E1310. The Fetal Brain: An Approach to Imaging and Diagnoses
  1. Saif Azam; LAC+USC Medical Center
  2. Shawdi Manouchehr-Pour; LAC+USC Medical Center; Olive View-UCLA Medical Center
  3. Jennifer Johnston; LAC+USC Medical Center; UT Health Science Center at Houston
  4. Daphne Walker; LAC+USC Medical Center
Structural anomalies of the brain occur in approximately 1 to 2 per thousand births globally and can be due to intrinsic anomalies or extrinsic factors related to the in utero environment. Early diagnosis of these malformations is crucial to guide clinical management, patient counseling and decision making. Screening based on genetic markers and serum or amniotic fluid analysis are important for risk stratification. However, fetal ultrasound (US) and magnetic resonance (MR) can be essential for confirming diagnoses. A large retrospective review demonstrated that up to 95% of fetal brain abnormalities can be detected on routine screening US. Adjunct imaging with MR can then confirm the findings and detect additional abnormalities with high sensitivity and specificity, particularly in the second and third trimesters. Accurate diagnosis portends compatibility with life, maternal and neonatal needs during pregnancy and delivery, and potential interventions in the neonatal period. As such, it is essential for radiologists to recognize both US and MR features of these pathologies to improve fetal outcomes.

Educational Goals / Teaching Points
Review developmental fetal neuroanatomy, discuss an approach to imaging the fetal brain, including ultrasound techniques and MRI protocols, review fetal brain malformations with discussion of differentials, mimics, and the spectrum of US and MR imaging findings, and discuss clinical management, including in utero and neonatal interventions, and their impact on fetal outcomes.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Selected cases include encephalocele (2D US images showing brain and meninges herniating through an occipital calvarial defect), Chiari II & myelomeningocele (MR images showing displacement of brainstem and cerebellar tonsils through the foramen magnum. Companion case demonstrating an open neural tube defect covered by a thin sac with protruding neural elements), acrania and anencephaly (2D US images demonstrating absence of the calvarium with angiomatous stroma resembling the brain, companion case showing absence of calvarium and fetal brain above the orbits), and agenesis of corpus callosum (MR images showing absence of the corpus callosum with colpocephaly and “bullhorn” appearance).

US is an instrumental tool in the initial detection of fetal brain dysmorphism. Findings of ventriculomegaly, absent cavum septum pellucidum, and abnormal posterior fossa morphology are key to recognize. However, US can be subject to technical limitations, including patient body habitus, amniotic fluid volume, fetal positioning, and variable calvarial ossification. Thus, MR imaging is often a useful adjunct. While fetal motion similarly causes technical challenges, tailored MR sequences including single shot fast spin echo, T2-weighted balanced steady state free precession, and standard T1 and diffusion weighted images together help reduce artifact and delineate lesion contents and anatomy. Given the implications of these findings in prognostication and decision making, it is imperative that radiologists recognize the spectrum of imaging findings in brain anomalies to make timely diagnoses.