Hydrocephalus

What is hydrocephalus?

Hydrocephalus is an abnormal buildup of cerebrospinal fluid (CSF) deep within the brain. This excess fluid causes the ventricles (cavities) within the brain to widen, putting harmful pressure on the brain’s tissues. Hydrocephalus may be present at or shortly after birth or may result over time from damage or injury.

CSF protects and cushions the brain and spine. The body typically produces enough CSF each day to flow through the ventricles and bathe the brain and spinal cord before being reabsorbed into the bloodstream. Excess buildup of CSF can keep the brain from functioning properly and cause brain damage or even death.

Symptoms of hydrocephalus can vary significantly from person to person and mostly depend on age.

In infants, signs and symptoms may include:

• A rapid increase in head size
• An unusually large head
• A bulge on the soft spot (fontanel) on the top of the head
• Vomiting
• Problems feeding
• Sleepiness
• Irritability
• Eyes that are fixed downward (“sun setting”) or are not able to turn outward
• Seizures 
• Slowing or loss of developmental progress like walking or talking

Older children and adults may experience:

Types of hydrocephalus     

Hydrocephalus may happen when something blocks the flow of CSF after it exits the ventricles. In some cases, CSF can still flow between the ventricles and the passages between them remain open. Reduced flow and absorption of CSF into specialized structures called arachnoid villi can also result in a buildup of CSF in the ventricles. 

Hydrocephalus also may happen when something blocks the flow of CSF along one or more of the narrow passages connecting the ventricles.

Types of hydrocephalus include:

• Normal pressure hydrocephalus (NPH): causes problems with walking, bladder control, and difficulties thinking and reasoning. The increase in cerebrospinal fluid in NPH happens slowly enough that the tissues around the ventricles compensate and the fluid pressure inside the head does not increase. NPH can happen in people of any age, but is most common in older adults. The symptoms of NPH usually get worse over time if it  is not treated. NPH can result from bleeding in the brain’s CSF (also known as subarachnoid or intraventricular hemorrhage), head trauma, infection, tumor, or a complication of surgery. However, many people develop NPH when none of these factors are present. It can be hard to diagnose NPH, with many people not receiving proper treatment. Early diagnosis and treatment improve the chance of a good recovery. Without treatment, NPH symptoms may worsen and cause death.
• Hydrocephalus ex-vacuo: results from brain damage caused by stroke or injury. When this happens, brain tissue around the ventricles shrinks, and the ventricles grow bigger because of this. It is not a true hydrocephalus but a hydrocephalus “look-alike” condition.

Who is more likely to get hydrocephalus?

Hydrocephalus can happen in children and adults. 

Babies may be born with hydrocephalus (called congenital hydrocephalus) or develop the condition shortly after birth. In these cases, some causes of hydrocephalus include:

• Inherited genetic abnormalities that block the flow of CSF
• Developmental disorders such as those associated with birth disorders in the brain or spinal cord
• Complications of premature birth such as bleeding within the ventricles
• Infection during pregnancy such as rubella that can cause inflammation in fetal brain tissue

Certain factors can increase the risk of developing hydrocephalus at any age, including:

• Brain or spinal cord tumors
• Infections of the central nervous system such as bacterial meningitis
• Injury or stroke that causes bleeding in the brain

How is hydrocephalus diagnosed and treated?

Diagnosing hydrocephalus

To diagnose hydrocephalus, a doctor will perform a neurological exam and order brain imaging and other tests based on age, symptoms, and known or suspected abnormalities in the brain or spinal cord.

The neurological exam may involve tests of:

• Muscle strength and reflexes
• Coordination and balance
• Vision, eye movement, and hearing
• Mental functioning and mood

Brain imaging and other tests that can help accurately diagnose hydrocephalus and rule out other conditions. Brain imaging for hydrocephalus may include: 

• Ultrasound: often the first test to diagnose infants because it is relatively simple and low risk. Ultrasound can detect hydrocephalus in a fetus.
• MRI (magnetic resonance imaging): can determine if the ventricles are enlarged, assess the CSF flow, and provide information about the brain tissue surrounding the ventricles. MRI is usually the initial test for diagnosing children and adults.
• CT (computed tomography): can show doctors if the ventricles are enlarged or if there is something blocking them. Doctors may use CT in an emergency situation.
• Spinal tap (lumbar puncture): allows doctors to estimate CSF pressure and analyze the fluid. It involves inserting a needle in the lower back and removing and testing some of the fluid. 
• Intracranial pressure monitoring: uses a small pressure monitor inserted into the brain or ventricles to measure pressure and detect the amount of swelling in the brain. If the pressure is too high, a doctor may drain the CSF to maintain the flow of oxygenated blood to the brain.
• Fundoscopic examination: uses a special device to view the optic nerve at the back of the eye. It can show evidence of swelling that indicates elevated pressure in the skull, which may suggest hydrocephalus.

Treating hydrocephalus

The most common treatment for hydrocephalus is surgery. There are two primary options to treat hydrocephalus with surgery:

1. A doctor inserts a shunt (tube) into the brain. They connect the shunt to another tube under the skin to drain the excess fluid into either the chest cavity or the abdomen so the body can absorb it. 
2. Endoscopic Third Ventriculostomy (ETV) improves the flow of CSF out of the brain. A doctor makes a tiny hole at the bottom of the third ventricle, which sends CSF there to relieve pressure. Sometimes a doctor will do this at the same time as choroid plexus cauterization to try and decrease the production of CSF. Choroid plexus cauterization uses electric current to burn the CSF-producing tissue (e.g., the choroid plexus) in the lateral ventricles in the brain, so the brain produces less CSF. 

Shunts require monitoring and regular medical checkups. Shunts generally work well, although they can stop working or lead to infection. When this happens, the CSF builds up in the brain again. To reduce the buildup of CSF, a doctor should replace the clogged shunt system.

A person may need multiple surgeries to repair or replace a shunt throughout their lifetime. Regular follow-up care by a physician is important to identify subtle changes that might point to problems with the shunt. People should seek medical help immediately if symptoms develop that suggest the shunt system is not working properly. Signs and symptoms of a shunt not working may include:

• Headache
• Double vision or sensitivity to light
• Nausea or vomiting
• Soreness of the neck or shoulder muscles
• Seizures
• Redness or tenderness along the shunt tract
• Low-grade fever
• Sleepiness or exhaustion
• Hydrocephalus symptoms coming back

While the success of treatment with shunts varies from person to person, some people recover almost completely after treatment and have a good quality of life. 

Many people diagnosed with hydrocephalus benefit from rehabilitation therapies and educational interventions in addition to surgery. Treatment by an interdisciplinary team of medical professionals, rehabilitation specialists, and educational experts is critical to a positive outcome. 

What are the latest updates on hydrocephalus?

NINDS, a component of the National Institutes of Health (NIH), is the leading federal funder of research on the brain and nervous system, including research on hydrocephalus. NINDS supports a wide range of studies that explore the complex mechanisms of normal and abnormal brain development, with the goal of finding better ways to prevent, treat, and ultimately cure disorders such as hydrocephalus.

NINDS supports the Hydrocephalus Clinical Research Network (HCRN), a collaboration of pediatric neurosurgery centers working together to improve the lives of children with hydrocephalus. HCRN centers pool their patient populations to more rapidly identify options for improved diagnosis, treatment, and outcomes in people with hydrocephalus. HCRN conducts multiple, simultaneous studies at its centers and maintains a patient registry. HCRN researchers are comparing an endoscopic procedure to standard shunt treatment to learn which will provide a better long-term cognitive outcome in infants.

Scientists supported by NINDS are studying the genetic changes associated with congenital hydrocephalus to gain a better understanding of the disorder and improve outcomes. 

In another NINDS-funded study, researchers are learning whether electrostimulation of neck muscles decreases intracranial pressure and increases the flow of CSF. Information gained from this research may lead to new methods of treatment for hydrocephalus.

NINDS-supported researchers continue to study shunts, the standard treatment for hydrocephalus. In one study, scientists want to gain a better understanding of what causes shunt obstruction, malfunction, and failure. Information from these studies may lead to improved treatment of the disorder. Other researchers funded by NINDS also are conducting studies to improve prevention and treatment of infections caused by shunts. Other scientists are creating a novel shunt which will allow doctors to divert the flow of CSF in a minimally invasive way, limit the need for shunt revisions, and reduce complications. Another NINDS-supported research project focuses on developing a smart shunt system, which will monitor intracranial pressure and appropriately drain excess CSF.

How can I or a loved one help involve care for people with hydrocephalus?

Clinical trials increase our understanding of hydrocephalus with the goal of improving how doctors treat it. Consider participating in a clinical trial so clinicians and scientists can learn more about hydrocephalus and related disorders. Clinical research with human participants helps researchers learn more about a disorder and perhaps find better ways to detect, treat, or prevent disease safely.

All types of study participants are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races, and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.