In Utero MR Imaging of Fetal Holoprosencephaly: A Structured Approach to Diagnosis and Classification

Holoprosencephaly spectrum: an up-to-date overview of classification, genetics and neuroimaging

Holoprosencephaly (HPE) is a complex forebrain congenital malformation with widely variable outcomes. It represents a disorder of ventral induction, which begins in the fifth gestational week. Its main feature is forebrain cleavage failure, which prevents the brain complete division into right and left hemispheres, the normal development of midline structures, and the deep brain structure. Based on the severity of prosencephalic cleavage failure, three classic forms (lobar, semilobar, and alobar) were described, and subsequently, interhemispheric variant (syntelencephaly) and septopreoptic variants were proposed. This review proposes a practical imaging approach to diagnosing HPE spectrum disorders, allowing an easier recognition and earlier diagnosis, which is essential for prenatal care and adequate parental counseling. In addition, we intend to simplify the understanding of HPE through a didactic discussion, schematic illustrations, and descriptions of each entity's current classification and critical neuroimaging features, as well as the main differential diagnosis of HPE.

Prenatal Imaging of Supratentorial Fetal Brain Malformation

This review article provides a comprehensive overview of fetal MR imaging in supratentorial cerebral malformations. It emphasizes the importance of fetal MR imaging as an adjunct diagnostic tool used alongside ultrasound, improving the detection and characterization of prenatal brain abnormalities. This article reviews a spectrum of cerebral malformations, their MR imaging features, and the clinical implications of these findings. Additionally, it outlines the growing importance of fetal MR imaging in the context of perinatal care.

Comparison of ultrasound and magnetic resonance imaging findings in evaluation of fetal congenital anomalies: A single-institution prospective observational study

Background

This study aimed to compare the ultrasound (USG) and fetal magnetic resonance imaging (MRI) findings in the evaluation of congenital fetal anomalies and to determine whether the management is changes significantly if MRI is combined with USG.

Methods

In this prospective observational cohort study, we performed fetal MRI in 90 consecutive cases of fetuses diagnosed or suspected as having congenital anomalies on a prior level II USG scan. We then compared the USG and MRI findings of each anomaly according to the diagnostic information yielded by each modality.

Results

Of 90 fetuses examined during 1 year study period, MRI and USG findings were equivalent in 13.3% of cases. MRI provided additional information in 68.8% cases, of which pregnancy management was changed in 5.6% cases. MRI provided additional information but did not change management in 63.3% of cases. USG provided additional information but did not change pregnancy management in 17.8% of cases. The difference was statistically significant with a p value of .000.

Conclusion

Fetal MRI is a significantly better modality than USG for detecting additional findings in anomalies of specific organ systems. Because of its high diagnostic yield for central nervous system (CNS) anomalies, it can be combined with USG for this subgroup. For non-CNS anomalies of genitourinary system, thorax, or in syndromic/complex malformations/conjoint twin pregnancy, it may be used as an adjunct to USG on a case to case basis. MRI has the potential to change the pregnancy management in few cases, but benefit is small to advocate a complete integration of MRI and USG for fetal anomaly scanning at present.

Holoprosencephaly: Review of Embryology, Clinical Phenotypes, Etiology and Management

Holoprosencephaly (HPE) is the most common malformation of the prosencephalon in humans. It is characterized by a continuum of structural brain anomalies resulting from the failure of midline cleavage of the prosencephalon. The three classic subtypes of HPE are alobar, semilobar and lobar, although a few additional categories have been added to this original classification. The severity of the clinical phenotype is broad and usually mirrors the radiologic and associated facial features. The etiology of HPE includes both environmental and genetic factors. Disruption of sonic hedgehog (SHH) signaling is the main pathophysiologic mechanism underlying HPE. Aneuploidies, chromosomal copy number variants and monogenic disorders are identified in a large proportion of HPE patients. Despite the high postnatal mortality and the invariable presence of developmental delay, recent advances in diagnostic methods and improvements in patient management over the years have helped to increase survival rates. In this review, we provide an overview of the current knowledge related to HPE, and discuss the classification, clinical features, genetic and environmental etiologies and management.

Sonography of fetal holoprosencephaly: a guide to recognize the lesser varieties

BACKGROUND

Alobar holoprosencephaly (HPE) is easily detected during a first-trimester screening examination, conversely, recognizing the lesser varieties may be difficult even in the second trimester.

OBJECTIVES

To describe the imaging findings of a cohort of fetuses with holoprosencephaly (HPE) and to elucidate the appearances of the different anatomical varieties.

MATERIALS AND METHODS

We reviewed medical records and stored images of pregnant women referred to our clinic because of a diagnosis or the suspicion of various forms of HPE. We reported the imaging characteristics, the presence of other associated anomalies, magnetic resonance findings, karyotype and autoptic examinations when available.

RESULTS

Alobar forms show great distortion of normal brain anatomy, with a single ventricle detectable during the first trimester of pregnancy. Extracerebral, face and karyotype abnormalities are often associated. In semilobar and lobar forms the septum pellucidum is typically absent in axial planes, with fused frontal horns, while posterior fossa is often normal. At multiplanar neurosonogram, anomalies involving corpus callosum and cortex development can be detected. Face abnormalities are mild in lobar forms: receding forehead, various degrees of hypotelorism and the presence of a single central maxillary incisor are reported.

CONCLUSIONS

The alobar forms are detectable since the first trimester, with a peculiar single ventricle and extremely frequent extracerebral and karyotype abnormalities. The semilobar and lobar forms are more challenging and the diagnosis is easily missed in a mid-trimester screening exam unless a careful evaluation of both cavum septi pellucidi and frontal horns as well is conducted.

Imaging Review of Obstetric Sequelae of Maternal Diabetes Mellitus

Diabetes mellitus, whether preexisting or gestational, poses significant risk to both the mother and the developing fetus. A myriad of potential fetal complications in the setting of diabetic pregnancies include, among others, congenital anomalies, delayed fetal lung maturity, macrosomia, and increased perinatal morbidity and mortality. Congenital anomalies most commonly involve the nervous, cardiovascular, genitourinary, and musculoskeletal systems. Delayed fetal lung maturity, probably secondary to hyperglycemia suppressing surfactant secretion, is a major determinant of perinatal morbidity and mortality. Besides the potential complications encountered during cesarean delivery in macrosomic fetuses, vaginal delivery is also associated with increased risks of shoulder dystocia, clavicular and humeral fractures, and brachial plexus palsy. Maternal complications are related to the increased risk of hypertensive diseases of pregnancy and associated preeclampsia and hemolysis, elevated liver function, and low platelets (HELLP) syndrome, as well as complications encountered at the time of delivery secondary to fetal macrosomia and cesarean delivery. Additional conditions encountered in the setting of maternal diabetes include polyhydramnios, placental thickening, and two-vessel umbilical cord, each of which is associated with adverse fetal and maternal outcomes including fetal growth restriction, preterm labor, placental abruption, and premature rupture of membranes. Imaging plays a vital role in the evaluation of the mother and the fetus and can provide invaluable information that can be used by maternal fetal medicine to manage this patient population effectively. The authors review the pathophysiologic alterations induced by diabetes in pregnancy, discuss the imaging spectrum of diabetic embryopathy, and provide a detailed review of potential associated maternal complications. Online supplemental material is available for this article. ^©RSNA, 2021.

Indications for magnetic resonance imaging of the fetal central nervous system: recommendations from the European Society of Paediatric Radiology Fetal Task Force

Fetal central nervous system MRI is a well-established method to complement a high-quality fetal ultrasound and to clarify sonographically detected abnormalities in complex pregnancies. However, there is still worldwide heterogeneity and confusion regarding the indications of fetal central nervous system MRI, which has roots in differences among countries regarding the performance of ultrasound examinations and legislation on pregnancy termination. The purpose of this article is to clarify the indications for fetal central nervous system MRI by focusing on the ultrasound findings that guide further investigation with MRI and highlight the strengths and the weaknesses of each modality on imaging the fetal central nervous system.

Fetal Magnetic Resonance Imaging (MRI) in Holoprosencephaly and Associations With Clinical Outcome: Implications for Fetal Counseling

Holoprosencephaly is the most common malformation of forebrain development and includes a wide spectrum of severity. The objective of this retrospective study was to evaluate fetal magnetic resonance imaging (MRI) associations with outcome. Of the 63 cases identified on antenatal ultrasonography, 28 cases were confirmed on fetal MRI. There were 17 live births; 9 patients died within the first month of life. There were 7 survivors. The vast majority were nonambulatory and required feeding support; none required respiratory support. We found that presence and number of non-holoprosencephaly-associated malformations was also associated with survival. Of 5 patients with 3 or more systemic anomalies, 4 died regardless of holoprosencephaly subtype and 1 was lost to follow-up. Patients with suspected holoprosencephaly on ultrasonography should have full body fetal MRI and echocardiogram to better evaluate systemic anomalies. Counseling should involve pediatric palliative care services to prepare families in caring for babies with limited life span.

Analysis of 270 fetuses with non-visualization of cavum septi pellucidi and vergae on in-utero magnetic resonance imaging

OBJECTIVE

To analyze a large retrospective cohort of fetuses in which the cavum septi pellucidi and vergae (CSPV) was not present or was not in its expected position on in-utero magnetic resonance imaging (iuMRI), in order to describe the possible causes of that finding and provide a diagnostic approach to assess such cases in clinical practice using iuMRI.

METHODS

This was a retrospective study of fetuses that underwent iuMRI at a single institution, over an 18-year period (2000-2017 inclusive), in which the CSPV was not visualized or was abnormal. All iuMRI studies were reviewed and classified as CSPV being not present, disrupted (visualization of remnants of an otherwise normally placed CSPV) or malpositioned (CSPV was present, but not in its expected position). We describe the neuropathology present in each of the groups.

RESULTS

Of the 270 fetuses that met the inclusion criteria, the CSPV was described as malpositioned in 150 (56%), disrupted in 71 (26%) and not present in 49 (18%). Malpositioned CSPV was present only in cases with agenesis of the corpus callosum and three specific patterns of malpositioning are described, depending on the location of the leaflets of the CSPV and fornix. Disrupted CSPV was present in fetuses with hydrocephalus or pathologies causing extensive brain parenchymal injury. Not present CSPV was found in cases with holoprosencephaly or when absence of the CSPV appeared to be an isolated finding.

CONCLUSION

We have described a large cohort of fetuses with non-visualization of a normal CSPV on iuMRI and present a categorical classification system based on the CSPV being not present, disrupted or malpositioned. This approach should help in the diagnosis of the underlying cause of a CSPV abnormality. © 2019 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Holoprosencephaly from conception to adulthood

Holoprosencephaly (HPE) consists of a spectrum of malformations related to incomplete separation of the prosencephalon. There is a wide clinical variability depending on the HPE subtype seen on imaging. Early postnatal lethality is common, however a significant fraction of newborns diagnosed with HPE will survive into childhood and even adulthood. Here we will review the clinical management of HPE during different ages from the prenatal period to adulthood.