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?