Hydrocephalus

What is hydrocephalus?

Hydrocephalus is a neurological disorder caused by an abnormal buildup of cerebrospinal fluid in the ventricles (cavities) deep within the brain. This excess fluid causes the ventricles 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.

Cerebrospinal fluid (CSF) is the clear, colorless fluid that protects and cushions your brain and spine. Cerebrospinal fluid flows through the ventricles and bathes the brain and spinal cord before being reabsorbed into the bloodstream. The body typically produces enough CSF each day and absorbs the same amount. 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 sucking or feeding
  • Sleepiness
  • Irritability
  • Eyes that are fixed downward ("sun setting") or are not able to turn outward
  • Seizures

 Symptoms in older children and adults may include:

  • Headache
  • Blurred or double vision
  • Nausea or vomiting
  • Problems with balance
  • Slowing or loss of developmental progress like walking or talking
  • Vision problems
  • Decline in school or job performance
  • Poor coordination
  • Loss of bladder control and/or frequent urination
  • Difficulty remaining awake or waking up
  • Sleepiness
  • Irritability
  • Changes in personality or cognition including memory loss

Symptoms in older adults may include:

  • Problems walking, often described as feet feeling "stuck"
  • Progressive mental impairment and dementia
  • General slowing of movements
  • Loss of bladder control and/or frequent urination
  • Poor coordination and balance

Who is more likely to get hydrocephalus?

The number of people who develop hydrocephalus or who are currently living with it is difficult to establish because the condition occurs in children and adults and can develop later in life. Some estimates report one to two of every 1,000 babies are born with hydrocephalus.

Babies may be born with hydrocephalus or develop the condition shortly after delivery. In these cases, hydrocephalus may be caused by:

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

Types of hydrocephalus

Communicating hydrocephalus occurs when the flow of CSF is blocked after it exits the ventricles. This form is called communicating because the CSF can still flow between the ventricles and the passages between them remain open. Reduced flow and absorption of CSF into specialized blood vessels called arachnoid villi can also result in a buildup of CSF in the ventricles. 

Non-communicating hydrocephalus happens when the flow of CSF is blocked along one or more of the narrow passages connecting the ventricles.

Normal Pressure Hydrocephalus (NPH) can be the result of 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. The increase in cerebrospinal fluid in NPH occurs slowly enough that the tissues around the ventricles compensate and the fluid pressure inside the head does not increase. NPH causes problems with walking, bladder control, and difficulties thinking and reasoning. Sometimes NPH can be mistaken for Alzheimer's disease. The symptoms of NPH usually get worse over time if the condition is not treated, although some people may experience temporary improvements.

Hydrocephalus ex-vacuo results from brain damage caused by stroke or injury. In these cases, brain tissues around the ventricles shrink, and the ventricles are bigger because of this. It is not a true hydrocephalus but a “hydrocephalus look-alike” condition.

How is hydrocephalus diagnosed and treated?

Diagnosing hydrocephalus

Hydrocephalus is diagnosed through a clinical neurological exam and by using brain imaging techniques and other tests based on age, symptoms, and known or suspected abnormalities in the brain or spinal cord.

The neurological exam may involve tests to determine:

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

Testing to accurately diagnose hydrocephalus and rule out other conditions may include the following:

  • Ultrasound is often the first test a doctor uses to diagnose infants because it is relatively simple and low risk. When used during routine prenatal exams, ultrasound may also detect hydrocephalus in unborn babies.
  • Magnetic resonance imaging (MRI) 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 used to diagnose adults.
  • Computed tomography (CT) can show doctors if the ventricles are enlarged or if there is an obstruction.
  • Spinal tap (lumbar puncture) allows doctors to estimate CSF pressure and analyze the fluid by 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 the pressure and detect the amount of swelling that may have occurred 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 suggests elevated intracranial pressure, which can be a result of hydrocephalus.

Treating hydrocephalus

Surgery to treat hydrocephalus involves two options:

  1. A shunt (tube) is surgically inserted into the brain and connected to a flexible tube placed under the skin to drain the excess fluid into either the chest cavity or the abdomen so it can be absorbed by the body. 
  2. Endoscopic Third Ventriculostomy (ETV) improves the flow of CSF out of the brain. A tiny hole is made at the bottom of the third ventricle and the CSF is diverted there to relieve pressure. Sometimes this is done in conjunction with choroid plexus cauterization to try and decrease the production of CSF.
    • Choroid plexus cauterization uses electric current to burn the CSF-producing tissue (i.e., the choroid plexus) in the lateral ventricles in the brain, so it produces less CSF. 

Shunt systems generally function well but they can fail to properly drain the CSF due to mechanical failure or infection. When this happens the CSF builds up in the brain again and earlier symptoms may recur. To reduce the buildup of CSF, the clogged shunt system is replaced to restore drainage of CSF.

Shunts require monitoring and regular medical checkups. Multiple surgeries may be needed to repair or replace a shunt throughout a person's lifetime. People should seek medical help immediately if symptoms develop that suggest the shunt system is not working properly. Signs and symptoms of shunt malfunction 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
  • Reoccurrence of hydrocephalus symptoms

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. Treatment by an interdisciplinary team of medical professionals, rehabilitation specialists, and educational experts is critical to a positive outcome. 

Supportive therapies for children may include:

  • Occupational and developmental therapists who can help children learn life skills and develop social behaviors
  • Special education teachers who can help tackle learning disabilities
  • Mental health providers or social workers who can provide emotional support and help families find services

Adults may also require similar support, including social workers, occupational therapists, and specialists in dementia care.

What are the latest updates on hydrocephalus?

The mission of the National Institute of Neurological Disorders and Stroke (NINDS) is to seek fundamental knowledge about the brain and nervous system and to use that knowledge to reduce the burden of neurological disease. NINDS, a component of the National Institutes of Health (NIH), conducts research and clinical studies to find better ways to prevent, treat, and ultimately cure disorders such as hydrocephalus.

NINDS helps support the Hydrocephalus Clinical Research Network (HCRN), a collaboration of pediatric neurosurgery centers working together to improve the lives of children with hydrocephalus. The HCRN centers pool their hydrocephalus patient populations to more rapidly study the potential for improved treatments. The HCRN conducts multiple, simultaneous studies at its centers and maintains a substantial registry of patients and procedures.

Hydrocephalus is a relatively common developmental abnormality, but its underlying mechanisms are not well understood. NINDS supports a wide range of studies that explore the complex mechanisms of normal and abnormal brain development. Research efforts include:

Cellular mechanisms involved with hydrocephalus, such as:

  • Gene mutations associated with congenital hydrocephalus
  • New information about how hydrocephalus affects brain nerve networks and brain function
  • Knowledge on how signals in the amniotic fluid and early CSF instruct neural stem cell behavior during the pivotal early stages of brain development
  • Hydrocephalus risk factors

New imaging methods to help physicians determine whether shunt surgery is likely to improve the cognitive and motor difficulties that often accompany NPH.

Diagnosing shunt malfunctions and reducing shunt infections. Shunts are the standard treatment of hydrocephalus, but shunts can malfunction, and repeated surgery may be needed. The rate of malfunction of shunts in children is estimated to be 40 percent in the first year after placement, and 10 percent per year after that. Current methods for diagnosing shunt malfunctions are often invasive and expensive. To help solve this problem, NINDS-funded researchers are working to develop a safe, cost-effective method for diagnosing shunt malfunctions using ultrasound.

Shunts also carry a high risk of infection. NINDS-funded scientists are attempting to identify and describe all the microorganisms present in CSF when shunts are placed, revised, and infected in order to improve prevention and treatment of CSF shunt infection.

More information about hydrocephalus research supported by NINDS and other NIH Institutes and Centers can be found using NIH RePORTER, a searchable database of current and past research projects supported by NIH and other federal agencies. RePORTER also includes links to publications and resources from these projects.

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Learn About Clinical Trials
Clinical trials are studies that allow us to learn more about disorders and improve care. They can help connect patients with new and upcoming treatment options.

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

Consider participating in a clinical trial so clinicians and scientists can learn more about hydrocephalus. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat, or prevent disease.

All types of volunteers 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.

For information about participating in clinical research visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for people with hydrocephalus at Clinicaltrials.gov, a searchable database of current and past federal and private clinical studies.

Where can I find more information about hydrocephalus?

Information may be available from the following resources: