Transcript Slide 1
UOG Journal Club: June 2012
Prenatal 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)
Background
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
Prenatal diagnosis and outcome of fetal posterior fossa fluid Collections
Gandolfi Colleoni et al., UOG 2012
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 Collections
Gandolfi Colleoni et al., UOG 2012
Methods
• 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
Outcomes
• Prenatal diagnosis was compared with autopsy or postnatal MRI • Follow-up through medical records or parental interviews
Prenatal diagnosis and outcome of fetal posterior fossa fluid Collections
Gandolfi Colleoni et al., UOG 2012
Normal posterior fossa at midgestation
Sagittal view
Tentorium Cavum Septi Pellucidi Cerebellar vermis
Axial view
Cisterna Magna 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 Collections
Gandolfi Colleoni et al., UOG 2012
Categorization of posterior fossa fluid collections (1)
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
Prenatal diagnosis and outcome of fetal posterior fossa fluid Collections
Gandolfi Colleoni et al., UOG 2012
Categorization of posterior fossa fluid collections (2)
Vermian hypoplasia Cerebellar hypoplasia Posterior fossa arachnoid cyst Findings Sagittal
Hypoplastic vermis with normal torcular Large cisterna magna with small cerebellum Cyst with mass effect resulting in distortion of the cerebellum
coronal Axial
Sonography in fetuses with posterior fossa fluid collections (PFFC), associations with other anomalies, intrauterine regression, outcome and accuracy of prenatal diagnosis
Cases (
n
) Associated Anomalies No follow up (
n
) TOP (
n
) Regression
in utero
(
n
) Sonographic diagnosis confirmed (
n
) Abnormal neurological development postnatally Isolated PFFC (
n
) PFFC with associated anomalies (
n
)
Blake’s pouch cyst Megacisterna magna Dandy – Walker malformation Vermian hypoplasia Cerebellar hypoplasia Arachnoid cyst Total (
n,
(%)) 32 27 26 17 2 1 105 8 9 16 11 2 0 46 3 4 7 9 0 0 23 2 2 11 2 2 0 19/105 (18) 11/27 6/21 0/8 0/6 0/0 0/1 17/63 (27) 17/18 16/17 16/19 6/8 2/2 1/1 58/65 (89) 1/20 2/16 3/5 1/3 0 1/1 8/45 (16) 1/5 1/4 2/2 2/2 0 0 6/13
Discordancies between fetal sonographic and MRI diagnoses and postnatal diagnoses in eight fetuses with posterior fossa fluid collections
Fetal sonography Blake’s pouch cyst Blake’s pouch cyst Megacisterna magna Dandy –Walker malformation Dandy –Walker malformation Dandy –Walker malformation Vermian hypoplasia Vermian hypoplasia Fetal MRI Blake’s pouch cyst Megacisterna magna Megacisterna magna Dandy –Walker malformation Dandy –Walker malformation Dandy –Walker malformation Vermian hypoplasia Vermian hypoplasia Postnatal diagnosis Arachnoid cyst Megacisterna magna Arachnoid cyst Dandy –Walker malformation and cortical malformation Joubert syndrome Hemorrhage Vermian hypoplasia and cortical malformation Normal brain
Prenatal diagnosis and outcome of fetal posterior fossa fluid Collections
Gandolfi Colleoni et al., UOG 2012
Discussion
• 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)
Prenatal diagnosis and outcome of fetal posterior fossa fluid Collections
Gandolfi Colleoni et al., UOG 2012
Strength of the study
• 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.
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.
Prenatal diagnosis and outcome of fetal posterior fossa fluid Collections
Gandolfi Colleoni et al., UOG 2012
Conclusions
Ultrasound and fetal MRI perform similarly in the characterization of fetal posterior fossa abnormalities, and a correct diagnosis can be made in about 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
Brainstem –vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
Background
• 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
Brainstem –vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
Median view of the fetal brain
2 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)
1
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 an objective 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
Methods
• 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
Ultrasound findings n
Controls Blake’s pouch cyst Vermian hypoplasia Dandy –Walker malformation
80 12 7 12
Results
Mean 9.1
23.0
34.9
63.5
BV angle ( ◦)
SD 3.5 2.8
5.4 17.6 Range 4 –17 19 –26 24 –40 45 –112 Mean 29.3
42.2
52.1
67.2
BT angle ( ◦)
SD 5.8 7.1
7.0
15.1 Range 21 –44 32 –52 45 –66 51 –112 Blake’s pouch cyst Vermian hypoplasia Dandy –Walker malformation 1= BV angle 2= BT angle
Brainstem –vermis and brainstem–tentorium angles allow accurate categorization of fetal upward rotation of cerebellar vermis
Volpe et al., UOG 2012
BV angle 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
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
• 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?