Prenatal diagnosis of posterior fossa anomalies: An overview

Med Preg12009; LXII (3-4): 157-163. Novi Sad: mart-april.

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STRUCNI CLANCI PROFESSIONAL ARTICLES Strucni clanak

Klinicki centar Vojvodine, Novi Sad Klinika za ginekologiju i akuserstvo' Institut za onkologiju, Sremska Kamenica Centar za dijagnosticki imidzing Klinicki centar Vojvodine, Novi Sad Klinika za neurologiju'

Professional article UOK 618.33-073:616.714 001: 10.2298iMPNS0904163N

PRENATALNA DIJAGNOSTIKA ANOMALIJA ZADNJE LOBANJSKE JAME PRENATAL DIAGNOSIS OF POSTERIOR FOSSA ANOMALIES - AN OVERVIEW

Aleksandra NOVAKOV-MIKIC 1, Katarina KOPRIVSEKZ, Milos LUC:IC 2 , Zoran BE LOPAVLOVIC 1, Sinisa STOJIC 1 i Slobodan SEKULIC 3 Sazetak - Prcgled mozdanih struktura je integralni deo svakog prenatalnog ultrazvucnog pregleda. Klasican pregled zadnje lobanjske jame obuhvata merenje i pregled morfologije cerebelurna. cisterne magne i cetvrte mozdane kornore u sagitalnim i aksijalnirn presecima. Tradicionalno se anornalije zadnje lobanjske jame dele na tri velike grupe - Dandy Walker malformaciju. Dandy Walker varijantu i megacisternu magnu. Novije klasifikacije anornalija zadnjc lobanjske jame baziraju se na anatomskom pristupu analizi morfologije zadnje lobanjske jame i dele ove malforrnacije na parcijalnu ili kornplctnu agenezu vermisa. koja moze biti izolovana iii deo sindroma, ccrcbelarnu i pontocerebelarnu hipoplaziju, te atrofiju cercbcluma. U clanku se prikazuju anomalije zadnje lobanjske jarne. te se ukazuje na cinjenicu da je. s obzirom na njihovu raznolikost u smislu prognoze, potrebno imati rnultidisciplinarni pristup ovom problernu. koji obuhvata kako dvodimenzionalni i trodimenzionalni ultrazvucni pregled, tako i pregled magnetnorn rezonancijam. ali i infektoloske i rnetabolicke pretrage. i zahteva zajednicki rad perinatologa. radiologa. neurolcga i gencticara te individualni pristup svakorn pojcdinacnorn slucaju. Kljucne reci: Prenatalna dijagnostika: Prenatalna ultrasonografija; Malforrnacije nervnog sistema: Zadnja lobaniska jama; Cerebelum: Cisterna magna: Cetvrta mozdana komora

Summary - Ultrasonography of the central nervous system is an integral part of a prenatal scan, and the development ol imaging technologies has led to better diagnostic possibilities Posterior/ossa anomalies have traditionally been divided into Dandy Walke malformation, Dandy Walker variation and megacisterna magna, but this approach, due to diversity of the extensive number ojpossible disorders covered by this classification, unables accurate prognosis and therefore adequate counselling. fJn alternative approach to the classification of posterior fossa anomalies is to divide them into agenesis of the veri/lis, winch could be partied or complete. cerebellar hypoplasia, pontocerebellar hypoplasia and cerebellar atrophy. Different ultrasonographic and magnetic resonance imagining ofappearances ofthe posteriorfossa anomalies in prenatal period are discussed in the article, as well as possible syndromes and prognosis ofdifferent entities. Diversitv ofanomalies of the central nervous system, and in particutar. subtle differences in prenatal appearances ofposteriorfossa anomalies. which may have major impact on the prognosis. demand a multidisciplinaiv approach that encompasses two-dimensional and three-dimensional ultrasound scan. magnetic resonance imaging infectious dis;a.\·es and metabolic disorders work-ups as well as individual approach to cve,y case involving ofa team ofexperts In thefield of perinatologv. radiology, paediatrics, neurology and genetics. Key words: Prenatal Diagnosis; Ultrasonography, Prenatal; Servo us System Malformations, Cranial Fossa. Posterior; Cerebellum; Cisterna Magna; Fourth I 'entricle

Uvod

Introduction

Pregled rnozdanih struktura je integralni deo svakog prenatalnog ultrazvucnog pregleda, a razvitkom ultrazvucnih aparata, trodimenzionalne ultrazvucne slike kao i koriscenjern magnetne rezonancije (MRI) radi razresenja svih slucajeva kod kojih ultrazvucni pregled ne moze da da sve odgovore. doslo je do podizanja nivoa mogucnosti diijagnostike anomalija zadnje lobanjske jame u prenatalnom periodu.

The examination of brain morphology is an integral part of every prenatal ultrasound scan and with the development of ultrasound. tv v odimensional, three dimensional as well as with the introduction of magnetic resonance imaging (MRI) in all the cases where ultrasonography could not give final answers, the level of prenatal diagnostic possibilities of posterior fossa anomalies has been raised.

Discussion

Diskusija Klasican bazicni pregled zadnje lobanjske jame obuhvata biornetri j u - meren ie transcerebelarnog

The classic basic scan of the posterior fossa encompasses biometry (measurement of transcerebe-

Adresa autora: Prof. dr Aleksandra Novakov-Mikic. Klinika za ginekologiju i akuscrstvo. 21000 Novi Sad. Branimira Cosica 37. E-mail: nlcksandranovakovrq.yahoo.corn

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Skracenice MRI UZ

Abbreviations - magnetna rezonacija - ultrazvuk

dijametra te sirine cisterne mazne na aksijalnom preseku i evaluaciju njene morfologije - izgled cerebeluma (postojanje dye dobro formirane hemisfere, te vermisa normalnog izgleda) i cisterne magne. Sledeci korak pregleda predstavlja analizu izgleda zadnje lobanjske jame u srcdnjem sagitalnom preseku, na kome se pregleda vermis - meri velicina i evaluiraju fisure, cetvrta mozdana komora i polozaj tentorijuma, te meri visina cerebeluma. I visina i sirina cerebeluma koreliraju sa gestacijskom staroscu, a cisterna magna ne bi trebalo da je sira od 10 mm [1-3] (slike 1 i 2).

Slika 1. Aksijalni presek zadnje lobanjske jame - ultrazvucni prikaz (a) i MRI prikaz (b)

Fig. 1. Posterior fossa, axial section ultrasound (a) and .\fRI (b)

Razvoj ultrasonografije doveo je do dijagnostike sve veceg broja anomalija zadnje lobanjske jame, a klasifikacija nije ujednacena, uglavnom zbog toga sto se, tradicionalno, anomalije dele na tri velike grupe - Dandy Walker malformaciju, Dandy Walker vanjantu i megacisternu magnu, ali ovaj pristup, zbog sirokog i razlicitog podrucja koje ovakva klasifikacija pokriva, onernogucava davanje tacnije prognoze [4]. U clanku se diskutuje 0 autohtonim anomal ijama zadnje lobanjske jame, a ne 0 stanjima koja se javljaju kao posledica drugih anornalija, tako da se ne razmatraju malformacije tipa Chiari J i Chiari II. Dandy Walker malformacija se ultrazvucno prikazuje kao hipoplastican vermis, rotiran ka gore, cetvrta komoraje cisticna (Slika 3a). Na MR tomogramu fetusa, sagitalni, aksijalni i koronalni T2 prikaz ilustruje potpunu agenziju cerebelarnog vermisa, siroko razdvojene cerebelarne hemisfere i veliku ekstraaksijalnu cistu zadnje 10banjske jame koja je u kontinuitetu sa cetvrorn rnozdanorn komorom, a na sagitalnim skenovima vidi se visoka pozicija torkulara Herophili (Slika 3b). Dandy Walker varijantu ultrazvucno karakterise nesto manja hipoplazija vermisa, uglavnom ograniceria na donji zadnji deo, manje je izrazena rotacija vermisa ka gore i manje ima nakupine tecnosti koja komunicira sa cetvrtorn komorom. Nalaz hipoplazije vermisa, rotacije vermisa ka gore i pomeranja tentorijuma ka gore, ima i prognosticki znacaj jer

MRI UZ

- magnetic resonance imaging - ultrasound

liar diameter and cisterna magna width on the axial scan) as well as evaluation of its morphology (two well formed cerebellar hemispheres, normal vermis and cisterna magna). The next step in the scan is the analysis of the posterior fossa anomaly in the midsagital scan, in which vermis is seen - its size and fissures are analyzed, as well as the fOLl11h ventricle and the position of tentorium. At this scan the cerebellar height and width may be measured. arid they should correlate with the gestational age. Cisterna magna should not be wider than 10 mm [1-3J (Fig. 1 and 2). . The development of ultrasonography led to diagnosis of increasing number of posterior fossa anomalies, with different classifications, mostlv because anomalies traditionally have been divided into three big groups - Dandy Walker malformation, Dandy Walker variant and megacisterna magna, but this approach, due to wide and different areas covered by this classification, prevents giving exact prognosis [4]. We discuss autohtonous posterior fossa anomalies, without discussing states that are consequences of other anomalies (Chiari 1 and Chiari II malformations). Dandy Walker malfomation is seen as a hypoplastic vermis rotated upwards, with cystic fourth ventricle (Fig. 3a). At MR tomogram of the fetus, sagital, axial i coronal T2 images show complete agenesis of cerebellar vermis, widely separated cerebellar hemispheres and big extraaxial cyst of the posterior fossa that is in continuity with the fourth ventricle. At sagital scans high position of torcular Herophili is seen (Fig. 3b). Dandy Walker variant is on ultrasound seen as a hypoplasia of vermis, mostly limited on a lower posterior part, the rotation of vermis upwards is less prominent and there is less fluid that communicates with the fourth ventricle. The finding of hypoplasia of vermis and its rotation upwards as well as the displacement of tentorium has prognostic value and

Slika 2. Sagitalni presek zadnjc lobanjske jame - ultrazv ucni prikaz ra) i !'vIR! prikaz t b)

Fig. 2. Posterior/ossa, sagitol section, ultrasound t a) and .ifNI (b)

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Slika 3. Dandy Walker malformacija - ultrazvucni prikaz (a) i \1RI prikaz (b) Fig. 3. Dandv iValker malformation, axial section, ultrasound (a) and MRI (b)

Slika 4. Megacisterna magna - ultrazvucni prikaz (a) i MRI prikaz (h) i prikaz aksijalnog preseka Fig. 4. Megacisterna magna - axial ultrasound scan (a) and \lRlromogram

znacajno korelira sajavljanjem i stepenom mentalne retardacije [5,6]. Kod megacisterne magne, cisterna magna jeste siroka, ali nema kompresije na cerebelum i slobodno komunicira sa subarahnoidalnim prostorom i cetvrtorn komorom [7-9] (Slika 4). Na sagitalnom i aksijalnom T2 MR tomogramu ploda sa megacisternom magnom vidi se povecanje retrocerebelarnog Iikvorskog prostora, prisutan je kornpletno formiran vermis i cerebelarne hemisfere. Cetvrta komora je normalne morfologije. Diferencijalna dijagnoza ovih anomalija je, upotrebom konvencionalnog dvodimenzionalnog ultrazvuka i koriscenjem samo aksijalnog preseka, veoma teska, te je, u detaljnom pregledu, neophodno koristiti sagitalni presek, kako srednji, tako i parasazitalni. Dobijanju adekvatnog uvida u detaljnu morfologiju pomaze i generisanje trodimenzionalne slike, gde se, na vrlo jednostavan nacin, moze brzo dobiti imidz koj i se moze detaljno analizirati i nakon sto je pregled zavrsen [10]. S obzirom na to da je jedan od osnovnih zadataka prenatalne dijagnostike da, na osnovu zakljucaka donesenih tokom pregleda, del prognozu datog stanja, ada, na primer, entitet koj i nazivamo Dandy Walker varijantom obuhvata agenezu vermisa bez uvecanja zadnje jame, ali i hipoplaziju vermisa, kao i sindrome kod koj ih se ova promena nalazi (Joubert, Walker-Warburg, rnutacija OPHN-1), hromozomopatije, lezije vaskularne i infektivne etiologije kao i polimalformativni kompleks, jasno je da je, koriscenjern samo tradicionalne klasifikacije, nemozuce ispuniti zadatak tacnije procene prognoze [4]. '-- Alternativna klasifikacija anomalija zadnje 10banjske jame bazira se na anatomskom pristupu analizi morfologije zadnje lobanjske jame i deli ove malformacije na agenezu vermisa, parcijalnu iii kompletnu, koja moze da bude izolovana iii deo sindrorna, hipoplaziju, cerebelarnu i pontocerebelarnu, te atrofiju cerebeluma [4]. Delimican iii kompletan defekt cerebelarnog verniisa javlja se sporadicno iii kao deo nekog genetskog sindroma i aneuploidije -. trizomije 21, Joubert sindrorna, Walker-Warburg sindroma, cereorookulomuskulamog sindroma, CHARGE). Pridru-

it correlates significantly with the degree of mental retardation [5,6]. In the case of megacisterna magna, the cisterna magna is wide, but there is no compression on the cerebellum and it freely communicates with the subarachnoid area and the forth ventricle [7-9]. On the sagital and axial T2 MR tomogram of the fetus with the rnegacisterna magna, an increase of retrocerebellar space is seen, as well as competely formed vermis and cerebellar hemispheres. The morphology of the forth ventricle is normal (Fig. 4). Differential diagnosis of these anomalies is vet l' difficult when it is confined to the use of conventional two-dimensional ultrasound and axial section, so in the detai led scan it is mandatory to use sagital section as well, both parasagital and midsagital. Three dimensional ultrasound helps acquiring the adequate information about the state of morphology giving the possibility of post exam analysis of images as well [10]. Taking into account the fact that one of the basic tasks of prenatal diagnosis is to give adequate prognosis of the anomaly and that. for example, the elltit l' that is called Dandy Walker variant consists of vermian agenesis without augmentation of the posterior fossa, but also with vermian hypoplasia, and it may be found in a number of syndromes - Joubert's, Walker Warburg's, OPHN-I mutation), chromosomal abnormalities, vascular lesions. consequences of infections as well as polymarfonnative complex, it is clear that, by using only the traditional classification, it is impossible to give adequate prognosis [4]. An alternative classification of posterior fossa anomalies is based on the anatomical approach to morphological analysis and divides these anomalies into agenesis of vermis. partial or complete. isolated or a part of a syndrome, hypoplasia, cerebellar and pontocerebellar, and cerebellar atrophy [4]. A partial or complete defect of cerebellar vermis is seen sporadically or as a part of a genetic syndrome and aneuploidy - trisomy 21, Sy Joubert. Sy Walker Warburg, cerebro-oculornuscular syndrome - CHARGE). Associated anomalies are found in

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zene anomalije mogu biti kako intra-, tako i ekstrakranijalne i nalaze se kod oko polovine slucajeva, a kod onih kod kojih nije bilo pridruzenih anornalija, razvoj moze da bude norrnalan, a javljanje promene sporadicno, s obzirom da se ne moze potpuno iskljuciti postojanje neke genetske veze, u sledecoj trudnoci treba posebnu paznju obratiti na neurosonogram ploda [4-6,11]. Dijagnoza hipoplazije cerebeluma bazira se na smanjenom transcerebelarnom dijametru i obuhvata heterogenu grupu porernecaja kako infektivne patologije, tako i hromozomopatija, ali i porernecaja razvoja cerebelarnog korteksa [4,12,13]. Na MR sagitalnom tomogramu ploda vidi se smanjenje volumena cerebeluma, (14 mrn: manje od 10 percentila za gestacijsku starost od 23 nedelje) i prosirenje retrocerebelarnog likvorskog prostora po tipu arahnoidne ciste bez komunikacije sa cetvrtorn mozdanom komororn. Insercija tentorijuma nije visoka. Navedena patoloska morfologija zadnje 10banjske jame moze da bude asocirana sa drugim razvojnim anomalijama poput bilateralne ventrikulomegalije i disgenezije korpusa kalozuma (Slika 5).

Slika 5. Hipoplazija cerebeluma-MR tomogram

Fig. 5 Cerebellar hypoplasia - JfR tomogram

Atrofija cerebeluma definise se kao smanjenje cerebelarnog volumena, ali sekundarno, kao posledica nekog procesa - hemoragije, tumora i s!. Mogucnost dijagnoza anomalije zadnje lobanjske jame zavisi od gestacije - embriogeneza cerebelarnog vermisa pocinje rostralno u srednjoj liniji tokom devete nedelje gestacijc, a fuzioni proces se nastavlja kaudalno, obrazujuci ostatak cerebelarnih hemisfera (neocerebelum), tako da su kompletni vermis i cerebelum potpuno formirani do kraja 15. nedelje [14]. S obzirom da se, cak i upotrebom transvaginalne sonografije u ranom drugom trirnestru, donji deo verrnisa cini otvorenim i postoji komunikacija izrnedu cisterne magne i cetvrte komore, dijagnoza ageneze verrnisa, posebno delimicna, ne moze da se postavi pre 18. nedelje

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about half of cases and mav be intra- and extracrania!' In the cases where there are no associated anomalies. development can be normal, although. since the association with genetic disorder cannot be completely excluded, in tile next pregnancy attention should be payed to detailed fetal neurosonogram [4-6.1 1]. The diagnosis of cerebellar hypoplasia is based on finding of a smaller transcerebellar diameter and is found in a heterogenous group of anomalies that may result from infection and chromosomal abnormalities. as well as anomalies of cerebellar cortical development [4,12.13 J. The MR sagital tomogram of the fetus shows a decrease of the cerebellar volume together with retrocerebellar liquor space enlargement (arachnoid cyst) without communication with the fourth ventricle. The tentorium insertion is not high. The Fep finding is assocated with bilateral ventriculomegaly and corpus callosum dysgenesis (Fig. 5). Atrophy of cerebellum is defined as finding of a smaller cerebellar volume. but it rnav be secondary to some other process - haemorrhage.jumour. etc. . The possibility of the posterior fossa anomalies depends on gestation - the ernbriogenesis of the cerebellar vermis starts rostrallv in the midline in the ninth week of gestation, and the fusion continues caudally. forming the rest of cerebellar hemispheres (neocerebellum), so that the vermis and cerebllum are completely formed by the end of the 15th week [14]. Since even with transvaginal sonography in the early second trimester the lower part of the vermis seems open, with communication between the cisterna magna and the fourth ventricle the diagnosis of agenesis of vermis, specially partial, cannot be made before 18 gestational weeks [3,15]. It is very important to keep in mind that all the changes in the posterior fossa cannot be called Dandy Walker malformation - enlargement of cisterna magna may only be a consequence of the verrnian rotation, which is a benign entity that can be seen on the axial scan, and if agenesis of vemis is suspected, the finding needs to be confirmed on sagital scans, and in the cases in which additional information is needed, MRI can be done [10,16-18]. Generally, in the cases when cisterna magna is enlarged, the transcerebellar diameter is smaller or the morphology of the vermis is pathological, further evaluation of the finding is needed. In the case of enlarged cisterna, depending whether cerebellar morphology is normal or not, whether there is adequate biometry. and whether there is associated ventriculornegaly, a differential diagnosis may be made of normal, rotated vermis, meaacisrerna magna, arachnoid cyst or Blake's pouch c;rst. ~

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gestacije [3, IS]. Veoma je vazno imati na umu da sve promene u zadnjoj lobanjskoj jami ne mozen~~ pripisati DWM - uvecanje cisterne magne moze biti samo posledica rotacije cerebelarnog vermisa, sto Je benigni entitet koj i se vidi na aksijalnim presecirna, i ukoliko se posumnja na agenezu vermisa. nalaz se mora proveriti na sagitalnim presecima, a u slucajevirna kada su potrebne dodatne inforrnacije, potrebnoje uraditi i MRI [10,16-18]. Uopsteno gledano, u slucaju da se na rutinsko:n ultrazvucnom pregledu nade cisterna magna veca nego sto je uobicajeno, smanjen transcerebelarni dijametar iii patoloski izgled verrnisa, daljoj evaluacij i stanja mora se prici shodno nalazu. U zavisnosu od toga da Ii je, u slucaju uvecane cisterne magne cerebehrna anatomija nonnalna iIi ne. biometrija normalna iii ne, odnosno da Ii postoj i ventrikulomegalija iii ne, diferencijalno-dijagnosticki moze doci u obzir norrnalan, rotirani vermis, megacisterna magna, arahnoidalna cista, iii cista Blejkovog spaga. U slucaju smanjenog transcerebelarnog dijametra, vazno Je da Ii je morfologija cerebeluma normalna iIi ne, da Ii je redukcija cerebeluma fokalna iii globalna, a difercncijalno-dijagnosticki kod globalne redukcije dolazi u obzir pontocerebelarna hipoplazija/cerebelarna hipoplazija kod OPHN 1, hromozomopatije, infekcije CMV, Joubert-ov sindrorn, Walker- Warburg-ovog sindrom, a kod fokalne redukcije displazija, ishernija i hernoragija. U slucajevima patoloske morfologije verrmsa, diferencijalno-dijagnosticki u obzir dolazi Chiari II kod defekta neuralne cevi, ageneza vermrsa I rom. boencefalosinapsa [4]. Kada dominantni nalaz na UZ/MR predstavlja agenezija cerebelarnog verrnisa sa hipogenezom cerebeluma rnanifestovanoz kroz smanjenje transcerebelarnoz dijarnetra, diferencijalno-d ijanosticki u obzir dolazi niz porernecaja u koj ima navcdena patologija predstavlja izolovani nalaz iii je samo deo kompleksnih sindrorna. Kao izolovana patologija, navedeno se moze videti u slucaju rombencefalosinapse (kongenitalna fuzija cerebralnih hernisfera, nukleusa dentatusa i gornjih cerebelarnih pedunkula, sa agenezijom verrnisa, u minornorn procent.u asimptornatska, u vecini slucajeva pracena ataksi[om, nevoljnim pokretima glave, usporernrn mental'nim razvojern i kompulsivnim ponasanjern r19]. Na MR tomogramu ploda sa rornbencefalosinapsom na sazitalnorn. aksijalnom i koronalnom T2 imidzu endokranijuma vidi se poremecaj razvoja cerebelarnog vermisa asociranoz sa izostankom separacije cerebelarnih hemisfera~i tipicnorn morfologijom cetvrte komore ikljucaonicai (Slika 6). ., . Kod agenezije cerebelarnog .ve~·mlsa diferencijalno-dijagnosticki dolazi u obzir I Joubertov smdrom (hipoplazija cerebelarnog v~n:llsa. sa karakteristicnim znakom tnolara, neuroloskim srmptormma. tahipnejom, usporenim mentalnim razvitkorn. karakteristicnim izgledom lica sa visokim obrvama, prominentnim celom, prcastim nosem sa navise okrenutim nozdrvarna, ovalnim ustirna, sa nadole spustenim uglovima [20,21], COACH sindrom (Ce-

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In the case of decreased transcerebellar diameter. it is important to establ ish whether cerebellar morphology is normal, and if the reduction is focal or global. A differential diagnosis in the case of global reduction includes pontocerebellar hypoplasia/cerebellarna hypoplasia in OPHN 1, chromosomal abnormality, CMV infectons. Joubert's syndrome, Walker Warburzovs svndrorne. In the cases of focal reduction the differential diagnoss includes dysplasia, ischemia and haemorrhage. In the cases of pathological morphology of vermis, the differential diagnosis includes Chiari II in neural tube defects, agenesis of vermis and rhomboencefalosynapsis [4]. When the dominant finding at the ultrasound or MRI is agenesis of cerebellar vermis associated with hypogenesis of the cerebellum (a smaller transcerebellar diameter), the differential diagnosis includes a number of disorders in which the mentioned pathology may be either isolated finding or a part of a complex syndrome. As isolated pathology this can be seen in the case of rhornbencephalosynapsis (congenital fusion of cerebellar hemispheres, nucleus dentatus and upper cerebellar peduncules, with agenesis of vermis) [19]. In the case of rhombencepbalosynapsis at the fetal MR tomogram on sagital, axial and coronal T2 image of endocranium shows developmental anomaly of the cerebellar vermis, associated with the lack of separation of cerebellar hernipsheres and typical morphology of the fourth ventricle ("key hole") (Fig. 6).

Slika 6. Rornbcnccfalosinapsa - ultruzvucni prikaz Fig. 6. Rhombencephulosynapsis - ultrasound scan

In the cases of agenesis of the cerebellar vermis the differential diagnosis may also include Sy cerebellar veJ"ll~is with charJoubert (hypoplasia acteristic inollar sign [2021 J. COACH syndrome (Cerebellar Vermis Hypo/Aplasia. Oligophrenia. Coneenital Ataxia. Ocular Coloboma. Hepatic FIhr().\~is) [22], Sy Aryrna (agenesis of vermisa. ocular anomalise. multicystic kidneys, liver disease) [23J, oculocerebrcutaneous syndrome [24J, Sy Walker-Warburg [25]. Sy Smith Lenili Opitz [26].

of

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rebellar Vermis Hypo/Aplasia, Oligophrenia, Congenital Ataxia, Ocular Coloboma, Hepatic Fibrosis) [22], Arima sindrom (ageneza vennisa, anomalije ociju, cisticne promene bubrega, oboljenja jetre) [23], okulocerebrokutani sindrom [24], WalkerWarburg sindrom [25], Smith Lemli Opitz sindrom

[26]. U detekciji razvojnih anomalija sa predominacijom patologije cerebelarnog vermisa MR je neophodan elemenat dijagnostickog algoritma. Stacionarni i triplanarni prikaz struktura Fep u tri ortogonalne ravni omogucava prikaz morfologije i dimnezija malornozdanih struktura, ali i mogucnost definisanja preseka i u ravnima, koji prate pravac pruzanja potencijalno deformisanog vermisa IIi ravruma koje su ortogonalne na (mal)rotirani vermis. Koriscenje opcionih ravni preseka ornogucava definisanje kvantitativnih neuroradioloskih indeksa, poput vrednosti tektofastigijalnog ugla, ugla izmedu superiornog i inferirnog veluma medulare i ugla koji formira dno cetvrte komore. Navedeni parametri imaju visoku prediktivnu vrednost u proceni porernecaja u vezi sa razvojem vermisa i IV komore.

Zakljucak Razvoj ultrasonografije doprineo je i razvoju novih nacina pregleda i klasifikacija anomalija zadnje lobanjske jame, koji vode ka tacnijoj prognozi, sto roditeljima daje mogucnost odluke 0 daljem toku trudnoce, Multidisciplinarni pristup anomalijama centralnog nervnog sistema, koj i obuhvata kako dvodimenzionalni i trodimenzionalni ultrazvucni pregled, tako i pregled magnetnom rezonancijom, ali i infektoloske i metabolicke pretrage, zahteva timski rad perinatologa, radiologa, neurologa i geneticara i individualni pristup svakom pojedinacnom slucaju.

In the detection of developmental anomalies with dominant pathology of the cerebellar vermis MR is a necessary element of diagnostic algorithm. Stationary and triplanar approach to the posterior fossa structures in three orthogonal planes.enables the display of morphology of the cerebellar structures. but also a possibility of defining a view of the planes that follow direction of a potentially deformed vermis and/or planes that are ortgonal to the (ma1)rotated vermis. Optional planes enable defining of quantitative neuroradioloical indexes. eg tectofastigial angle. angle between superior and inferior veluma medulare and angle that forms the fourth ventricle floor. Those parameters have' high predictive values in the evaluation of disorders in the development of the vermis and the fourth ventricle.

Conclusion The development of ultrasonography has led to the need of defining new scanning protocolsand a classification of posterior fossa anomalies, leading to a more accurate prognosis, which enables the parents to make decision as far as the further course and management of the pregnancy is concerned. A multidisciplinary approach to the anomalies of the central nervous system. in which two-dirnesional and three-dimensonal ultrasound scan as well as MRI is done and infectious and metabolic examinations, requires a team work of perinatologist, radiologist. neurologist and geneticist and individual approach to every single case.

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