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Congenital Abnormalities of the Posterior Fossa1 Zurich Open Repository and Archive University of Zurich Main Library Strickhofstrasse 39 CH-8057 Zurich www.zora.uzh.ch Year: 2015 Congenital abnormalities of the posterior fossa Bosemani, Thangamadhan ; Orman, Gunes ; Boltshauser, Eugen ; Tekes, Aylin ; Huisman, Thierry A G M ; Poretti, Andrea Abstract: The frequency and importance of the evaluation of the posterior fossa have increased signifi- cantly over the past 20 years owing to advances in neuroimaging. Nowadays, conventional and advanced neuroimaging techniques allow detailed evaluation of the complex anatomic structures within the poste- rior fossa. A wide spectrum of congenital abnormalities has been demonstrated, including malformations (anomalies due to an alteration of the primary developmental program caused by a genetic defect) and disruptions (anomalies due to the breakdown of a structure that had a normal developmental potential). Familiarity with the spectrum of congenital posterior fossa anomalies and their well-defined diagnostic criteria is crucial for optimal therapy, an accurate prognosis, and correct genetic counseling. The authors discuss the spectrum of posterior fossa malformations and disruptions, with emphasis on neuroimaging findings (including diagnostic criteria), neurologic presentation, systemic involvement, prognosis, andrisk of recurrence. DOI: https://doi.org/10.1148/rg.351140038 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-112443 Journal Article Published Version Originally published at: Bosemani, Thangamadhan; Orman, Gunes; Boltshauser, Eugen; Tekes, Aylin; Huisman, Thierry A G M; Poretti, Andrea (2015). Congenital abnormalities of the posterior fossa. Radiographics, 35(1):200-220. DOI: https://doi.org/10.1148/rg.351140038 Note: This copy is for your personal non-commercial use only. To order presentation-ready copies for distribution to your colleagues or clients, contact us at www.rsna.org/rsnarights. 200 Congenital Abnormalities of the Posterior Fossa1 Thangamadhan Bosemani, MD Gunes Orman, MD The frequency and importance of the evaluation of the posterior Eugen Boltshauser, MD fossa have increased significantly over the past 20 years owing to Aylin Tekes, MD advances in neuroimaging. Nowadays, conventional and advanced Thierry A. G. M. Huisman, MD neuroimaging techniques allow detailed evaluation of the complex Andrea Poretti, MD anatomic structures within the posterior fossa. A wide spectrum of congenital abnormalities has been demonstrated, including Abbreviations: CHARGE = coloboma, heart malformations (anomalies due to an alteration of the primary de- defect, choanal atresia, retarded growth and de- velopmental program caused by a genetic defect) and disruptions velopment, genital abnormality, and ear abnor- NEUROLOGIC/HEAD AND NECK IMAGING mality, CMV = cytomegalovirus, CSF = cere- (anomalies due to the breakdown of a structure that had a normal brospinal fluid, DWM = Dandy-Walker malfor- developmental potential). Familiarity with the spectrum of congeni- mation, OMIM = Online Mendelian Inheritance in Man, PCH = pontocerebellar hypoplasia tal posterior fossa anomalies and their well-defined diagnostic crite- ria is crucial for optimal therapy, an accurate prognosis, and correct RadioGraphics 2015; 35:200–220 genetic counseling. The authors discuss the spectrum of posterior Published online 10.1148/rg.351140038 fossa malformations and disruptions, with emphasis on neuroimag- Content Codes: ing findings (including diagnostic criteria), neurologic presentation, 1From the Section of Pediatric Neuroradiology, systemic involvement, prognosis, and risk of recurrence. Division of Pediatric Radiology, Russell H. Mor- © gan Department of Radiology and Radiological RSNA, 2015 • radiographics.rsna.org Science, Johns Hopkins University School of Medicine, Charlotte R. Bloomberg Children’s Center, Sheikh Zayed Tower, Room 4174, 1800 Orleans St, Baltimore, MD 21287-0842 (T.B., G.O., A.T., T.A.G.M.H., A.P.); and Department Introduction of Pediatric Neurology, University Children’s Hospital, Zurich, Switzerland (E.B., A.P.). Re- Over the past 2 decades, significant advances in pre- and postnatal cipient of a Certificate of Merit award for an neuroimaging techniques, the development of next-generation ge- education exhibit at the 2013 RSNA Annual netic sequencing, and an increase in animal model research have led Meeting. Received February 17, 2014; revision requested May 16 and received June 9; accepted to more accurate definition and classification of congenital abnor- July 7. For this journal-based SA-CME activity, malities of the posterior fossa and a better understanding of their the authors, editor, and reviewers have disclosed no relevant relationships. Address correspon- pathogenesis. Classifications of congenital posterior fossa abnormali- dence to A.P. (e-mail: [email protected]). ties based on neuroimaging, molecular genetic, and developmental biologic criteria have been proposed (1–3). SA-CME LEARNING OBJECTIVES Congenital posterior fossa anomalies may result from inherited After completing this journal-based SA-CME (genetic) or acquired (disruptive) causes (4,5). A malformation is de- activity, participants will be able to: fined as a congenital morphologic anomaly of a single organ or body ■ Discuss the importance of precise part due to an alteration of the primary developmental program diagnosis of congenital posterior fossa caused by a genetic defect (6). Gene mutations causing malforma- anomalies. tions may be de novo (ie, new in the affected child, rather than pres- ■ Describe the relevant neuroimaging ent in or transmitted by the parents) or inherited from the parents. findings using a detailed anatomic de- scription to classify and categorize vari- Inherited mutations are transmitted in different patterns (eg, au- ous anomalies. tosomal recessive, X linked) with differences in recurrence risk for ■ List the clinical, genetic, and prognos- further offspring and for potential transmission of mutations from tic factors that can help improve commu- the patients to their children. The latter is the case for autosomal nication with clinicians and patients. recessive–inherited diseases (from an unaffected mother or father to See www.rsna.org/education/search/RG. her or his child), autosomal dominant–inherited diseases (from an affected mother or father to her or his child), X-linked diseases (from an affected mother to her son), and mitochondrially inherited dis- eases (from an affected mother to her child). A disruption is defined as a congenital morphologic anomaly caused by the breakdown of an anatomic structure that had a normal developmental potential (6). Disruptive causes include prenatal infection, hemorrhage, and isch- emia, among others. Disruptions are acquired lesions without risk of RG • Volume 35 Number 1 Bosemani et al 201 major implications for genetic counseling and TEACHING POINTS family planning secondary to the significant dif- ■ A malformation is defined as a congenital morphologic anom- ference in recurrence risk between a malforma- aly of a single organ or body part due to an alteration of the tion and a disruption. Neuroimaging plays a key primary developmental program caused by a genetic defect. Gene mutations causing malformations may be de novo (ie, role in the diagnosis of posterior fossa abnormali- new in the affected child, rather than present in or transmit- ties, and the challenge for the neuroradiologist is ted by the parents) or inherited from the parents. Inherited to provide the clinician with precise and up-to- mutations are transmitted in different patterns (eg, autosomal date diagnostic information. recessive, X linked) with differences in recurrence risk for further In this article, we discuss congenital poste- offspring and for potential transmission of mutations from the patients to their children. The latter is the case for autosomal rior fossa abnormalities in terms of the normal recessive–inherited diseases (from an unaffected mother or fa- anatomy of the posterior fossa, imaging techniques ther to her or his child), autosomal dominant–inherited diseases and strategy, and the most important congenital (from an affected mother or father to her or his child), X-linked abnormalities of the posterior fossa, making use of diseases (from an affected mother to her son), and mitochon- a simple classification scheme based on the neuro- drially inherited diseases (from an affected mother to her child). A disruption is defined as a congenital morphologic anomaly imaging-based scheme proposed by Doherty et al caused by the breakdown of an anatomic structure that had (8). For each disorder, we summarize the key neu- a normal developmental potential. Disruptive causes include roimaging findings that are needed for the diagno- prenatal infection, hemorrhage, and ischemia, among oth- sis and review the pattern of inheritance, systemic ers. Disruptions are acquired lesions without risk of recurrence. involvement, and long-term neurologic prognosis However, a genetic predisposition to disruptive lesions such as dominant mutations in COL4A1 may be present. to emphasize the high clinical relevance of an ac- ■ Each part of the cerebellum (vermis and hemispheres) may curate diagnosis. Although cerebellar agenesis and be hypoplastic and/or dysplastic, resulting in global cerebellar global cerebellar hypoplasia may result from either involvement or predominantly vermian involvement. Predomi- a malformation or a disruption, we discuss these nant involvement of
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