We report an autopsy case of tuberous sclerosis complex (TSC) in a 20-week gestational age female fetus. The brain showed lesions suggestive of early cortical tubers and subependymal hamartomatous nodules. The large cells within these nodular clusters were variably immunoreactive for glial fibrillary acidic protein (GFAP) and vimentin and negative for synaptophysin and neurofilament. Subependymal radial glia expressed both vimentin and GFAP, but subpial radial glia either did not express these markers (in contrast to an age-matched control) or were absent. Tuberin expression was noted in heterotopic neurons in the white matter and brain cells consistent with Cajal Retzius cells in the neocortical molecular layer, very weakly in superficial cortical neurons, neurons in the basal ganglia, Purkinje cells and external granular cells of cerebellum, cranial nerve nuclei neurons, occasional germinal matrix cells, ependymal cells, choroid plexus epithelium, and pituitary gland neuroendocrine cells; it was not seen within the cells of subependymal nodules. The pattern of tuberin immunoreactivity was similar to that which we have observed in older TSC patients. Proliferating cell labeling indexes were comparable in the germinal matrix of the TSC patient and an age-matched control. Abnormal subpial radial glia may be responsible for some of the neuronal migration abnormalities that appear to result in neocortical tubers.

Extensive surgical resections of neocortical cerebral tissue (including hemispherectomies) from 13 infants and children with infantile spasms showed that 12 of 13 specimens contained either malformative and dysplastic lesions of the cortex and white matter (sometimes with associated hamartomatous proliferation of globular cells), or destructive lesions possibly acquired as a result of anoxic-ischemic injury, or a combination of the two. In brain tissue from 4 patients, coarse neuronal cytoplasmic fibrils resembling neurofibrillary tangles were seen in areas of dysplastic brain on silver-stained (Bielschowsky technique) sections. Immunohistochemical (immunoperoxidase) study of cortical lesions containing globular cells employing primary antibodies to glial fibrillary acidic protein and synaptophysin as markers of astrocytic and neuronal differentiation, respectively, revealed that many cells showed astrocytic and/or neuronal features, suggesting the local proliferation of primitive or multipotential neuroectodermal cells as one substrate for this seizure disorder. Morphological abnormalities of a severe degree and wide extent in the resected tissue (e.g., in one patient with hemimegalencephaly) often showed features to suggest that they may represent variants of tuberous sclerosis. These most likely result from abnormal movement and/or local proliferation of neuroectodermal precursors that have migrated from the germinal matrix to the cortical mantle. Cellular, molecular and neurophysiological study of these abnormalities is likely to yield information about basic molecular mechanisms of brain malformation and injury important in the pathogenesis of infantile spasms and other forms of focal or generalized epilepsy.

Tissues from three cases of hemimegalencephaly (HME) causing intractable seizures treated by cortical resection were studied using immunohistochemical, ultrastructural, and morphometric techniques. Severe cortical dysplasia was seen in all cases and included lesions best characterized as hemilissencephaly and polymicrogyria. Blurring of the cortex-white matter junction, the presence of large neuronal heterotopias, and neuronal cytomegaly were frequent observations. Immunohistochemical analysis demonstrated cellular colocalization of astrocytic markers glial fibrillary acidic protein and vimentin in one case of hemilissencephaly. Morphometric data showed significant increases over controls in neuronal profile area in all cases of HME. Neuronal cell density was increased significantly above controls in one of the cases. The study shows that HME results from severe cortical dysplasia which may be caused by multiple insults, manifest in one of several ways, and reflects abnormal or altered signals that regulate cortical morphogenesis.

The cytoskeletal abnormalities of cortical neurons in human cerebral cortical dysplasia were compared by immunohistochemical methods to the neurofibrillary tangles of Alzheimer's disease (AD). Surgical specimens from cortical resections performed for the treatment of intractable childhood seizures as well as autopsied samples from AD patients were analyzed with different antibodies directed against high- or medium-molecular mass neurofilament epitopes, phosphorylated or non-phosphorylated forms of neurofilaments, ubiquitin, the microtubule-associated protein tau, and paired helical filaments (PHF), a defining feature of AD tangles. A strong abnormal increase in immunoreactivity to the high and medium molecular mass neurofilament epitopes was seen in hypertrophic neurons of cortical dysplasia. These neurofilamentous accumulations of cortical dysplasia as well as AD tangles also displayed immunoreactivity with antibodies against phosphorylated and non-phosphorylated neuro-filament epitopes, tau and ubiquitin. Only the AD tangles, however, were immunoreactive to the antiserum to PHF. These results replicate and extend our previous findings that the neurofibrillary accumulations in cerebral cortical dysplasia share some common antigens with the neurofibrillary tangles of AD but do not demonstrate immunoreactivity to PHF antiserum. The results also suggest that the cytoskeletal abnormalities observed in neurons of cortical dysplasia may result in part from alterations in the level of expression, in phosphorylation state or in transport of cytoskeletal components.