title: Prenatal diagnosis of 'isolated' Dandy-Walker malformation: imaging findings and prenatal counselling.
abstract: OBJECTIVE
  The purpose of this article is to improve prenatal imaging diagnosis and counselling for cases of 'isolated' Dandy-Walker malformation (DWM) in the light of recent literature, which has demonstrated a potential good clinical and intellectual outcome of fetuses presenting with DWM characterised by partial vermian agenesis (identification of two fissures and three lobes) and absence of associated anatomical anomalies.
  
  
  METHODS
  This is a retrospective observational study of six consecutive prenatal cystic posterior fossa malformations, diagnosed as DWM, encountered in a national reference centre for posterior fossa malformations over a 2-year period.
  
  
  RESULTS
  In all cases, DWM was diagnosed as isolated (without any associated central nervous system or extra-central nervous system malformations and normal standard karyotype). Despite good-quality imaging, including fetal magnetic resonance imaging (MRI), prenatal analysis of the vermis was impossible because of limited identification of fissuration and lobulation. In three cases, a cytogenetic anomaly was found, including 6p subtelomeric deletion (n = 2) and partial 4 qter deletion associated with partial 7p trisomy (n = 1). One fetus with 6p deletion was terminated. In four of the five postnatal cases, MRI confirmed the diagnosis of DWM but provided only limited information for vermian analysis. In one case, postnatal MRI showed a large Blake's pouch cyst with rotated but complete vermis associated with a marked mass effect on the distal part of the tentorium. Of the four babies born with postnatal diagnosis of DWM, all required ventriculoperitoneal shunting because of early postnatal hydrocephalus.
  
  
  CONCLUSIONS
  When fetal MRI is necessary to exclude additional cerebral lesions in the diagnosis of DWM, we highlight the inaccuracy of magnetic resonance for anatomical analysis of the vermis. We also emphasise the potential high incidence of subtelomeric anomalies in isolated DWM, especially 6p deletion. In the postnatal period, paediatricians should look for postnatal hydrocephalus even if the ventricular size is normal or slightly dilated on prenatal imaging.
authors.affiliation: Département d'Imagerie Pédiatrique et Foetale, Hôpital Femme Mère Enfant, Université Claude Bernard Lyon I, Lyon, France. laurent.guibaud@chu-lyon.fr
authors.forename: Laurent
authors.initials: L
authors.lastname: Guibaud
authors.forename: Anne
authors.initials: A
authors.lastname: Larroque
authors.forename: Dorothée
authors.initials: D
authors.lastname: Ville
authors.forename: Damien
authors.initials: D
authors.lastname: Sanlaville
authors.forename: Marianne
authors.initials: M
authors.lastname: Till
authors.forename: Pascal
authors.initials: P
authors.lastname: Gaucherand
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Pracros
authors.forename: Vincent
authors.initials: V
authors.lastname: des Portes
mesh_terms: D000328:Adult; D002531:Cerebellum / Q000002:abnormalities; D003616:Dandy-Walker Syndrome / Q000150:complications / Q000175:diagnosis* / Q000601:surgery; D005260:Female; D005817:Genetic Counseling; D005865:Gestational Age; D006801:Humans; D006849:Hydrocephalus / Q000209:etiology / Q000473:pathology / Q000601:surgery; D007231:Infant, Newborn; D008279:Magnetic Resonance Imaging; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D012189:Retrospective Studies; D016896:Treatment Outcome; D017287:Ventriculoperitoneal Shunt / Q000379:methods*