While the fetal brain is developing, the body is gradually building a “great wall” of resistance to possible damage and external aggression. Like the adult, the infant’s skull is made up of several bones. However, these bones are not yet fused after birth. This gives the head a degree of plasticity that helps to make delivery easier. During the first few months of life, the bones begin to deposit calcium and the skull bones fuse with each other to form a complete skull that protects the brain. Before the bones fuse, the infant brain is at its most vulnerable. The brain is surrounded by fluid. Cerebrospinal fluid (CSF) is found in the brain and spinal cord, and also deep within the cavities of the brain called ventricles. This cerebrospinal fluid (CSF) system functions to nourish the brain and cushion it from impact. The ventricles are surrounded by brain tissue and abundant blood vessels, which are responsible for brain nutrition and circulation. In the premature brain, these vessels are very thin and fragile, and can be easily damaged. Diagnosis of brain injury Although rare, the brain of a preterm infant may be damaged during pregnancy, during delivery, shortly after birth, and in the first few weeks of life. In general, brain injury may occur when the brain is deprived of oxygen or blood sugar, when a blood vessel in the brain ruptures, causing bleeding, or, in rare cases, when there is some kind of blow to the head. Diagnosing a brain injury can be complicated. Because the brain is in many ways the control center for all body functions, a brain injury may cause symptoms in other parts of the body. However, sometimes there are no obvious symptoms of a brain injury. In addition, sometimes a brain injury can be diagnosed immediately, but its long-term effects cannot be predicted. For example, if an infant suffers a brain injury that causes bleeding, this bleeding may be diagnosed and treated quickly. However, if the hemorrhage causes irreversible brain damage, signs and symptoms of long-term disability, such as cerebral palsy, may not be evident for a short time. The area of brain damage may be large or small. However, the severity of the effects of the injury, especially long-term effects, is usually determined by the site of the injury. Brain function is highly shaped and sometimes large areas of damage can be healed as long as the brain establishes new pathways to send and receive commands, and sometimes, even when the damage is small, the brain cannot heal and is left with long-term damage. In the first few days of life, it is difficult, if not impossible, to diagnose and predict the outcome of long-term effects in preterm infants. Imaging techniques such as brain ultrasound (HUS) and magnetic resonance imaging (MRI) are often used clinically to confirm brain injury. Head ultrasound is performed regularly during the first week of life in preterm infants. If a brain problem is suspected, diagnostic MRI scans are continued if necessary.