In addition, “islands” of neurons that are relatively unaffected can exist between ulegyria affected neurons. Ulegyria can develop bilaterally or unilaterally, though the former is more commonly diagnosed.Ulegyria can affect many parts of the brain including the cerebral cortex, parasagittal areas and posterior regions of the brain, such as the parietal and occipital lobes. These areas are situated either near artery rich regions or near a major cerebral artery. For instance, specifically in neonatal children, ulegyria-affected areas are found near the posterior cerebral artery or near the artery rich region between the middle and posterior regions of the brain, often referred to as watershed regions.Neurons affected by ulegyria exhibit properties that differ from normally functioning neurons. For instance, ulegyria affected neurons experience gliosis in which glial cells, specifically astrocytes, build up near and around neurons. Ulegyria affected neurons also display decreases in their white matter content, showing signs of sclerosis, which is characterized by the deterioration of myelin in neurons. However, in regions of grey matter, large dense aggregates of myelin are present. Ulegyria affected neurons also display metabolic disorders which could be linked to the disease phenylketonuria and disruptions in the urea cycle. Hypoglycemia and  hypoxia are also thought to accompany the symptoms of ulegyria-affected neurons as well. Causes
Ulegyria develops as a result of a brain injury called cerebral ischemia surrounding the time of an infants birth. Oftentimes, fetal hypoxic-ischemic brain injuries occur as a result of a pregnancy complications such as placental abruption, cord accident, or cardiovascular stress due to a difficult delivery.
The germinal matrix is a part of the brain that normally disappears as the fetal brain develops but during this process it is not unusual for changes in vessel volume to cause a vessel to burst. According to recent microscopic studies, the most common location for a cerebral hemorrhage is where the medullary veins drain to the terminal vein in the sub-ependymal region. It has been hypothesized that because pre-term babies dont have fully developed sympathetic nervous systems, they cannot react as well to low oxygen saturation levels caused by the cerebral hemorrhage. Although babies born at full-term are still susceptible to this, they are likely to respond better and thus, tend to have better outcomes in response to low-oxygen events. Ascending intrauterine infections
Recent research has found a connection between intrauterine infections and inflammation in the mother and an increased likelihood of perinatal brain damage in the fetus. This study suggested that intrauterine infections in the mother could affect glial cells and toll-like receptors (TLRs) which are important in moderating the inflammatory response in the fetal brain. When glial cells and TLRs are negatively affected they are not able to react to developing inflammation in the brain as well. The connection between ascending intrauterine infections and perinatal brain damage is a developing research theory but a more detailed explanation of the connection is not yet known. Signs and symptoms
Ulegyria was found in about 1/3 of patients with defects caused by circulatory disease in the perinatal period.