Ulegyria is a diagnosis used to describe a specific type of cortical scarring in the deep regions of the sulcus that leads to distortion of the gyri. Ulegyria is identified by its characteristic "mushroom-shaped" gyri, in which scarring causes shrinkage and atrophy in the deep sulcal regions while the surface gyri are spared. This condition is most often caused by hypoxic-ischemic brain injury in the perinatal period. The effects of ulegyria can range in severity, although it is most commonly associated with cerebral palsy, intellectual disability and epilepsy. N.C. Bresler was the first to view ulegyria in 1899 and described this abnormal morphology in the brain as “mushroom-gyri." Although ulegyria was first identified in 1899, there is still limited information known or reported about the condition.
Anatomy
The physical features of ulegyria consist of small radial scars which occupy the cortical sulci. Overall, the physical structure of affected areas in the brain is described as a “mushroom”-like shape in which the gyri are unusually large and the sulci become wider deeper in the cortex. N.C. Bresler, the first person to view a brain with ulegyria in 1899, coined the phrase mushroom gyri. He also named the disorder, basing it off the Latin root ule, meaning scar. This mushroom-like structure is the result of the lower parts of the ulegyria-affected area being more prone to deterioration, while the upper gyri are usually spared. However, the entire affected area shrinks and presents brown coloration as a result of ulegyria. 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 infant's 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. A lack of oxygen to the brain contributes to the formation of lesions usually near the three main cerebral arteries, located near the parietal lobe and occipital lobes of the brain. The cause of perinatal brain injuries includes:
1. cerebral ischemia 2. cerebral hemorrhage 3. ascending intrauterine infections. Some risk factors for perinatal brain injuries include: low birth weight, preterm birth, poor perinatal cardiorespiratory fitness, and artificial ventilation.
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