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Prenatal diagnosis of open and closed spina bifida
1Department of Obstetrics and Gynecology, Policlinico S. Orsola-Malpighi and University of Bologna, Bologna, Italy.
Insights
Antenatal ultrasound can differentiate open from closed spina bifida. Normal cranial anatomy on ultrasound suggests closed spina bifida, while abnormal findings indicate open spina bifida.
Area of Science:
- Medical imaging
- Prenatal diagnosis
- Neurology
Background:
- Spina bifida is a complex neural tube defect.
- Accurate antenatal differentiation between open and closed forms is crucial for management.
Purpose of the Study:
- To establish sonographic criteria for distinguishing antenatal open and closed spina bifida.
Main Methods:
- Retrospective analysis of 66 fetal spina bifida cases diagnosed between 1997 and 2004.
- Evaluation of ultrasound findings, including cranial anatomy and amniotic fluid alpha-fetoprotein levels.
Main Results:
- Open spina bifida (93%) was consistently associated with cranial anomalies ('banana' and 'lemon' signs).
- Closed spina bifida (7%) typically showed unremarkable cranial anatomy.
- Elevated amniotic fluid alpha-fetoprotein indicated open defects, while normal levels suggested closed defects.
Conclusions:
- Sonographic assessment of cranial anatomy is key for differentiating antenatal spina bifida types.
- Closed spina bifida constitutes a small percentage of in utero diagnoses.
Objective:
To identify criteria useful for differentiating closed from open spina bifida antenatally.
Patients And Methods:
A retrospective study of cases of spina bifida diagnosed in a referral center between 1997 and 2004.
Results:
Of 66 cases of fetal spina bifida diagnosed at a median gestational age of 21 (range, 16-34) weeks, detailed follow-up was available for 57. Of these, open defects were found in 53 (93.0%) and closed defects in four (7.0%). Closed spina bifida was associated in two cases with a posterior cystic mass with thick walls and a complex appearance, while in two cases the spinal lesion could not be clearly differentiated from an open defect, particularly at mid-gestation. Open spina bifida was always associated with typical alterations of cranial anatomy, including the so-called 'banana' and 'lemon' signs, while in closed spina bifida the cranium was unremarkable. When the data were available, levels of amniotic fluid alpha-fetoprotein were always abnormally elevated with open spina bifida and within normal limits with closed forms.
Conclusion:
In this study 7% of cases of spina bifida diagnosed in utero were closed. The differentiation between open and closed forms is best shown by the sonographic demonstration of abnormal or normal cranial anatomy.
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