When the body develops, there are specific regions of the brain that serve as focal points for forming certain organs. The area that helps to create the fully-formed brain is known as the germinal matrix. It consists of a layer of cells near the fluid-containing ventricles of the brain.
Cells in the germinal matrix are not fully differentiated. This lack of differentiation means that they can develop into either grey matter cells, called neurons, or white matter cells, called glia or glial cells. In response to hormone signals sent out by other parts of the brain, these immature cells will travel and differentiate as needed. These cells exist beneath a layer of glial cells known as ependyma.
The germinal matrix is supplied by a large network of blood vessels, in a state known as vascularization. Vascularization allows the cells of this region to have access to plenty of oxygen and nutrients. In turn, these immature cells can have the resources they require to migrate away from the matrix and become differentiated brain cells.
Activity in the germinal matrix peaks between 8 and 28 weeks during embryonic development. If this region is damaged during this time, the results can be life-threatening. During the second trimester of pregnancy, most spontaneous fetal deaths are thought to be caused by damage of this nature.
Damage to the matrix creates a condition known as a germinal matrix hemorrhage (GMH). It may occur before birth, or within several hours following birth. A hemorrhage involves bleeding inside of the brain, and a GMH may rupture the ventricles, increasing the damage to the brain.
The fragility of the germinal matrix makes it particularly susceptible to hemorrhage. Vascularlization creates conditions of high blood pressure in this area, increasing the chances of a blood vessel rupturing. Nearby capillaries are often not fully formed, and there is a sharp turn in the blood vessels entering the area, which further cause opportunities for problems. For these reasons, trauma to this part of the brain can quickly result in extensive damage.
When a GMH occurs, it may stay confined to the matrix itself, which improves chances of survival. At times, the bleeding will spread to other brain regions, and damage the ventricles. After the ventricles have been damaged, bleeding may spread to the white matter of the brain. Diffuse damage can cause severe medical conditions including cerebral palsy, seizure conditions, and mental disabilities. Often, this medical condition will be fatal, particularly if it occurs at an early stage of development.