MHz sector probes. In a
Prenatal Diagnosis 2015, 35, 717–723
© 2015 John Wiley & Sons, Ltd.
P. Volpe et al.
718
smallnumber of cases (23, 7%), an additional transvaginal assessment was performed, mainly because of poor transabdominal image of the fetal anatomy. Stored images were examined by two operators, with extensive experience in first trimester scanning, who were unaware of the pregnancy outcomes. The operators examined the posterior brain in mid-sagittal view by visualizing and measuring three spaces between the sphenoid and occipital bone: the BS, a hypoechoic area between the posterior border of the sphenoid bone and the anterior border of the fourth ventricle (4 V); the fourth ventricle or IT, an anechoic area between the posterior border of the brain stem and the choroids plexus of the fourth ventricle; and the cisterna magna, another fluid space between the choroids plexus of the fourth ventricle and the anterior border of the occipital bone (Figure 1). The brain stem to occipital bone (BSOB) was defined as the vertical distance between the anterior border of the fourth ventricle, anteriorly and the occipital bone, posteriorly, representing the fourth ventricle – cisterna magna complex. The BS to BSOB ratio was also calculated as previously described.12 Reference measurements for BS, BSOB diameter, and BS to BSOB diameters ratio were obtained in the control group. The agreement and bias for measurements by a single operator, who made two repeated measurements from the same image, and by two different operators, who produced measurements from the same image independently, were investigated from 92 images selected randomly from the database. Then, to assess the outcome of the second group of fetuses with absence of one of the three posterior spaces, we conducted a retrospective study over a period of 6 years (January 2009–December 2014). Fetuses were identified by searching the Viewpoint database (ViewPoint 5.6.8.428, ViewPoint Bildverarbeitung GmbH, Weßling, Germany) of our referral centers. Fetal karyotype was available in 13 of these cases. Detailed information on the outcome of the pregnancies was obtained by medical records and interview with the parents and their physicians.
Statistical analysis In the control group, reference ranges with fetal CRL for BS diameter, BSOB diameter, BS diameter to BSOB diameter ratio were obtained with regression analysis. Delta values for each parameters were calculated in relation to fetal CRL. The distribution of values was normal for all parameters in the control groups as demonstrated by Kolmogorov–Smirnov test. An independent sample t-test was used to determine the significance of differences in delta values for all parameter between the controls and the cases. The Bland-Altman analysis was needed to assess the intra and inter-observer variability for BS diameter and BSOB diameter in the control group and through the cases. Kruskal–Wallis test was used to compare the significance of the difference between the two measurements. A P value less than 0.05 was considered statistically significant. All data were analyzed with statistical software package SPSS 15.0 (SPSS, Chicago, Illinois, USA).
RESULTS The median CRL at the time of the scan was 64 mm (range 45–80) in controls and 58 mm (range 46–680.8) in the study group. In the control group, there was a significant increase with CRL in BS diameter (1.5862 + 0.02185 × CRL in mm; SD 00.36; R2 = 00.1114), BSOB diameter (10.7193 + 0.04143 × CRL in mm: SD 00.5711; R2 = 00.1496). The BS diameter to BSOB diameter ratio decreased with CRL (00.7829 + 0.003170 × CRL in mm; SD 00.048; R2 = 00.08161). These results are consistent with those reported in literature. The bias (mean difference) and 95% limits of agreement between paired measurements of BS and BSOB by the same operator and by two different sonographers are reported in Tables 1 and 2. No intra-observer variability was found significant for all measurements (00.33, 0.29, and 0.45
Table 1 Intra-observer variability for brain stem diameter, brain stem to occipital bone diameter, brain stem/brain stem to occipital bone diameters ratio in the normal population Parameters
Bias
P
Limits of agreement
BS diameter
0.9383
0.33
0.21 to
0.15
BSOB diameter
1.0000
0.29
0.25 to
0.15
BS/BSOB ratio
0.127
0.45
0.18 to
0.25
BS, brain stem; BSOB, brain stem to occipital bone.
Table 2 Inter-observer variability for brain stem diameter, brain stem to occipital bone diameter, brain stem/brain stem to occipital bone diameters ratio in the normal population
Figure 1 Mid-sagittal view of the fetal face and brain at 12 weeks showing the three posterior brain spaces. Nuchal translucency and thalamus are also seen. NT, nuchal translucency; T, thalamus; BS, brain stem; IT, intracranial translucency; CM, cisterna magna
Prenatal Diagnosis 2015, 35, 717–723
Parameters
Bias
P
Limits of agreement
BS diameter
0.9622
0.49
0.32 to
0.29
BSOB diameter
0.9855
0.39
0.20 to
0.15
BS/BSOB ratio
0.9953
0.59
0.39 to
0.15
BS, brain stem; BSOB, brain stem to occipital bone.
© 2015 John Wiley & Sons, Ltd.
Posterior brain anomalies
719
Table 3 Outcomes in fetuses where posterior fossa anomaly was suspected at the first trimester scan
Karyotype
US findings at mid-trimester scan
Outcome
Case
US finding at 11 to 14 weeks
1
PB cyst
AVSD
Yes
Trisomy 18
—
TOP at 14 weeks
2
PB cyst
HLHS
No
46, XY, der(5)t(5;8) (p15.33; q24.3)pat
—
TOP at 14 weeks
3
PB cyst
No
No
No
DWM–ACC
TOP at 20 weeks
Associated anomalies at 11 to 14 weeks
High risk for aneuploidies
4
PB cyst
No
No
No
BPC–CDH
TOP at 20 weeks
5
PB cyst
Vascular ring, micrognathia
Yes
Triploidy
—
TOP at 13 weeks
6
PB cyst
No
Yes
Trisomy 18
—
TOP at 14 weeks
7
PB cyst
No
No
No
DWM
8
PB cyst
Exomphalos, BCLP
Yes
Trisomy 13
—
TOP at 13 weeks
9
PB cyst
No
No
Mos 92, XXYY [36]/46, XY[9]
DWM–COA
TOP at 21 weeks
10
PB cyst
No
No
46, XY, del(5)t(5;6) (p13;q15)mat
—
TOP at 14 weeks
11
PB cyst
Hydrops, HRHS
Yes
No
—
IUD
12
PB cyst
TOF, abdominal cyst
Yes
Triploidy
—
TOP at 13 weeks
13
PB cyst
Severe cerebral ventriculomegaly, hydrotorax
Yes
45, X0
—
TOP at 13 weeks
14
PB cyst
Megacystis, strawberry-shaped head
Yes
Trisomy 18
—
TOP at 13 weeks
15
OSB
No
No
46, XY
—
TOP at 17 weeks
16
OSB
No
No
—
—
TOP at 14 weeks
17
OSB
SUA, megacystis
Yes
—
—
TOP at 14 weeks
18
OSB
No
No
—
—
TOP at 16 weeks
19
Cephalocele
Micrognathia, radial aplasia
Yes
—
—
TOP at 14 weeks
20
Cephalocele
No
No
46, XX
—
TOP at 14 weeks
21
Cephalocele
No
No
46, XX
—
TOP at 13 weeks
Alive
US, ultrasound; PB, posterior brain; OSB, open spina bifida; AVSD, atrio-ventricular septal defect; HLHS, hypoplastic left heart syndrome; BCLP, bilateral cleft lip and palate; HRHS, hypoplastic right heart syndrome; TOF, tetralogy of Fallot; SUA, single umbilical artery; DWM, Dandy–Walker malformation; ACC, agenesis of corpus callosum; BPC, Blake’s pouch cyst; CDH, congenital diaphragmatic hernia; COA, aortic coarctation; IUD, intrauterine death.
respectively); furthermore there was no significant difference between measurements made by two different operators for all parameters (0.49, 0.39, and 0.59, respectively). In the study group made of 21 fetuses (Table 3), only two of the three posterior brain spaces were recognized because the border between the fourth ventricle and the cisterna magna was not visualized. These fetuses had always associated severe anomalies. In 10/21 fetuses (cases 1, 2, 5, 6, 8–10, and 12–14), a chromosomal anomaly was found, and in seven of these cases, malformations were diagnosed sonographically by 11 to 14 weeks. In 4/21 fetuses (cases 3, 7, 10, and 12) a posterior fossa cystic anomaly was detected at mid-trimester scan [three Dandy–Walker malformations (DWM), and one Blake’s pouch cyst (BPC)]. In one of these fetuses, a chromosomal anomaly was associated (case 9). In 4/21 fetuses (cases 15–18), a diagnosis of OSB was made at a median of 15 weeks (range 13–17) of gestation. In 3/21 fetuses (cases 19–21), a diagnosis Prenatal Diagnosis 2015, 35, 717–723
of cephalocele was made at 13 weeks of gestation. In the last fetus (case 11), a major heart defect and hydrops were associated. The fetus died in utero 5 days after the diagnosis. Overall, 19 couples requested termination of pregnancy. This was performed within 14 weeks in 14 cases, and in 9 of these cases, it was not possible to obtain reliable post-mortem conclusion because reliable diagnoses of abnormal cerebellum are extremely difficult at this early stage. In the other cases, autopsy always confirmed the antenatal diagnosis. One pregnancy with a fetus affected by isolated DWM continued till term. The infant is alive and well but the neurological outcome at present is uncertain because of the very short follow-up (4 months old). Comparisons of BS diameter, BSOB diameter, and BS/BSOB ratio in controls and cases with Dandy–Walker complex, chromosomal anomalies, OSB, and cephalocele are reported in Table 4 (Figures 2–4). © 2015 John Wiley & Sons, Ltd.
P. Volpe et al.
720
Table 4 Comparison of brain stem diameter, brain stem to occipital bone diameter, brain stem/brain stem to occipital bone ratio in controls and cases with posterior fossa cyst, open spina bifida, and cephalocele Parameters
Posterior fossa cyst
OSB
Cephalocele
BS diameter
0.83
0.0055
0.011
BSOB diameter
ORIGINAL ARTICLE
Abnormal sonographic appearance of posterior brain at 11–14weeks and fetal outcome P. Volpe1*, B. Muto1, U. Passamonti2, G. Rembouskos1, V. De Robertis1, G. Campobasso1, A. Tempesta1, G. Volpe3 and T. Fanelli1 1
Fetal Medicine Unit, Di Venere and Sarcone Hospitals, Bari, Italy Fetal Medicine Unit, Galliera Hospital, Genoa, Italy 3 Department of Obstetrics and Gynecology, University of Bari, Bari, Italy *Correspondence to: Paolo Volpe. E-mail: [email protected] 2
ABSTRACT Objective The aim of this retrospective study was to describe the sonographic appearance of the posterior brain anatomy in normal fetuses at 11 to 14 weeks of pregnancy and to determine the fetal outcome when one of the posterior brain anatomical space is not recognized. Methods Two groups of patients were included in the study: a control group of consecutive 311 healthy fetuses with a normal sonogram and a study group of 21 fetuses with absence of one of the three posterior brain spaces. In each fetus, images of the mid-sagittal view of the fetal face and brain at 11 to 14 weeks of gestation were obtained. Results In all fetuses with absence of one of the three posterior brain spaces, a severe anomaly, including open spina bifida, cephalocele, Dandy–Walker complex, and chromosomal aberrations, was associated.
Conclusion Our study indicates that the sonographic finding characterized by the absence of one of the three posterior brain spaces seems to facilitate not only the detection of open spina bifida, as previously reported, but also of other neural tube defects, such as cephalocele, and is an important risk factor for cystic posterior brain anomalies, and/or chromosomal abnormalities. Thus it seems a poor prognostic finding for major fetal abnormalities. © 2015 John Wiley & Sons, Ltd.
Funding sources: None Conflicts of interest: None declared
INTRODUCTION
METHODS
Recent publications show improvement in the detection of fetal abnormalities in the first trimester during pregnancy.1–4 According to the recent literature, evaluation of the posterior fossa anatomy and its measurement might improve the detection rate of several posterior fossa anomalies including Chiari II malformation.5–11 At 11 to 14 weeks of gestation it is possible to visualize and measure three spaces in the posterior brain. These posterior brain spaces are: the brain stem (BS), the fourth ventricle, or intracranial translucency (IT), and the cisterna magna. Such anatomical spaces are commonly evaluated in the mid-sagittal view of the fetal face assessed at 11 to 14 weeks by ultrasound as part of the nuchal translucency (NT) measurement. Anomalies of the posterior brain spaces, including their measurement, have been proposed as markers of posterior fossa anomalies.6–14 The aim of this study was to describe the sonographic appearance of the posterior cranial fossa anatomy in normal fetuses at 11 to 14 weeks of pregnancy and to determine the fetal outcome when one of the aforementioned anatomical spaces is not recognized.
This was a retrospective study of a pregnant population undergoing first trimester scan in two referral centers for prenatal diagnosis, including both patients at low risk and patients referred because of an increased risk for chromosomal and anatomic defects. Two groups of patients were included: a control group of consecutive 311 healthy fetuses with a normal sonogram and a study group of 21 fetuses with absence of one of the three posterior brain spaces. In each fetus, images of the mid-sagittal view of the fetal face and brain at 11 to 14 weeks of gestation, following the recommendations of the Fetal Medicine Foundation, were obtained. In all cases, crown– rump length (CRL) and NT thickness were measured, and the nasal bone, ductus venosus, and tricuspid valve flow were assessed; a detailed examination of the fetal anatomy for the detection of major defects was also performed. Maternal biochemistry (free b-human chorionic gonadotrophin and pregnancy-associated plasma protein A) was also available. All examinations were performed trans-abdominally, using a Voluson E8 (GE Medical Systems, Zipf, Austria) with RAB 4 to 8 MHz and RM6C matrix 1 to 7 MHz sector probes. In a
Prenatal Diagnosis 2015, 35, 717–723
© 2015 John Wiley & Sons, Ltd.
P. Volpe et al.
718
smallnumber of cases (23, 7%), an additional transvaginal assessment was performed, mainly because of poor transabdominal image of the fetal anatomy. Stored images were examined by two operators, with extensive experience in first trimester scanning, who were unaware of the pregnancy outcomes. The operators examined the posterior brain in mid-sagittal view by visualizing and measuring three spaces between the sphenoid and occipital bone: the BS, a hypoechoic area between the posterior border of the sphenoid bone and the anterior border of the fourth ventricle (4 V); the fourth ventricle or IT, an anechoic area between the posterior border of the brain stem and the choroids plexus of the fourth ventricle; and the cisterna magna, another fluid space between the choroids plexus of the fourth ventricle and the anterior border of the occipital bone (Figure 1). The brain stem to occipital bone (BSOB) was defined as the vertical distance between the anterior border of the fourth ventricle, anteriorly and the occipital bone, posteriorly, representing the fourth ventricle – cisterna magna complex. The BS to BSOB ratio was also calculated as previously described.12 Reference measurements for BS, BSOB diameter, and BS to BSOB diameters ratio were obtained in the control group. The agreement and bias for measurements by a single operator, who made two repeated measurements from the same image, and by two different operators, who produced measurements from the same image independently, were investigated from 92 images selected randomly from the database. Then, to assess the outcome of the second group of fetuses with absence of one of the three posterior spaces, we conducted a retrospective study over a period of 6 years (January 2009–December 2014). Fetuses were identified by searching the Viewpoint database (ViewPoint 5.6.8.428, ViewPoint Bildverarbeitung GmbH, Weßling, Germany) of our referral centers. Fetal karyotype was available in 13 of these cases. Detailed information on the outcome of the pregnancies was obtained by medical records and interview with the parents and their physicians.
Statistical analysis In the control group, reference ranges with fetal CRL for BS diameter, BSOB diameter, BS diameter to BSOB diameter ratio were obtained with regression analysis. Delta values for each parameters were calculated in relation to fetal CRL. The distribution of values was normal for all parameters in the control groups as demonstrated by Kolmogorov–Smirnov test. An independent sample t-test was used to determine the significance of differences in delta values for all parameter between the controls and the cases. The Bland-Altman analysis was needed to assess the intra and inter-observer variability for BS diameter and BSOB diameter in the control group and through the cases. Kruskal–Wallis test was used to compare the significance of the difference between the two measurements. A P value less than 0.05 was considered statistically significant. All data were analyzed with statistical software package SPSS 15.0 (SPSS, Chicago, Illinois, USA).
RESULTS The median CRL at the time of the scan was 64 mm (range 45–80) in controls and 58 mm (range 46–680.8) in the study group. In the control group, there was a significant increase with CRL in BS diameter (1.5862 + 0.02185 × CRL in mm; SD 00.36; R2 = 00.1114), BSOB diameter (10.7193 + 0.04143 × CRL in mm: SD 00.5711; R2 = 00.1496). The BS diameter to BSOB diameter ratio decreased with CRL (00.7829 + 0.003170 × CRL in mm; SD 00.048; R2 = 00.08161). These results are consistent with those reported in literature. The bias (mean difference) and 95% limits of agreement between paired measurements of BS and BSOB by the same operator and by two different sonographers are reported in Tables 1 and 2. No intra-observer variability was found significant for all measurements (00.33, 0.29, and 0.45
Table 1 Intra-observer variability for brain stem diameter, brain stem to occipital bone diameter, brain stem/brain stem to occipital bone diameters ratio in the normal population Parameters
Bias
P
Limits of agreement
BS diameter
0.9383
0.33
0.21 to
0.15
BSOB diameter
1.0000
0.29
0.25 to
0.15
BS/BSOB ratio
0.127
0.45
0.18 to
0.25
BS, brain stem; BSOB, brain stem to occipital bone.
Table 2 Inter-observer variability for brain stem diameter, brain stem to occipital bone diameter, brain stem/brain stem to occipital bone diameters ratio in the normal population
Figure 1 Mid-sagittal view of the fetal face and brain at 12 weeks showing the three posterior brain spaces. Nuchal translucency and thalamus are also seen. NT, nuchal translucency; T, thalamus; BS, brain stem; IT, intracranial translucency; CM, cisterna magna
Prenatal Diagnosis 2015, 35, 717–723
Parameters
Bias
P
Limits of agreement
BS diameter
0.9622
0.49
0.32 to
0.29
BSOB diameter
0.9855
0.39
0.20 to
0.15
BS/BSOB ratio
0.9953
0.59
0.39 to
0.15
BS, brain stem; BSOB, brain stem to occipital bone.
© 2015 John Wiley & Sons, Ltd.
Posterior brain anomalies
719
Table 3 Outcomes in fetuses where posterior fossa anomaly was suspected at the first trimester scan
Karyotype
US findings at mid-trimester scan
Outcome
Case
US finding at 11 to 14 weeks
1
PB cyst
AVSD
Yes
Trisomy 18
—
TOP at 14 weeks
2
PB cyst
HLHS
No
46, XY, der(5)t(5;8) (p15.33; q24.3)pat
—
TOP at 14 weeks
3
PB cyst
No
No
No
DWM–ACC
TOP at 20 weeks
Associated anomalies at 11 to 14 weeks
High risk for aneuploidies
4
PB cyst
No
No
No
BPC–CDH
TOP at 20 weeks
5
PB cyst
Vascular ring, micrognathia
Yes
Triploidy
—
TOP at 13 weeks
6
PB cyst
No
Yes
Trisomy 18
—
TOP at 14 weeks
7
PB cyst
No
No
No
DWM
8
PB cyst
Exomphalos, BCLP
Yes
Trisomy 13
—
TOP at 13 weeks
9
PB cyst
No
No
Mos 92, XXYY [36]/46, XY[9]
DWM–COA
TOP at 21 weeks
10
PB cyst
No
No
46, XY, del(5)t(5;6) (p13;q15)mat
—
TOP at 14 weeks
11
PB cyst
Hydrops, HRHS
Yes
No
—
IUD
12
PB cyst
TOF, abdominal cyst
Yes
Triploidy
—
TOP at 13 weeks
13
PB cyst
Severe cerebral ventriculomegaly, hydrotorax
Yes
45, X0
—
TOP at 13 weeks
14
PB cyst
Megacystis, strawberry-shaped head
Yes
Trisomy 18
—
TOP at 13 weeks
15
OSB
No
No
46, XY
—
TOP at 17 weeks
16
OSB
No
No
—
—
TOP at 14 weeks
17
OSB
SUA, megacystis
Yes
—
—
TOP at 14 weeks
18
OSB
No
No
—
—
TOP at 16 weeks
19
Cephalocele
Micrognathia, radial aplasia
Yes
—
—
TOP at 14 weeks
20
Cephalocele
No
No
46, XX
—
TOP at 14 weeks
21
Cephalocele
No
No
46, XX
—
TOP at 13 weeks
Alive
US, ultrasound; PB, posterior brain; OSB, open spina bifida; AVSD, atrio-ventricular septal defect; HLHS, hypoplastic left heart syndrome; BCLP, bilateral cleft lip and palate; HRHS, hypoplastic right heart syndrome; TOF, tetralogy of Fallot; SUA, single umbilical artery; DWM, Dandy–Walker malformation; ACC, agenesis of corpus callosum; BPC, Blake’s pouch cyst; CDH, congenital diaphragmatic hernia; COA, aortic coarctation; IUD, intrauterine death.
respectively); furthermore there was no significant difference between measurements made by two different operators for all parameters (0.49, 0.39, and 0.59, respectively). In the study group made of 21 fetuses (Table 3), only two of the three posterior brain spaces were recognized because the border between the fourth ventricle and the cisterna magna was not visualized. These fetuses had always associated severe anomalies. In 10/21 fetuses (cases 1, 2, 5, 6, 8–10, and 12–14), a chromosomal anomaly was found, and in seven of these cases, malformations were diagnosed sonographically by 11 to 14 weeks. In 4/21 fetuses (cases 3, 7, 10, and 12) a posterior fossa cystic anomaly was detected at mid-trimester scan [three Dandy–Walker malformations (DWM), and one Blake’s pouch cyst (BPC)]. In one of these fetuses, a chromosomal anomaly was associated (case 9). In 4/21 fetuses (cases 15–18), a diagnosis of OSB was made at a median of 15 weeks (range 13–17) of gestation. In 3/21 fetuses (cases 19–21), a diagnosis Prenatal Diagnosis 2015, 35, 717–723
of cephalocele was made at 13 weeks of gestation. In the last fetus (case 11), a major heart defect and hydrops were associated. The fetus died in utero 5 days after the diagnosis. Overall, 19 couples requested termination of pregnancy. This was performed within 14 weeks in 14 cases, and in 9 of these cases, it was not possible to obtain reliable post-mortem conclusion because reliable diagnoses of abnormal cerebellum are extremely difficult at this early stage. In the other cases, autopsy always confirmed the antenatal diagnosis. One pregnancy with a fetus affected by isolated DWM continued till term. The infant is alive and well but the neurological outcome at present is uncertain because of the very short follow-up (4 months old). Comparisons of BS diameter, BSOB diameter, and BS/BSOB ratio in controls and cases with Dandy–Walker complex, chromosomal anomalies, OSB, and cephalocele are reported in Table 4 (Figures 2–4). © 2015 John Wiley & Sons, Ltd.
P. Volpe et al.
720
Table 4 Comparison of brain stem diameter, brain stem to occipital bone diameter, brain stem/brain stem to occipital bone ratio in controls and cases with posterior fossa cyst, open spina bifida, and cephalocele Parameters
Posterior fossa cyst
OSB
Cephalocele
BS diameter
0.83
0.0055
0.011
BSOB diameter
