Persistent cystic evagination of the area membranacea under inferior vermis in cerebellar vallecula due to nonperforation of foramen of Magendie
Diagnostic criteria
Normal vermian size, anatomy in midline sagittal view
< 30° anticlockwise rotation of vermis
Normal size of cisterna magna (CM)
CM septa may be bowed laterally
4th ventricle (V4) choroid plexus (CP) at superior margin of BPC
A Blake pouch (BP) is a normal embryological structure quite frequently seen with modern equipment
IMAGING
General Features
Ultrasonographic Findings
MR Findings
Imaging Recommendations
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Gross Pathologic & Surgical Features
CLINICAL ISSUES
Presentation
Natural History & Prognosis
DIAGNOSTIC CHECKLIST
Consider
Image Interpretation Pearls
Reporting Tips
Selected References
AIUM practice parameter for the performance of detailed diagnostic obstetric ultrasound examinations between 12 weeks 0 days and 13 weeks 6 days. J Ultrasound Med. ePub, 2020
Kau T et al: Blake's pouch cysts and differential diagnoses in prenatal and postnatal MRI: a pictorial review. Clin Neuroradiol. 30(3):435-45, 2020
Garcia-Rodriguez R et al: First-trimester cystic posterior fossa: reference ranges, associated findings, and pregnancy outcomes. J Matern Fetal Neonatal Med. 1-10, 2019
Paladini D et al: Hindbrain morphometry and choroid plexus position in differential diagnosis of posterior fossa cystic malformations. Ultrasound Obstet Gynecol. 54(2):207-14, 2019
Pertl B et al: The fetal posterior fossa on prenatal ultrasound imaging: normal longitudinal development and posterior fossa anomalies. Ultraschall Med. 40(6):692-721, 2019
Martinez-Ten P et al: Non-visualization of choroid plexus of fourth ventricle as first-trimester predictor of posterior fossa anomalies and chromosomal defects. Ultrasound Obstet Gynecol. 51(2):199-207, 2018
Wüest A et al: Enlarged posterior fossa on prenatal imaging: differential diagnosis, associated anomalies and postnatal outcome. Acta Obstet Gynecol Scand. 96(7):837-43, 2017
D'Antonio F et al: Systematic review and meta-analysis of isolated posterior fossa malformations on prenatal imaging (part 2): neurodevelopmental outcome. Ultrasound Obstet Gynecol. 48(1):28-37, 2016
Azab WA et al: Blake's pouch cyst. Surg Neurol Int. 5:112, 2014
Contro E et al: Open fourth ventricle prior to 20 weeks' gestation: a benign finding? Ultrasound Obstet Gynecol. 43(2):154-8, 2014
Leibovitz Z et al: Assessment of fetal midbrain and hindbrain in mid-sagittal cranial plane by three-dimensional multiplanar sonography. Part 2: application of nomograms to fetuses with posterior fossa malformations. Ultrasound Obstet Gynecol. 44(5):581-7, 2014
Paladini D et al: Abnormal or delayed development of the posterior membranous area of the brain: anatomy, ultrasound diagnosis, natural history and outcome of Blake's pouch cyst in the fetus. Ultrasound Obstet Gynecol. 39(3):279-87, 2012
Volpe P et al: Brainstem-vermis and brainstem-tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis. Ultrasound Obstet Gynecol. 39(6):632-5, 2012
Malinger G et al: The fetal cerebellum. Pitfalls in diagnosis and management. Prenat Diagn. 29(4):372-80, 2009
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References
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KEY FACTS
Terminology
Imaging
Top Differential Diagnoses
Clinical Issues
Diagnostic Checklist
TERMINOLOGY
Abbreviations
Blake pouch cyst (BPC)
Definitions
Persistent cystic evagination of the area membranacea under inferior vermis in cerebellar vallecula due to nonperforation of foramen of Magendie
Diagnostic criteria
Normal vermian size, anatomy in midline sagittal view
< 30° anticlockwise rotation of vermis
Normal size of cisterna magna (CM)
CM septa may be bowed laterally
4th ventricle (V4) choroid plexus (CP) at superior margin of BPC
A Blake pouch (BP) is a normal embryological structure quite frequently seen with modern equipment
IMAGING
General Features
Ultrasonographic Findings
MR Findings
Imaging Recommendations
DIFFERENTIAL DIAGNOSIS
PATHOLOGY
General Features
Gross Pathologic & Surgical Features
CLINICAL ISSUES
Presentation
Natural History & Prognosis
DIAGNOSTIC CHECKLIST
Consider
Image Interpretation Pearls
Reporting Tips
Selected References
AIUM practice parameter for the performance of detailed diagnostic obstetric ultrasound examinations between 12 weeks 0 days and 13 weeks 6 days. J Ultrasound Med. ePub, 2020
Kau T et al: Blake's pouch cysts and differential diagnoses in prenatal and postnatal MRI: a pictorial review. Clin Neuroradiol. 30(3):435-45, 2020
Garcia-Rodriguez R et al: First-trimester cystic posterior fossa: reference ranges, associated findings, and pregnancy outcomes. J Matern Fetal Neonatal Med. 1-10, 2019
Paladini D et al: Hindbrain morphometry and choroid plexus position in differential diagnosis of posterior fossa cystic malformations. Ultrasound Obstet Gynecol. 54(2):207-14, 2019
Pertl B et al: The fetal posterior fossa on prenatal ultrasound imaging: normal longitudinal development and posterior fossa anomalies. Ultraschall Med. 40(6):692-721, 2019
Martinez-Ten P et al: Non-visualization of choroid plexus of fourth ventricle as first-trimester predictor of posterior fossa anomalies and chromosomal defects. Ultrasound Obstet Gynecol. 51(2):199-207, 2018
Wüest A et al: Enlarged posterior fossa on prenatal imaging: differential diagnosis, associated anomalies and postnatal outcome. Acta Obstet Gynecol Scand. 96(7):837-43, 2017
D'Antonio F et al: Systematic review and meta-analysis of isolated posterior fossa malformations on prenatal imaging (part 2): neurodevelopmental outcome. Ultrasound Obstet Gynecol. 48(1):28-37, 2016
Azab WA et al: Blake's pouch cyst. Surg Neurol Int. 5:112, 2014
Contro E et al: Open fourth ventricle prior to 20 weeks' gestation: a benign finding? Ultrasound Obstet Gynecol. 43(2):154-8, 2014
Leibovitz Z et al: Assessment of fetal midbrain and hindbrain in mid-sagittal cranial plane by three-dimensional multiplanar sonography. Part 2: application of nomograms to fetuses with posterior fossa malformations. Ultrasound Obstet Gynecol. 44(5):581-7, 2014
Paladini D et al: Abnormal or delayed development of the posterior membranous area of the brain: anatomy, ultrasound diagnosis, natural history and outcome of Blake's pouch cyst in the fetus. Ultrasound Obstet Gynecol. 39(3):279-87, 2012
Volpe P et al: Brainstem-vermis and brainstem-tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis. Ultrasound Obstet Gynecol. 39(6):632-5, 2012
Malinger G et al: The fetal cerebellum. Pitfalls in diagnosis and management. Prenat Diagn. 29(4):372-80, 2009
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