From "Lemon" and "Banana" Signs to Clinical Management: A Case Report of a Mid-Trimester Chiari II Malformation Diagnosis

Chiari II malformation is a significant structural anomaly of the posterior fossa, characterized by the downward herniation of the cerebellum and brainstem, and is frequently associated with open neural tube defects.Early prenatal detection is critical for multidisciplinary clinical management and parental counselling.This report describes the prenatal diagnosis of a Chiari II malformation in an 18-week gestation fetus.Routine neurosonography revealed the classic sonographic markers of the "lemon sign," which is frontal bone scalloping, and the "banana sign," which is abnormal cerebellar morphology in the presence of an open lumbosacral myelomeningocele.The identification of these markers allowed for a prompt and comprehensive clinical evaluation and informed reproductive decision-making.The lemon and banana signs remain highly reliable sonographic markers for identifying Chiari II malformation during the mid-trimester anomaly scan.Systematic screening protocols are essential for the accurate detection of these findings.