Hydrocephalus also known as “water on the brain” is an accumulation of cerebrospinal fluid in the ventricles (certain spaces in the brain), leading to their enlargement and swelling. It most often occurs in children either at birth or after birth but may also occur in adults and the elderly.
Cerebrospinal fluid (CSF) is a clear body fluid that occupies the ventricles in the brain, the space between the skull and the brain and the space around the spinal cord. Everyone produces spinal fluid inside their brains every minute of their lives.The fluid is similar to the liquid portion of blood and contains various salts and products such as sodium and glucose. The fluid is primarily produced in connected chambers within the brain known as ventricles. The fluid circulates through the ventricles and around the brain and spinal cord. Eventually it is reabsorbed over the surface of the brain into large veins which carry the fluid back to the heart. This orderly cycle of spinal fluid production, flow and absorption maintains a protective enviroment to the nervous system. In addition, there is no loss of fluids or salts contained in the spinal fluid. The total amount of cerebrospinal fluid is about 150 ml, and about 500 ml is produced every day, which indicates its very active circulation.
Hydrocephalus is that state in which something has occurred to prevent this orderly procession of events. When the circulation or absorption of this fluid is blocked, or excessive fluid is produced, the volume of fluid in the brain becomes higher than normal. The accumulation of fluid puts pressure on the brain forcing it against the skull and damaging or destroying the tissues. The relative build up of spinal fluid in the brain of infants can lead to permanent injury or even death if not treated. In infants, fluid accumulates in the brain causing the fontanelle (soft spot) to bulge and the head to expand. The infant’s head expands because the bones that make up the skull have not yet fused (joined) together. At about age 5 years the bones of the skull usually fuse therefore at this age the head no longer expands.
It is very important to realize that hydrocephalus is the result of some event on the nervous system and that a child’s prognosis is not so much based on the hydrocephalus as the cause of the hydrocephalus.
What Are Some Of The Causes Of Hydrocephlus?
While many cases have no clear cause, the following have been associated with the development of hydrocephalus: bleeding, infection, trauma, tumors, vascular problems, congenital defects and structural problems. Some occur during pregnancy and others after birth. In addition, a small number can be transmitted genetically.
In small children, hydrocephalus may be associated with infections acquired before birth, injury occuring during the birth process, congenital defects, tumors of the brain, infections that affect the brain and injury before or after birth (including bleeding into the brain due to injury). Myelomeningocele, a congenital disorder involving the incomplete closure of the spinal column is strongly associated with hydrocephalus.
In older chuildren, hydrocephalus can be caused by tumors of the brain or spinal cord, infections of the brain, bleeding anywhere in the brain or injury.
Symptoms And Signs Of Hydrocephalus
The early symptoms of hydrocephalus include enlarged head, bulging fontanelles (soft spots of the head) with or without enlagement of the head size, separated sutures (separation of the various points where the skull bones join) and vomiting. Later on the child becomes irritable and has poor temper control. There is spasm of the muscles and much later there is decreased mental function, delayed development, slow or restricted movement, difficulty feeding, excessive sleepiness and urinary incontinence (loss of bladder control). There may be brief, shrill, high pitched cry and slow groth in children below five years of age.
In older infants and children the symptoms vary depending on the amount of damage caused by pressure in the brain. The symptoms may include headache, vomiting, vision changes, crossed eyes, uncontrolled eye movements, loss of coordination, poor gait (walking pattern), mental cnfusion or psychosis and changes in facial and brow contours, eye spacing or protrusion.
When a physician taps fingertips on the skull, there may be abnormal sounds associated with thinning and separation of skull bones. The veins of the skull veins may appear dilated. The circumference of the head may be large or only part of the head may be enlarged, most commonly the frontal area. The eyes may be depressed with a “setting sun” sign where the white portion of the eye is visible above the colored portion of the eyes. Neurological examination may show specific deficits and reflexes may be abnormal for the age of the child.
If a diagnosis of hydrocephalus has been made there are rarely options other than surgery for treatment. The goal of treatment is to reduce or prevent brain damage by improving the flow of cerebrospinal fluid (CSF). Surgery is the main treatment. The obstruction may be surgically removed if possible. More often than not, the blockage cannot be removed and the fluid needs to bypass the normal circulation. If the the obstruction cannot be removed, a shunt may be placed within the brain to allow CSF flow to bypass the obstructed area. A shunt is an insert plastic tube less than an eigth of an inch thick that allows fluid to flow through it in one direction. There is usually a valve system that regulates the flow as well as a reservoir or “bubble”which can be felt through the skin. This reservoir allows for sampling of the spinal fluid with the use of a tiny needle if indicated to test for function of the shunt or infection. Shunting CSF to an area outside the brain such as the right atrium of the heart or the abdominal cavity is an alternative to shunting within the brain. Removing or cauterization (destroying by burning) the parts of the brain that produce CSF may reduce CSF production. There are many different shunts systems on the market. Like all foreign bodies, the shunts can malfunction or become infected which will lead to the replacement of the shunt system.
In addition to these operations, certain types of hydrocephalus can be treated by making a tiny hole internally in the ventricle to reestablish normal flow. This operation is becoming more popular due to better surgcal instruments and imaging techniques now available. However shunting from the ventricles of the brain to the right atrium of the heart and the abdominal cavity is still the technique used all over the world.
Prognosis Or Expectations
If hydrocephalus is not treated, the death rate is high (50-60%). Those who do survive have varying degrees of intellectual, physical and neurological disabilities. The outlook for treated hydrocephalus varies depending on the cause. 80% of children who survive for the first year will have a fairly normal life span. Approximately one third will have normal intellectual function but neurologic difficulties may persist.