uog journal club: prenatal diagnosis and outcome of fetal posterior fossa fluid collections
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UOG Journal Club: June 2012Prenatal diagnosis and outcome of fetal posterior fossa fluid collections
Gandolfi Colleoni G, Contro E, Carletti A, Ghi T, Campobasso G, Rembouskos G, Volpe G, Pilu G, Volpe P
Volume 39, Issue 6, Date: June 2012, pages 625–631
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe P, Contro E, De Musso F, Ghi T, Farina A, Tempesta A,Volpe G, Rizzo N, Pilu G
Volume 39, Issue 6, Date: June 2012, pages 632–635
Journal Club slides prepared by Dr Aly Youssef(UOG Editor for Trainees)
Posterior Fossa Fluid Collections
Wide spectrum of different entities and associated outcomes
Similar anatomic as well as sonographic appearance
Diagnostic errors common
Advances in prenatal imaging allows more detailed evaluation
Background
Objective: to evaluate the diagnostic accuracy of fetal neurosonography and magnetic resonance imaging (MRI) in cases of posterior fossa fluid collections and to assess the
outcome of affected infants
Prenatal diagnosis and outcome of fetal posterior fossa fluid CollectionsGandolfi Colleoni et al., UOG 2012
• Prospective observational study
• All fetuses with abnormal posterior fossa fluid collections
• Detailed multiplanar neurosonographic evaluation
• Whenever possible, serial sonograms and prenatal MRI were
performed and fetal karyotype was obtained
• Prenatal diagnosis was compared with autopsy or postnatal MRI
• Follow-up through medical records or parental interviews
Methods
Outcomes
Prenatal diagnosis and outcome of fetal posterior fossa fluid CollectionsGandolfi Colleoni et al., UOG 2012
Normal posterior fossa at midgestation
Sagittal view
Axial view
Cavum Septi Pellucidi
Cisterna Magna
Tentorium
Cerebellar vermis
NB The Torcular Herophili is difficult to image on ultrasound due to acoustic shadowing from the skull bones. In the current study its position was inferred by observing the angulation of the tentorium
Prenatal diagnosis and outcome of fetal posterior fossa fluid CollectionsGandolfi Colleoni et al., UOG 2012
Blake’s pouch cyst Megacisterna magna Dandy–Walker malformation
Findings Upward rotation of an intact vermis with normal
torcular
Cisterna magna >10mm with intact and normally positioned cerebellum
Upward rotation of the vermis (normal or hypoplastic) with
elevated torcular
Sagittal
Axial
Categorization of posterior fossa fluid collections (1)
Prenatal diagnosis and outcome of fetal posterior fossa fluid CollectionsGandolfi Colleoni et al., UOG 2012
Vermian hypoplasia Cerebellar hypoplasia Posterior fossa arachnoid cyst
Findings Hypoplastic vermis with normal torcular
Large cisterna magna with small cerebellum
Cyst with mass effect resulting in distortion of the cerebellum
Sagittal
Axial
Categorization of posterior fossa fluid collections (2)
coronal
Prenatal diagnosis and outcome of fetal posterior fossa fluid CollectionsGandolfi Colleoni et al., UOG 2012
Cases
(n)
Associated
Anomalies
No
follow
up (n)
TOP
(n)
Regression
in utero
(n)
Sonographic
diagnosis
confirmed
(n)
Abnormal neurologicaldevelopment postnatally
Isolated PFFC (n)
PFFC with associated
anomalies (n)
Blake’s pouch cyst
32 8 3 2 11/27 17/18 1/20 1/5
Megacisterna magna
27 9 4 2 6/21 16/17 2/16 1/4
Dandy–Walker
malformation
26 16 7 11 0/8 16/19 3/5 2/2
Vermian hypoplasia
17 11 9 2 0/6 6/8 1/3 2/2
Cerebellar hypoplasia
2 2 0 2 0/0 2/2 0 0
Arachnoid cyst
1 0 0 0 0/1 1/1 1/1 0
Total (n, (%))
105 46 23 19/105 (18)
17/63 (27)
58/65 (89)
8/45 (16)
6/13
Sonography in fetuses with posterior fossa fluid collections (PFFC), associations withother anomalies, intrauterine regression, outcome and accuracy of prenatal diagnosis
Fetal sonography Fetal MRI Postnatal diagnosis
Blake’s pouch cyst Blake’s pouch cyst Arachnoid cyst
Blake’s pouch cyst Megacisterna magna Megacisterna magna
Megacisterna magna Megacisterna magna Arachnoid cyst
Dandy–Walker malformation Dandy–Walker malformationDandy–Walker malformation and
cortical malformation
Dandy–Walker malformation Dandy–Walker malformation Joubert syndrome
Dandy–Walker malformation Dandy–Walker malformation Hemorrhage
Vermian hypoplasia Vermian hypoplasiaVermian hypoplasia and cortical
malformation
Vermian hypoplasia Vermian hypoplasia Normal brain
Discordancies between fetal sonographic and MRI diagnoses and postnatal diagnoses in eight fetuses with posterior fossa fluid collections
• Fetal neurosonography allows accurate prenatal diagnosis
• The diagnosis with sonography was correct in almost 90% of cases.
• High diagnostic accuracy may be due to the multiplanar approach
• MRI of limited value with the use of meticulous neurosonography
(1/51 cases in the present study)
Discussion
Prenatal diagnosis and outcome of fetal posterior fossa fluid CollectionsGandolfi Colleoni et al., UOG 2012
Strength of the study
Weakness• About one quarter of our patients were lost to follow-up
• Postnatal assessment of survivors was performed by different pediatricians who did not use a standard protocol.
• This is the largest prospective series published so far of posterior fossa fluid collections recognized in utero
• Results provide useful information for assessment and counseling in these cases.
Prenatal diagnosis and outcome of fetal posterior fossa fluid CollectionsGandolfi Colleoni et al., UOG 2012
Ultrasound and fetal MRI perform similarly in the characterization of fetal posterior fossa abnormalities, and a correct diagnosis can be made inabout 90% of cases
Megacisterna magna and Blake’s pouch cysts are the most common antenatal diagnoses. They are risk factors for associated anomalies. When isolated, they have a good chance of intrauterine resolution and a normal developmental outcome in over 90% of cases
Dandy–Walker malformation and vermian hypoplasia have a guarded prognosis, with a very high likelihood of associated anomalies and/or neurologic impairment
Conclusions
Prenatal diagnosis and outcome of fetal posterior fossa fluid CollectionsGandolfi Colleoni et al., UOG 2012
• Fetal posterior fossa fluid collections associated with upward rotation of the cerebellar vermis range from benign asymptomatic conditions to severe abnormalities associated with neurological impairment
• The most frequent of these anomalies, Blake’s pouch cyst, vermian hypoplasia and Dandy–walker malformation, have a similar sonographic appearance but a very different prognosis
• A specific diagnosis with either ultrasound or magnetic resonance imaging is possible, but is frequently difficult and relies mostly upon subjective criteria
Background
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
2
1
1. Brainstem–vermis (BV) angle (between a line drawn tangentially to the dorsal aspect of the brain stem and a second line drawn tangentially to the ventral contour of the cerebellar vermis)
2. brainstem–tentorium (BT) angle (between the first line and a third line tangential to the lower edge of the tentorium)
Median view of the fetal brain
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
Objective: to evaluate the diagnostic contribution of anobjective approach based on the brainstem–vermis (BV)
angle and the brainstem–tentorium (BT) angle to the diagnosis of posterior fossa fluid collections
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
• Retrospective study
• BV and BT angles were measured in fetuses with posterior fossa
fluid collections with upward rotation of the cerebellar vermis
• Prospectively collected normal fetuses at mid-gestation (controls)
• Measurements were obtained from median views of the fetal brain
• Both 2D images and 3D volumes were used for measurements
Methods
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
Results
Ultrasound findings n BV angle (◦) BT angle (◦)
Mean SD Range Mean SD Range
Controls 80 9.1 3.5 4–17 29.3 5.8 21–44
Blake’s pouch cyst 12 23.0 2.8 19–26 42.2 7.1 32–52
Vermian hypoplasia 7 34.9 5.4 24–40 52.1 7.0 45–66
Dandy–Walker malformation
12 63.5 17.6 45–112 67.2 15.1 51–112
Blake’s pouch cyst Dandy–Walker malformationVermian hypoplasia
1= BV angle 2= BT angle
• Controls always had a BV angle <18º and a BT angle<45º• The BV and BT angle significantly increased in each of the three subgroups of anomalies• The angle increasing with increasing severity of the condition.• There was more overlapping of the BT angle among groups
BT angleBV angle
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
Limitations of the study
• Retrospective study
• Reproducibility and repeatability of measurements unknown
• The number of abnormal cases was relatively small (esepecially vermian hypoplasia)
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
Conclusion
Brainstem–vermis and brainstem–tentorium angles are objective findings which may be useful in differentiating fetal posterior fossa fluid collections that are sonographically similar but carry a very different prognosis
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
Discussion points
Brainstem–vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
• What are the different types of posterior fossa fluid collections?
• Is it possible to accurately classify these fetal posterior fossa fluid collections by 2D/3D prenatal ultrasound?
• What is the role for fetal MRI in patients with fetal posterior fossa fluid collections?
• Does this paper provide concrete evidence to base accurate prognoses for the different fetal posterior fossa fluid collections?
• In the light of the present data, how should women with fetal posterior fossa fluid collections be counselled?