MEGA CISTERNA MAGNA

MEGA CISTERNA MAGNAdr. Cordova ArridhoBook ReadingModerator:Dr. H. Nuswil Bernolian, Sp.OG(K)DEPARTMENT OBSTETRICS DAN GYNECOLOGY FACULTY OF MEDICINE SRIWIJAYA UNIVERSITYDR. MOH. HOESIN GENERAL HOSPITAL PALEMBANG

TERMINOLOGYIMAGING FINDINGS

Axial ultrasound shows a relatively mature thirdtrimester brain in a fetus with trisomy 18. An enlargedcisterna magna, measuring > 10 mm, is identified(arrow).

Sagittal ultrasound at midline in the same patient showsan intact, echogenic vermis (curved arrow) along withthe enlarged cisterna magna (arrow).DIFFERENTIAL DIAGNOSIS Absent vermis Cystic dilation of fourth ventricle in direct communication with enlarged cisterna magna Hydrocephalus commonly present Associated with agenesis of the corpus callosumDandy-Walker malformationDIFFERENTIAL DIAGNOSIS Partially absent inferior vermis Torcular Herophili not elevated Hydrocephalus typically absentArachnoid cyst Inferior vermis may appear absent- Vermis incompletely formed before 18 weeksNormal early cerebellar developmentDIFFERENTIAL DIAGNOSIS 1/3 infratentorial Extraaxial CSF-containing lesion Mass effect on adjacent brainDandy-Walker variant Doppler flow identifiable in lesion Other associated abnormalities presento Cardiomegalyo Hydrocephaluso Dilated neck vesselso HydropsVein of Galen malformation

10PATHOLOGYThought to be in same spectrum as Dandy-Walker malformation and variantTorcular Herophili is in normal positionElevated in Dandy-Walker malformationCompletely formed vermis and cerebellar hemispheresGeneral FeaturesCLINICAL ISSUESUsually an incidental findingPart of multiple findings seen with trisomy 18PresentationGender Isolated MCMNo specific sex predilection MCM associated with trisomy 18More often seen in male fetusesDemographics If isolated likely has no adverse clinical outcomeNatural History & PrognosisDIAGNOSTIC CHECKLISTToo steep a scanning angle may simulate a MCMCarefully document vermis to rule out Dandy-Walker variant

Image Interpretation Pearls

Thank You..Wassalamualaikum,wr,wb