Pictorial Essay: CME ArticleThe Fetal Posterior Fossa: Clinical Correlation of Findings on Prenatal Ultrasound and Fetal Magnetic Resonance ImagingOh, Karen Y. MD*; Rassner, Ulrich A. MD*; Frias, Antonio E. Jr MD†; Kennedy, Anne M. MD*Author Information *Assistant Professor (Oh), Visiting Instructor (Rassner), Associate Professor (Kennedy), Department of Radiology and †Assistant Professor, Department of Obstetrics and Gynecology, Division of Maternal-Fetal Medicine, University of Utah Hospital, Salt Lake City, UT. Received for publication February 2, 2007; accepted March 25, 2007. The authors have disclosed that they have no financial interests in or relationships with any commercial companies pertaining to this educational activity. Lippincott Continuing Medical Education Institute, Inc. has identified and resolved all faculty conflicts of interest regarding this educational activity. Reprints: Karen Y. Oh, MD, Department of Radiology, University of Utah Hospital, SOM 1A71, 30 N 1900 E, Salt Lake City, UT 84132 (e-mail: Karen.firstname.lastname@example.org). Ultrasound Quarterly: September 2007 - Volume 23 - Issue 3 - p 203-210 doi: 10.1097/RUQ.0b013e318063d65 Buy Take the CME Test Metrics Abstract Objectives: Recognize posterior fossa anomalies on ultrasound and magnetic resonance imaging and appreciate imaging pitfalls that may lead to misdiagnosis. Materials and Methods: Cases are presented to illustrate normal development and various anomalies. Postnatal studies and autopsy are used for correlation with prenatal imaging. Results: Normal anatomy and anomalies are demonstrated. Pitfalls such as cystic hygroma, pseudomasses, and use of nonstandard scan planes are illustrated. Conclusions: Recognizing normal developing structures is an important component of performing fetal ultrasound. Documentation of the cerebellum, vermis, and cisterna magna are required for posterior fossa evaluation in any American Institute of Ultrasound in Medicine-certified practice. Normal variations are common, and understanding the anatomy is vital to avoid misdiagnosis and to accurately characterize abnormalities. © 2007 Lippincott Williams & Wilkins, Inc.