Presentation
Routine antenatal ultrasound at 20 weeks of gestation.
Patient Data
The lemon sign, as seen by the pinched-up frontal bones, gives the skull the shape of a lemon. The posterior fossa and cisterna magna are also small in size. Additionally, instead of being dumbbell-shaped, the cerebellum appears curved like a banana.
Case Discussion
Some fetal cranial abnormalities like the lemon sign and banana sign identified during second-trimester ultrasound may indicate the presence of an open spina bifida and neural tube defect. Their presence should alert the sonographer to search extensively for the associated neural defects. However, the lemon sign can be seen normally in fetuses.
This fetus had an associated open spine defect and meningomyelocele in the thoracic region.
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