Objective: To clarify the pathogenetic significance of the topographic distribution of leptomeningeal glioneuronal heterotopia, a common finding in holoprosencephaly.
Design: Gross, histological, and immunohistochemical observations of alobar holoprosencephaly in brain specimens taken at autopsy.
Setting: Referral center.
Materials: Brains removed at autopsy from five consecutive patients with alobar holoprosencephaly.
Main outcome measures: Immunoperoxidase staining for glial fibrillary acidic protein.
Results: In all brains, leptomeningeal glioneuronal heterotopia showed an identical distribution, ranging from the basal prosencephalon to the pons, with the thickest distribution occurring in the basal prosencephalon.
Conclusion: The constant localization implicates leptomeningeal glioneuronal heterotopia in severe dysgenesis of midline prosencephalon, the basic pathogenesis of the anomaly.