Criteria for the prenatal diagnosis of holoprosencephaly

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.

Disorders of prosencephalic development

Abnormal ventral induction may result in disorders of formation, cleavage, and midline development of prosencephalic structures. Holoprosencephaly is a developmental field defect of impaired cleavage of prosencephalon. The most widely accepted classification of holoprosencephaly recognizes three major varieties: the alobar, semilobar and lobar types, according to the severity of the malformation. The brain malformations, characterized by the fusion of the cerebral hemisphere along the midline are commonly associated with facial anomalies. Corpus callosum agenesis and septo-optic dysplasia are disorders of prosencephalic midline development, and usually have less severe presentations but still, affected subjects may suffer from neurodevelopmental retardation, and/or endocrinologic and visual disorders. In this article we report an up-to-date of pathogenesis, prenatal sonographic findings, differential diagnosis and prognosis of the aforementioned anomalies.

First trimester three-dimensional transvaginal imaging of alobar holoprosencephaly associated with proboscis and hypotelorism (ethmocephaly) in a 46,XX fetus

A 19-year-old woman was scanned at 10(+6) weeks gestation by 2D-3D ultrasound. The fetus had a crown-rump length of 40.9 mm, with the cephalic pole occupied by a single cystic cavity measuring 10.6 x 7.7 x 6.8 mm and severe hypotelorism associated with mid-facial hypoplasia. 3D ultrasound confirmed the malformations seen on the 2D scan and enabled the visualization of a proboscis and a low-set right ear. Fetal karyotyping was performed by chorionic villus sampling. Due to major fetal malformations of the fetus, the patient opted for termination of pregnancy. First trimester sonographic diagnosis of holoprosencephaly relies on bilateral visualization of choroid plexuses in what has been called the 'butterfly' sign. Differential diagnosis between holoprosencephaly and hydranencephaly may be difficult in the first trimester of pregnancy. However, midline structures such as falx cerebri, interhemispheric fissure and third ventricle are present in hydranencephaly and are absent in alobar holoprosencephaly, and thalami are never fused in hydranencephaly. 3D ultrasound has demonstrated an increased definition of anatomical abnormalities of malformations, compared with 2D ultrasound, and has proven to be crucial in the decision-making process of parents and in later prenatal counseling, especially in this case where necroscopy examination was refused by the parents. Images obtained by 3D ultrasound gave detailed insight into this ventral midline anomaly, depicting much of the disordered prosencephalic development.

Two-dimensional ultrasound is accurate in the diagnosis of fetal craniofacial malformation

OBJECTIVE

To assess the accuracy of antenatal ultrasound in the diagnosis of craniofacial malformations and to compare two-dimensional with three-dimensional ultrasound.

METHODS

This was a retrospective study in which the archives of our ultrasound laboratory were searched for cases with an ultrasound diagnosis of craniofacial malformation in the period 1986-2001. No attempt was made to look for false-negative diagnoses.

RESULTS

Sixty cases with an antenatal diagnosis of a craniofacial malformation were found: 37 with cleft lip/palate; 17 with heterogeneous dysmorphisms (including mostly micrognathia and craniosynostosis) and 6 with miscellaneous craniofacial malformations. Associated anomalies were present in 48/60 (80%) cases, and holoprosencephaly (25 cases) was the most frequent of these. In 43 (72%) cases the diagnosis was made before 24 weeks' gestation. Postnatal follow-up was available for 43 cases and there was always complete correlation between antenatal and postnatal diagnoses. Cleft lip/palate was always accurately differentiated from cleft lip. Three-dimensional ultrasound was performed in 12 cases and was successful in 11. However, it did not provide further diagnostic information with regard to the two-dimensional scan.

DISCUSSION

Current two-dimensional ultrasound in expert hands allows an accurate diagnosis of craniofacial abnormalities from early gestation. In our hands, three-dimensional ultrasound did not add any valuable diagnostic information. Three-dimensional ultrasound may facilitate the understanding of the lesion by the parents and facilitate communication with the plastic surgeons. However, these potential benefits need to be carefully weighed against the costs of the ultrasound instrumentation, increased examination time and training of personnel.

Brains and faces in holoprosencephaly: pre- and postnatal description of 30 cases

OBJECTIVE

To investigate the prenatal appearance of the holoprosencephaly spectrum.

METHODS

A database of 1750 fetuses with congenital anomalies identified by ultrasound was prospectively collected from 1987 to 2000. Among them, 30 cases (1.7%) with holoprosencephaly were prenatally identified and described.

RESULTS

The prevalence of holoprosencephaly in the Health Region of the National Center for Fetal Medicine in Norway was 1.26 : 10 000; the sex distribution (male : female) was 1.4 : 1. Holoprosencephaly was found in one dichorionic twin pregnancy and one pair of conjoined twins. Among the 30 cases of holoprosencephaly, 18 were alobar, five were semilobar, two were lobar, two were lobar variants, and three were anencephalic. The facial features varied considerably. Sixty-seven per cent (20/30) had associated structural anomalies that were not related to the cerebral and facial holoprosencephaly condition. Thirty-seven per cent (11/30) had detectable chromosome aberrations and 23% (7/30) had nonchromosomal syndromal origin. The size or shape of the head was abnormal in 83% (25/30) of holoprosencephaly cases.

CONCLUSION

This study indicates that holoprosencephaly represents a heterogeneous entity with different etiologies and clinical appearances. The fact that holoprosencephaly features are found associated with particular conditions such as fronto-nasal dysplasia (2/30; 6.7%), agnathia-otocephaly (3/30; 10%), and anencephaly (3/30; 10%), suggests that these may be underreported conditions in other large holoprosencephaly series.

Alobar holoprosencephaly at 9 weeks gestational age visualized by two- and three-dimensional ultrasound

We present the ultrasound detection of alobar holoprosencephaly (HPE) with cyclopia in an embryo of 9 weeks 2 days last menstrual period (LMP)-based gestational age; the crown-rump length (CRL) was 22 mm. The use of three-dimensional (3-D) ultrasound made additional diagnostic ultrasound tomograms possible, and the volume reconstructions improved the imaging and the understanding of the condition.

A unique case of holoprosencephaly

Holoprosencephaly is known as a spectrum of cranio-facial dysmorphia. Cyclopia is supposed to be the most extreme variant. An even more affected case, with agenesis of the eyes and orbits, is reported.

Congenital nasal pyriform aperture stenosis as a presenting feature of holoprosencephaly

Congenital nasal pyriform apertures stenosis (CNPAS), a recently recognized uncommon cause of nasal airway obstruction, can be a life-threatening circumstance in the neonate. This study's experience with six cases confirmed the suggestion that CNPAS represents a manifestation of holoprosencephaly. Management of this condition depends firstly on the overall prognosis of the patient and secondly the severity of obstruction. Patients with poor overall prognosis should be managed conservatively with an oropharyngeal airway. In patients with a good outlook, the choice of treatment is conservative for those with less severe obstruction and surgical correction for those with complete obstruction. The ability to pass a No. 5Fr catheter (O.D. 1.67 mm) may be a guide to the choice of treatment. An increase in awareness among otolaryngologists on the nature of CNPAS is necessary to improve overall management of such patients.

Prenatal diagnosis of central nervous system abnormalities

Fetal anomalies have been the subject of innumerable publications both in the prenatal and neonatal literature. This has significantly increased in the last 10 years, mainly because of the advent of high-resolution ultrasound equipment and improvement of scanning techniques. In addition, guidelines issued by professional organizations involved in prenatal diagnosis have encouraged a more universal approach to the imaging and documentation of prenatal findings. The fetal central nervous system is the most frequently investigated organ system, mainly because of its easy accessibility and prominence even in the early stages of embryologic development. The biparietal diameter was the first fetal measurement to be widely used in determining gestational age. As investigators gained more experience, the appearance of ultrasound images achieved the resolution that allows direct comparisons with gross specimens and more recent sophisticated techniques of computed tomography and magnetic resonance imaging. Now endovaginal ultrasound can document early first trimester development and compare it to known embryologic landmarks. Interest in demonstrating the ultrasound counterpart of central nervous system structures in the early stages of development has resulted in a plethora of articles proving the unique ability of ultrasound in imaging the developing fetus. In view of all these developments, the beginning ultrasound specialist is faced with the challenge and responsibility not only of being familiar with the literature but also of the mastery of scanning techniques that allow accurate prenatal diagnosis. It is therefore helpful to review key developmental milestones in embryologic life and correlate them with the corresponding prenatal ultrasound appearance. In addition, the changing appearance of the developing fetus has created a need for a systematic approach in the evaluation of structures so routine protocols can be established. This has been the subject of other publications that allow the novice to draw from the cumulative experience of different centers around the world. It is important to pay attention to the specifics described in the literature when duplicating results in one's laboratory. The frustration of not being able to reproduce results is common, especially when technical limitations prevent imaging under ideal conditions. This is especially true in patients who are first seen in the later third trimester with no prior prenatal care.(ABSTRACT TRUNCATED AT 400 WORDS)

Alobar holoprosencephalic embryo detected via transvaginal sonography

The incorporation of high-frequency transvaginal probes in commercial ultrasonic equipment allows now for the earlier detection of fetal malformations and the possibility of interrupting pregnancy when such an anomaly is incompatible with postnatal life. We describe here a case of alobar holoprosencephaly associated with serious facial anomalies, diagnosed via transvaginal sonography during the 10th week of amenorrhea. A cytogenetic study was carried out by transabdominal chorial biopsy and diagnostic confirmation by necropsy was made after termination. In order to be able to counsel patients on the advisability of future pregnancies we stress the importance of making a cytogenetic study of the embryo.

Early transvaginal sonographic diagnosis of alobar holoprosencephaly

Holoprosencephaly is a cerebral anomaly resulting from incomplete cleavage of the primitive prosencephalon or forebrain. Early detection of this anomaly is very important since the most severe form is incompatible with life. The diagnosis also signals the need for a chromosomal determination since chromosomal abnormalities have been associated with this anomaly. An early diagnosis of alobar holoprosencephaly at 14 weeks' gestation, employing transvaginal sonography, is reported. Our findings are compared with prenatal transabdominal sonographic findings of holoprosencephaly which have been reported during the last decade in the literature.

Holoprosencephaly: a developmental field defect

Holoprosencephaly refers to a spectrum of craniofacial malformations including cyclopia, ethmocephaly, cebocephaly, and premaxillary agenesis. Etiologic heterogeneity is well documented. Chromosomal, genetic, and teratogenic factors have been implicated. Recognition of holoprosencephaly as a developmental field defect stresses the importance of close scrutiny of relatives for mild forms such as single median incisor, hypotelorism, bifid uvula, or pituitary deficiency.

Antenatal diagnosis of fetal intracranial anomalies

Defects in the central nervous system (CNS) are the most devastating of the various fetal malformations that can be sonographically diagnosed. The sonographer often initiates a decision-making process that presents the patient with difficult options. An accurate and reliable sonographic diagnosis becomes an essential part of this evolving aspect of obstetric care. In this paper, some of the major defects of the CNS that have been diagnosed sonographically are presented with a brief outline of the pathologic features, diagnostic features, the prognosis, as well as management options. Most of these malformations are serious enough so that termination of pregnancy is usually offered if the diagnosis is made prior to the age of viability and, for some malformations (ie, hydranencephaly, alobar holoprosencephaly), even later. Intrauterine treatment, principally ventriculoamniotic shunting, remains an investigational procedure. A diagnosis of a serious or lethal malformation allows the obstetrician to choose not to perform a cesarean section because of fetal distress or dystocia due to macrocephaly in such "doomed" fetuses. On the other hand, cesarean section may be the preferred route of delivery for fetuses with other malformations (eg, meningomyelocele).

Genetic causes of mental handicap and opportunities for prevention

Prior to 1970 nearly one half of severe mental handicap (IQ less than 50) was unexplained and genetic causes were recognized in one third of all patients. In recent years the genetic contribution has risen to 50%, with the decline in importance of environmental causes and the growing recognition of X-linked forms of mental retardation and chromosomal microdeletion syndromes. Recognition of genetic conditions is vital for accurate assessment of recurrence risks and in order, in some instances, to provide specific prenatal diagnosis. With full utilization of existing prenatal screening procedures and a more detailed family history, severe mental handicap due to genetic conditions should be reduced by 30-40%.