What Is Hydrocephalus?

"Water" or, Rather, Cerebrospinal Fluid on the Brain

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Hydrocephalus is the buildup of cerebrospinal fluid (CSF) within the brain's hollow spaces (ventricles). The excessive fluid increases pressure inside the skull, affecting the brain's ability to function normally.

CSF is a clear fluid that bathes and cushions the brain, protecting and providing it with vital nutrients. CSF flows around the spinal cord and through the brain's ventricles before being reabsorbed into the bloodstream.

This article reviews key facts about hydrocephalus, including its types, symptoms, causes, diagnosis, treatment, and outlook.

Healthcare provider looking at brain scans

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Types of Hydrocephalus

Hydrocephalus can occur at any age but is most common in babies and older adults. The two main types are:

  • Noncommunicating (obstructive) hydrocephalus develops when a blockage occurs along one or more of the passages connecting the ventricles. As a result, CSF cannot flow freely among the ventricles.
  • Communicating hydrocephalus occurs when CSF cannot adequately be reabsorbed into the bloodstream. It's called "communicating" because the CSF can still flow normally within the ventricles.

Hydrocephalus is also sometimes categorized as congenital or acquired hydrocephalus. Congenital hydrocephalus is present at birth, whereas acquired hydrocephalus develops after birth.

The following two forms of acquired hydrocephalus can develop in adults:

  • Normal pressure hydrocephalus (NPH) is a communicating hydrocephalus that can strike at any age but is more common in adults 60 or older. It's characterized by widened ventricles but normal CSF pressure.
  • Hydrocephalus ex vacuo is usually seen in older individuals. It develops when the brain tissue surrounding the ventricles shrinks. CSF volume increases within the ventricles to try and fill the extra space.

Hydrocephalus Symptoms

Hydrocephalus symptoms often occur due to increased pressure within the skull (increased intracranial pressure).

In congenital hydrocephalus, symptoms may include:

  • A head that is larger than normal
  • A bulge at the soft spot on top of the head (fontanelle)
  • Eyes that stay looking down
  • Vomiting
  • Problems feeding
  • Sleepiness or unusual fussiness
  • Seizures

In older children and adults, hydrocephalus symptoms include:

  • Headache (usually worse when lying down, coughing, or having a bowel movement)
  • Vision problems (e.g., double vision)
  • Nausea or vomiting
  • Poor balance or coordination
  • Drowsiness
  • Loss of previously acquired skills (e.g., walking)
  • Change in personality or behavior

There are also symptoms specific to the type of hydrocephalus, especially regarding normal pressure hydrocephalus.

The three hallmark symptoms of NPH include:

  • Gait (manner of walking) disturbance: People move slowly with a broad base. They often have trouble picking up their feet, as if they were glued to the ground.
  • Mild dementia: Diminished concentration, short-term memory loss, and apathy (a lack of emotion) may occur.
  • Bladder dysfunction: A strong urge to urinate (urgency), an increased need to urinate (frequency), and in severe cases, loss of bladder control (urinary incontinence) can develop.


Hydrocephalus has many potential causes, depending on the type.

Congenital hydrocephalus can be caused by inherited genetic abnormalities or developmental disorders affecting the brain's CSF flow.

Acquired hydrocephalus in babies is most commonly caused by a brain bleed, often due to prematurity.

Other causes of hydrocephalus in babies include:

Normal pressure hydrocephalus may be caused by a brain bleed or tumor, head trauma, or meningitis. In around half of NPH cases, the cause remains unknown.

Hydrocephalus ex-vacuo is usually caused by a stroke or an injury to the brain. It may also occur in older individuals whose brain shrinks with age or in those with Alzheimer's disease.


The diagnosis of hydrocephalus starts with a detailed medical history and neurological exam. Imaging tests and a spinal tap are also vital diagnostic tools. In some cases, intracranial pressure monitoring may be required.

Imaging Tests

The type of imaging test used to evaluate hydrocephalus depends on the age of the patient:

MRI: Preferred Diagnostic Test for Hydrocephalus

An MRI is often the preferred test for diagnosing hydrocephalus. Using magnetic fields and radio waves, an MRI can help assess CSF flow and reveal whether the ventricles are enlarged.

Spinal Tap

A spinal tap (lumbar puncture) is performed in a healthcare provider's office or a hospital. A thin needle is placed into the person's lower back. The pressure of the CSF is measured, and then up to 50 cubic centimeters (cc) of CSF is removed for analysis.

Spinal taps can also be therapeutic because they often temporarily relieve a person's hydrocephalus symptoms.

Intracranial Pressure Monitoring

In some cases, such as after severe head trauma, intracranial pressure (ICP) monitoring may be used to detect and measure CSF pressure.

ICP monitoring is performed in the hospital by a neurosurgeon (a surgeon who treats nervous system conditions). It requires the placement of a catheter (a thin tube) through the skull into the brain. The catheter measures the CSF pressure.

If the pressure gets too high, the CSF may need to be drained to ensure adequate oxygenation to the brain.


Hydrocephalus is a serious condition that is treated with brain surgery. That said, surgery is not a cure. Instead, it helps relieve symptoms and lower the pressure in the skull.

Ommaya Reservoir

An Ommaya reservoir is a device that's implanted under the skin of the scalp and attached to a catheter that extends into a brain ventricle. This allows CSF to be aspirated from the reservoir rather than by lumbar puncture. Shunt surgery may still required after initially managing hydrocephalus with an Ommaya reservoir.

Shunt Surgery

The most common surgery for hydrocephalus involves placing a shunt (a thin, hollow tube) to reroute the extra CSF away from the brain, lowering the pressure within the skull.

During shunt surgery, a neurosurgeon places the shunt through an opening in the skull into the ventricle. The shunt tubing is then passed under the skin into another area of the body (usually the abdominal cavity), where the CSF drains.

Are Shunts Permanent?

Shunts often remain in place for the duration of a person's life, but that is not always necessary. Additional shunt surgery may be needed if the shunt malfunctions. Children with hydrocephalus who receive a shunt will need multiple surgeries over their lifetime as they grow.

Endoscopic Third Ventriculostomy

Sometimes, a surgery called endoscopic third ventriculostomy is performed.

During this surgery, an endoscope (a long, thin device attached to a tiny camera) and special surgical tools inserted through the endoscope are used to make a small hole in the brain's third ventricle. This hole creates a pathway for the excess CSF to flow in and around the brain.


The outlook for those living with hydrocephalus depends on factors like the hydrocephalus cause, severity, type of symptoms, and promptness of treatment.

As an example, after shunt placement, adults with normal pressure hydrocephalus may notice an improvement in their cognitive (thinking and memory) skills, walking, and bladder problems within days after surgery.

Others may not experience improvement for weeks or months. For some people, one or more symptoms may persist or recur.

Ultimately, there is no way to predict precisely how beneficial surgery will be for anyone. Generally speaking, though, the sooner hydrocephalus is diagnosed and treated, the better the chances for a successful outcome.

Ongoing Care for Children With Hydrocephalus

Children with hydrocephalus may experience delays in reaching milestones like sitting, crawling, standing, walking, and talking. Early rehabilitation therapy can help children improve, adapt, and cope with development or physical impairments.


Hydrocephalus is associated with the abnormal buildup of cerebrospinal fluid within the brain's ventricles. Babies with hydrocephalus may have unusually large heads. Older children and adults typically develop symptoms like headaches and vision problems.

The diagnosis of hydrocephalus involves a brain imaging test, like an ultrasound or MRI. Treatment consists of brain surgery, typically placing a shunt in the brain to drain the excess CSF.

A Word From Verywell

Hydrocephalus is a complex, lifelong condition. The upside is that a good, if not great, recovery is possible with early diagnosis and treatment.

If you or a loved one are being treated for hydrocephalus, consider seeking support from an organization like Hydrocephalus Association. Support resources, whether a helpline, community network, or pen pal program for children, can be a tremendous source of comfort and emotional guidance.

9 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Colleen Doherty, MD
 Colleen Doherty, MD, is a board-certified internist living with multiple sclerosis.