Embryonal cell nests in human cerebellar nuclei

Spontaneous cerebellar dysplasias in BrlHan: WIST@Jcl rats

Focal disturbed laminar architecture in cerebellar vermis was observed in 25 out of 100 (25%) males, and 25 out of 100 (25%) females of BrlHan: WIST@Jcl rats. The cortical molecular and granular layers were haphazardly distributed around the primary and/or secondary fissures. The stellate and basket cells positively stained with parvalbumin immunohistochemistry were observed exclusively in the separated molecular layer. Purkinje cells were found at the boundary between the molecular and the granular layers. Glial fibrillary acid protein (GFAP) immunohistochemistry revealed disarranged fibers of the Bergman glial cells. Based on the incidence of this spontaneous cerebellar lesion, it was presumed to be related to certain genetic factors of this rat strain.

Intracranial meningiomas associated with glial tumours: a review based on 54 selected literature cases from the literature and 3 additional personal cases

The simultaneous occurrence of meningioma and glioma is extremely rare. Three new cases and 54 adequately described in the literature are analyzed. Clinical diagnosis may be difficult due to discrepancy between clinical and radiological findings. Unexpected clinical deterioration following removal of a tumour and relapse simulating recurrence may occur. The introduction of CT technology does not seem to have offered the expected contribution to the early diagnosis of these coincidental lesions, at least before the introduction of the newer generation scanners or MRI. While removal of both tumours in one session yielded the best results, surgery for the sole glioma appeared to be associated with an unacceptably high mortality. Although several aetiopathogenetic hypotheses have been suggested for explaining this curious association, coincidental meningioma and glioma are most likely to be different primary brain tumours occurring randomly in the same individual.

Neurogenesis and gliogenesis in the human brain

The primary germinal neural epithelium lines the ventricular system of the brain and shows intense mitotic activity. Neuroblasts migrate from a juxtaluminal position to establish neural centres and, when this task is completed, the definitive ependymal epithelial lining of the ventricles develops, shifting the remnants of the germinal epithelium to a subendymal location. The subendymal layer continues to proliferate giving rise to glia in the postnatal brain. Premature arrest of migration of neuroblasts leads to the accumulation of heterotopic nests anywhere along the migratory path. Within such ectopia, neurons may make normal connections or they may remain undifferentiated and later become tumorigenic. The subependymal layer has long been considered the site of original of periventricular gliomas. Some migrating neuroblasts establish secondary germinal centres far removed from the ventricular system. An example of this is the external granular layer of the cerebellum which, in man, persists for the first 6 months of life. Cerebellar neuroblastomas could originate directly from this layer in the neonate, or from remnants of this layer in older individuals.