Glial fatty metamorphosis. An abnormal response of premyelin glia frequently accompanying periventricular leukomalacia.

Within the developing nervous system, there is a complex relationship between the accumulation of sudanophilic lipids in glial cells and gestational and postnatal age. Sudanophilic lipids accumulate to a small degree as a stage of normal premyelin lipogenesis, but large amounts of such accumulations may be considered abnormal. The dividing line between the normal and the abnormal (glial fatty metamorphosis) must be defined for each region of the nervous system, since the time and rate of myelination vary widely. Examination of the brains of premature infants routinely coming to autopsy utilizing the oil red O technic on gelatin-embedded frozen sections has allowed this definition to be made in at least some situations. Glial fatty metamorphosis is characterized by an absolute increase in the amount of lipid droplets in the glial precursor cells and by an absolute increase in the ratio of lipid-containing cells to the total cell population. It is more easily recognized in the corpus callosum in cases of periventricular leukomalacia, but may occur in other disease states, and appears to represent a response of metabolically active immature glial cells to metabolic stress (hypoxia-acidosis).