Groups of histopathologic abnormalities in brains of very low birthweight infants.

The neuropathologic changes in brains of very premature infants are well recognized but relatively few studies have attempted to identify if specific neuropathologic features cluster together. These data could assist in determining pathogenetic mechanisms of immature brain injury. The goal of this study is to identify which, if any, combinations of histologic features occur together. We identified the presence or absence of 19 histologic features in the brains of 67 infants from a multicenter study of 1,665 prematurely born infants whose birthweight was 500-1,500 grams. We used clustering algorithms and factor analysis to group pathologic features that occurred together. Our results indicate that certain histopathologic features do cluster. For example, telencephalic white matter astrocytosis occurs in 2 groups: 1) associated with amphophilic globules, and, 2) in an uncorrelated group, associated with focal macrophage deposits and coagulative necroses. Parenchymal hemorrhage was not found to be associated with any telencephalic leukoencephalopathy, regardless of whether characterized by rarefaction, astrocytosis, focal coagulative necroses, or foci of macrophages in the white matter. Intraventricular hemorrhage and germinal matrix hemorrhage were not seen together more often than by chance expectation. Intraventricular hemorrhage was only marginally associated with parenchymal hemorrhage. Our data indicate that specific histopathologic features tend to preferentially cluster with each other in groups. This clustering may represent the manifestation of a common mechanism for each. These data should be valuable indicators for future research attempting to establish pathogenesis.