Hydrocephalus is the buildup of cerebrospinal fluid in the brain. Most patients who have hydrocephalus need shunt placement surgery. The shunt reroutes excess fluid to an area in the body where it can be safely reabsorbed.

Watch Guy McKhann, MD and Co-Chief of Neurosurgery's Functional Division explain hydrocephalus:

Columbia Neurosurgery Co-Chief Functional Division, Guy McKhann explains adult hydrocephalus

Within the skull is a network of four ventricles connected by narrow passageways. Through this network, called the ventricular system, a clear fluid called cerebrospinal fluid (CSF) flows to provide support and nourishment to the brain.

CSF is produced by the choroid plexus and then continuously cycles through the ventricular system, and around the brain and spinal cord, to deliver nutrients and pick up waste. Then the CSF flows to small cavities in the skull where it can be absorbed by the bloodstream.

When the cycling process is disrupted, fluid builds up in the brain. Because the skull is rigid and cannot accommodate the buildup of fluid, intracranial pressure rises; this is hydrocephalus. Left untreated, hydrocephalus can damage brain tissue and be life-threatening.

Various problems may bring about hydrocephalus. Physicians classify each instance according to what causes it to arise, using one or more of the following terms:

  • Communicating hydrocephalus: CSF flows unobstructed through the ventricular system but is not properly absorbed into the bloodstream.
  • Noncommunicating hydrocephalus: The flow of CSF through the ventricular system is obstructed, often by a brain cyst or brain tumor.
  • Compensated hydrocephalus: The ventricles gradually expand to accommodate an increase in the volume of CSF, and then they stop expanding as intracranial pressure becomes normalized. (Usually diagnosed incidentally during adulthood and asymptomatic.)

Hydrocephalus ex-vacuo: usually occurs during adulthood; it is the result of a condition or disease that causes a loss of brain tissue and therefore an increase in ventricle size. Possible causes include traumatic brain injury, Alzheimer disease, or stroke.

Physicians further distinguish among cases of hydrocephalus on the basis of when they develop:

  • Congenital hydrocephalus is present at birth as a result either of genetic abnormalities or events during fetal development.

Acquired hydrocephalus results from another disease or condition, such as head trauma, brain tumor or brain cyst.


Symptoms of hydrocephalus depend on an individual’s age and the type of hydrocephalus.

Because an infant’s head still has sutures, the skull can expand slightly in response to the buildup of fluid. Therefore, macrocephaly is a common sign of hydrocephalus among infants and young children.

Additional common symptoms for infants include:

  • Vomiting
  • Poor feeding
  • Unusual sleepiness
  • Irritability
  • Eye gaze pointed downward
  • Progressive weakness and spasticity

Children and adults may experience:

  • Vomiting and nausea
  • Headache
  • Lethargy
  • Visual disturbances, such as diplopia or blurred vision
  • Poor balance
  • Incoordination
  • Abnormal gait
  • Memory loss
  • Cognitive deterioration
  • Changes in personality


Usually a neurological examination is performed to identify any changes in brain function and mental status. This exam consists of evaluating motor function, eye movements, swallowing, hearing, sense of smell, sensation, balance, and coordination.

If a neurological condition is suspected, imaging tests may be ordered to visualize the brain and discover whether the ventricles have expanded, which would indicate a buildup of cerebrospinal fluid (CSF). These tests can also identify brain abnormalities, such as a brain tumor, brain cyst, or malformation, if present. Different imaging studies are most appropriate for patients of certain ages:

  • Ultrasonography is used for infants.
  • Plain X-ray is used for infants or children.
  • Computed tomography (CT) scan can be used for children and adults.
  • Magnetic resonance imaging (MRI) is the method more frequently chosen for children and adults; it can show greater detail and distinguish between more conditions than CT scan.

Risk Factors

Hydrocephalus occurs when the delicate balance of cerebrospinal fluid (CSF) cycling is disrupted. The balance is disrupted when CSF is overproduced, not properly absorbed or blocked by an obstruction such as a brain tumor. Hydrocephalus is usually the result of a disease or condition, including:

  • Brain tumor or cyst
  • Congenital malformation, such as Chiari malformation and Dandy-Walker syndrome
  • Head trauma, including intracerebral hemorrhage and intracranial hematoma
  • Central nervous system infection, such as meningitis
  • Aqueductal stenosis

Hydrocephalus can occur at any age.


The Columbia Adult Hydrocephalus multidisciplinary team is one of the most experienced and knowledgeable in the world, evaluating and treating hundreds of patients annually. Our neurosurgeons use the latest surgical techniques to treat hydrocephalus, resulting in the best possible outcomes.

Often hydrocephalus is a secondary condition, and therefore once the primary condition or disease is treated, hydrocephalus goes away too. For instance, brain tumors can obstruct the flow of cerebrospinal fluid (CSF), causing hydrocephalus. Once the brain tumor is surgically removed, CSF can flow normally and hydrocephalus goes away.

However, if hydrocephalus does not resolve after a primary condition or disease is treated, surgical treatment for the hydrocephalus itself is typically required. Most often, patients undergo ventricular shunt surgery. Some patients may be candidates for endoscopic third ventriculostomy or even endoscopic third ventriculostomy with choroid plexus cauterization. 

Ventricular shunt surgery

If a patient’s symptoms improve with spinal fluid drainage, shunt surgery, which is usually brief and safe, is recommended. The goal of placing a shunt is to divert CSF into a region of the body where it can be absorbed, such as the peritoneal cavity or a vein just above the heart. The shunt is a soft tube that is just over 2 mm in diameter, and the synthetic material from which it is made is generally very well tolerated by the human body. The entire shunt is implanted either within the skull or under the skin; no components of the shunt are visible outside of the body.

Between the shunt catheter in the brain and the catheter that goes to the abdomen or bloodstream, there is a one-way valve that regulates CSF flow through the shunt. Regulating CSF flow is essential because if there is too much flow, the ventricles will collapse and bleeding can occur. If there is too little flow, the patient’s symptoms will not improve.

All shunts that our neurosurgeons implant contain a magnetically programmable valve. This allows us to fine-tune the shunt function over time to maximize patient safety and minimize complications.

Endoscopic third ventriculostomy

In some cases of noncommunicating hydrocephalus, the blockage can be bypassed using endoscopic surgery. In this type of surgery, an endoscope and microinstruments are manipulated through a minimally invasive, computer-guided approach into the ventricle. A small hole is made in the floor of the third ventricle, allowing CSF to flow out of the brain. When successful, this type of surgery corrects the hydrocephalus without requiring a shunt implantation.

Endoscopic third ventriculostomy with choroid plexus cauterization

For some infants, endoscopic third ventriculostomy can be performed with the addition of choroid plexus cauterization. After this procedure, the choroid plexus produces less CSF.

Ventricular shunt surgery complications and follow-up

Although shunting is a relatively straightforward procedure, complications can arise, which underscores the importance of selecting a neurosurgeon experienced in treating this condition. The most common possible complications are infection and shunt failure.

Patients treated at Columbia have access to world-renowned neurosurgeons experienced in treating hydrocephalus. Our neurosurgeons have strict protocols in place to keep infection rates as low as possible and to select only the shunt implants best for their patients.

Our center has an overall complication rate in hydrocephalus shunt surgery of less than 5 percent. This is far better than the 10 to 25 percent rates reported in large studies in the medical literature.

Patients who are surgically treated for hydrocephalus will need long-term follow-up to optimize shunt function and minimize complications. Shunt valves may need to be reprogrammed over time to ensure patients are getting the best clinical benefit.