Severe fetal brain dysgenesis with focal calcification

Intracranial calcification in childhood: a review of aetiologies and recognizable phenotypes

Intracranial calcification (ICC) is a common finding on neuroimaging in paediatric neurology practice. In approximately half of all cases the calcification occurs in damaged, neoplastic, or malformed brain. For the large number of other disorders in which ICC occurs, no common pathogenetic mechanism can be suggested. Congenital infection, particularly with cytomegalovirus, accounts for a significant proportion of all cases. However, some genetic diseases, in particular Aicardi-Goutières syndrome, Band-like calcification, and RNASET2-related disease, may mimic congenital infection; therefore, a full consideration of the radiological and clinical features is necessary before concluding that congenital infection is the cause. In some disorders calcification is a universal finding, in others it is a frequent occurrence, and in some it is only an occasional finding. Characteristic patterns of calcification are seen in a number of conditions, and a systematic approach to the identification and description of radiological findings, taken together in the context of the clinical scenario, allows a diagnosis to be made in many cases. Nonetheless, there remain a number of presumed genetic disorders associated with ICC for which the underlying molecular cause has not yet been identified.

Aicardi-Goutières syndrome with emphasis on sonographic features in infancy

BACKGROUND

Aicardi-Goutières syndrome (AGS) is a severe familial, mostly autosomal recessive encephalopathy, first described in 1984. The clinical picture and genetic abnormalities are heterogeneous. US findings in AGS have thus far not been systematically described.

OBJECTIVE

The purpose of this study was to analyse sonographic features in AGS and to compare them to CT/MRI.

MATERIALS AND METHODS

Four male infants with AGS, two brothers, underwent imaging between the ages of 4 weeks and 6 months.

RESULTS

Sonographically isolated mineralization of lenticulostriate vessels, dilatation of the lateral ventricles, subependymal cysts, and diffuse and focal hyperechogenicity of the periventricular white matter and basal ganglia, respectively, were the abnormal findings, that may be present even before the development of major neurological symptoms.

CONCLUSION

Early cranial US is able to visualize the whole spectrum of cerebral anomalies in AGS: calcifying microangiopathy, white matter disease and unusual subependymal cysts. The imaging pattern is similar to that of congenital viral infection of the central nervous system, which may mislead the genetic counseling.

Recurrent pseudo-TORCH appearances of the brain presenting as "Dandy-Walker" malformation

Dandy-Walker malformation (DWM) is a developmental abnormality characterized by cystic dilatation of the fourth ventricle, complete or partial agenesis of the cerebellar vermis, and enlarged posterior fossa with upward displacement of the lateral sinuses, tentorium, and torcula. Calcification of brain tissue is a feature of congenital infection, particularly those involving the TORCH ( Toxoplasma gondii , rubella virus, Cytomegalovirus, and herpesvirus) group. An autosomal-recessive congenital infection-like syndrome with intracranial and extracranial calcifications has been categorized as pseudo-TORCH syndrome. We describe two male siblings diagnosed as DWM by ultrasound and by in utero and postmortem magnetic resonance imaging (MRI) but in whom the neuropathology revealed features of intracranial necrosis and calcification in the absence of extracranial calcific deposition. The fetal anomaly was identified by routine prenatal ultrasound scan at 16 weeks. In both cases the postmortem MRI showed bilateral ventriculomegaly with distortion of the overlying cortices, enlarged posterior fossa with a cyst related to small cerebellar hemispheres, and an incomplete cerebellar vermis. The diagnosis of DWM was offered. The histology revealed hypoplastic cerebral hemispheres with poorly cellular developing cortex. The white matter and periventricular matrix were disrupted by areas of necrosis and calcification not associated with any inflammatory infiltration, organisms, inclusions, or giant cells. To our knowledge, these two male siblings are the 1st cases that show pseudo-TORCH syndrome with distinctive intracranial calcification presenting as DWM. An autosomal-recessive or X-linked inheritance needs to be considered. Our study confirms the relevance of the multidisciplinary teamwork involved in the diagnosis of these complex cases.

Pena-Shokeir phenotype (fetal akinesia deformation sequence) revisited

BACKGROUND

Pena and Shokeir described the phenotype of two sisters in 1974, and subsequently their features have become recognized as a sequence of deformational changes related to decreased or absent fetal movement (fetal akinesia deformation sequence [FADS]), because of the work of Moessinger (1983).

METHODS

Identification of reported cases by searching Online Mendelian Inheritance in Man, Medlines, the London Dysmorphology Database, and the references found in these articles. These case reports were reviewed, tabulated, and summarized.

RESULTS

It is now possible to recognize at least 20 familial types of Pena-Shokeir phenotype (PSP), based on the differences found in the reports of the natural history and pathology found at fetal and newborn autopsy. In addition, characteristic changes in the central nervous system seen with embryonic/fetal vascular compromise have been recognized in many reported cases. Most of the reported cases of PSP/FADS related to vascular compromise are sporadic, but familial cases have also been reported.

CONCLUSION

Lack of fetal movement (fetal akinesia) in humans produces a recognizable sequence of deformations. Many developmental processes must be accomplished for fetal movement to be normal, and for extra-uterine life to be sustainable. Prenatal diagnosis is possible through real-time ultrasound studies as early as 12 weeks. Most reported cases die in utero, at birth, or in the newborn period. Advances in embryo/fetus pathology have led to the recognition of the many familial subtypes, allowing improved genetic counseling and early recognition in subsequent pregnancies.

Band-like intracranial calcification with simplified gyration and polymicrogyria: a distinct "pseudo-TORCH" phenotype

The combination of intracranial calcification and polymicrogyria is usually seen in the context of intrauterine infection, most frequently due to cytomegalovirus. Rare familial occurrences have been reported. We describe five patients-two male-female sibling pairs, one pair born to consanguineous parents, and an unrelated female-with a distinct pattern of band-like intracranial calcification associated with simplified gyration and polymicrogyria. Clinical features include severe post-natal microcephaly, seizures and profound developmental arrest. Testing for infectious agents was negative. We consider that these children have the same recognizable "pseudo-TORCH" phenotype inherited as an autosomal recessive trait.

Less invasive autopsy: benefits and limitations of the use of magnetic resonance imaging in the perinatal postmortem

The decline in the postmortem (PM) autopsy rate in the United Kingdom paralleled the change in public perception of this procedure after the organ retention crisis in 2000. The introduction of magnetic resonance imaging (MRI) in the fetal, perinatal, and pediatric autopsy led some investigators to propose that MRI could replace the conventional PM. We assessed the role of MRI in fetal autopsy as an addition or a potential replacement method to the conventional PM and to evaluate the benefits and limitations of each technique. We retrospectively reviewed the PM and MRI examination of 100 fetuses. The MRI was limited to the brain or brain and spinal cord. Forty-six cases involved termination of pregnancy; 30 were intrauterine fetal deaths/stillbirths; 16 were premature deliveries followed by neonatal death; and 8 were miscarriages. The mean gestational age of all cases was 25.54 weeks (range: 13-41 weeks). In 54 of the 90 full PMs, there was a complete agreement between the MRI and autopsy findings on the morphology of the brain and spine. Despite this agreement, the information gained at the PM was relevant to find the cause or mechanism of death in 20 of 54 cases (37%). In 24 autopsies the MRI added valuable information to the autopsy. However, if MRI had been the only investigation, essential information would have been lost in 17 of 24 cases (71%). In 12 cases the PM was clearly superior to the MRI. The integrated result obtained from the traditional autopsy remains crucial in determining the cause or mechanism of the malformation or of the fetal/perinatal death and accordingly is important for the counseling offered to parents regarding the recurrence risk for future pregnancies.

Clinical and molecular phenotype of Aicardi-Goutieres syndrome

Aicardi-Goutieres syndrome (AGS) is a genetic encephalopathy whose clinical features mimic those of acquired in utero viral infection. AGS exhibits locus heterogeneity, with mutations identified in genes encoding the 3'-->5' exonuclease TREX1 and the three subunits of the RNASEH2 endonuclease complex. To define the molecular spectrum of AGS, we performed mutation screening in patients, from 127 pedigrees, with a clinical diagnosis of the disease. Biallelic mutations in TREX1, RNASEH2A, RNASEH2B, and RNASEH2C were observed in 31, 3, 47, and 18 families, respectively. In five families, we identified an RNASEH2A or RNASEH2B mutation on one allele only. In one child, the disease occurred because of a de novo heterozygous TREX1 mutation. In 22 families, no mutations were found. Null mutations were common in TREX1, although a specific missense mutation was observed frequently in patients from northern Europe. Almost all mutations in RNASEH2A, RNASEH2B, and RNASEH2C were missense. We identified an RNASEH2C founder mutation in 13 Pakistani families. We also collected clinical data from 123 mutation-positive patients. Two clinical presentations could be delineated: an early-onset neonatal form, highly reminiscent of congenital infection seen particularly with TREX1 mutations, and a later-onset presentation, sometimes occurring after several months of normal development and occasionally associated with remarkably preserved neurological function, most frequently due to RNASEH2B mutations. Mortality was correlated with genotype; 34.3% of patients with TREX1, RNASEH2A, and RNASEH2C mutations versus 8.0% RNASEH2B mutation-positive patients were known to have died (P=.001). Our analysis defines the phenotypic spectrum of AGS and suggests a coherent mutation-screening strategy in this heterogeneous disorder. Additionally, our data indicate that at least one further AGS-causing gene remains to be identified.

Mutations in genes encoding ribonuclease H2 subunits cause Aicardi-Goutières syndrome and mimic congenital viral brain infection

Aicardi-Goutières syndrome (AGS) is an autosomal recessive neurological disorder, the clinical and immunological features of which parallel those of congenital viral infection. Here we define the composition of the human ribonuclease H2 enzyme complex and show that AGS can result from mutations in the genes encoding any one of its three subunits. Our findings demonstrate a role for ribonuclease H in human neurological disease and suggest an unanticipated relationship between ribonuclease H2 and the antiviral immune response that warrants further investigation.