FIG 1.

PIK3CA pathogenic variant. Case 2 at 31 weeks 3 days' gestation. Megalencephaly, polymicrogyria, polydactyly hydrocephalus syndrome due to a PIK3CA heterozygous pathogenic variant. The fronto-occipital diameter is >6 SDs above the mean for gestation. Enlarged bilateral ganglionic eminences (arrows, A) are seen on T2-weighted single-shot FSE and DWI (A and B). Diffusion-weighted b = 0 image (C) and T2*-weighted EPI (D) confirm the absence of hemorrhage as the cause for ganglionic eminence enlargement. Abnormal opercularization is present with Sylvian fissures lined by peri-Sylvian polymicrogyria (E). Postaxial polydactyly is seen on sonography with arrow indicating a rudimentary sixth digit medial to the fifth digit of the hand (F).