Clinical and molecular data in cases of prenatal localized overgrowth disorder: major implication of genetic variants in PI3K-AKT-mTOR signaling pathway.

OBJECTIVES: To describe clinical and molecular findings in a French multicenter cohort of fetuses with prenatal diagnosis of congenital abnormality and suspicion of a localized overgrowth disorder (LOD) suggestive of genetic variants in the PI3K-AKT-mTOR signaling pathway. METHODS: We analyzed retrospectively data obtained between 1 January 2013 and 1 May 2020 from fetuses with brain and/or limb overgrowth referred for molecular diagnosis of PI3K-AKT-mTOR pathway genes by next-generation sequencing (NGS) using pathological tissue obtained by fetal autopsy. We also assessed the diagnostic yield of amniotic fluid. RESULTS: During the study period, 21 subjects with LOD suspected of being secondary to a genetic variant of the PI3K-AKT-mTOR pathway were referred for analysis. Of these, 17 fetuses had brain overgrowth, including six with isolated megalencephaly (MEG) and 11 with hemimegalencephaly (HMEG). Of the six with MEG, germline variants were identified in four cases, in either PIK3R2, AKT3 or MTOR, and a postzygotic PIK3R2 variant was found in the other two cases. Of the 11 with HMEG, a postzygotic PIK3CA variant was found in three fetuses with extracerebral features of PIK3CA-related overgrowth spectrum, and in seven fetuses with isolated HMEG. No pathogenic variant was identified in the 11th case with HMEG. Four fetuses with limb overgrowth also had one or more lymphatic malformations (LM) and harbored a postzygotic PIK3CA variant. NGS on cultured amniocytes performed in 10 cases, of which nine had been found positive on analysis of pathological fetal tissue, showed variants in four, in either PIK3CA, PIK3R2 or AKT3. CONCLUSIONS: Isolated MEG or HMEG may lead to identification of genetic variants in the PI3K-AKT-mTOR signaling pathway. Cases of limb overgrowth and LM or isolated HMEG are likely associated with PIK3CA variants. © 2021 International Society of Ultrasound in Obstetrics and Gynecology.

Two different prenatal imaging cerebral patterns of tubulinopathy.

To illustrate the prenatal cerebral imaging features associated with tubulinopathy, we report on five affected fetuses from unrelated families, with a de-novo heterozygous variant in a tubulin gene (TUBA1A, TUBB2B or TUBB3). We identified two distinct prenatal imaging patterns related to tubulinopathy: a severe form, characterized by enlarged germinal matrices, microlissencephaly and a kinked brainstem; and a mild form which has not been reported previously in the prenatal literature. The latter form is associated with non-specific features, including an asymmetric brainstem, corpus callosal dysgenesis, a lack of Sylvian fissure operculization and distortion of the anterior part of the interhemispheric fissure with subsequent impacted medial borders of the frontal lobes, the combination of which, in the absence of additional extracerebral anomalies, is highly suggestive of tubulinopathy. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Prenatal diagnosis of pericallosal curvilinear lipoma: specific imaging pattern and diagnostic pitfalls.

We report the first series of cases of pericallosal curvilinear lipoma (CL) diagnosed prenatally and highlight the limitations in identifying a specific prenatal imaging pattern using ultrasound and magnetic resonance imaging (MRI). In all five of our cases, on ultrasound, the main feature leading to referral was a short corpus callosum. This subtle callosal dysgenesis was associated with a band of hyperechogenicity surrounding the corpus callosum, mimicking the pericallosal sulcus, which increased in size during the third trimester in three of the four cases in which sonographic follow-up was performed. On T2-weighted MRI, this band showed typical hypointensity in all cases; in contrast, on T1-weighted imaging, in only one case was there hyperintensity, suggestive of fat, as seen typically in the postnatal period. For appropriate prenatal counseling regarding outcome, it is important to identify or rule out CL when mild corpus callosal dysgenesis is observed. One should be aware of subtle diagnostic findings, such as a thin band of echogenicity surrounding the corpus callosum that is seen as a band of hypointensity on T2-weighted fetal MRI, and which may increase in size during gestation. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Refining the phenotypical and mutational spectrum of Taybi-Linder syndrome.

Taybi-Linder syndrome (TALS, OMIM 210710) is a rare autosomal recessive disorder belonging to the group of microcephalic osteodysplastic primordial dwarfisms (MOPD). This syndrome is characterized by short stature, skeletal anomalies, severe microcephaly with brain malformations and facial dysmorphism, and is caused by mutations in RNU4ATAC. RNU4ATAC is transcribed into a non-coding small nuclear RNA which is a critical component of the minor spliceosome. We report here four foetuses and four unrelated patients with RNU4ATAC mutations. We provide antenatal descriptions of this rare syndrome including unusual features found in two twin foetuses with compound heterozygosity for two rare mutations who presented with mild intrauterine growth retardation and atypical dysmorphic facial features. We also carried out a literature review of the patients described up to now with RNU4ATAC mutations, affected either with TALS or Roifman syndrome, a recently described allelic disorder.

[Fetal transcerebellar diameter measured in screening ultrasound: Feasibility and reproducibility]. / Mesure du diamètre transverse du cervelet en échographie de dépistage : faisabilité et fiabilité.

OBJECTIVE: The aim of the study was to evaluate feasibility and reproducibility of fetal transcerebellar diameter measurement during second and third trimester ultrasound mass screening by junior and senior physicians. MATERIALS AND METHODS: A monocentric prospective study was conducted at the tertiary care teaching hospital in Lyon, including patients undergoing their second or third trimester planned ultrasound exam. For each patient, a resident and a senior practitioner measured each fetal transcerebellar diameter, during a blinded experiment, according to the transcerebellar plane described by the International Society of Ultrasound in Obstetrics and Gynecology. Images have been scored on 4 criteria. The inter-observer variability for transcerebellar diameter and image quality was assessed using an intra-class correlation coefficient. Image quality has been analyzed according to pregnancy term and to fetal presentation. RESULTS: Sixty-six patients were included, 44 patients before and 22 patients after 30 weeks. Inter-observer variability of transcerebellar diameter measurement was 0.4%. Inter-observer variability of image quality was 13.5%. Image quality was not significantly different between seniors and residents (P=0.06). Gestational age and fetal presentation did not affect significantly image quality (P=0.42) and (P=0.64) respectively. CONCLUSION: Transcerebellar diameter measurement during mass screening is simple and reliable. Posterior fossa abnormalities can be explored through its measurement.

Prenatal diagnosis of cobblestone lissencephaly associated with Walker-Warburg syndrome based on a specific sonographic pattern.

We report a specific sonographic cerebral pattern of cobblestone lissencephaly (CL) that has not been described previously. This pattern was encountered in four index cases and allowed prenatal diagnosis of CL associated with Walker-Warburg syndrome. The pattern included both an outer echogenic band with reduced pericerebral space, corresponding to an infra- and supratentorial extracortical layer of neuroglial overmigration on pathological examination, and a 'Z'-shaped appearance of the brainstem. This pattern was found as early as 14 weeks' gestation in one of our cases.

[Head and neck superficial venous malformations]. / Malformations veineuses superficielles cervico-faciales. Mise au point.

Management of vascular malformations and vascular tumors has recently been maximized by the establishment of an accurate clinical and histological classification and by the development of multidisciplinary expert consultations. Head and neck localizations of venous malformations are common, thus maxillo-facial surgeons should be aware of the characteristics of this pathology and the principles of its management. Diagnosis is mainly clinical and must be certified by Doppler-ultrasonography and contrast enhanced magnetic resonance imaging with T2 fat-saturation sequence. Therapeutic decision depends on the volume of the lesion, and on functional, cosmetic and psychological complaints. Sclerotherapy is now the preferred treatment of head and neck venous malformations. It is performed in specialized interventional radiology units by intralesional injections of sclerosing solution under fluoroscopic guidance. Surgery is useful in some cases, either on its own or following sclerotherapy. In case of bulky lesion, it is necessary to search for and prevent a severe coagulopathy before planning any intervention.

[Is alfa-interferon still current in the management of Kasabach-Merritt syndrome?]. / L'interferon alfa a-t-il encore des indications dans la prise en charge du syndrome de Kasabach-Merrit ?

Kasabach-Merritt syndrome (KMS), characterized by thrombocytopenia, may complicate vascular tumors such as kaposiform hemangioendothelioma and tufted angioma. We report on two infants, respectively 2 months and 15 days old at the onset of symptoms, the first of whom presented with a left cervico-occipito-scapular hemangioma with parotid extension, and the second with a vascular tumor located on the left shoulder with fast extension on the left inferior hemithorax and the left arm. Thrombocytopenia (< 20 G/L) was associated in both cases. Treatment comprised first high-dose corticosteroids (2mg/kg) in association with vincristine (1mg/m(2)/week). Interferon was introduced as third-line treatment at 3 MIU/m(2)/day. In the first patient, interferon was effective both on thrombocytopenia and tumor in 2 months. In the second patient, the first interferon treatment was not effective despite 6 months of therapy. However, a second treatment 8 years later was successful. After 10 and 3 years follow-up, respectively, there were no side effects and most particularly no neurologic complications. These two observations open the discussion of the role of interferon (3 MIU/m(2)/day) as well as new therapies in the control of angiogenesis in case of failure of first-line treatment of complicated KMS vascular tumors.

Distortion of the anterior part of the interhemispheric fissure: significance and implications for prenatal diagnosis.

In order to illustrate the significance of a new anatomical finding, distortion of the interhemispheric fissure (DIHF) associated with impacted medial borders of the frontal lobes, we report a retrospective observational study of 13 fetuses in which DIHF was identified on prenatal imaging. In 10 cases there were associated anatomical anomalies, including mainly midline anomalies (syntelencephaly (n=2), lobar holoprosencephaly (n=1), Aicardi syndrome (n=2)), but also schizencephaly (n=1), cortical dysplasia (n=1) and more complex cerebral malformations (n=3), including neural tube defect in two cases. Chromosomal anomaly was identified in two cases, including 6p deletion in a case without associated central nervous system anomalies and a complex mosaicism in one of the cases with syntelencephaly. In two cases, the finding was apparently isolated on both pre- and postnatal imaging, and the children were doing well at follow-up, aged 4 and 5 years. The presence of DIHF on prenatal imaging may help in the diagnosis of cerebral anomalies, especially those involving the midline. If DIHF is apparently isolated on prenatal ultrasound, magnetic resonance imaging is recommended for careful analysis of gyration and midline, especially optic and olfactory structures. Karyotyping is also recommended.

Prenatal unilateral cerebellar hypoplasia in a series of 26 cases: significance and implications for prenatal diagnosis.

OBJECTIVE: To define imaging patterns of unilateral cerebellar hypoplasia (UCH), discuss possible pathophysiological mechanisms and underline the etiology and prognosis associated with these lesions. METHODS: In this retrospective study we reviewed the charts of 26 fetuses diagnosed between 2003 and 2011 with UCH, defined by asymmetrical cerebellar hemispheres with or without decreased transverse cerebellar diameter. The review included analysis of the anatomy of the cerebellar hemispheres, including foliation, borders and parenchymal echogenicity, and of the severity of the hypoplasia. Data from clinical and biological work-up and follow-up were obtained. RESULTS: Our series could be divided into two groups according to whether imaging features changed progressively or remained constant during follow-up. In Group 1 (n = 8), the progression of imaging features, echogenic cerebellar changes and/or hyposignal in T2*-weighted MR images were highly suggestive of ischemic/hemorrhagic insult. In Group 2 (n = 18), imaging features remained constant during follow-up; UCH was associated with abnormal foliation in three proven cases of clastic lesions, a cystic lesion was noted in three cases of PHACE (posterior fossa anomalies, hemangioma, arterial anomalies, cardiac abnormalities/aortic coarctation, eye abnormalities) syndrome and, in the remaining cases, UCH remained unchanged, with no imaging pattern typical of hemorrhage. In 24 cases the infant was liveborn and follow-up was continued in 23, for a mean period of 3 years. Among these, neurological complications were identified in seven (in one of seven (at a mean of 46 months) in Group 1 and in six of 16 (at a mean of 35 months) in Group 2). The surface loss of cerebellar hemisphere was > 50% in 19/24 fetuses and the vermis was clearly normal in appearance in 19/24. Predisposing factors for fetal vascular insult were identified in eight cases: these included maternal alcohol addiction, diabetes mellitus, congenital cytomegalovirus infection and pathological placenta with thrombotic vasculopathy and infarctions. CONCLUSION: UCH is defined as a focal lesion of the cerebellum that may be secondary to hemorrhage and/or ischemic insult, suggesting a clastic origin, particularly when imaging follow-up reveals changes over time. UCH may also be a clue for the prenatal diagnosis of PHACE syndrome. The amount of surface loss of cerebellar hemisphere does not correlate with poor prognosis. UCH with normal vermis is often associated with normal outcome.

Prenatal abnormal features of the fourth ventricle in Joubert syndrome and related disorders.

Joubert syndrome and related disorders (JSRD) are characterized by absence or underdevelopment of the cerebellar vermis and a malformed brainstem. This family of disorders is a member of an emerging class of diseases called ciliopathies. We describe the abnormal features of the brain, particularly the fourth ventricle, in seven fetuses affected by JSRD. In three cases abnormality of the fourth ventricle was isolated and in four cases there were associated malformations. The molar tooth sign (MTS) was always present and visible on two-dimensional ultrasound and, when performed, on three-dimensional ultrasound and magnetic resonance imaging. The fourth ventricle was always abnormal, in both axial and sagittal views, presenting pathognomonic deformities. It is important to identify JSRD, preferably prenatally or at least postnatally, due to its high risk of recurrence of about 25%. A detailed prenatal assessment of the fourth ventricle in several views may help to achieve this goal.

Role of three-dimensional ultrasound measurement of the optic tract in fetuses with agenesis of the septum pellucidum.

OBJECTIVES: To construct reference ranges for fetal optic tract mean diameter and to report measurements in fetuses with agenesis of the septum pellucidum (SP). METHODS: Three-dimensional volumes of the optic chiasm were acquired in 98 normal fetuses during routine sonographic examination at 21-36 weeks' gestation and the diameters of the posterior left and right optic tracts were measured offline. A polynomial regression approach (mean and SD model) was used to compute reference charts for the mean fetal optic tract diameter measurements. In addition, 23 volumes were acquired in fetuses with SP agenesis for offline measurement of optic tract diameter. Complete follow-up was obtained in 13 of these 23 cases. RESULTS: In normal fetuses, the optic tract diameter increased linearly throughout gestation. There was no evidence of increased variability with gestational age (constant SD). Normal charts and equations for Z-score calculation were constructed. Among the 13 fetuses with SP agenesis and complete follow-up, nine had normal measurements, of which eight had normal vision postnatally. Four had hypoplastic optic tract, defined as mean optic tract diameter Z-score below - 3. Of these, two underwent termination of pregnancy and pathological examination confirmed hypoplasia of the tract, one showed signs of hypoplasia at magnetic resonance imaging and postnatal examination confirmed blindness, and one had a hypoplastic measurement for only one tract and was born with poor vision and abnormal bilateral eye movements. CONCLUSION: We present new reference charts for mean fetal optic tract diameter. In fetuses with agenesis of the SP, sonography of the optic tract might be a useful tool to assess its development and may help in prenatal counseling.