Kim Annink

42 Chapter 2 is defined by atrophy of the deeper sulcal portions of the cerebral cortex, thereby sparing the crown, and is most pronounced in the watershed regions of the three major cerebral vessels (35–38). More recently, ulegyria has also been described in three infants with intrauterine asphyxia scanned at seven to eight days after birth by Volpe and Pasternak (38). Ulegyria is a hallmark of perinatal asphyxia in term born neonates with HIE, yet it is not exclusive for infancy (36,37). The acute phase of ulegyria is characterized by extensive neuronal loss and signs of hypoxic-ischemic injury at postmortem histopathological stainings, such as neuronal vacuolization, chromatolysis and an influx of macrophages in the bases of the sulci (39). Thereafter, ulegyria is characterized by atrophic changes and gliosis of the subcortical white matter, eventually leading to the so called ‘mushroom gyri’ with a preserved crown on top of a thin stalk of fibrous glial scar tissue (35,37,39). Ulegyria might be caused by distinctions in cortical perfusion, the crown of the gyri is better perfused than tissue at the bottom of the sulci, thereby causing the typical ‘mushroom shaped gyri’ after hypoxic events (40). Even though, to our knowledge, ulegyria has not yet been described in the cerebellum, the pattern of extensive PC loss at the bases of the sulci in the vermis (vermian ‘ulefolia’) seems relatively comparable to ulegyria. In the present study, no significant differences were found in total PC count between the anterior and posterior lobes of the vermis. Nevertheless, previous studies have shown that the extent of PC death is not uniform over the cerebellum. PC susceptibility to ischemia is partly dependent on whether PCs express zebrin II or not. Zebrin negative PCs were more vulnerable for hypoxic-ischemia in rodent models (26). Furthermore, there is variability in vulnerability of PCs between lobules; PCs in lobules IX and X seem more resistant to death (26). Additional research is needed to investigate differences in the vulnerability of different lobules in the vermis of neonates with HIE. There were some limitations to this study. The first limitation was the small research population (n=22). This diminished the power of the study and therefore we were not able to investigate the relationship between timing of death and PC injury. The second limitation was that terminal events after withdrawal of care, such as hypoxic events, could have led to additional injury to H&E stained sections of the vermis (18). Due to the variability between death and tissue collection the phenotype scoring system might have been influenced by postmortem timing. Furthermore, it was not feasible to determine the normal distribution of PCs in term born infants