Case Report: Dichorionic-Diamniotic Twin Pregnancy Complicated by a Migrational Anomaly Mimicking a Brain Neoplasm

Abstract

Background Fetal brain anomalies have a wide differential diagnosis including: (1) congenital genetic and vascular disorders; (2) acquired causes such as infection and hypoxic-ischemic injury; and rarely (3) neoplasm. Fetal brain anomalies are also infrequently seen. Consequently, there is limited literature describing methods of distinguishing these conditions, barring the presence of the most characteristic findings on imaging. Objective The purpose of this report is to describe the critical parts of our workup that helped us distinguish a fetal brain migrational disorder from a neoplasm. Study Design Case report of a single patient seen at Tripler Army Medical Center and Children’s Hospital of Los Angeles Case Summary (Results) 24-year-old gravida 1 with a dichorionic-diamniotic twin pregnancy was found to have an intracranial abnormality in Twin A on a transabdominal ultrasound performed at 16w1d gestation. Serial prenatal ultrasounds and complementary fetal magnetic resonance imaging (MRI) studies were performed to distinguish a possible fetal brain tumor from a migrational disorder. Fetal MRIs performed at 19w1d and 23w0d demonstrated a mass-like region increasing in size which was interpreted as highly suggestive of an enlarging fetal brain tumor. Ultimately, additional radiologic findings of fluid filled clefts and polymicrogyria visualized at 32 weeks led to a definitive diagnosis of a fetal migrational disorder. Conclusion Features used to diagnose fetal brain anomalies are often nonspecific and develop throughout a gestation. Most of these diagnoses require multiple imaging studies carried out over time to identify key features, and characteristic key features often do not present until very late in a gestation. The differential diagnosis of a dysplastic appearing mass-like region growing in size throughout a pregnancy should include fetal migrational disorders.