What is Hydrocephalus?

Jason T
May 10, 2024
8 min read

Updated: Dec 18, 2025

Diagram showing hydrocephalus with enlarged brain ventricles compared to normal ventricles, illustrating excess cerebrospinal fluid (CSF) buildup and increased pressure on the brain — *Clear, educational, and suitable for clinical or pediatric reference.*

What is Hydrocephalus?

Hydrocephalus is a condition in which there is an excess build-up of CSF (cerebrospinal fluid), a clear fluid surrounding the brain. The excessive accumulation of CSF results in an abnormal dilation of spaces in the brain called ventricles. This dilation causes harmful pressure to build up on the brain and surrounding connective tissues.

Hydrocephalus, often referred to as “Water on the Brain,” literally means “watery head” in Greek — “hydro” meaning water, and “cephalus” referring to the head.

“Hydrocephalus can happen at ANY age”

Hydrocephalus is life-threatening and has a 75% chance of causing long-lasting brain damage and motor disability, and approximately a 30% rate of cognitive disability. More than 50% of hydrocephalus cases are congenital (present at birth).

What Are Ventricles?

The ventricular system is a set of four interconnected cavities (ventricles) in the brain where cerebrospinal fluid (CSF) is produced. Within each ventricle is the choroid plexus, a network of ependymal cells involved in CSF production.

The ventricular system is continuous with the central canal of the spinal cord (from the fourth ventricle), allowing CSF to circulate. The ventricular system and central canal are lined with ependymal cells, a specialized form of epithelium.

What Is CSF (Cerebrospinal Fluid)?

Cerebrospinal fluid is the clear fluid surrounding the brain and spinal cord and has three critical functions:

Acts as a shock absorber, protecting brain tissue from impact and excessive movement
Transports nutrients to the brain and removes waste
Regulates pressure changes between the cranium and spinal column

Common Causes

A variety of medical conditions can cause hydrocephalus. In many children, the condition is present at birth and is referred to as congenital hydrocephalus.

Most congenital cases are thought to result from a complex interaction of genetic and environmental factors, including exposure to radiation, mold, viruses, bacteria, genetic defects, trauma in utero, or motor-vehicle accidents.

Aqueductal Obstruction (Stenosis)

The most common cause of congenital hydrocephalus is obstruction (narrowing or blockage) of the cerebral aqueduct, a narrow passageway between the third and fourth ventricles.
NO FEVER

Neural Tube Defects / Myelomeningocele

Spina bifida, meaning “open spine,” refers to conditions where the structures supporting and protecting the spinal cord are impaired.

Intraventricular Hemorrhage

An acquired form of hydrocephalus most commonly affecting premature newborns. It occurs when fragile blood vessels near the ventricular lining rupture, leading to scarring or blockage of CSF absorption pathways.

Meningitis (Bacterial or Viral)

Inflammation of the meninges surrounding the brain and spinal cord.
FEVER PRESENT

Head Trauma

Trauma may damage brain tissue or blood vessels. Blood entering CSF pathways can obstruct or restrict fluid flow.

Tumors

In children, brain tumors most often occur in the posterior fossa. As tumors grow, they may compress or block the ventricles.

Cysts

Arachnoid cysts are congenital and may occur anywhere in the brain. In children, they are often located near the third ventricle or posterior fossa.

Dandy-Walker Syndrome

A condition involving enlargement of the fourth ventricle due to partial or complete blockage of CSF outlets, often associated with developmental defects.

Healthcare professional in a hospital emergency room holding an infant while observing early warning signs of hydrocephalus, illustrating symptom recognition and the importance of timely medical evaluation — *Understanding early warning signs can help caregivers seek urgent medical assessment when it matters most.*

Symptoms — How to Recognize It

“If you suspect hydrocephalus, DO NOT HESITATE — the child’s life is in danger.”

Infants (0–1 year)

Abnormally enlarged head
Tense or bulging fontanel
Thin or stretched scalp with prominent veins
NO FEVER in congenital cases
Vomiting, drowsiness, irritability
“Sun-setting” eyes
Seizures, poor appetite

Children (1–8 years)

Headache (rubbing head or ears)
Nausea, vomiting
NO FEVER in congenital cases
Lethargy, poor coordination
Personality changes
Loss of motor skills
Seizures

Adults (8+ years)

Headache
Difficulty staying awake
Balance or coordination problems
Bladder control issues
Visual impairment
Cognitive decline

Elderly

Shuffling gait
Memory loss
Headache
Bladder incontinence
Nausea, vomiting, drowsiness

What Can You Do?

Go to the hospital immediately. Hydrocephalus can be misdiagnosed as a viral illness and treated with antibiotics, which will not help congenital hydrocephalus and may allow further brain damage to occur. Surgical intervention is often required urgently.

Healthcare professional discussing diagnostic imaging and symptoms of hydrocephalus with a physician while holding an infant, illustrating early evaluation of cerebrospinal fluid (CSF) buildup — *Early recognition and medical assessment can be life-saving.*

Diagnosing Hydrocephalus

“Parents should remember: this is NOT your fault.”

Doctors will review medical history, perform neurological exams, and order imaging such as ultrasound (infants), CT scans, or MRI. Head circumference, birth history, and developmental milestones are critical in determining treatment options.

Hydrocephalus Treatments

Hydrocephalus can be treated in only three or four ways with current medical technology “2018“. The problem area may be treated directly “removing the cause of CSF obstruction”, or indirectly by diverting the fluid somewhere else. In some cases, two procedures are performed, one to divert the CSF temporarily, and another on a later stage to remove the cause of the obstruction.

Shunt - Often in the emergency setting hydrocephalus is treated at the beginning with a “Shunt”. A shunt is a flexible but sturdy silastic tube. A shunt system consist of the shunt, a catheter, and a valve. One end of the catheter is placed within a ventricle inside the brain, but also may be placed potentially within a cyst or site close to the spinal cord. The other end of the catheter is commonly placed within the abdominal cavity, but may also be placed at other sites within the body so excess CSF can be absorbed. “Shunt systems are not perfect devices” Complications may include mechanical failure, infections, obstructions, length, improper flow “too much or too little CSF” or deterioration. Each time the Shunt has a malfunction potential for brain damage increases exponentially.

Medical diagram of a pediatric hydrocephalus shunt system showing cerebrospinal fluid (CSF) draining from the brain ventricles through a catheter to the abdominal cavity — **Pediatric Hydrocephalus Shunt Placement: Diagram Showing Cerebrospinal Fluid (CSF) Drainage From the Brain to the Abdominal Cavity**

2. Obstruction Removal - Neurosurgery is performed to remove the blockage, cyst, tumor that is causing the blockage of CSF flow. CT - Cat scans and MRI’s are needed to see if this is an option, your Neurosurgeon will know once they have all the data and information for them to assess weather removing the obstruction is possible. Ultrasound has now been recommended for patients in the infant range where the fontanels are still open, ultrasound can give a high quality picture and resolution of the brain tissue highlighting potentially operable obstructions.

3. Endoscopic Third Ventriculostomy “ETV” - This surgery involves making a hole in the floor of the third ventricle to allow free flow of spinal fluid into the basil cisterns for absorption of CSF. Many neurosurgeons “do not” perform ETV on children below the age of 2 due to the failure rate of up to 40%. However, ETV has the benefit of consistent pressure, flow and the lack of non natural parts within the body, this reduces the chance of malfunction leading to brain damage or death. Depending on the hydrocephalus ETV has a patency rate for up to five years with a 50%-80% no malfunction rate. “Candidacy” - ETV is clearly appropriate for treating “obstructive non-communication hydrocephalus” It is controversial as to weather it is effective in treating non-obstructive communication hydrocephalus. Although some neurosurgeons have used it successfully in these cases with a 1.0% infection rate.

4. Endoscopic Third Ventriculostomy & Choriod Plexus Cauterization “ETV & CPC” - This technique combines ETV with a procedure called Choroid Plexus Cauterization “CPC”. CPC is where your neurosurgeon in the middle of the ETV inserts a specialized tool “wire” to cauterize the CP tissue beginning at the right foramen of Monro, and following it back to the typically mobile glomus choroideum in the atrium. Your neurosurgeon will have more details to explain the procedure, however by combining ETV and CPC the chances of successfully holding proper Intracranial CSF fluid pressure increase, infection rates decrease to 1.0% or less and raise the success rate of the procedures in general.

TYPES OF HYDROCEPHALUS

Communication VS Non-Communicating Definition

Communicating - Communicating Hydrocephalus is when the flow of CSF is blocked after exiting the ventricles, however CSF is still able to flow between the ventricles but is blocked from draining out.

Non-Communicating - Non-Communicating Hydrocephalus also known as “Obstructive” Hydrocephalus occurs from “Aqueductal stenosis” a narrowing of the tube “aqueduct of Sylvius” that flows between the 3rd ventricle and 4th ventricle before exiting to the spine. “This is the most common cause of Hydrocephalus”

Long Term Outcome

“There is Hope” - The prognosis for patients diagnosed with hydrocephalus is difficult to predict, although there is some correlation between the specific “cause” of the hydrocephalus, the time between when symptoms began, diagnosis & treatment, as well as the age of the patients can influence the outcome. Brain Damage and complications are further compounded by the presence of associated disorders, the degree to which decompression “relief of CSF pressure or build-up” following shunt placement can also further complicate risks. Parents and guardians should be aware that up to 70% of hydrocephalus patience suffer from both cognitive and physical development disorders.

However “There is Hope” - Those affected by hydrocephalus benefit from rehabilitation therapies and educational interventions, many children go on to lean normal lives with few limitations. Treatment by an interdisciplinary team of medical professionals, rehabilitation specialists, and educational experts are critical to a positive outcome.

Although most children with hydrocephalus are within the normal range of intelligence, most experience “specific” learning difficulties. Immediate memory and auditory/verbal information may be intact, however, there is a rapid loss of information over time and difficulty in retrieving the appropriate bit of information due to brain tissue damage. Most students find it hard to organize themselves, plan ahead and think flexibly. In addition, some may experience difficulty in understanding the passage of time or understand when matters are urgent.

There are many resources out there to help you guide your child through this difficult emergency.

For more information contact your physician and don’t be afraid to ask questions or seek support groups.

Hydrocephalus Association www.hydroassoc.org
Hydrocephalus Foundation INC www.hydrocephalus.org
National Hydrocephalus Foundation www.nhfonline.org
MedlinePlus: Hydrocephalus www.nlm.nih.gov/medlineplus/hydrocephalus.html
Mayo Clinic.com www.mayoclinic.com/health/hydrocephalus/DS00390
National Institute of Neurological Disorders www.ninds.nih.gov/disorders/hydrocephalus/hydrocephalus.html

We never know what can happen, its always good to be prepared and have the knowledge we need to help those who need it.

Special Thank you to The Stollery Children's Hospital

Stollery Children's Hospital Foundation

“This material is for information purposes only and is taken from The Canadian Red Cross / Alberta Heart & Stroke Foundation & Alberta Health Services. This information should not be used in place of medical, Technical advice, instructor, and/or treatment. If you have questions, speak to your local Physician or Safety Training Facility.”

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