The Application of Clinical Genetics (Jul 2022)
Utility of Measuring Fetal Cavum Septum Pellucidum (CSP) Width During Routine Obstetrical Ultrasound for Improving Diagnosis of 22q11.2 Deletion Syndrome: A Case-Control Study
Abstract
Christy L Pylypjuk,1 Shiza F Memon,2 Bernard N Chodirker3 1Department of Obstetrics, Gynecology and Reproductive Sciences (Section of Maternal-Fetal Medicine), Children’s Hospital Research Institute of Manitoba, University of Manitoba, Winnipeg, MB, Canada; 2Department of Obstetrics, Gynecology & Reproductive Sciences, University of Manitoba, Winnipeg, MB, Canada; 3Departments of Pediatrics and Child Health (Section of Genetics and Metabolism) & Biochemistry and Medical Genetics, University of Manitoba, Winnipeg, MB, CanadaCorrespondence: Christy L Pylypjuk, WN5002, HSC Women’s Hospital, 820 Sherbrook Street, Winnipeg, MB, R3A 1R9, Canada, Tel +1 204 787-4821, Fax +1 204 787-2920, Email [email protected]: To evaluate the utility of measuring fetal cavum septum pellucidum (CSP) width during routine, mid-pregnancy ultrasound for improving diagnosis of 22q11.2 deletion syndrome amongst fetuses with and without conotruncal anomalies.Patients and Methods: This was a retrospective case-control study (2005– 2016). Fetuses and newborns with 22q11.2 deletion and/or conotruncal cardiac anomalies were identified using a regional, clinical database. A control group was assembled in a 2:1 ratio to create three groups for comparison: i) 22q11.2 deletion syndrome; ii) isolated conotruncal anomalies; and iii) controls. Eligibility was restricted to those with stored ultrasound images between 18– 22 weeks’ gestation and a minimum biparietal diameter of 40 mm. Post-processing measurement of CSP width was performed in a standardized fashion by two blinded and independent study personnel. Descriptive and inferential statistics, regression modeling, and receiver operator curves (ROC) were used to compare outcomes between groups and evaluate sensitivity/specificity of CSP width as a marker of 22q11.2 deletion syndrome.Results: Twenty-nine cases of 22q11.2 deletion and 64 cases of isolated conotruncal anomalies were matched to 186 healthy controls. Cases with 22q11.2 deletion syndrome had significantly larger CSP widths (5.36 mm; SD=1.2) compared to those with isolated conotruncal anomalies (3.75 mm; SD=1.11) and healthy controls (2.93 mm; SD=0.57; p 4.3 mm, fetuses with 22q11.2 deletion can be accurately identified with good sensitivity (89.7%) and specificity (84%).Conclusion: Fetuses with 22q11.2 deletion syndrome have dilated CSPs when compared to those with isolated conotruncal anomalies or controls. Because CSP dilation can be evaluated during routine mid-pregnancy ultrasound using standard images of the fetal head, measurement could easily be incorporated to enhance prenatal diagnosis of this phenotypically diverse condition.Keywords: DiGeorge syndrome, 22q11 microdeletion, cavum septum pellucidum, prenatal diagnosis, fetal ultrasound, neurosonography
