The taenia-tela choroidea-choroid plexus complex has been proposed as an imaging marker to differentiate Dandy-Walker malformation from Blake’s pouch cyst on prenatal MRI. However, radiologic-pathologic correlation remains limited.

To characterize the taenia-tela choroidea-choroid plexus complex in normal and Dandy-Walker malformation fetuses and assess its visibility on routine prenatal MRI.

Nine fetal autopsy specimens with Dandy-Walker malformation and eight gestational age-matched controls with normal posterior fossa were reviewed for taenia-tela choroidea-choroid plexus complex characteristics and correlated with available MRI. Separately, 100 fetal brain MRIs (gestational age 21–38 weeks) including normal cases and posterior fossa cystic malformations were retrospectively and independently reviewed by two pediatric neuroradiologists. Visibility of the tela choroidea and fourth ventricular choroid plexus was scored as confident, borderline, or not visible. Interobserver agreement was calculated using weighted kappa with 95% confidence intervals (CI).

Pathologic examination demonstrates that in the normal fetal posterior fossa, the choroid plexus lies adjacent to the inferior medullary velum, whereas in Dandy-Walker malformation it is displaced inferolaterally. The tela choroidea in normal controls is thin and composed of a single-meningeal layer that delaminates into two membranes, while in Dandy-Walker malformation, the tela choroidea is thickened, formed by two layers of arachnoid membrane lined by attenuated choroid plexus epithelium. On fetal MRI, the tela choroidea visibility was rated as either confident or borderline confident in 53-72% (53-72/100), with moderate visibility in 28–33% (28-33/100) of cases, with moderate agreement (κ 0.49, 95% CI 0.34–0.62). The choroid plexus was confidently visible in 21–27% (21-27/100) of cases, with fair agreement (κ 0.27, 95% CI 0.10–0.44).

On histopathologic evaluation, the tela choroidea is outstretched and thickened with inferolateral displacement of the choroid plexus in Dandy-Walker malformation. However, taenia-tela choroidea complex visibility on prenatal MRI is variable, especially in normal cases, which may limit its reliability as a diagnostic marker for posterior fossa cystic malformations.