Hyperdense cerebral lesion in childhood tuberous sclerosis: computed tomographic demonstration and neuropathologic analysis.

A child with focal intractable seizures and electroencephalographic evidence of a highly epileptogenic focus was found to have a high-density, wedge-shaped lesion in the left parietal region on cerebral computed tomography. The lesion extended from the ventricular to the pial surfaces and did not enhance after contrast infusion. Biopsy confirmed the diagnosis of tuberous sclerosis. Atypical features of tuberous sclerosis on computed tomography are reviewed and the possible pathogenesis of the lesion is discussed.

Obstructed neuronal migration along radial glial fibers in the neocortex of the reeler mouse: a Golgi-EM analysis.

The interrelationship of radial glial fibers (RGF) and young neurons migrating to the neocortex of normal and reeler mutant mice at 17 days of gestation are reconstructed from serial and from closely spaced thin sections. The glial fibers are identified unequivocally by correlated light and electron microscopy by means of the Golgi-gold toning method of Fairén and associates. The migrating cell in the normal animal is closely apposed to and coiled about the RGF throughout most of its ascent. In the terminal few microns of its movement, however, it begins rapidly to differentiate and at the same time surrenders its close attachment to the RGF. In the reeler, by contrast, the migrating cell maintains normal apposition to the RGF only until it enters the cortex. There its leading process is unable to pass between the surfaces of the RGF and those of postmigratory elements. Abnormally extensive contact between the glial fiber and the somata of postmigratory cells appears to be sustained in the mutant. The upward migration of the young neuron is terminated in the depths of the cortex and the cell soma gives rise to a profusion of small processes. This study affirms the critical role served by RGF as guides to neuronal migration and provides evidence that abnormal adhesions between postmigratory cells and the RGF obstruct neuronal migration in the reeler mouse.

Determinants of cell shape and orientation: a comparative Golgi analysis of cell-axon interrelationships in the developing neocortex of normal and reeler mice.

Patterns of dendritic development in the neocortex of normal and reeler E15-17 mouse embryos are studied in Golgi impregnations. Interactions between dendrites and axon-rich strata appear to be critical determinants of dendritic morphology in both genotypes. Firstly, axon-dendrite proximity appears to stimulate dendritic sprouting, elongation and branching. Secondly, the position of the axon-rich strata with respect to the differentiating cell appears to determine the direction of dendritic growth and thereby the ultimate configuration of the dendritic arbor. With regard to specific cell configurations, a multipolar form is generated when the cell is embedded in an axon-rich zone. A monopolar or bipolar configuration is achieved when the cell lies in the axon-poor cortical plate and addresses and axon-rich stratum with one or both radially extended migratory processes. Such variations in the configuration of neurons with polar dendritic systems may be observed uniquely in the mutant cortex because axon-rich zones are stratified anomalously at multiple levels in the cortical plate. As a consequence, polar dendritic systems develop from either the superior, the inferior or both somatic poles of postmigratory cells. Pyramidal cells may, therefore, develop a normal upright or an abnormal "upside-down" disposition. Regardless of the orientation of the polar dendritic system, the axon emerges from the inferior aspect of the cell suggesting that there has been no rotation of the original migratory axis of the cell.