Refining the Neuroimaging Definition of the Dandy-Walker Phenotype

Abstract

Background and purpose: The traditionally described Dandy-Walker malformation comprises a range of cerebellar and posterior fossa abnormalities with variable clinical severity. We aimed to establish updated imaging criteria for Dandy-Walker malformation on the basis of cerebellar development.

Materials and methods: In this multicenter study, retrospective MR imaging examinations from fetuses and children previously diagnosed with Dandy-Walker malformation or vermian hypoplasia were re-evaluated, using the choroid plexus/tela choroidea location and the fastigial recess shape to differentiate Dandy-Walker malformation from vermian hypoplasia. Multiple additional measures of the posterior fossa and cerebellum were also obtained and compared between Dandy-Walker malformation and other diagnoses.

Results: Four hundred forty-six examinations were analyzed (174 fetal and 272 postnatal). The most common diagnoses were Dandy-Walker malformation (78%), vermian hypoplasia (14%), vermian hypoplasia with Blake pouch cyst (9%), and Blake pouch cyst (4%). Most measures were significant differentiators of Dandy-Walker malformation from non-Dandy-Walker malformation both pre- and postnatally (P < .01); the tegmentovermian and fastigial recess angles were the most significant quantitative measures. Posterior fossa perimeter and vascular injury evidence were not significant differentiators pre- or postnatally (P > .3). The superior posterior fossa angle, torcular location, and vermian height differentiated groups postnatally (P < .01), but not prenatally (P > .07).

Conclusions: As confirmed by objective measures, the modern Dandy-Walker malformation phenotype is best defined by inferior predominant vermian hypoplasia, an enlarged tegmentovermian angle, inferolateral displacement of the tela choroidea/choroid plexus, an obtuse fastigial recess, and an unpaired caudal lobule. Posterior fossa size and torcular location should be eliminated from the diagnostic criteria. This refined phenotype may help guide future study of the numerous etiologies and varied clinical outcomes.

FIGURE.

Dandy-Walker phenotype: MR imaging criteria. Balanced steady-state sequence (0.8-mm section thickness, 0.4-mm section spacing) in the sagittal (A), parasagittal (B), and axial (C) planes and coronal T2WI (1-mm section thickness, 0-mm section spacing, D) and axial T1WI (1-mm section thickness, 0-mm section spacing, E) from a neonate show inferior predominant VH, an enlarged tegmentovermian angle at 35° (thick-lined angle, A), an obtuse fastigial angle at 119° (thin-lined angle, A), an unpaired caudal lobe (ie, tail-sign; thin arrow, A), and inferolateral displacement of the taenia–tela choroidea complex and choroid plexus distant from the vermis (thick arrows, B–E). Similar findings are seen in the same patient on fetal MR imaging at 22 weeks’ gestational age in sagittal (F) and parasagittal single-shot T2WI (3-mm section thickness, 0-mm section spacing, G). Note a normal torcular position (stars); the torcular position is variable in all forms of posterior fossa abnormalities/anomalies and should not be considered in isolation as an interpretive criterion in the differential diagnosis.