Marginal glioneuronal heterotopias in nine cases with and without cortical abnormalities

Extracerebral ectopic mass with huge cysts in the anterior cranial cavity

In the present study, an unusual example of malformation in a 9-day-old-girl, in whom an extracerebral ectopic mass with cysts was found in the anterior cranial cavity, is reported. The brain proper was well developed. The mass was connected to the cerebral base and consisted of neuroglial tissue showing various characteristics of differentiation, including cerebellar cortex and monoaminergic neurons. The ectopia may have developed from the mediobasal portion of the embryonic telencephalon.

Experimentally induced leptomeningeal glioneuronal heterotopia and underlying cortical dysplasia of the lateral limbic area in rats treated transplacentally with methylmercury

Leptomeningeal glioneuronal heterotopia (LGH) is a developmental anomaly sometimes observed at the surface of human brains with severe malformations. We experimentally induced LGH in brains of rat pups by transplacental exposure to methylmercury. Histopathological profiles of the induced LGH, including the spatio-temporal predominance of the manifestation, suggest some aspects of the histogenesis of this malformation. Pregnant rats on embryonic day 8 (E8), E11, E13, E16, E18 or E21 were treated orally with a single administration of 20 mg/kg methylmercury chloride, and the brains of their delivered offspring were examined on postnatal day 7 (P7) and P28. The incidence of LOH varied significantly according to the treatment day: it was almost exclusively restricted to individuals treated on E13. Furthermore, all the induced LGH was confined to the subarachnoid space dorsal to the rhinal fissure, unilaterally or bilaterally. A part of the nest was connected to the underlying cortical surface of the lateral limbic area, where glia limitans and basal lamina were disrupted. Narrow stripes of disarrangement of cortical neurons underlying the bridges were observed. The P7 LGHs consisted mainly of neurons, some of which were GABA-immunolabeled. and a small number of astrocytes as well as endogenous blood vessels and fibroblasts. LGHs in P28 brains consisted mainly of GFAP-positive astrocyte processes. An additional experiment with double administrations of 5-bromo-2-deoxyuridine (BrdU) and methylmercury on E13 disclosed an abnormally widespread distribution of labeled neurons throughout all cortical layers underlying the LGH in P28 brains. Thus, cerebral LGH would be induced if a developing brain were insulted at the early stage of neurogenesis. accompanied by cortical dysplasia.

The role of Glial-Pial barrier lesions and impaired vascularization in anomalous formation of cortical convolutions

The abnormal patterns of cerebral convolutions range from severe to small anomalies restricted to tertiary gyri and sulci. Lesions within Glial-Pial barrier were found in examined cases with cortical developmental abnormalities. Anomalies and impaired function of vessels penetrating the cortex from meningeal plexus coexisted often with Glial-Pial barrier lesions. We are able to say that our cases constitute a group of graded changes demonstrating that both observed developmental lesions vascular and/or Glial-Pial barrier damage may result in cortical anomalies. Their formation and character depend on the stage of cortical maturation when analyzed lesions occur.

A transgene insertion at perinatal lethality (ple) is associated with abnormalities of the cortex

In an inbred genetic background, mice homozygous for a transgene insertion at perinatal lethality (ple) were found to be significantly smaller than their heterozygous or wild-type siblings at birth, and rarely survived for more than 48 h. Homozygous progeny of ple mice obtained from a cross with a different strain were viable, but were still not obtained in the expected numbers, demonstrating some deleterious affect of this mutation even in a hybrid genetic background. Homozygous mice demonstrate variable expression of abnormalities in brain development. These usually appear as focal cortical ectopias, but also include other abnormalities, such as polymicrogyria. The genomic sequences corresponding to the region disrupted by the transgene were cloned by isolating a junction fragment between transgenic and wild-type sequences, which was then used to obtain the corresponding region of wild-type genomic DNA. Since some probes from this region do not hybridize with genomic DNA from homozygous ple mice, it appears likely that a deletion event coincided with the transgene insertion.

Clinicopathological findings associated with agenesis of the corpus callosum

Seven hundred five cases of agenesis of the corpus callosum (ACC) are reviewed from the literature (n = 660) and from our own observations (n = 45). The diagnosis was made or confirmed using neuroradiological techniques (n = 519) and necropsy or surgery (n = 231). Association with abnormalities often of chromosomes 8, 11, 13-15 and 18 suggests their involvement in abnormal corpus callosum (CC) morphogenesis. Four syndromes (e.g. Aicardi, acrocallosal, Andermann and Shapiro) are characterized by ACC, while others are only sporadically associated (e.g. fetal alcohol syndrome, Dandy-Walker syndrome, Leigh disease, Arnold-Chiari II syndrome). In non-Aicardi patients, the male-to-female ratio was 3:2 and X-linked recessive inheritance is postulated to play a role in some cases. Common abnormalities in acallosal patients included: mental retardation (MR), 73% [corrected]; seizures, 42%; ocular anomalies, 42%; gyral abnormalities, 32%; hydrocephalus, 23%; other central nervous system (CNS) lesions, 29%; costovertebral defects, 24%. Developmental disabilities are not attributable to absence of the CC per se, but due to other CNS malformation or dysfunction, which may be genetic or non-genetic. Future research using recombinant DNA techniques will enable isolation and identification of specific chromosomal defects in those cases with a genetic abnormality.