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CASE REPORTS
NUMBER 3-4 YEAR 2008
Dandy-Walker Syndrome Variety in the Context of a Polimalformative Syndrome. The Limits of Conventional Ultrasound Examination
1 Department of Ob.-Gyn., County Emergency Hospital Satu Mare,
2 1st Clinic of Ob.- Gyn., Dumitru Popescu Clinical Hospital, Timisoara,
3 Dept. of Anatomy,
4 Bega Clinic of Ob.-Gyn., Victor Babes University of Medicine and Pharmacy, Timisoara

Correspondence to:
Mircea Gheorghe Muncean, 2/6 I.C. Bratianu Av., , Satu Mare, Tel. +40-729-977999
Email: mmuncean@yahoo.com
REZUMAT
O mare parte a malformatiilor cerebrale pot fi identificate inca din viata intrauterina, in special pe parcursul examinarii morfologice de trimestrul al doilea, efectuata la 20-24 saptamini de gestatie. Sindromul Dandy-Walker este o anomalie foarte rara, care consta din asocierea hidrocefaliei de diverse grade, largirea cisternei magna si agenezia totala sau partiala a vermisului cerebelos, care poate fi vizualizata ca o imagine chistica ce face legatura intre ventriculii III si IV. Aceasta situatie "clasica" poate fi detectata sau doar suspicionata inca din viata intrauterina. De la aceasta asociere pot exista diverse variante, majoritatea fara semiologie intrauterina. in urma introducerii examinarii cerebrale tomografice (CT) sau prin rezonanta magnetica nucleara (RMN), aceasta definitie a putut fi largita, ea cuprinzind la ora actuala: 1). malformatia Dandy-Walker clasica (largirea fosei posterioare, agenezia vermisului cerebelos, tentoriu inalt, hidrocefalie); 2). varianta Dandy-Walker (hipoplazia variabila a vermisului cerebelos, cu sau fara largirea fosei posterioare); 3). megacisterna magna (cisterna magna largita, cu pastrarea integritatii vermisului cerebelos si a ventriculului IV). Hidrocefalia a fost in mod clasic considerata ca un element esential de diagnostic, ea putind apare in evolutie, chiar la citeva luni postpartum. Tehnica ecografica actuala, ce permite examinarea fetala intrauterina 3D, prin care examinatorul poate obtine orice incidenta 2D, este necesara pentru evaluare, metoda cea mai valoroasa fiind TUI, cu posibilitatea prelucrarii volumului achizitionat prin alegerea incidentei, in care se pot efectua o serie de sonograme 2D consecutive, tehnica similara RMN.

ABSTRACT
A significant number of brain malformations can be identified during intrauterine life using ultrasonography, especially doing a morphological scan at 20-24 weeks of gestational age. The Dandy-Walker syndrome is a very rare abnormality (its incidence is 1/25000-1/35000 newborns, which involves the association of: ventriculomegaly in various degrees, enlarged cysterna magna, partial or total agenesis of the cerebelar vermis, which can be visualized as a cystic image between the 3rd and 4th ventricles. This "classic" form can usually be detected or suspicioned from intrauterine life. The other forms cannot be diagnosed before delivery, all clinical signs starting to develop after birth. As a result of the introduction of CT examination or the MRI investigations, this definition can be enlarged, including the following: 1). the classic Dandy Walker malformation (enlarged posterior fossa, partial or complete agenesis of the cerebellar vermis, the high position of the tentorium, hydrocephaly); 2). megacysterna magna (i.e. enlarged cysterna, the cerebellar vermis and the fourth ventricle are normal); 3). Dandy Walker variant (variable cerebellar vermis hypoplasia, mild enlargement of the posterior fossa). Hydrocephaly was usually considered as an essential element to the diagnosis of this abnormality, and it can even appear in evolution a few month after delivery. Our case was an extremely rare variety, without any signs during intrauterine life, all the symptoms starting after delivery, the diagnosis being confirmed by MRI examination, which used some new incidences for examination of the cerebellum, some of them being extended to the intrauterine fetal ultrasound scanning. In 3D ultrasound examination the most valuable method for cerebellum seems to be TUI (Tomographic Ultrasound Imaging), a multislice method which offers the examiner the possibility to rotate the volume and choose the best incidence in which he can use different consecutive 2D slices.
INTRODUCTION

The Dandy-Walker syndrome, first described in 1914, indicates the association of :1,2
1. Ventriculomegaly in various degrees;
2. Enlargement of posterior cranial fossa;
3. Partial or total agenesis of the cerebelar vermis, which can be visualized as a cystic image between the 3rd and 4th ventricles.
As a result of the introduction of CT examination or using the MRI investigations this definition can be enlarged including the following:3
1. The classic Dandy Walker malformation (dilated posterior fossa, agenesis of the cerebellar vermis, high position of the tentorium, hydrocephaly);
2. Megacysterna magna (i.e. enlarged cysterna, the cerebellar vermis and the 4th ventricles remaining normal);
3. Dandy Walker variant (variable cerebellar vermis hypoplasia, with or without the dilation of the posterior fossa).
Hydrocephaly was usually considered as an essential element in the diagnosis of this abnormality, and it can even appear in evolution a few months after delivery.
The standard intrauterine fetal ultrasound examinations or the postnatal transphontanellar ultrasonography don’t often reveal the Dandy-Walker variant, the assessment of these cases being obtained postnatal, only undergoing an MRI examination.4-9
To identify these cases, the medical literature suggests using a hinder incidence to the standard transcerebral incidence, yet determining only the severe anatomical variants of the syndrome. Other fetal malformations are often associated to determining the diagnosis of this particular syndrome.

CASE REPORT

A 32 years old primigravida, with a correct follow-up clinical and ultrasound assessment, with a Down syndrome risk score based on NT, embryologic biometry, serum level of βhCG and αFP of 1/1674 (at a normal value less than 1/250), was diagnosed with low site placenta implantation, observed at 12 weeks of gestation.
At 20 weeks gestational age, at a morphological ultrasound scan, no fetal malformation was observed, the intracranial structures were normal, the cerebellar vermis was present in standard examination and the ventricular cavities were also normal for this gestational age. Marginal placenta praevia was confirmed, without any clinical signs (uterine bleeding).
At 31 weeks gestational age the pregnant woman presented false premature labor that was treated with tocolytic, uterosedative and antispastic agents. The prevention of hyaline membrane disease was performed by administrating corticosteroids (Celestone). Marginal placenta praevia was reconfirmed at an ultrasound examination.
At 33 weeks gestational age the pregnant woman presented a minor uterine bleeding episode followed by massive hemorrhage at a few hours. An emergency cesarean section was performed. During the caesarean section marginal accreta placenta praevia was confirmed.
Figure 1. Normal aspect of fetal morphology at 12 weeks gestational age.
Figure 2. Normal ultrasound aspect of cerebellum at 20 weeks of gestation.

Figure 3. Cranial fetal presentation, placenta praevia.
Figure 4. CPR in 1st day (20 minutes after birth).
The newborn, a female of 2140 gr. with Apgar index of 6 at one minutes and 7 at five minutes presented transitory apnea. She had PPV with O2 100% and later with O2 40%. Cardiopulmonary radiography showed a fixed elevation of the right diaphragm suggesting a congenital right phrenic nerve paresis with a peribronchovascular trauma. At that moment, the newborn presented transient tachipnea of newborn (“wet lungs”, with prominent vascular markings and fluid in the fissures).
24 hours postnatally the status of the newborn became deteriorated with cyanosis, hypotonia, low blood pressure and low O2 saturation (Silvermann score 5/6). CPR showed right pneumothorax with pneumomediastine. The symptomatology was improved with orotracheal intubation and continuous mechanical ventilation associated with continuous pleural drainage. After four weeks complete remission was noticed.
Starting with the second week of life, the cranial perimeter increased progressively (starting from 31.5 cm at birth to 34 cm at two weeks, 35 cm at three weeks, 40 cm at eight weeks).
Once the hydrocephaly had been acknowledged a transfontanellar ultrasonography was performed, showing the following: well differentiated central tissue, LV = 19 mm, RV = 21mm with non homogeneous transsonic content, dilation of anterior horns with hiperechogenic walls, moderate dilation of the third ventricle, intermediary mass present. The aspect pleaded for medium form evolutive bicavity hydrocephaly.
Most often, hydrocephaly is caused by obstruction of Sylvius aqueduct, Lushka or Magendie holes. Rarely, the hydrocephaly appears through increased of CRL production or decreased of absosbtion capacity in subarachnoidian space, arterio-venous malformations.
Isolated hydrocephaly is frecvently caused by congenital obstruction of Sylvius aqueduct wich makes the connection between third and fouth ventricles.
The most frequent anomaly with hydrocephaly is the meningocele with Arnold-Chiari malformation. After birth, hydrocephaly can be caused by cerebral bleeding or cerebral infections.
The studied case was of a premature newborn (gestational age of 33 weeks) born through Caesarean Section (marginal placenta praevia) with fetal distress with transitory tachipnea of the newborn and pneumothorax secondary to therapy (CPAP endonasal) and phrenic nerve paralysis.
Starting from the second week of life the newborn presented progressive hydrocephaly initially confirmed as being posthemorhagic (CRL Pandy reaction positive, transfontanellar US), any other possible causes of hydrocephaly being excluded at the moment.
Still, the association of progressive hydrocephaly was installed early postnatal with phrenic nerve paresis, which raised the suspicion of a complex malformation syndrome, with indication for MRI. The MRI report confirmed important bilateral dilation of intracerebral liquid cavities, with important subsequent compression of cerebral parenchyma; it also revealed the presence of a cerebral arterio-venous malformation at cortical level, in front of anterior horn of right lateral ventricle (3/3/2 cm), with presence of drainage vessels and regional blood accumulation (hyposignal T1 and hypersignal T2), without fixing contrast substance. MRI also revealed partial agenesis (inferior and anterior) of the cerebellar vermis with moderate enlargement of the fourth ventricle and wide communication with cysterna magna, described as a variety of Dandy-Walker syndrome. Pituitary gland and orbits were normal.
MRI conclusions:
1. Triventricular massive hydrocephaly;
2. Cerebral arterio-venous right malformation, with cerebral bleeding in subacute stage;
3. A variant of Dandy-Walker syndrome.
Figure 5. Right pneumothorax (a), and image after intubation and aspirative
drainage (b).
Figure 6. CP 40 cm, 8th week of life, progressive hydrocephaly.

Figure 7. Transfontanellar sonographic images of hydrocephaly.
 

CONCLUSIONS

1. The studied case is a variety of Dandy-Walker syndrome with partial agenesis of the anterior and inferior cerebellar vermis.
2. Positive diagnosis was based on MRI report.
Figure 8. MRI suggestive imaging for antero-inferior hypoplasia of
cerebellar vermis (a, b, c).
3. Standard incidence of prenatal ultrasound examination of the cerebellum does not allow the imaging of this variety of the syndrome.
4. Conventional transfontanellary ultrasound has limitations in the diagnosis of this particular malformation.
5. Diagnosis is possible using prenatal US examination of the cerebellum in new, unconventional slides, taken from the MRI technique, using even the transversal and oblique subcerebellum incidence.
6. Using the newest ultrasound technique (3D and 4D scanning of the head) the obstetrician can obtain almost the same slices as MRI examination using the specific methods such as Magic Cut, TUI, niche mode, performing some new incidences for the examination of the cerebellum. Some of them can be extended to the ultrasound intrauterine fetal scanning, especially when using 3D ultrasound technique the examiner can select and obtain any 2D slice necessary for optimal assessment. In 3D ultrasound examination the most valuable method for cerebellum seems to be TUI (Tomographic Ultrasound Imaging), a multislice method, similar to MRI, which offers to the examiner the possibility to rotate the volume and choose the best incidence, in which he can use different consecutive 2D slices.10
REFERENCES

1. Klein O, Pierre-Kahn A, Boddaert N, et al. Dandy-Walker malformation: prenatal diagnosis and prognosis. Childs Nerv Syst 2003;19:484-9.
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4. Ulm B, Ulm MR, Deutinger J, et al. Dandy–Walker malformation diagnosed before 21 weeks of gestation: associated malformations and chromosomal abnormalities. Ultrasound Obstet Gynecol 1997;10:167-70.
5. Ecker JL, Shipp TD, Bromley B, et al. The sonographic diagnosis of Dandy-Walker and Dandy-Walker variant: associated findings and outcomes. Prenat Diagn 2000;20:328-32.
6. Has R, Ermis H, Yuksel A, et al. Dandy-Walker malformation: a review of 78 cases diagnosed by prenatal sonography. Fetal Diagn Ther 2004;19:342-7.
7. Cioata IT, Motoc A, Cretu A, et al. Transvaginal high resolution ultrasound in early screening of fetal malformations. Timisoara Med J 2003;1(53):47-9.
8. Babcock CJ, Chong BW, Salamat MS, et al. Sonographic anatomy of the developing cerebellum: normal embriology can resemble pathology. AJR 1996;166:427-33.
9. Murray JC, Johnson JA, Bird TD. Dandy-Walker malformation: etiologic heterogenity and empiric recurrence risk. Clin Genet 1985;28:272.
10. Hata T, Yanagihara T, Matsumoto M, et al.: Three-dimensional sonographic features of fetal central nervous system anomaly. Acta Obstet Gynecol Scand 2000;79:635-9.



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