Hydrocephalus (hy-dro-SEF-uh-lus) is an abnormal buildup of fluid inside the skull. This excess fluid often creates pressure on the brain and may result in mental and physical handicaps.

Why Is the Baby's Head So Big?

When Liz saw her baby brother in the hospital nursery, she was upset by his appearance. His head seemed huge. The doctor explained that John had hydrocephalus, or too much fluid within his skull. Because he was a newborn, the bones in his head had not yet grown together, which allowed his head to expand with the pressure caused by the extra fluid. The doctor warned Liz's family that the excess fluid may have squeezed and damaged John's brain, but it was too soon to tell for sure.

What Is Hydrocephalus?

Hydrocephalus refers to fluid buildup in and around the brain. The term comes from two Greek words: hydro meaning “water,” and cephalie meaning “brain.” Hydrocephalus often is called “water on the brain,” but the brain and spinal cord are actually bathed in cerebrospinal fluid (CSF). Tissues lining the inside of the brain make CSF, which is a mixture of water, protein, sugar, and minerals, to cushion and protect the brain.

When babies are born with hydrocephalus, excess fluid and pressure inside the skull cause the skull bones to pull apart and the head to enlarge.

When babies are born with hydrocephalus, excess fluid and pressure inside the skull cause the skull bones to pull apart and the head to enlarge.
Illustration by Frank Forney. © 2016 Cengage Learning®.

What Causes Hydrocephalus?

Often medical professionals cannot determine the cause of hydrocephalus, but sometimes they can. As of 2016, approximately one in 1,000 babies was born with the condition, which is known as congenital hydrocephalus. It may occur because the brain did not develop properly or because the fetus was infected with German measles (rubella), herpes, cytomegalovirus, or other viruses, or with microscopic organisms called protozoa. In addition, at least 80 percent of babies who have the congenital disorder spina bifida (a birth defect that leaves an opening in the spinal cord and spinal column) also develop some degree of hydrocephalus.

In infants, children, and adults, brain tumors * can cause hydrocephalus by blocking the flow of CSF. Hydrocephalus also can result from meningitis, an infection of the linings of the brain and spinal cord, and by bleeding in the brain due to a stroke * or a head injury. Infants born very prematurely frequently experience bleeding in the ventricles of the brain, which often leads to hydrocephalus. Hydrocephalus is less common in adults.

How Is Hydrocephalus Treated?

Babies suspected of having hydrocephalus receive careful monitoring. John's head kept getting bigger and ultimately his doctor used a CT scan * and an MRI * to examine his brain.

Some forms of hydrocephalus require no treatment, but most, like John's, require surgery. The surgeon placed a device called a shunt in John's brain to drain the excess CSF. Shunts are thin flexible tubes that pass through the skull and drain some of the excess CSF into the bloodstream or the abdomen, where it is reabsorbed by the body. This procedure relieves pressure on the brain, but it does not cure the brain damage that has occurred already.

Most babies born with hydrocephalus live if they receive treatment, but about 60 percent have physical or mental handicaps. Liz's baby brother John was lucky. He was one of the children who did not have any mental or physical disabilities because of hydrocephalus.

What Is Normal Pressure Hydrocephalus?

Normal pressure hydrocephalus (NPH) is a condition that typically affects older adults. Rather than having a consistently high level of CSF in the skull, individuals with NPH have a normal level of CSF most of the day, but experience occasional, short-lasting spikes in CSF. Eventually, those spikes cause brain damage, and patients may have symptoms such as dementia * , incontinence * , and walking problems. Sometimes, the symptoms lead to a mistaken diagnosis of Alzheimer's disease * .

NPH can result from a stroke, meningitis, head trauma, brain tumor, or other injury, but usually doctors do not know why it arises. A shunt to drain excess CSF works in some patients, and as of 2016 research was underway to find additional treatments.

See also Brain Tumor • Cytomegalovirus (CMV) Infection • German Measles (Rubella) • Herpes Simplex Virus Infections • Meningitis • Spina Bifida • Stroke • Toxoplasmosis


Books and Articles

Mohanty, Aaron. 100 Questions & Answers about Hydrocephalus. Burlington, MA: Jones & Bartlett Learning, 2012.

“What You Should Know about Folic Acid.” Genetic Center at Children's Hospital Medical Center of Akron. http://www.cdc.gov/ncbddd/folicacid/documents/wsk.pdf (accessed April 4, 2016).

Websites NINDS.gov . http://www.ninds.nih.gov/disorders/hydrocephalus/hydrocephalus.htm (accessed April 4, 2016).


Hydrocephalus Association. 4340 East-West Highway, Suite 905, Bethesda, MD 20814. Toll-free: 888-598-3789. Website: http://www.hydroassoc.org (accessed April 4, 2016).

* dementia (dih-MEN-shuh) is a loss of mental abilities, including memory, understanding, and judgment.

* incontinence (in-KON-tih-nens) is loss of control of urination or bowel movement.

* MRI is short for magnetic resonance imaging, which produces computerized images of internal body tissues based on the magnetic properties of atoms within the body.

* tumors (TOO-morz) are abnormal growths of body tissue that have no known cause or physiologic purpose. Tumors may or may not be cancerous.

* stroke is a brain-damaging event usually caused by interference with blood flow to the brain. A stroke may occur when a blood vessel supplying the brain becomes clogged or bursts, depriving brain tissue of oxygen. As a result, nerve cells in the affected area of the brain, and the specific body parts they control, do not properly function.

* CT scan is the shortened name for computed tomography (toe-MAH-gruh-fee), which uses computers to view structures inside the body.

* Alzheimer's disease (ALTS-hymerz) is a condition that leads to gradually worsening loss of mental abilities, including memory, judgment, and abstract thinking, as well as changes in personality.

Disclaimer:   This information is not a tool for self-diagnosis or a substitute for professional care.

(MLA 8th Edition)