What is Hydrocephalus?

Hydrocephalus got it's name from the greek roots hydro (water) and cephalus (head). It is sometimes called "water on the brain". The "water" in this case however is actually cerebrospinal fluid. Cerebrospinal fluid is a clear fluid produced primarily within the lateral ventricles (fluid filled spaces) of the brain. In each of our four ventricles, small flower-like tufts called choroid plexus produce cerebrospinal fluid at a constant rate. The fluid flows through small channels into the space surrounding the brain and the spinal cord, where it also functions as a cushion. A small amount of CSF is also produced by the spinal cord. Cerebrospinal fluid is normally circulated until it is eventually absorbed in the bloodstream. This creating and absorption is a slow process compared to the circulation of blood in our bodies, but it is ongoing throughout our entire lives. This fluid is important because it supplies nutrients and proteins to the brain and carries waste tissues away from brain cells.

The problem arises when the pressure inside the skull is too great, causing the cerebrospinal fluid to damage the brain by pressing against it with too much force, possibly stretching or compressing the brain tissue. The ventricles of the brain also enlarge, putting further pressure on the brain tissue. This brain damage can manifest itself in many forms, including cerebral palsy.

It is this elevated pressure which causes hydrocephalus. This can occur generally in one of two ways. The first is due to the cerebrospinal fluid not being absorbed at the end of it's circulation. The second way is a result of a blockage or malformation of either the ventricles or pathways, preventing the cerebrospinal fluid from finishing it's circulation and being absorbed. Since the brain continues to create cerebrospinal fluid at a steady rate, pressure gradually builds up in either case. In the case of infants developing hydrocephalus, sometimes their head circumference grows to an abnormal size. This is possible because the bones of the skull are not yet fused, and so the head can stretch and grow in an attempt to bring down the pressure of the cerebrospinal fluid. In adults this swelling is not possible, so there might not be any outward physical sign pointing to hydrocephalus.

People of any age can develop hydrocephalus, due to a head trauma, brain hemorrhage, or possibly as an after effect of a disease. Meningitis infections can create pus and debris which may block the pathways which circulate the cerebrospinal fluid. Cerebrospinal fluid circulation can also be blocked by tumors growing in the brain.

While Adults of any age can develop hydrocephalus, it can also occur in infants, and can be present at birth (possibly cause of cerebral palsy).

One way hydrocephalus can occur in an infant is due to the formation of a cyst (known as a Dandy Walker Cyst). Dandy Walker cysts come about during early embryonic development, while the brain is still forming. The cyst grows in the cerebellum and usually has many blood vessels which connect it to the brain, making removal by surgery nearly impossible. The cause of Dandy Walker cysts are not known. A small number of cases have been attributed to the inheritence of a faulty gene from both parents, known as an autosomal recessive inheritance. The majority of Dandy Walker cases however have no direct cause.

In the past the most common reason for the onset of hydrocephalus was spina bifida, although this is less common that it was 25 years ago, since spina bifida has been greatly reduced.

Symptoms of Hydrocephalus.

As mentioned above, a very visible sign of hydrocephalus in infants can be an abnormally large head. Symptoms in an infant may also include vomiting, sleepiness, irritability, an inability to look upwards, and seizures. The inability to look upwards, also known as "sunset eyes", is due to the increased pressure in the skull pressing on important nerves running from the brain to the muscles responsible for eye movement. If cerebrospinal fluid pressure remains high for too long, permanent damage can be done to the optic nerves, resulting in blindness.

Older children and adults will not exhibit larger than normal head circumference, but symptoms may include headache, nausea, vomiting and, sometimes, blurred vision. There may be problems with balance, delayed development in walking or talking, and poor coordination. If the cerebrospinal fluid pressure remains high for prolonged periods, blindness can still occur to the older child or adult.

If completely untreated hydrocephalus can cause the brain stem to become compressed so much that the heart can stop or breathing may cease. The compression of the cerebrellum, while not as serious as a compressed brain stem, may still lead to swallowing, speaking and breathing problems, or can cause cerebral palsy to develop in fetuses and infants.

As hydrocephalus progresses, people may experience more of these symptoms, or the severity may increase.

There are several behaviorial symptoms of hydrocephalus as well.

Treatment of Hydrocephalus.

Treatment of hydrocephalus typically involves the insertion of a shunt (a hollow flexible tube) into the ventricular system of the brain which then diverts the flow of cerebrospinal fluid into another region of the body (often the abdominal cavity or a chamber of the heart) where it can be absorbed. Surgeons can adjust the pressure valve located within the shunt to maintain a normal pressure for the cerebrospinal fluid within the ventricles. It was common practice to insert only 8 or 12 inches of tubing into the abdominal cavity, requiring surgery later on to lengthen the shunt as the child grew. Now it is commonplace to insert 36 or more inches into the abdominal cavity. As the child grows, length of tubing is pulled out of the abdominal cavity, thereby ending the mandatory lengthening surgery.

Another treatment option is known as a third ventriculostomy. A third ventriculostomy is a procedure which surgically opens a channel between the third ventricle and a small area under the brain. This is meant to reestablish circulation of the cerebrospinal fluid. This surgury was common before the invention of the shunt, but it had high mortality rates and was dropped in favor of inserting shunts to treat hydrocephalus. Recently, doctors have been attempting the surgery again, with the aid of new techniques and technologies, and the treatment looks promissing in certain cases.

Statistics

• In the United States, slightly more than 1 birth per 1000 are affected by hydrocephalus.
• Hydrocephalus is one of the most common "birth defects" and afflicts in excess of 10,000 babies each year.
• More than 50% of hydrocephalus cases are congenital (meaning present at birth, not necessarily handed down by genes).
• There are over 70,000 discharges a year from hospitals in the United States with a diagnosis of hydrocephalus.
• As many as 75% of children with hydrocephalus will have some form of motor disability. This can be in the form of cerebral palsy.
• Over the past 25 years, death rates associated with hydrocephalus have decreased from 54% to 5%.
• Over the past 25 years, mental retardation due to hydrocephalus has decreased from 62% to 30%.
• There are 25,000 shunt operations performed each year in the United States. Of those, at least 18,000 are initial shunt placement procedures.
• 85% of people with shunts have had at least two shunt operations.
• Studies show that the risk of shunt failure in an infant's first year is as high as 30%.