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Congress: ECR25
Poster Number: C-26580
Type: Poster: EPOS Radiologist (educational)
DOI: 10.26044/ecr2025/C-26580
Authorblock: L. Topuria; Tbilisi/GE
Disclosures:
Lika Topuria: Nothing to disclose
Keywords: CNS, Interventional vascular, Neuroradiology brain, MR, MR-Angiography, MR-Diffusion/Perfusion, Ablation procedures, Angioplasty, Biopsy, Arteriovenous malformations, Embolism / Thrombosis, Grafts
Findings and procedure details

After an examination of MRI diagnostic images, the characteristic features of the disease became evident. The results underline that DWM is frequently associated with other CNS anomalies. Almost two-thirds of patients have grey matter abnormalities such as pachygyria, polymicrogyria, or heterotopic GM.

Fig 6: Axial 2Wl in the same case shows callosal dysgenesis with polymicrogyria →.
Callosal dysgenesis is common and often results in widely separated lateral ventricles with prominent occipital horns, known as colpocephaly. In 75-90% of patients, obstructive hydrocephalus is evident, primarily due to aqueduct stenosis. MRI findings: Classically, DWM consists of the triad of a large posterior fossa with a high-inserting venous sinus confluence, a large PF cyst extending backward from the fourth ventricle with torcular-lambdoid inversion, and varying degrees of vermian and cerebellar hemispheric hypoplasia.
Fig 10: An axial T2-weighted MRI scan that shows hydrocephalus, a large cerebrospinal fluid cyst in the posterior fossa, thinned occipital bone (arrows), and hypoplastic cerebellar hemispheres with a winged appearance (c).
The straight sinus, sinus confluence, and tentorial apex are elevated above the lambdoid suture ("lambdoid-torcular inversion"). The transverse sinuses descend at a steep angle from the torcular herophili toward the sigmoid sinuses. The occipital bone may appear scalloped, focally thinned, and remodelled with all posterior fossa cysts. The falx cerebelli is usually absent in DWM. The floor of the fourth ventricle is present and appears normal. The anterior medullary velum, fastigium, and choroid plexus are absent, and the fourth ventricle opens dorsally to a variably sized CSF-containing cyst that balloons posteriorly behind and between the cerebellar hemisphere remnants. If callosal dysgenesis is present, the lateral ventricles are widely separated and may have unusually prominent occipital horns.
Fig 8: Dandy-Walker malformation with cerebellar dysplasia in a 4-month-old infant. A, Coronal fast spin-echo (3000/102 [TR/TE]) image shows that the vermis is hypoplastic and the posterior fossa large, with the cerebellar hemispheres widely separated. The cerebellar hemispheres have an abnormal folial pattern, compatible with dysplasia. The cerebral hemispheres are abnormal with marked thinned white matter, enlarged ventricles, and shallow sulci. B, Axial fast spin-echo (3500/112) image shows, in addition to the large posterior fossa fluid collection and dysplastic cerebellar hemispheres, an abnormality of the pons, which is small and has a ventral cleft.
Fig 9: MRI of the head: А) Axial Т1-weighted image showed colpocephaly (black and white arrows) and enlarged massa intermedia (white arrows); В) Sagittal Т1-weighted image demonstrated corpus callosum hypoplasia in the region of the splenium (black and white arrow), aqueductal stenosis (white arrow), and polygyria.
Fig 11: An axial T1-weighted MRI scan showing ventriculomegaly and a superiorly displaced posterior fossa cyst.
In Dandy-Walker variant form, cerebellar vermian hypoplasia and cystic fourth ventricular dilatation are also observed while posterior fossa volume remains normal.
Fig 7: Dandy- Walker variant in a 13-year-old girl with thoracal scoliosis. Sagittal T1-weighted MRI shows agenesis of the corpus callosum and a hypoplastic inferior vermis. The fourth ventricle is enlarged slightly, but the posterior fossa typically is normal in size.6
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