Intraventricular hemorrhage (IVH) is bleeding into the ventricles of the brain. One characteristic of the immature brain is a weakness of the blood vessels next to the ventricles. The ventricles are cavities that store cerebrospinal fluid (CSF) which nourishes the brain. Of particular concern is a collection of tiny and fragile blood vessels in the germinal matrix, which is the area of brain adjacent to the floor of the ventricles. This is a part of the brain that is active during fetal development but that disappears at about the 35 th week of pregnancy. These blood vessels are thin and vulnerable to fluctuations in blood flow through them, which can cause them to rupture and bleed. The younger and smaller the baby, the higher the risk these blood vessels may be ruptured, usually in the first few days of life. A rupture causes blood to flow into a ventricle or ventricles of the brain.
IVH is categorized into grades of severity: grade I is considered mild, grade II moderate, and grade III & IV severe. About 50% of extremely premature babies will sustain an IVH, whereas only about 15% of older premature babies, many of whose germinal matrix has already disappeared, will have an IVH.
If the IVH is classified as grade I or II, the chance that there will be long-term damage is small because the blood remains contained within the ventricles and the additional fluid does not cause excessive pressure.
In grade III IVH, the bleeding is substantial enough to cause a swelling or obstruction of the narrow channels feeding into and out of the ventricles. This may interfere with the normal replenishment and flushing of the CSF. The result can be hydrocephalus, which is a build up of CSF in the ventricles, which puts pressure on surrounding brain tissues. This can then result in injury to that area of brain under pressure. If the bleeding is more severe, blood that has flowed into and filled the ventricles will permanently block CSF flow and lead to hydrocephalus with enlargement of the head, excessive pressure within the skull, and the need for a surgical intervention to relieve the pressure. A small tube or catheter called a ventriculoperitoneal shunt (VP shunt) is inserted to drain off the spinal fluid.
A grade IV IVH results from congestion to the brain tissue around the ventricles when a large IVH has occurred. This results in bleeding into the brain tissue itself with destruction of that area of brain. Lasting brain damage is almost always the result, the severity of which is determined by the extent and location of the bleeding.
Because premature babies have fragile blood vessels, an IVH can occur simply as a result of changes to blood pressure and flow that occurs with birth. Although blood pressure changes occur in most people without bleeding, in the premature baby, the walls of the vessels are vulnerable during these changes. Blood pressure fluctuations can occur as a result of many different conditions, and are often a result of difficulties at the time of birth or lung and breathing complications.
Mechanical ventilation, which is often needed immediately after the birth of a premature baby, can also lead to fluctuations in blood flow. This is particularly likely when the baby is breathing out of sync with the ventilator, which creates additional pressures within the lung and blood vessels in the brain. Much work has been done over the years in an attempt to reduce this particular risk factor and improve a baby’s assisted breathing in general.
The bleeding of IVH occurs typically within the first 48 hours following birth, and it is very unlikely to occur again at a later date.
There are two main ways in which IVH can potentially cause damage. First, IVH may affect the flow of CSF in the ventricles and second, IVH may cause damage to brain tissue adjacent to the ventricles. Once damage has occurred to brain tissue, it cannot be reversed. However, physical damage to brain tissue does not necessarily mean damage to brain function. The areas of the brain that are often affected by an IVH, those adjacent to the ventricles, are those responsible for motor functions. Commonly, problems with vision and hearing, and other higher cognitive functions are associated. The extent of any long-term effect will often depend on the severity of the bleeding: babies with severe IVH are likely to develop some kind of neurological disability. Cerebral palsy (CP), a condition that interferes with motor coordination, is frequent. There is however, a wide range of disability with CP: those with hemiplegia are affected on one side of body only and children with milder forms of spastic diplegia, affecting only the legs, are usually able to walk with minimal supports.
Luckily, many babies who have a mild IVH go on to develop normally or with only minimal disabilities associated with learning.