The term hydrocephalus is derived from the Greek words "hydro" meaning water and "cephalus" meaning head. As the name implies, it is a condition marked by excessive accumulation of fluid in the brain. Although hydrocephalus was once known as "water on the brain," the "water" is actually cerebrospinal fluid (CSF) – a clear fluid that surrounds the brain and spinal cord. The excessive accumulation of CSF results in an abnormal widening of spaces in the brain called ventricles. This widening creates potentially harmful pressure on the tissues of the brain.
The ventricular system is made up of four ventricles connected by narrow passages. Normally, CSF flows through the ventricles, exits into cisterns (closed spaces that serve as reservoirs) at the base of the brain, bathes the surfaces of the brain and spinal cord, and then reabsorbs into the bloodstream.
The balance between production and absorption of CSF is critically important. Because CSF is made continuously, medical conditions that block its normal flow or absorption will result in an over-accumulation of CSF. The resulting pressure of the fluid against brain tissue causes hydrocephalus.
Hydrocephalus may be congenital or acquired. Congenital hydrocephalus is present at birth and may be caused by either events or influences that occur during fetal development, or genetic abnormalities. Acquired hydrocephalus develops at the time of birth or at some point afterward. This type of hydrocephalus can affect individuals of all ages and may be caused by injury or disease.
Two other forms of hydrocephalus that primarily affect adults are hydrocephalus ex-vacuo and normal pressure hydrocephalus. Hydrocephalus ex-vacuo occurs when stroke or traumatic injury causes damage to the brain. In these cases, brain tissue may actually shrink. Normal pressure hydrocephalus can happen to people at any age, but it is most common among the elderly. It may result from a subarachnoid hemorrhage, head trauma, infection, tumor or complications of surgery. However, many people develop normal pressure hydrocephalus even when none of these factors are present for reasons that are unknown.
Symptoms of hydrocephalus vary with age, disease progression and individual differences in tolerance to the condition. For example, an infant's ability to compensate for increased CSF pressure and enlargement of the ventricles differs from an adult's. The infant skull can expand to accommodate the buildup of CSF because the sutures (the fibrous joints that connect the bones of the skull) have not yet closed.
- Rapid increase in head circumference or an unusually large head size
- Downward deviation of the eyes
Older Children and Adults
- Headache followed by vomiting
- Papilledema (swelling of part of the optic nerve)
- Blurred or double vision
- Downward deviation of the eyes
- Problems with balance, poor coordination and walking
- Urinary incontinence
- Slowing or loss of developmental progress
- Lethargy, drowsiness, irritability or other changes in personality
- Memory loss
Normal Pressure Hydrocephalus
- Problems with walking
- Impaired bladder control leading to urinary frequency or incontinence
- Progressive mental impairment
- A general slowing of movements
The symptoms above are the most typical ways in which progressive hydrocephalus manifests itself, but symptoms may vary significantly from one person to the next.
Hydrocephalus is diagnosed through clinical neurological evaluation and by using cranial imaging techniques such as ultrasonography, CT, MRI or pressure-monitoring techniques. Your doctor will select the appropriate diagnostic tool based on age, clinical presentation and the presence of known or suspected abnormalities of the brain or spinal cord.
Hydrocephalus is most often treated by surgically inserting a shunt system, which diverts the flow of CSF from the central nervous system to another area of the body where it can be absorbed as part of the normal circulatory process.
A shunt is a flexible and sturdy plastic tube. A shunt system consists of the shunt, a catheter and a valve. One end of the catheter is placed within a ventricle inside the brain or in the cerebrospinal fluid outside the spinal cord. The other end of the catheter is commonly placed within the abdominal cavity, but may also be placed at other sites in the body such as a chamber of the heart or areas around the lung where the CSF can drain and be absorbed. A valve located along the catheter maintains one-way flow and regulates the rate of CSF flow.
Some people can be treated with an alternative procedure called third ventriculostomy. In this procedure, a neuroendoscope – a small camera that uses fiber optic technology to visualize small and difficult to reach surgical areas – allows your doctor to view the ventricular surface. Once the scope is guided into position, a small tool makes a tiny hole in the floor of the third ventricle, which allows the CSF to bypass the obstruction and flow toward the site of resorption around the surface of the brain.
Source: National Institute of Neurological Disorders and Stroke