What is Hydrocephalus?

What is hydrocephalus?

Hydrocephalus is an abnormal accumulation of fluid in the ventricles (brain cavities) deep within the brain. This excess fluid/water causes the ventricles to widen, putting pressure on the brain’s tissues.

Cerebrospinal fluid (CSF) is the clear, colourless fluid that protects and cushions the brain and spine.  Normally, 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.  However, when the normal flow or absorption of CSF is blocked it can result in a build-up of CSF.  The pressure from too much CSF can keep the brain from functioning properly and cause brain damage and even death.

Fortunately, there are treatment options that can restore normal levels of CSF.  Though treatment is often helpful, it may take multiple surgeries to treat hydrocephalus.  (Hydrocephalus is the most common reason for brain surgery in young children.)  With treatment many people lead normal and productive lives.

Hydrocephalus can affect anyone at any age but is most common in infants and older adults.  Some of these cases can be associated with abnormalities in the brain and spinal cord during pregnancy.  
The two major types of hydrocephalus are called communicating hydrocephalus and non-communicating 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, the passages between which remain open.  Reduced flow and absorption of CSF into specialized blood vessels called arachnoid villi can also result in a build-up of CSF in the ventricles and communicating hydrocephalus. 

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

Two additional types of hydrocephalus include:

• 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 than normal because of this.  Strictly speaking, this is not a true hydrocephalus, but rather, a “hydrocephalus look-alike” condition.
• Normal Pressure Hydrocephalus (NPH) can be the result of bleeding in the brain’s CSF (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.

What causes hydrocephalus?

Hydrocephalus may be present at birth (congenital) or may develop over time as a result of injury or disease (acquired).  Except for hydrocephalus secondary to physical obstruction of CSF passages within the brain or skull by blood or tumor, the exact causes of hydrocephalus are still not well understood.

Congenital 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.

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

• brain or spinal cord tumours
• infections of the central nervous system such as bacterial meningitis
• injury or stroke that causes bleeding in the brain.

What are the symptoms?

The symptoms of hydrocephalus can vary significantly from person to person and mostly depend on age.  Conditions other than hydrocephalus can cause similar symptoms so it is important to see a doctor to receive proper diagnosis and treatment.

Infants
Signs and symptoms of hydrocephalus in infants 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 (also called “sun setting”) or are not able to turn outward
• seizures.

Older children, young adults, and middle-aged adults
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.

Older adults
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.

How is hydrocephalus diagnosed?

Hydrocephalus is diagnosed through a clinical neurological exam and by using brain imaging techniques and other tests based on

Brain imaging and other tests
Tests to accurately diagnose hydrocephalus and rule out other conditions may include:

• 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 have 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.
• Fundoscopic examination uses a special deviceto 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.

What is the current treatment?

Surgical treatments
Hydrocephalus is treated with one of two surgical options:

• 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. 
• 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 once again begins to build up in the brain and earlier symptoms may recur.   To reduce the build-up of CSF, the clogged shunt system is replaced to restore drainage of CSF.  
Shunts require monitoring and regular medical check-ups.  Multiple surgeries may be needed to repair or replace a shunt throughout a person’s lifetime.  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.

Other treatments
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 behaviours
• 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 is the prognosis?

If left untreated, hydrocephalus can be fatal.  Early diagnosis and successful treatment improve the chance for a good recovery.

With the benefits of surgery, rehabilitative therapies, and educational interventions, many people with hydrocephalus live relatively normal lives.

The symptoms of NPH usually get worse over time if the condition is not treated, although some people may experience temporary improvements.

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.

---

“Hydrocephalus Fact Sheet”, NINDS, Publication date April 2020.

NIH Publication No. 20-NS-385