Anomalies of the Posterior Fossa and the Spinal Cord- Fetal MRI Chen Hoffmann, MD Neuroradiology Sheba Medical Center, Israel Affiliated to Tel-Aviv University XIX SYMPOSIUM NEURORAGIOLOGICUM BOLOGNA OCTOBER 4-9, 2010
Indications Ventricular dilatation Ventricular asymmetry Malformations Disease found in siblings in previous pregnancies Vascular malformations Infectious diseases
Indications (cont’) US is the first imaging of choice When US is abnormal the MR is done to verify the diagnosis and to identify additional malformations US can be suboptimal (head position) Vermis is formed by 18 weeks GA
Anomalies of the Posterior Fossa Small PF (Chiari II) Cystic anomalies (Dandy-Walker, arachnoid cyst, mega cisterna magna) Others (rhombencephalosynapsis, Walker Warburg syn., vascular)
Myelomeningocele + Chiari II © Erin S. Schwartz, CHOP
Chiari II Small PF Downward herniation of cerebellum and brainstem Cervicomedullary kink 4 th ventricle elongated with no posterior point Open dysraphism (MMC) in 100%
22w GA: Chiari II & Myelomeningocele on US Postnatal MRI: In Utero Repair © Orit Glenn, UCSF
Missed MMC 33 weeks GA Ventricular dilatation Partial agenesis of corpus callosum No associated anomalies known After birth- MMC! Only one image showed a cystic mass not in the midline
Additional Anomalies
Differential Diagnosis: Sacrococcygeal Teratoma
Differential Diagnosis: Currarino Syndrome
Suspected Chiari III
sagital axial Cranial Meningoencephalocele Post natal US
Cranial Meningoencephalocele Pre OP © Liat Ben Sira, TAMC
Cranial Meningoencephalocele Post OP MR Bone anomm.Diastemat.Post op PF
22w GA: Lumbar spine bony anomaly on US © Orit Glenn, UCSF
Postnatal MRI at one day of age confirms findings of fetal MRI Dx: segmental spinal dysgenesis
Cystic Anomalies Dandy walker malformation Blake’s pouch Arachnoid cyst Mega cisterna magna
Dandy-Walker Complex Dandy-Walker Complex Dandy-Walker Complex Tentorium elevated Tentorium elevated Posterior fossa is enlarged Posterior fossa is enlarged Hypo genetic vermis and anti-clockwise rotated Hypo genetic vermis and anti-clockwise rotated Brainstem compressed Brainstem compressed
Dandy-Walker Complex The cerebellar hemispheres are dysplastic The 4 th ventricle is opened to the cisterna magna
Blake’s Pouch 22 weeks GA Large PF Lower part of the vermis is not formed Posterior part of the 4 th ventricle is open to the cisterna magna
Arachnoid Cyst A cystic lesion posterior to the cerebellum Vermis is intact A thin septum between the cyst and the cisterna magna
Others
Walker-Warburg Syn. Age of 1 week
Rombencephalosynapsis Fused cereballar hemispheres Absent vermis Absent primary fissure Narrow 4 th ventricle in Ax plane (key hole shape) +/- septo-optic dysplasia
29w GA: Post. Fossa Mass on US, ? Subdural © Orit Glenn, UCSF
31w GA: Follow-up MRI Dx: dural sinus malformation
Vein of Gallen Malformation A-V fistula between deep choroidal arteries and the median prosencephalic vein Of Markovski
The Chaim Sheba Medical Center Tel Hashomer, Israel