What Are the Double Lines of the Fetal Cavum Septi Pellucidi on Ultrasound?

OBJECTIVE: To demonstrate the significance of the double line appearance of the septi pellucidi laminae (SPL) on fetal ultrasound. METHOD: A total of 522 uncomplicated singleton pregnancies (15 to 39 weeks' gestational age) with fetal ultrasounds were enrolled. The presence of a single versus double line SP as well as measurement of the cavum septi pellucidi (CSP) was determined retrospectively. Ultrasound settings from the CSP images were recorded. Thickness of the SPL was measured in 20 ultrasound and 14 MRI cases; histology was reviewed from one neonate. Maternal BMI and gestational age were also recorded. RESULTS: The presence of double line SPL is a normal sonographic finding, seen in 47% (188/403) of normal fetuses. Thickness of the SPL in 10 cases with double line averaged 1.4 mm and in 10 cases with single line averaged 0.8 mm; MRI measurements were within 0.1 mm of the corresponding ultrasound measurements. Double line cavum was more often seen with mid-dynamic contrast range settings (5, 6) rather than high range settings (7-10) (P value <.05). The double line was only visualized on ultrasound when the angle of insonation was at or near perpendicular to the laminae; it was never visualized on coronal ultrasound imaging or MRI imaging. CONCLUSION: A double line septum pellucidum lamina is a normal finding seen in almost 50% of uncomplicated singleton pregnancies. It may be attributed to borders of cell layers within each lamina that form separate specular reflections on both sides; this can be accentuated by ultrasound settings and beam angulation.

Ultrasound and Magnetic Resonance Imaging of Agenesis of the Corpus Callosum in Fetuses: Frontal Horns and Cavum Septi Pellucidi Are Clues to Earlier Diagnosis.

OBJECTIVES: We hypothesized that: (1) fetal frontal horn (FH) morphology and their proximity to the cavum septi pellucidi (CSP) can assist in suspecting complete agenesis of the corpus callosum (cACC) and partial agenesis of the corpus callosum (pACC) earlier than known indirect ultrasound (US) findings; (2) FHs assist in differentiating a true CSP from a pseudocavum; and (3) magnetic resonance imaging (MRI) is useful in learning FH morphology and pseudocavum etiology. METHODS: Thirty-two patients with cACC and 9 with pACC were identified on an Institutional Review Board-approved retrospective review. Of the 41 cases, 40 had prenatal US, and 21 had prenatal MRI; 17 had follow-up neonatal US, and 14 had follow-up neonatal MRI. Variables evaluated retrospectively were the presence of a CSP or a pseudocavum, ventricle size and shape, and FH shape (comma, trident, parallel, golf club, enlarged, or fused). Displacement between the inferior edge of the FH and the midline or cavum/pseudocavum was measured. RESULTS: Fetal FHs had an abnormal shape in 77% ≤20 weeks' gestation, 86% ≤24 weeks, and 90% >24 weeks. Frontal horns were laterally displaced greater than 2 mm in 85% ≤20 weeks, 91% ≤24 weeks, and 95% >24 weeks. The CSP was absent in 100% of cACC cases and 78% of pACC cases, and a pseudocavum was present in 88% of cACC cases and 78% of pACC cases across gestation. Magnetic resonance imaging confirmed US pseudocavums to be focal interhemispheric fluid or an elevated/dilated third ventricle. CONCLUSIONS: Frontal horns assist in assessing ACC ≤24 weeks and throughout gestation. Pseudocavums, often simulating CSPs, are common in ACC. Frontal horn lateral displacement and abnormal morphology, recognized by MRI correlations, are helpful in differentiating a pseudocavum from a true CSP. A normal CSP should not be cleared on screening US unless normally shaped FHs are seen directly adjacent to it.

Ultrasound Measurements of Frontal Horns and the Cavum Septi Pellucidi in Healthy Fetuses in the Second and Third Trimesters of Pregnancy.

OBJECTIVES: To assess the visualization rate and size of the frontal horns (FHs) and cavum septi pellucidi (CSP) in healthy fetuses throughout pregnancy. METHODS: After Institutional Review Board approval, 522 consecutive uncomplicated singleton pregnancies between 15 and 39 gestational weeks were enrolled in the study. Ultrasound measurements of the anterior horn width (AHW), center from the horn distance (CFHD), distance from the FHs to the CSP, and CSP width were retrospectively performed using axial transventricular or transcerebellar planes. Available maternal body mass indices were recorded. RESULTS: At least 1 FH was seen in 78% of the cases. The mean AHW decreased over the second trimester and plateaued in the third trimester. The CFHD plateaued in the second trimester and increased in the third trimester. Downside FHs were generally larger than upside FHs. More FHs were measured in transventricular (69%) than transcerebellar (31%) planes. Frontal horns were seen with high, low, and no confidence in 57%, 21%, and 22% of cases, respectively. No-confidence rates were 17% in the second trimester and 42% in the third trimester. The CSP was not visualized in 4% of cases; 15 of 19 cases of a nonvisualized CSP were scanned between 18 and 37 weeks. Mean body mass indices ± SDs were 27.6 ± 6.7 kg/m2 for the patients in cases of a visualized CSP and 32.4 ± 9.1 kg/m2 for the patients in cases of a nonvisualized CSP. CONCLUSIONS: Normative data for the fetal FH and CSP width were established. Frontal horns are more frequently seen on transventricular views and are difficult to confidently assess in the late third trimester. This study challenges previously reported data that the CSP is seen in 100% of cases from 18 to 37 weeks.

Enlarged Cavum Septi Pellucidi and Vergae in the Fetus: A Cause for Concern.

OBJECTIVES: To investigate fetal cases identified at our institution to determine whether an enlarged cavum septi pellucidi or cavum vergae is associated with other fetal abnormalities and whether its presence warrants more detailed investigation of the fetus. METHODS: In a retrospective study, 15 high- and low-risk patients undergoing prenatal sonography who had an enlarged cavum septi pellucidi or cavum vergae identified were reviewed. Data were collected for the sonographic study indication, gestation age at diagnosis of a prominent cavum, and associated anomalies. Follow-up outcome data regarding further imaging, karyotype, diagnosis of brain anomaly, and associated congenital abnormalities were obtained. RESULTS: Fifteen patients met the inclusion criteria. Nine patients were identified as having a prominent cavum septi pellucidi, and 6 were identified as having a prominent cavum vergae. The mean gestational age ± SD was 22.7 ± 5.9 weeks. Eleven patients made it to delivery. Of the 15 patients, 4 were thought to have trisomy 21, and 13 had congenital anomalies. Outcomes included 10 major adverse outcomes, 4 cases with normal development or minor abnormalities, and 1 lost to follow-up. An isolated dilated cavum on prenatal sonography was seen in 5 cases: 1 with lissencephaly on a neonatal examination, 3 premature deliveries (1 demise, 1 hospice, and 1 normal), and 1 unknown. CONCLUSIONS: Our cohort had many associated clinical anomalies: 3 confirmed trisomy 21 and 1 probable trisomy 21, 2 genetic disorders, and 10 major adverse outcomes, 5 of which were grave. Although we studied a small cohort, we conclude that an enlarged cavum septi pellucidi or cavum vergae warrants consideration of genetic counseling, which may include noninvasive prenatal testing (cell-free DNA), amniocentesis with microarray testing, or both.

Simplifying the ultrasound findings of the major fetal chromosomal aneuploidies.

Sonographic aneuploidy markers and structural anomalies associated with the 5 most common chromosomal aneuploidies are organized and simplified to highlight the many sonographic findings that are commonly seen with each aneuploidy. Identification of these findings allows families to have the option to pursue prenatal genetic testing to confirm or exclude chromosomal abnormalities suggested by such prenatal ultrasound findings and make informed decisions about the subsequent management of their pregnancy. We review the most common major human chromosomal aneuploidies, including trisomies 21, 18, and 13; Turner syndrome; and triploidy. The focus is on the major structural anomalies seen with each of these, as well as ultrasound markers (findings associated with increased risk of chromosomal abnormality but also seen in normal fetuses). The role of clinical information such as maternal serum screening and new cell-free fetal DNA screening is also reviewed. As patients do not usually present for fetal ultrasound with a known diagnosis, a concise knowledge of ultrasound and clinical findings will alert radiologists to concerning cases and prompt a guided search for important associated anomalies. Fetal ultrasound can be challenging owing to the many findings and sometimes technically difficult evaluation. By simplifying the ultrasound findings seen with the major chromosomal abnormalities and highlighting the role of clinical history, we hope that an informed search for specific sonographic findings can be performed; thereby, reducing missed diagnoses.