Prenatal prognosis of congenital diaphragmatic hernia using magnetic resonance imaging measurement of fetal lung volume

OBJECTIVES

To investigate the correlation between fetal lung volume (FLV), measured with magnetic resonance imaging (MRI), and postnatal mortality in newborns with prenatally diagnosed isolated congenital diaphragmatic hernia (CDH).

METHODS

In a 4-year prospective multicenter study, 77 fetuses with isolated CDH diagnosed between 20 and 33 weeks' gestation underwent fast spin-echo T2-weighted lung MRI. These MRI-FLV measurements were compared with a previously published normative curve obtained in 215 fetuses without thoracoabdominal malformations and with normal ultrasound biometric findings. FLV measurements were correlated with postnatal survival. The mean gestational age at MRI was 31.3 weeks.

RESULTS

The measured/expected FLV ratio was significantly lower in the newborns with CDH who died compared with those who survived (23.6 +/- 12.2 vs. 36.1 +/- 13.0, P < 0.001). When the ratio was below 25%, there was a significant decrease in postnatal survival (19% vs. 40.3%, P = 0.008). Survival was significantly lower for neonates when one lung could not be seen by fetal MRI compared with those fetuses with two visible lungs on MRI (17.9% vs. 62.1%, P < 0.001).

CONCLUSION

In isolated CDH, FLV measurement by MRI is a good predictor of postnatal mortality due to pulmonary hypoplasia.

Fetal hemangiopericytoma with an associated cerebral anomaly

We report the first case of infantile hemangiopericytoma explored prenatally by fetal ultrasonography and magnetic resonance imaging (MRI). It was associated with a developmental cerebral anomaly identified on MRI. The largest lesions of the multifocal hemangiopericytoma were located in the soft tissue adjacent to the left temporal bone, and smaller lesions were found in the lumbar area and in the retroperitoneum. MRI showed no connection between the tumor and the fetal brain but there was anomalous cerebral gyration in the region and the Sylvian fissure beneath the tumor was enlarged. The pregnancy was terminated because of the severe brain anomalies and postmortem examination confirmed the prenatal findings. Microscopic analysis of the tumor tissue showed branching vessels which are typical of hemangiopericytoma. The lesions in our case occurred in association with macrosomia with visceromegaly detected at autopsy, suggesting a possible role of tumor suppressor genes.

A primal sketch of the cortex mean curvature: a morphogenesis based approach to study the variability of the folding patterns

In this paper, we propose a new representation of the cortical surface that may be used to study the cortex folding process and to recover some putative stable anatomical landmarks called sulcal roots usually buried in the depth of adult brains. This representation is a primal sketch derived from a scale space computed for the mean curvature of the cortical surface. This scale-space stems from a diffusion equation geodesic to the cortical surface. The primal sketch is made up of objects defined from mean curvature minima and saddle points. The resulting sketch aims first at highlighting significant elementary cortical folds, second at representing the fold merging process during brain growth. The relevance of the framework is illustrated by the study of central sulcus sulcal roots from antenatal to adult age. Some results are proposed for ten different brains. Some preliminary results are also provided for superior temporal sulcus.

Intellectual prognosis of the Dandy-Walker malformation in children: the importance of vermian lobulation

Half of patients with the Dandy-Walker malformation (DWM) have normal intellectual development. We aimed to identify feature on MRI associated with good intellectual prognosis. We reviewed 20 patients with DWM diagnosed on MRI, mean age 14.6+/-9.9 years. We assessed their intellectual development and related it to the MRI features. We found two groups with a statistically different intellectual outcome. All 14 patients with normal intellectual development had a normal lobulation of the vermis, without supratentorial anomalies. Of the six patients with mental retardation, three had an abnormal vermis, together with dysgenesis of the corpus callosum. In the other three, there were normal vermian anatomy with associated anomalies. Normal lobulation of the vermis, in the absence of any supratentorial anomaly, appears to be a good prognostic factor in DWM. Preservation of cerebrocerebellar pathways and neonatal plasticity could explain the normal intellectual development. These findings might be useful in prenatal diagnosis.

Prenatal diagnosis of hypoplasia of the corpus callosum in association with non-ketotic hyperglycinemia

Abnormalities of the corpus callosum are often associated with a poor prognosis due to the anatomical defect itself and associated anomalies that include malformations and inherited metabolic disorders. We report a case of the prenatal diagnosis of hypoplasia of the corpus callosum that was associated with non-ketotic hyperglycinemia. Metabolic disorders are a known association with corpus callosum abnormalities and carry a dismal prognosis. A diagnosis of non-ketotic hyperglycinemia should be considered when a fetus presents with an abnormality of the corpus callosum. A literature search reviews other inherited diseases associated with hypoplasia of the corpus callosum.

Arthrogryposis multiplex congenita and cerebellopontine ischemic lesions in sibs: recurrence of prenatal disruptive brain lesions with different patterns of expression?

Arthrogryposis multiplex congenita (AMC) is a heterogeneous group of disorders in which prolonged decrease or absence of fetal movements results in a series of deformational anomalies. The rate of recurrence ranges from 25% in some recessive forms of myogenic arthrogryposis or of primary anterior horn cell loss, to less than 1% in anoxic-ischaemic damage. Cerebral clastic processes are considered as sporadic. We report on a non-consanguineous family in which the first child was affected by AMC and the following pregnancy was terminated because cerebellum hypoplasia was suspected at ultrasound and confirmed by fetal magnetic resonance imaging. Post-mortem findings demonstrated pontocerebellar ischaemic-haemorrhagic injuries. The occurrence of these neurologic abnormalities in the same family suggests a common mechanism, which might correspond to a same genetic defect with different patterns of expression. This is the first prenatal report suggesting that an 'ischaemic' process, usually recognised as sporadic could in fact be due to an inherited abnormality. Careful prenatal follow-up of third-trimester fetal brain development may be required in pregnant women with a family history of AMC.

Antenatal diagnosis of spinal lipomas

OBJECT

The purpose of this study was to highlight the key prenatal diagnostic features of fetal spinal lipomas.

METHODS AND RESULTS

All fetuses in whom a spinal lipoma was suspected prenatally or diagnosed postnatally were included in the study. Lumbosacral lipoma was diagnosed in 16 fetuses (group 1), but at birth 3 of these were found to have other forms of occult dysraphism. In 2 other fetuses (group 2) a meningocele was suspected but at birth these lesions were found to be lumbosacral lipomas. The lipomas were covering large meningoceles in 13 fetuses and filling the cul-de-sac in 2 others. Three sets of parents decided on termination. Of the 13 children born with a spinal lipoma, 9 were operated on and 4 were managed conservatively. At the last follow-up, 7 were neurologically intact.

CONCLUSION

The distinction between meningomyelocele and spinal lipoma is possible antenatally. The differential diagnosis between lipoma and the other forms of occult dysraphism is more difficult.

Local and spatial factors determining HIV-1 protease substrate recognition

Insertional mutagenesis of the Escherichia coli thymidylate synthase (TS) was used to address substrate recognition of HIV-1 protease in a well characterized structural context. By modifying the TS conformation while maintaining its enzymic activity, we investigated the influence of protein folding on protease-substrate recognition. A slight destabilization of the TS structure permitted the cleavage of a target site, which was resistant in the native TS. This result supports a dynamic interpretation of HIV-1 protease specificity. Exposure time of the potential cleavage site, which depends on the stability of the global conformation, must be compatible with the cleavage kinetics, which are determined by the local sequence. Cleavage specificity has been described as the consequence of cumulative interactions, globally favourable, between at least six amino acids around the cleavage site. To investigate influence of local sequence, we introduced insertions of variable lengths in two exposed loops of the TS. In both environments, insertion of only two amino acids could determine specific cleavage. We then inserted libraries of dipeptides naturally cleaved by the HIV-1 protease in order to assess the limitations of established classifications of substrates in different conformational contexts.

Determination of the anatomical location of an antenatal intestinal occlusion by magnetic resonance imaging

Intestinal occlusion occurs in approximately 1 in 3000 births. Its diagnosis can be made in utero with ultrasound however, determination of its precise location is difficult to achieve. We report herein the feasibility of diagnosing and locating a fetal small-intestine occlusion with the use of magnetic resonance imaging.

Fetal lung volume measurement by magnetic resonance imaging in congenital diaphragmatic hernia

OBJECTIVE

To study the potential for prenatal magnetic resonance imaging to predict pulmonary hypoplasia in congenital diaphragmatic hernia.

DESIGN

Prospective observational study.

SETTING

Tertiary care centre.

PARTICIPANTS

Thirteen cases of congenital diaphragmatic hernia (11 left, 2 right) without associated anomalies and 74 controls.

METHODS

Measurements by magnetic resonance imaging of fetal lung volume were achieved. In the control fetuses, a regression analysis was performed to associate fetal lung volume with gestational age. This yielded a formula allowing calculation of the expected fetal lung volume as a function of gestational age. In the cases with congenital diaphragmatic hernia, the observed/expected fetal lung volume ratio was compared with perinatal outcome.

MAIN OUTCOME MEASURES

Neonatal mortality and pulmonary hypoplasia, which was defined as lung/body weight ratios less than 0.012.

RESULTS

The expected fetal lung volume was derived from the following formula: Fetal lung volume (mL) = exp (1.24722 + 0.08939 x gestational age in weeks). The observed/expected fetal lung volume ratio was significantly lower in congenital diaphragmatic hernia (median: 0.31, range: 0.06-0.63), than in controls (median: 0.99, range: 0.42-1.94). This ratio was significantly less in the infants with congenital diaphragmatic hernia who died (median: 0.26, range: 0.06-0.63) compared with those who survived (median: 0.46, range: 0.35-0.56). The observed: expected fetal lung volume ratio was significantly correlated with the post mortem lung: body weight ratio.

CONCLUSION

In isolated congenital diaphragmatic hernia, fetal lung volume measurement by magnetic resonance imaging is a potential predictor of pulmonary hypoplasia and postnatal outcome. Further studies are required to establish the clinical value of magnetic resonance imaging for the prenatal assessment of fetal lungs.

[Prenatal semiology of diastematomyelia]

Diastematomyelia is a rare spinal malformation characterized by a division of the spinal cord. More often, the two hemicords are separated by a midline and sagittal osseous or fibrocartilaginous spur. In this report we describe two cases of diastematomyelia detected at routine second trimester detailed sonography and further assessed by MRI and spiral CT with surface shaded 3D-reconstructions. In addition to providing diagnosis, prenatal evaluation helps differentiate between diastematomyelia with good or bad prognosis.

A mathematical model for experimental gene evolution

The purpose of this paper is to determine the optimal mutation rate for random mutagenesis procedures used to make mutant libraries for subsequent screening. When the mutation rate is low, the probability of achieving a rare beneficial mutation is low. When the mutation rate is high, the probability of producing lethal mutations which result in loss of function is also high. We demonstrate that between these two extremes, an optimal mutation rate exists for experimental gene improvement. This rate depends strongly on the number of simultaneous mutations required for a beneficial change of the gene, but only weakly on the number of possible lethal mutations. This model predicts that when mutagenesis is performed at the optimum mutation rate, at least 63% (1--e(-1)) of the cloned genes in a mutant library will be non-functional.

Prenatal diagnosis and postnatal follow-up of pericallosal lipoma: report of seven new cases

BACKGROUND AND PURPOSE

Pericallosal lipomas are rare tumors. Few reports have included their imaging characteristics. Furthermore, little is known about their evolutive course. Our purpose was to describe the imaging features of seven cases of pericallosal lipoma diagnosed in utero and followed up after birth.

METHODS

We reviewed seven cases of pericallosal lipoma diagnosed by obstetric sonography (n = 7) and examined by fetal MR imaging (n = 5). Analysis of the complementary findings provided by fetal MR imaging was conducted. All findings were correlated with the postnatal imaging and clinical findings.

RESULTS

Obstetric sonography easily showed the pericallosal lipoma in all seven patients. In one, however, it was misinterpreted as intracranial hemorrhage. The morphology and integrity of the underlying corpus callosum were less easy to assess by using sonography. Fetal MR imaging confirmed the fatty content and location of the lesion in all five cases. It showed the choroidal extension in two patients and the type of associated callosal anomaly in another patient better than did sonography. In two patients, the lipoma grew, as revealed by subsequent postnatal MR imaging. The results of the neurologic examinations remained normal for the five surviving patients at a mean follow-up of 3 years (1 month-9 years).

CONCLUSION

Obstetric sonography is able to easily show pericallosal lipoma. Fetal MR imaging may be useful to characterize the lipomatous nature and the extension of the lipoma and the status of the corpus callosum. Long-term follow-up is necessary to understand the clinical consequences of such lesions.

Fetal lung volume: estimation at MR imaging-initial results

PURPOSE

To plot normal fetal lung volume (FLV) obtained with fast spin-echo magnetic resonance (MR) images against gestational age; to investigate the correlation between lung growth and fetal presentation, sex, and ultrasonographic (US) biometric measurements; and to investigate its potential application in fetuses with thoracoabdominal malformations.

MATERIALS AND METHODS

In a prospective multicenter study, 336 fetuses suspected of having central nervous system disorders underwent fast spin-echo T2-weighted lung MR imaging. Data obtained at 21-38 weeks gestation in 215 fetuses without thoracoabdominal malformations and with normal US biometric findings were selected for an FLV normative curve. FLV measurements obtained at pathologic examination with an immersion method were compared with MR FLV measurements in 11 fetuses. MR FLV values in 16 fetuses with thoracoabdominal malformations were compared with the normative curve.

RESULTS

Normal FLV increased with gestational age as a power curve; the spread of values increased with age. Interobserver correlation was excellent (R(2) = 0.96). FLV measurements at MR imaging were 0.90 times those at pathologic examination. A constant ratio (0.78) between FLV on the left and right sides was observed. No significant difference in FLV was observed between fetal presentations. Normal FLV was observed in all fetuses with cystic adenomatoid malformations and in four of six with oligohydramnios. Lowest FLV values were observed in fetuses with diaphragmatic hernia.

CONCLUSION

In fetuses with normal lungs, FLV distribution against gestational age is easily assessed in utero with fast spin-echo T2-weighted MR imaging. These preliminary findings illustrate the potential for comparing FLV measurements in fetuses at risk of lung hypoplasia with normative values.

Prenatal diagnosis of sporadic Apert syndrome: a sequential diagnostic approach combining three-dimensional computed tomography and molecular biology

Apert syndrome is characterized by coronal craniosynostosis, midfacial hypoplasia, symmetrical syndactyly of the hands and feet described as 'mitten-like' with varying degrees of mental retardation. It results from a mutation of the fibroblast growth factor-2 (FGFR2) gene. In the absence of a family history, prenatal diagnosis may be difficult based on sonography alone. We report a case in which the prenatal diagnosis of Apert syndrome was suspected by ultrasonography, established by three-dimensional computed tomography scan (3DTS) and confirmed by the detection of a mutation on amniotic cells. This underscores the usefulness of a sequential diagnostic approach combining 3DTS and molecular biology in cases in which sonography alone is not con- clusive.

Intracranial venous anomalies associated with atretic cephalocoeles

BACKGROUND

Midline scalp lesions are frequent in children. They include soft-tissue masses and atretic meningocoeles. Their recognition is important as their treatment differs. Intracranial venous anomalies are known to be associated with atretic cephalocoeles.

MATERIALS AND METHODS

A retrospective study was undertaken to assess the frequency of intracranial venous anomalies associated with atretic meningocoeles (AT). Thirty-one patients with AT were studied by MRI. There were 13 meningocoeles and 14 encephalocoeles; 4 have not yet received surgery.

RESULTS

Venous anomalies were found when the cephalocoeles lay above the torcular. They include absence of the straight sinus and duplication of the longitudinal sinus.

CONCLUSION

Venous anomalies are frequent in atretic cephalocoeles and are part of the dysraphic state.

The contribution of prenatal diagnosis to the understanding of malformative intracranial cysts: state of the art

This review evaluates the contribution of prenatal diagnosis to the understanding of intracranial cysts. We describe the outcome of 54 fetuses in which prenatal investigations indicated the presence of such lesions. The cysts were diagnosed between 20 and 30 weeks of gestation. Most (63%) were supratentorial and interhemispheric. There was only a single sylvian cyst. In the infratentorial compartment, median retrocerebellar cysts were predominant. Incisural cysts accounted for 14.8% of the series. Nine pregnancies were interrupted because of the presence of associated brain disorders. Forty-five children are alive. Thirty-four had neuropsychological tests. Cysts rarely progressed, most frequently stabilized and often regressed postnatally. Hydrocephalus was rare. In two cases delivery was precipitated at 36 weeks to allow urgent treatment of rapidly evolving cysts. Thirteen children (28.2%) were treated postnatally, in general for developing cysts. The median follow-up for the whole series exceeds 4 years. Behavior, neurological development, and intelligence are normal in 88% of the cases, and 91% have a normal neurological status. Prognosis at the time of the prenatal consultation was correct in 89% of the cases. We emphasize the value of prenatal magnetic resonance imaging and karyotype studies to limit risks of incorrect prognosis.

The intracytoplasmic domain of the Env transmembrane protein is a locus for attenuation of simian immunodeficiency virus SIVmac in rhesus macaques

The human and simian immunodeficiency virus (HIV-1 and SIVmac) transmembrane proteins contain unusually long intracytoplasmic domains (ICD-TM). These domains are suggested to play a role in envelope fusogenicity, interaction with the viral matrix protein during assembly, viral infectivity, binding of intracellular calmodulin, disruption of membranes, and induction of apoptosis. Here we describe a novel mutant virus, SIVmac-M4, containing multiple mutations in the coding region for the ICD-TM of pathogenic molecular clone SIVmac239. Parental SIVmac239-Nef+ produces high-level persistent viremia and simian AIDS in both juvenile and newborn rhesus macaques. The ICD-TM region of SIVmac-M4 contains three stop codons, a +1 frameshift, and mutation of three highly conserved, charged residues in the conserved C-terminal alpha-helix referred to as lentivirus lytic peptide 1 (LLP-1). Overlapping reading frames for tat, rev, and nef are not affected by these changes. In this study, four juvenile macaques received SIVmac-M4 by intravenous injection. Plasma viremia, as measured by branched-DNA (bDNA) assay, reached a peak at 2 weeks postinoculation but dropped to below detectable levels by 12 weeks. At over 1.5 years postinoculation, all four juvenile macaques remain healthy and asymptomatic. In a subsequent experiment, four neonatal rhesus macaques were given SIVmac-M4 intravenously. These animals exhibited high levels of viremia in the acute phase (2 weeks postinoculation) but are showing a relatively low viral load in the chronic phase of infection, with no clinical signs of disease for 1 year. These findings demonstrated that the intracytoplasmic domain of the transmembrane Env (Env-TM) is a locus for attenuation in rhesus macaques.

[Contribution of MRI in the evaluation of fetal malformations]

MRI was first used 10 years ago for the study of fetal morphology. This non invasive technique is mainly advocated for the study of fetus brain. Principle indications for MRI are Examinations are performed at 0.5 and 1.5 Tesla. Minimal study consists of T2 sequences in the 3 dimensions and T1 in one. Maternal premedication using hydroxizyne dichlorhydrate (25mg) can be proposed to avoid fetal movements. The main advantage of MRI compared with US is to detect gyral and neuronal migration anomalies, cerebral signs, of tuberous sclerosis and recent hemorrhagic lesions.

Variable constraints on the principal immunodominant domain of the transmembrane glycoprotein of human immunodeficiency virus type 1

Lentiviruses have in their transmembrane glycoprotein (TM) a highly immunogenic structure referred to as the principal immunodominant domain (PID). The PID forms a loop of 5 to 7 amino acids between two conserved cysteines. Previous studies showed that envelope (Env) glycoprotein functions of feline immunodeficiency virus (FIV) could be retained after extensive mutation of the PID loop sequence, in spite of its high conservation. In order to compare Env function in different lentiviruses, either random mutations were introduced in the PID loop sequence of human immunodeficiency virus type 1 (HIV-1) or the entire HIV-1 PID loop was replaced by the corresponding PID loop of FIV or simian immunodeficiency virus (SIV). In the macrophage-tropic HIV-1 ADA Env, mutations impaired the processing of the gp160 Env precursor, thereby abolishing viral infectivity. However, 6 of the 108 random Env mutants that were screened retained the capacity to induce cell membrane fusion. The SIV and FIV sequences and five random mutations were then introduced in the context of T-cell-line-adapted HIV-1 LAI which, although phenotypically distant from HIV-1 ADA, has an identical PID loop sequence. In contrast to the situation for HIV-1 ADA mutants, the cleavage of the Env precursor was unaffected in most HIV-1 LAI mutants. Such mutations, however, resulted in increased shedding of the gp120 surface glycoprotein (SU) from the gp41 TM. The HIV-1 LAI Env mutants showed high fusogenic efficiency. Three Env mutants retained the capacity to mediate virus entry in target cells, although less efficiently than the wild-type Env, and allowed the reconstitution of infectious molecular clones. These results indicated that in HIV-1, like FIV, the conserved PID sequence can be changed without impairing Env function. However, functional constraints on the PID of HIV-1 vary depending on the structural context of Env, presumably in relation to the role of the PID in the interaction of the SU and TM subunits and the stability of the Env complex.

Shared usage of the chemokine receptor CXCR4 by primary and laboratory-adapted strains of feline immunodeficiency virus

Strains of the feline immunodeficiency virus (FIV) presently under investigation exhibit distinct patterns of in vitro tropism. In particular, the adaptation of FIV for propagation in Crandell feline kidney (CrFK) cells results in the selection of strains capable of forming syncytia with cell lines of diverse species origin. The infection of CrFK cells by CrFK-adapted strains appears to require the chemokine receptor CXCR4 and is inhibited by its natural ligand, stromal cell-derived factor 1alpha (SDF-1alpha). Here we found that inhibitors of CXCR4-mediated infection by human immunodeficiency virus type I (HIV-1), such as the bicyclam AMD3100 and short peptides derived from the amino-terminal region of SDF-1alpha, also blocked infection of CrFK by FIV. Nevertheless, we observed differences in the ranking order of the peptides as inhibitors of FIV and HIV-1 and showed that such differences are related to the species origin of CXCR4 and not that of the viral envelope. These results suggest that, although the envelope glycoproteins of FIV and HIV-1 are substantially divergent, FIV and HIV-1 interact with CXCR4 in a highly similar manner. We have also addressed the role of CXCR4 in the life cycle of primary isolates of FIV. Various CXCR4 ligands inhibited infection of feline peripheral blood mononuclear cells (PBMC) by primary FIV isolates in a concentration-dependent manner. These ligands also blocked the viral transduction of feline PBMC by pseudotyped viral particles when infection was mediated by the envelope glycoprotein of a primary FIV isolate but not by the G protein of vesicular stomatitis virus, indicating that they act at an envelope-mediated step and presumably at viral entry. These findings strongly suggest that primary and CrFK-adapted strains of FIV, despite disparate in vitro tropisms, share usage of CXCR4.

Structural and functional analysis of surface domains unique to bacteriophage T4 thymidylate synthase

The bacteriophage T4 genome encodes most of its own enzymes for dNTP synthesis, which form a complex in infected Escherichia coli. The T4 thymidylate synthase (TS) and the T4 deoxycytidylate deaminase (CD) catalyze sequential reactions and are physically linked within this complex [McGaughey, K. M., Wheeler, L. J., Moore, J. T., Maley, G. F. , Maley, F., and Mathews, C. K. (1996) J. Biol. Chem. 271, 23037-23042]. From the crystal structure of T4TS [Finer-Moore, J. S., Maley, G. F., Maley, F., Montfort, W. R., and Stroud, R. M. (1994) Biochemistry 33, 15459-15468], it appears that three regions corresponding to insertions relative to E. coli TS lie on one side of the enzyme surface. We have investigated the residual activity of T4TS in response to complete deletion or substitution mutagenesis of these insertions. Two deletions generated in the small domain (residues 70-103) reduced the TS activity to 0.2% and 0.7% of the wild-type activity, with the latter able to complement growth of a thyA- E. coli strain in the absence of thymidine. By insertion of exogenous sequences variable in length and in sequence into these deletion mutants, enzyme activity increased to 44% that of the wild type. Restoration of the TS activity depended mostly on the hydrophobicity of the inserted residues. The sites of insertions also displayed distinct permissiveness for accommodating the exogenous insertions. Deletions and substitutions near the C-terminus resulted in complete inactivation of the T4TS. Proteolysis experiments revealed that the modified surface loops of the small domain were still accessible and flexible for protein-protein interactions. We have used ELISA to detect a physical association between T4TS and T4CD and compared the binding affinity of WT T4TS for two purified insertion mutants of T4CD. The results obtained showed that the native sequences of the small domain inserts are not required for T4TS/T4CD complex formation.