Fetal Megalencephaly with Cortical Dysplasia at 18 Gestational Weeks Related to Paternal UPD Mosaicism with PTEN Mutation

Fetal macrocephaly: Pathophysiology, prenatal diagnosis and management

Macrocephaly means a large head and is defined as a head circumference (HC) above the 98th percentile or greater than +2SD above the mean for gestational age. Macrocephaly can be primary and due to increased brain tissue (megalocephaly), which in most cases is familial and benign or secondary. The latter may be due to various causes, including but not limited to communicating or non-communicating hydrocephalus, cerebral edema, focal and pericerebral increased fluid collections, thickened calvarium and brain tumors. Megalocephaly can be syndromic or non-syndromic. In the former, gyral and structural CNS anomalies are common. It is important to exercise caution when considering a diagnosis of megalocephaly due to limitations in the accuracy of HC measurement, lack of nomograms for specific populations, inconsistencies between prenatal and postnatal HC growth curves and progression over time. The degree of macrocephaly is important, with mild macrocephaly ≤2.5SD carrying a good prognosis, especially when one of the parents has macrocephaly and normal development. Cases in which the patient history and/or physical exam are positive or when parental HC are normal are more worrisome and warrant a neurosonogram, fetal MRI and genetic testing to better delineate the underlying etiology and provide appropriate counseling.

Cat-Ear-Line: A Sonographic Sign of Cortical Development?

OBJECTIVES

Diagonal echogenic lines outside the lateral ventricle have often been observed in the anterior coronal planes of the normal fetal brain by neurosonography. We have observed abnormal shapes of these echogenic lines in cases of malformation of cortical development (MCD). We named the ultrasound finding "cat-ear-line" (CEL). This study aimed to examine how and when CEL develops in normal cases compared with MCD cases.

METHODS

We retrospectively examined the fetal brain volume dataset acquired through transvaginal 3D neurosonography of 575 control cases and 39 MCD cases from 2014 to 2020. We defined CEL as the hyperechogenic continuous lines through subplate (SP) and intermediate zone (IZ), pre-CEL as the lines that existed only within the SP, and abnormal CEL as a mass-like or mosaic shadow-like structure that existed across the SP and IZ. All fetuses in the MCD group had some neurosonographic abnormalities and were ultimately diagnosed with MCD.

RESULTS

The CEL was detected in 97.9% (369/377) of the control group from 19 to 30 weeks. The CEL visualization rate of the MCD group in the same period was 40.0% (14/35) which was significantly lower than that of the control group (P < .001).

CONCLUSIONS

From this study, it appears that the CEL is an ultrasound finding observed at and beyond 19 weeks in a normally developing fetus. In some MCD cases, pre-CEL at and beyond 19 weeks or abnormal CEL was observed. Maldeveloped CEL at mid-trimester may help identify cases at-risk of subsequent MCD.

Thyroid hypogenesis is associated with a novel AKT3 germline variant that causes megalencephaly and cortical malformation

The molecular mechanisms involved in thyroid organogenesis have not been fully elucidated. We report a patient with a de novo germline AKT3 variant, NM_005465.7:c.233A > G, p.(Gln78Arg), who presented with congenital hypothyroidism in addition to typical AKT3-related brain disorders. The report of this patient contributes to delineating the associated yet uncertain endocrine complications of this AKT3 disease-causing variant.