Congenital Posterior Fossa Malformationseradiology.bidmc.harvard.edu/LearningLab/genito/Barnett.pdfCongenital Posterior Fossa Malformations Annika Barnett, Harvard Medical School Year

Congenital Posterior Fossa

Malformations

Annika Barnett, Harvard Medical

School Year III

Gillian Lieberman, MD

Jan 30-Feb 24, 2012 Annika Barnett, MSIII


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Agenda • Our Patient: History, Findings, and Diagnosis

• Facts about Dandy-Walker Complex

• Dandy Walker Malformation

• Dandy Walker Variant

• Mega Cisterna Magna

• Posterior Fossa Cyst

• Potential Causes

• Associated Anomalies

• Prognosis

• Our Patient: Outcome

• Summary

Annika Barnett, MSIII


3 3

Our Patient: Clinical History

• Female G4P1 presenting for full fetal

survey at 21 wks

• h/o gestational diabetes

• no family h/o genetic disorders



4 4

Our Patient: Full Fetal Survey at 21 Wks

•Dilated 4th

ventricle

•Posterior fossa

cyst

communicating

with 4th

ventricle



BIDMC, PACS

Axial U/S

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Our Patient: Summary of Findings

• Dilated Fourth Ventricle

• Absence of cerebellar vermis

• Enlargement of posterior fossa

• Findings consistent with a posterior fossa

malformation



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Our Patient: Differential Diagnosis

• Congenital CNS Anomalies

– Chiari Malformation

– Encephalocele

– Holoprosencephaly

– Septo-optic dysplasia

– Dandy-Walker Malformation



7

Menu of Tests

• Fetal Ultrasound

• Fetal MRI

• Which is better?



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MRI vs. U/S

• Study at Brigham and Women’s Hospital compared diagnosis of fetal anomalies with MRI vs. U/S

• Compared diagnosis of 27 fetuses with anomalies

• 57% of the cases involved CNS anomalies

• In 62% of those cases, both modalities correctly diagnosed the anomaly

• MRI provided additional information (such as agenesis of corpus callosum) in half of those cases

• Concluded that MRI may be value as an adjunct to U/S in evaluating CNS anomalies

Frates M C et al. Radiology 2004;232:398-404



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Our Patient: Diagnosis

Findings on ultrasound were consistent with

Dandy-Walker Malformation



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Now that we have a diagnosis, lets

find out more about Dandy-Walker

Complex



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Dandy-Walker Complex • Malformation of posterior fossa

– Pathogenesis unknown but thought to be due to

arrest of development of hindbrain around 7-10 week

gestation

• Spectrum of disease that includes:

– Dandy-Walker malformation

– Dandy-Walker variant

– Mega Cistern Magna

– Posterior Fossa Arachnoid Cyst

• Occurs in 1:30,000 births

• Seen in 4-12% of all babies with hydrocephalus



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• Prognosis


• Summary



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Dandy-Walker Malformation

– Triad of Malformations

• Cystic dilation of fourth ventricle

• Complete or partial agenesis of the cerebellar

vermis

• Enlarged posterior fossa with displacement of

the tentorium and torcular and lateral sinus

– Diagnosed after 18 weeks – closure of

cerebellar vermis should happen by that

time



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We now know how to recognize

Dandy-Walker Malformations.

Let’s look at some classic

examples on Ultrasound and MRI



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Companion Patient 2: Dandy-Walker Malformation

on Ultrasound

Courtesy of Dr. Debenedectis

Posterior fossa cyst

communicating with

dilated 4th ventricle

Axial Sagittal



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Companion Patient 3:

Dandy Walker Malformation on Ultrasound



communicating with


Axial Sagittal



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Companion Patient 4: Dandy Walker

Malformation On U/S and MRI

Kolble N et al. Prenatal Diagnosis 2000; 20:318-327


communicating with


T2/C-/Axial Axial



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Poe L B et al. Radiographics 1989; 9:801-826

Companion Patient 5: Dandy-Walker

Malformation on MRI

•Dilated 3rd ventricle

•Posterior fossa cyst communicating with dilated 4th ventricle

•Agenesis of corpus callosum

T1/C-/Sagittal T1/C-/Axial



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Companion Patient 6: Dandy-Walker malformation on MRI

Levine D et al. Radiology 1999;211:609-617

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•Normal corpus callosum

•Posterior fossa cyst displacing cerebellum and tentorium

T2/C-/Sagittal



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Companion Patient 7: Dandy-Walker on MRI


T2/C-/Coronal T2/C-/Axial

•Posterior fossa cyst

communicating with dilated 4th

ventricle

•Ventriculomegaly



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• Prognosis


• Summary



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Dandy-Walker Variant

– Cerebellar dysgenesis without enlargement

of the posterior fossa

– Variable hypoplasia of the cerebellar vermis

– Better prognosis



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Companion Patient 8: Dandy-Walker

Variant on U/S

Ecker J L et al. Prenatal Diagnosis 2000;20:328-332

Cleft of cerebellar vermis

Axial



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Companion Patient 9: Dandy-Walker variant on Ultrasound


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Axial



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Companion Patient 10: Dandy-Walker variant on MRI


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T2/C-/Axial



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• Prognosis


• Summary



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Mega Cisterna Magna • Enlarged posterior fossa caused by

enlarged cisterna magna

• Cisterna magna drains fourth ventricle

• Cerebellum and fourth ventricle are normal

• Treated with cisternotomy



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Companion Patient 11: Mega Cisterna

Magna on MRI

Hamid HA. Egypt Journal of Human Genetics 2007;8:115-120.

T1/C-/Sagittal

Mega Cisterna Magna

visualized as a

retrocerebellar fluid

collection



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• Prognosis


• Summary



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Posterior Fossa Arachnoid Cyst • Retrocerebellar arachnoid cyst that displaces

cerebellum anteriorly

• Causes mass effect on cerebellum and fourth

ventricle

• Looks similar to Mega Cisterna Magna on MRI

– Differentiate the two with ventriculogram (Mega

Cisterna Magna communicates with subarachnoid

space)

• Treated with marsupialization of cyst



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Companion Patient 9: Posterior Fossa

Arachnoid Cyst on MRI

Hamid HA. Egypt Journal of Human Genetics 2007;8:115-120.

Posterior fossa

cyst causing

compression of

cerebellum and

fourth ventricle



T1/C-/Sagittal

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• Prognosis


• Summary



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Potential Causes

– Chromosomal Aneuploidy

– Sporadic Mutation

– Environment Exposure – Alcohol, Rubella

– Multifactorial etiology



34









• Prognosis


• Summary



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Associated Anomalies

• Intracranial

– Ventriculomegaly (Seen in companion pt. 7)

– Agenesis of Corpus Callosum (Seen in companion pt. 5)

• Extracranial

– Cardiac Defects (most common)

– Renal Abnormalities

– Facial Abnormalities

– Extremity abnormalities



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Our Patient: Hydronephrosis on Ultrasound

Right and Left kidney

with dilated calyces

Coronal

BIDMC, PACS



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Companion Patient 10: Micrognathia associated with a Dandy-Walker variant on

Ultrasound

Mernagh J R et al. Radiographics 1999;19:S229-S241 37

Sagittal



38









• Prognosis


• Summary



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Prognosis • Variable and hard to predict

– Some have mental and physical handicaps while others develop normally

– ~25% mortality rate – mostly due to associated anomalies

– Prognosis worse in children with chromosomal aneuploidy and associated anomalies

• Treatment aimed at control of hydrocephaly



40









• Prognosis


• Summary



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Our Patient: Outcome

• Amniocentesis was normal

• Patient decided not to terminate

pregnancy and delivered baby at 35 wks

• Received further treatment at Children’s

Hospital of Boston Neurology

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42









• Prognosis


• Summary



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Summary

• Posterior Fossa Malformations exist in a spectrum of diseases collectively known as the Dandy-Walker complex

• Dandy-Walker Malformation is the most severe and involves a triad of malformations easily diagnosed with U/S and MRI

• Dandy-Walker complex is associated with many other congenital abnormalities and chromosomal aneuploidy which can be predictive of a worse prognosis



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References

• Ecker J L et al. The Sonographic Diagnosis of Dandy-Walker and Dandy-Walker Varient: Associated findings and outcomes. Prenatal Diagnosis 2000;20:328-332

• Frates M C et al. Fetal Anomalies: Comparison of MR Imaging and US for diagnosis. Radiology 2004;232:398-404

• Hamid HA. Dandy-Walker Malformation. Egypt Journal of Human Genetics 2007;8:115-120.

• Kolble N et al. Dandy-Walker Malformation: Prenatal diagnosis and outcome. Prenatal Diagnosis 2000; 20:318-327

• Levine D et al. Obstetric MRI Imaging. Radiology 1999;211:609-617

• Mernagh J R et al. US Assessment of the Fetal Head and Neck: A State of the Art Pictorial Review. Radiographics 1999;19:S229-S241

• Poe L B et al. Congenital Central Nervous System Anomalies. Radiographics 1989; 9:801-826



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Acknowledgments

• Dr. Monica Agarwal

• Dr. Carolynn Debenedectis

• Dr. Gillian Lieberman



Documents

Congenital Posterior Fossa Malformationseradiology.bidmc.harvard.edu/LearningLab/genito/Barnett.pdfCongenital Posterior Fossa Malformations Annika Barnett, Harvard Medical School Year