From the Greek words “hydro” (water) and “cephalus” (head), hydrocephalus is often referred to as ‘water on the brain’.
Rather than water, however, it is the accumulation of cerebrospinal fluid (CSF) that characterizes hydrocephalus. Hydrocephalus is the most common congenital defect of the brain and spine with 1 in 500 infants born with this condition. Although it can occur in adults, hydrocephalus is more common in children, especially infants, and causes potential damage to the brain.
At about 6 weeks in utero, the fetus beings to produce cerebrospinal fluid (CSF), a clear liquid surrounding the brain and spinal cord. Normally, this fluid bathes the ventricular system of the brain—(the brain includes four ventricles (cavities) connected by narrow pathways)—and is then absorbed into the bloodstream. Hydrocephalus is usually caused by either an obstruction or overproduction of CSF leading to its accumulation and an increased intracranial pressure.
The root causes of hydrocephalus are not completely clear. According to the National Institutes of Health (NIH), there are over 180 possible causes of hydrocephalus. While it may result from genetic inheritance or developmental disorders such as those associated with neural tube defects including spina bifida and encephalocele, other possible causes include complications of premature birth, diseases such as meningitis, tumors, traumatic head injury, obesity or subarachnoid hemorrhage causing a blockage of fluid.
While there is no cure for hydrocephalus, ANA is committed to the most comprehensive care for those who come to us from among the 1 million Americans who suffer from this disease.
Read our guide to Hydrocephalus and Shunts: Frequently Asked Questions for more information.
Types of Hydrocephalus
There are two main classifications for hydrocephalus:
- Communicating (or non-obstructive)
- Non-communicating (or obstructive)
Both communicating and non-communicating hydrocephali can be subdivided into congenital (present at birth) and acquired (occurs following birth).
Communicating hydrocephalus can also be subdivided into normal pressure hydrocephalus (NPH) and hydrocephalus ex-vacuo.
Also known as non-obstructive hydrocephalus, communicating hydrocephalus occurs when the flow of cerebrospinal fluid (CSF) is blocked after it exits the ventricles. This form is called communicating because the CSF can still flow between the ventricles, which remain open.
Normal Pressure Hydrocephalus (NPH)
This type only affects people ages 50 years or older. It may develop after a stroke or injury. As opposed to other types of hydrocephalus, NPH develops slowly due to the gradual blocking of CSF drainage, which subsequently causes slow fluid buildup over time. The enlarged ventricles then press on the brain and cause symptoms. These include dementia-like signs similar to Alzheimer’s disease, and walking difficulties that resemble Parkinson’s disease. That’s why the diagnosis is often problematic. The good news, however, is that unlike those conditions, NPH can be resolved.
In most cases, the cause of NPH is undetermined. However, NPH can occur due to bleeding in the brain following a head injury, stroke, brain tumor, meningitis (an infection of the tissue surrounding the brain), or even following brain surgery.
Since diagnosis is complicated by the fact that many people assume the symptoms of NPH (difficulty walking/gait disturbances, cognitive challenges/mild dementia, urinary urgency or incontinence) are related to aging, it is important to recognize that those symptoms may be part of NPH, which is a treatable condition.
Hydrocephalus ex-vacuo occurs from brain damage caused by stroke or injury. In this condition, there may be an actual shrinkage of brain substance. Although there is more cerebrospinal fluid (CSF) than usual, and the ventricles are enlarged, the CSF pressure may or may not be elevated in hydrocephalus ex-vacuo.
This dilation of the cerebral ventricles, which is due to loss of brain tissue, is a common result of brain diseases such as luekoystrophies (a group of rare genetic disorders that affect the central nervous system), multiple sclerosis, multiple strokes, Alzheimer’s disease, Huntington’s disease and other related diseases.
Non-communicating hydrocephalus — also called obstructive hydrocephalus — occurs when the flow of cerebrospinal fluid (CSF) is blocked along one or more of the narrow passages connecting the ventricles.
Causes and Symptoms of Hydrocephalus
Whether communicating or non-communicating, hydrocephalus can be subdivided into two different causal categories:
Affecting one out of every 1,000 newborns, congenital hydrocephalus is the type that is present at birth. Congenital hydrocephalus is a buildup of excess cerebrospinal fluid (CSF). The extra fluid can increase pressure in the baby’s brain, which then causes brain damage and physical as well as mental problems. Discovering the condition early and treating it quickly can help limit any long-term problems. But long-term effects greatly depend on the cause of the fluid buildup, how bad it gets, and how the baby responds to treatment. Early treatment (before age 4 months) is important to help limit or prevent brain damage. However, congenital hydrocephalus is now often diagnosed before birth through a routine ultrasound. Treatment focuses on reducing the amount of fluid in the brain to relieve pressure.
Congenital hydrocephalus is caused by a complex interaction of genetic and environmental factors during fetal development. One of the most common causes of congenital hydrocephalus is “aqueductal stenosis” (a narrowing of the aqueduct of Sylvius, a cerebral aqueduct). Another common cause of hydrocephalus is a neural tube defect (NTD).
Other Causes of Congenital Hydrocephalus Include:
- Birth defect (such as spina bifida)
- Genetic defect
- Mother’s infections during pregnancy (such as rubella, mumps, toxoplasmosis or syphilis)
Medical Problems Associated with Congenital Hydrocephalus May Include:
- Chiari malformations, an abnormality at the base of the brain where the spinal column joins the skull
- Craniosynostosis, when the bones in the skull fuse together before the brain has stopped growing
- Dandy-Walker syndrome, when the fourth ventricle is enlarged because of partial or complete closure of its outlets
- Hydranencephaly, a rare condition in which the brain’s cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid
- Vein of Galen aneurysmal malformations, a tangled mass of dilated vessels supplied by an enlarged artery
Symptoms of Congenital Hydrocephalus Include:
- Abnormal head enlargement
- Downward deviation of eyes
- Headache, irritability, nausea, sleepiness, vomiting
- Prominent scalp veins
- Skull bones may feel separated
- Tense, bulging fontanel
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. The following conditions may cause CSF obstruction and subsequently acquired hydrocephalus:
- Bleeding (hemorrhage)
- Brain trauma (i.e., result of injury)
- Brain tumor
- Cyst (i.e., a fluid-filled sac)
- Infection (e.g., cerebral abscess, bacterial meningitis)
Premature births may be a risk factor for hydrocephalus. Hemorrhaging, traumatic brain injury, and infection are seen in some premature births.
Symptoms of Acquired Hydrocephalus Include:
- Chronic headaches
- Cognitive challenges or complaints
- Difficulty walking/gait disturbances
- Urinary urgency or incontinence
Pseudotumor cerebri (PTC) is caused by high pressure in the fluid surrounding the brain. Pseudotumor cerebri means “false brain tumor” because it mimics a tumor or hydrocephalus. The difference between PTC and hydrocephalus is that PTC fluid is encased in the extracellular space (located around each brain cell) rather than in the ventricles. In essence, then, the ventricles are compressed with PTC and expanded in the case of hydrocephalus. PTC is often associated with overweight adolescents or sudden weight gain (such as in pregnancy). It is sometimes treated with shunting.
Hydrocephalus is diagnosed through a neurological evaluation and by using cranial imaging techniques.
The following imaging techniques may be used to evaluate the possibility of hydrocephalus:
- Computed tomography (CT) scanning used to assess the size of cranial ventricles and other structures
- Magnetic resonance imaging (MRI) used to assess the size of cranial ventricles and other structures
- MRI cine – a special MRI technique that estimates the flow of CSF from one ventricle to the next
- Ultrasonography to assess for hemorrhage or progression of infant hydrocephalus
This surgical treatment is the most common and successful treatment option for those with hydrocephalus. Shunting, which began in the 1950’s, entails the placement of a tube (shunt) in one of the brain’s ventricles or into the space of fluid in the spine. In order for the spinal fluid to be safely absorbed, the shunt extends to the peritoneal cavity (the area which houses the organs in the belly), the chest cavity, or the heart.
Most patients undergo shunt placements, including the following types. The choice of shunt depends on the type and blockage location that results in the hydrocephalus.
Ventriculo-peritoneal (VP) shunt – (most common) Shifts fluid from the brain into the peritoneal cavity (a fluid-filled gap between the walls of the abdomen and the organs in the abdomen)
Ventriculo-pleural (VPL) shunt– Shifts fluid from the brain into the pleural cavity (space between the two pleura of the lungs)
Ventriculo-atrial (VA) shunt or “vascular shunt”– Shifts fluid from the brain to the right atrium of the heart
Although a shunt works well and saves many lives, at ANA, we recognize that complications may occur with its use. These include infection, malfunction, or shunt failure. A shunt may also disconnect, or become outgrown. Our neurosurgeons are fully equipped to help avoid and rectify any shunt problems.
Endoscopic Third Ventriculostomy (ETV)
The neurosurgeons at ANA are adept at this minimally invasive procedure, relevant for patients for whom the condition follows certain criteria. ETV employs a tiny camera (neuroendoscope) and tiny surgical instruments to make an opening in the floor of the brain’s third ventricle, traditionally a difficult area to reach via surgery. This fiber optic technology allows the neurosurgeon to view the surface of the ventricle. Trapped fluid can drain through its normal pathway. When this procedure is successful, neither a shunt nor further treatment is required.
Hydrocephalus Recovery and Rehabilitation
Our Vigilance With Patients is Ongoing.
We educate our patients to become vigilant for any signs of malfunction. Statistics show that an estimated 50% of shunts fail within two years, and 20-50% of ETVs close up within five years.4 Infection may be less common, but does occur. In the case of any problem or malfunction, the sooner care is sought, the better the chance of a successful outcome.
Prompt and effective treatment of hydrocephalus, on which we pride ourselves at ANA, is the determining factor in long-term prognosis. As we explain to those with hydrocephalus and their families, this condition can obviously affect physical, as well as cognitive development. Our goal at ANA is to utilize our team approach for patients to benefit from educational and rehabilitation services that supplement our treatment. Our compassionate and conscientious staff ensures that we guide and support patients and their families through the entire process.
- Kast J, Duong D, Nowzari F, Chadduck WM, Schiff SJ. Time-related patterns of ventricular shunt failure. Childs Nerv Syst. 1994;10(8):524-528.