HYDROCEPHALUS
BY
HEATHER L. MCGEE
BIOLOGY 300
SPRING 2001
TABLE OF CONTENTS
I. INTRODUCTION . . . . . . . . . 1
II. COMPOSITION . . . . . . . . . 1
III. EFFECTS . . . . . . . . . . 3
IV. TREATMENT . . . . . . . . . 5
V. SUMMARY . . . . . . . . . . 7
VI. REFERENCES . . . . . . . . . 9
VII. TABLE . . . . . . . . . . 10
I. INTRODUCTION
Hydrocephalus is from Greek origin meaning “water in the head”. The water is cerebrospinal fluid (CSF), a clear liquid that is produced in the ventricles or cavities inside the brain. CSF passes from one ventricle to the next through narrow pathways until all four ventricles are reached, and then the CSF circulates around the brain’s surface. A little CSF secretes down the spinal cord and absorbed back into the bloodstream. The absorption takes place through specialized veins with a sieve-like surface. CSF is constantly being produced, circulated and absorbed. Hydrocephalus results when CSF is prevented from circulation or reabsorb ion. Hydrocephalus can also occur when too much CSF is produced, but this type is very rare. When hydrocephalus is left untreated, there is a death rate of fifty to sixty percent. Survivors with untreated hydrocephalus have various degrees of physical, neurological and intellectual disabilities. The prognosis for treated hydrocephalus varies with each case, but overall eighty percent will have a fairly normal life span. Although neurological difficulties may persist, approximately one-third will have normal intellectual function (Bayston, 1995A; Yahoo, 2001).
II. COMPOSITION
With hydrocephalus caused from CSF lack of circulation or reabsorb ion, CSF accumulates and causes raised pressure in the brain. This causes ventricles to swell and the brain tissue is stretched and dented. High CSF levels also cause an interference with blood supply to the brain. This also leads to oxygen and glucose deprivation to the brain. This amount of pressure is particularly harmful to young babies and children because lack of fusion in the skull bones. This pressure, caused by hydrocephalus, leads to an increase in head size (Association for Spina Bifidia and Hydrocephalus, 2001A; Bayston, 1995A).
Several conditions can cause hydrocephalus. A genetic disorder can cause the disease, but this is uncommon. With a genetic disorder, other family members will be affected. The most common cause of hydrocephalus in non-genetic. Congenial hydrocephalus is referred to babies that are born with the disease. The actual cause of congenial hydrocephalus is usually impossible to determine. Often, the cause is assumed to be related to the baby’s development at birth. This can be narrowed to the damage of the local blood supply or infection (Bayston, 1995A).
Another non-genetic cause of hydrocephalus is spina difida. At least eighty percent of people with spina difida have some degree of hydrocephalus. In this case, the CSF flow is disturbed due to the abnormal brain structure located at the back portion of the head. This type of hydrocephalus develops during the early stages of pregnancy. Recently fewer babies are born with spina difida, but the hydrocephalus numbers are pointing to premature babies and maternal ill health or smoking as the leading cause. Often head injuries can also disrupt the CSF flow in the brain (Bayston, 1995A).
Acute infections of the membranes surrounding the brain can also lead to hydrocephalus. The infection, referred to as meningitis, causes CSF pathways to become blocked due to debris and pus. Meningitis can occur in previously healthy babies that develop a serious bloodstream infection after birth, but meningitis can also occur in anyone in any age group. Meningitis can be greatly by the HIB vaccine (Bayston, 1995A).
Hydrocephalus can also be caused by the obstruction of cysts in the ventricles and brain tumors. Dandy-Walker cysts block the fourth ventricle of the brain. These cysts in turn create an obstruction of CSF. Brain tumors can also obstruct the flow of CSF by the tumor’s size, and in most cases cause an overall swelling of the brain. In a variety of cases, brain tumors found in adults resulted in the blockage of one of the connecting pathways between ventricles (Bayston, 1995A).
III. EFFECTS
There are several immediate effects due to the interference with the blood supply to the brain. Most of these effects can be returned to normal in the CSF is returned to normal pressure. In most cases, this problem has occurred for a prolonged amount of time before treatment is assessed (Bayston, 1995B).
Throughout the duration of inhibited blood supply very fine blood vessels begin to die in the brain. If prompt action is taken, this process can be successfully reversed. After the very fine blood vessels begin to die, the next stage cannot be reversed. The actual nerve calls in the brain sustain progressive damage. This process eventually leads to the nerve cells destruction (Bayston, 1995B).
Major functions such as thought, learning and co-coordinated skills are associated with the portion of the brain that receives the most damage from hydrocephalus. These major functions begin to deteriorate because that area of the brain is most affected. There are several aspects that must be evaluated in determining the severity of hydrocephalus. The precise effects of hydrocephalus differ among individuals. The effects of the disease are also further complicated by other abnormalities. Preexisting degrees of ability and personality can also determine the extent of damage from hydrocephalus. For example, learning disorders are common among individuals with hydrocephalus, but the extent of the learning disorder varies with each individual (Bayston, 1995B).
Subtle problems of hand co-ordination with what the person sees may reflect the practical implications of hydrocephalus. Often, there is some degree of clumsiness. This clumsiness allows for difficulty performing certain tasks. Also, there may be some major problems in concentration and reasoning. The lack of concentration can be seen directly when learning in the home or education in school. The lack of reasoning may be seen directly when requiring a sympathetic but skilled approach to problem solving. For example, the simple everyday tasks like getting out of bed or brushing teeth must be taught consistently and repetitively. These tasks must be seen as individual actions instead of a complicated series. Again, this learning process reflects the amount of damage to the nerve cells located in the brain. Professional advice is recommended when dealing with the psychological development in children and adolescents with hydrocephalus. Often, changes caused by puberty appear at an earlier age with hydrocephalus individuals. This may cause distressing problems on a mind that is still emotionally very immature (Bayston, 1995B).
The eyes also show an effect of hydrocephalus. The blood supply to the back of the eye places a stress on the eye. This occurs when the CSF pressure is raised. Blindness may occur from permanent damage to the optic nerve. In babies, the “Sunset” eye sign is very common. “Sunset” eye is described when the eyes are fixed in a downward position. This condition is due to the CSF pressure affecting nerves from the brain that controls eye movement (Bayston, 1995B).
High CSF pressure can cause other conditions unrelated to blood supply when left untreated. Heartbeat and breathing are controlled from the brain stem, and high CSF pressure can cause the brain stem to compress leading to the heart and breathing to stop. This problem is very uncommon due to the fact that high CSF pressure is usually detected before this can occur (Bayston, 1995B).
IV. TREATMENT
No specific treatment is needed for some forms of hydrocephalus. Some forms of hydrocephalus are temporary and no long-term treatment is required. Most often, hydrocephalus requires surgical treatment. Drug treatment was used for many years, but this type of treatment gave unpleasant side effects and wasn’t always successful. The surgical treatment involves shunting device inserted into the swollen portions of the brain. Any type of treatment doesn’t cure hydrocephalus, but treatment controls the pressure exerted by CSF (Association for Spina Bifidia and Hydrocephalus, 2001A).
In theory, the treatment of hydrocephalus is relatively simple. A tube should be inserted into the swollen ventricles to drain the excess fluid. This procedure would return the pressure inside the brain to normal. In the past attempts to complete this procedure were unsuccessful due to rejection of the tubing, infection or blockage. During the 1950’s, John Holter developed a device made of silicone rubber called the Holter valve. This device was a great success and become the treatment of choice for hydrocephalus. This success encouraged more surgeons to develop procedures to improve not only shunts, but also the treatment of hydrocephalus in general (Bayston, 1995C).
The Holter valve was the first successful shunt. A shunt is very simple in structure. The shunt acts as a drain to divert the accumulated CSF from the obstructed pathways and returns it to the bloodstream. The shunt contains a system of tubes with a valve to control backflow and the overall rate of drainage. Although, there are several different shunt appearances, most shunts operate in a very similar way. No one shunt is better or worse than another, and the type of shunt chosen is based on several factors: surgeon’s experience with the shunt type, cost and personal preference (Bayston, 1995C).
Ventriculo-atrial (VA Shunt) and ventriculo-peritoneal (VP Shunt) are the two main types of shunts. The VA shunt was first used in the treatment of hydrocephalus. The VA shunt is inserted so that a series of tubes and valves drains the excess CSF from the brain ventricles into the heart. The most popular shunt is the VP shunt. The VP shunt drains the CSF from the brain into the abdominal cavity (Association for Spina Bifidia and Hydrocephalus A, 2001; Bayston, 1995C).
Despite the advances of shunt technology, there is always the reality of complications. The types of complications can be summarized into three categories: under-drainage, over-drainage and infection. Under-drainage occurs when fluid is not removed from the head quickly enough. This most common problem allows hydrocephalus symptoms to return. Under-drainage can occur from blockage in the lower or upper tubes of the shunt tissue. This complication can also occur from the overall shunt breaking or the disconnection of shunt parts. These complications allow for either a sudden or gradual rise in CSF pressure. This sudden rise in CSF pressure can result in unconsciousness and emergency treatment is required. The gradual increase in CSF pressure can lead to severe headaches, vomiting, dizziness and cold. Over-drainage occurs then the shunt allows CSF to drain more quickly than it is produces. Usually, this complication occurs very suddenly shortly after the shunt is inserted. If this occurs very rapidly, delicate blood vessels are torn as the ventricles of the brain collapse due to over-drainage. These symptoms lead to haemorrhage, and the blood may be removed. If over-drainage occurs gradual, the ventricles become silt-like as they collapse. When this occurs, the opposite shunt complication occurs, under-drainage. Often, bacteria cause shunt infections. Bacteria from the skin get into the CSF and often contaminate the shunt at the time of operation. Antibiotics have shown no success at fighting this complication, and other measures are only temporary. Current technological advances have made shunts more resistant to bacterial infection. These new advances have reduced bacterial infections located in shunts by more than eighty percent. When bacterial infection occurs in the VP shunt, redness and swelling occurs over the shunt tubing and occasional fever and abdominal pain is also present. The VA shunt bacterial infection is rare, but when this type of bacterial infection occurs, several symptoms are present. Tiredness, poor appetite, irritability, skin rashes and aches and pains occur when the VA shunt bacterial infection is present (Bayston, 1995C).
V. SUMMARY
Cerebrospinal fluid (CSF) is a clear fluid located inside the ventricles of the brain. The CSF flows over the surface of the brain and down the spinal column to protect the spinal cord and brain, and the fluid is absorbed into the bloodstream. Hydrocephalus occurs when the normal pathways are blocked inhibiting the drainage of the CSF. Pressure is exerted inside the brain because CSF is not drained and more is produced (Association for Spina Bifidia and Hydrocephalus, 2001B).
Hydrocephalus can be treated in various ways, but the surgical technique is the most favored. A pathway is made to drain the excess fluid from the brain. This pathway is called a shunt. This shunt treatment can control the effects of hydrocephalus. The durability of the shunt is designed for a lifetime, but the shunt may need revision or stop working all together. Any problems that arise due to shunts must be treated with emergency attention (Association for Spina Bifidia and Hydrocephalus, 2001B).
The disabilities caused by hydrocephalus vary among individuals. Learning disabilities such as problems with short-term memory, poor concentration and organizational skills are caused from hydrocephalus. Co-ordination problems are also caused from hydrocephalus. Although most hydrocephalus individuals posses learning disabilities, mainstream education with special help fits their special needs. Hydrocephalus individuals may also participate in sports that do not have extreme contact (Table 1)(Association for Spina Bifidia and Hydrocephalus, 2001B).
VI. REFERENCES
1. Association for Spina Bifidia and Hydrocephalus. 2001A. Hydrocephalus. Retrieved January 17, 2001, from the World Wide Web: http://www.asbah.org/index.html
2. Association for Spina Bifidia and Hydrocephalus. 2001B. Information for parents/parents to be about hydrocephalus. Retrieved January 17, 2001, from the World Wide Web: http://www.asbah.org/parenth.html
3. Bayston, Roger. 1995A. Part one – hydrocephalus: what is it and what causes it. Hydrocephalus Network News. Retrieved January 17, 2001, from the World Wide Web: http://www.asbah.org/baystart1.html
4. Bayston, Roger. 1995B. Part two – the effects of hydrocephalus. Hydrocephalus Network News. Retrieved January 17, 2001, from the World Wide Web: http://www.asbah.org/baystart2.html
5. Bayston, Roger. 1995C. Part three – the treatment of hydrocephalus. Hydrocephalus Network News. Retrieved January 17, 2001, from the World Wide Web: http://www.asbah.org/baystart3.html
6. Yahoo. 2001. Hydrocephalus. Retrieved January 17, 2001, from the World Wide Web: http://www.adam.com.
IX. TABLE
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HYDROCEPHALUS
Shunt types Ventriculo-atrial
Ventriculo-peritoneal
Identify shunt infections Twenty-four hours
Treat shunt infections Seven to ten days
IQ response High verbal
Low performance
Extracurricular activities Non-contact only
Special Education Needs None
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TABLE 1. General information concerning the disease hydrocephalus (Bayston, 1995A; Bayston, 1995B; Bayston 1995C).