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This fluid accumulation and the resulting effects are the defining symptoms of hydrocephalus. The most serious possible effect of fluid accumulation is that the increase in intracranial pressure can cause seizures and other neurological symptoms, and may lead to mental disability. Hydrocephalus may be a congenital condition or may occur due to other causes later in life.
Hydrocephalus has an incidence rate of about 0.1%, or one in every 1,000 live births. Once an incurably fatal condition, there is now an effective surgical treatment for hydrocephalus; however the surgery does have risks and complications.
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Causes and Symptoms
Most cases of hydrocephalus are caused by blockage in the outflow of cerebrospinal fluid. Fluid can enter the brain freely, but cannot easily exit, and this imbalance causes fluid to accumulate in the ventricles of the brain. In other cases, cerebrospinal fluid may be overproduced. Head injuries, infections, and stroke can also cause hydrocephalus.
In infants who are born with hydrocephalus, the most noticeable symptom of the condition is the head enlargement that results from fluid accumulation. In adults and older children this head enlargement does not occur, as the bones of the skull have hardened and fused. Symptoms of hydrocephalus typically appear earlier in adults and older children for this very reason – since their skulls cannot expand to accommodate extra fluid, intracranial pressure increases much earlier.
In infants, one of the most common signs of hydrocephalus, in addition to an enlarged head, is an inability to look upwards. Infants may also show signs such as vomiting, irritability, sleepiness, and seizures.
In older children and adults, symptoms of hydrocephalus include nausea, vomiting, headaches, blurred vision, problems with balance, and seizures. Children may be developmentally delayed.
Note that hydrocephalus does not usually cause intellectual disability when it is diagnosed and treated early. If the condition is left untreated in an infant, or in cases of rapid and massive onset of fluid accumulation, the brain may sustain damage which may lead to intellectual disability.
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The most commonly used hydrocephalus treatment is the surgical placement of a shunt system that diverts cerebrospinal fluid from the brain to another part of the body. Commonly the fluid is diverted to the peritoneal cavity. The shunt system comprises a plastic tube, catheter, and valve, and is placed so that fluid can drain only one way.
While the shunt system is an effective treatment, there are several possible complications and risks. Shunts can malfunction or fail, or become infected. Any of these situations can lead to rapid onset of symptoms. Over-drainage, which occurs when the shunt drains fluid faster than it is produced, can be equally dangerous.
Finally, there is the simple fact that shunts need replacing. Particularly when a young child is fitted with a shunt, the device will need to be refitted or replaced multiple times during childhood.