Congenital hydrocephalus

Congenital hydrocephalus is when a child is born with an excessive accumulation of cerebrospinal fluid (CSF) in the brain. CSF is a clear fluid that surrounds the brain and spinal cord. This excess fluid causes an abnormal widening of spaces in the brain called ventricles (ventriculomegalia) and can create a harmful pressure on brain tissue. Symptoms of hydrocephalus vary and may include an unusually large head with thin, transparent scalp, bulging forehead with increased spaces between the bones of the skull (fontanelles), and a downward gaze. Other symptoms may include seizures, abnormal reflexes, slow heartbeat and respiratory rate, headaches, vomiting, irritability, weakness, and visual problems.

It is caused by genetic and non-genetic factors. The most common cause of congenital hydrocephalus are variations (mutations) in the L1CAM gene, where there is a narrow passageway between the third and fourth ventricles (aqueductal stenosis). Other causes include mutations in many other genes, brain and/or spinal cord malformations, infections, bleeding inside the cavities of the brain (intraventricular hemorrhage), trauma, exposition to certain drugs (teratogens) or a congenital tumor of the brain. Congenital hydrocephalus can be an isolated malformation or be part of a syndrome where there are other associated malformations. It is most often treated by surgically inserting a shunt system to transport the excess CSF and allow for re-absorption. If left untreated, blindness and continuing mental deterioration may occur.

Hydrocephalus may be subdivided according to the particular defect that exists in the brain and whether the cerebrospinal fluid pressure is high or normal:

• Communicating hydrocephalus is when there is no blockage (obstruction) in the ventricules but the fluid is not absorbed readily, or there is too much fluid to be absorbed.
• Noncommunicating (obstructive) hydrocephalus is when there is a blockage of the CSF causing widening (dilation) of the pathways that are located upstream of the block, resulting in an increased pressure inside the brain.

There are also 2 other forms of hydrocephalus that usually affect only adults:

• Normal-pressure hydrocephalus is where the ventricules are expanded but the pressure inside the nervous system is normal.
• Hydrocephalus ex-vacuo occurs when stroke or traumatic injury cause damage to the brain and the brain tissue may shrink.

Hydrocephalus may also be classified in congenital or acquired. Acquired hydrocephalus develops at the time of birth or at some point afterward and may be caused by injury or disease.