Merck Manual

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Stephen J. Falchek

, MD, Nemours/Alfred I. duPont Hospital for Children

Reviewed/Revised Jul 2023
Topic Resources

Hydrocephalus is an accumulation of extra fluid in the normal spaces within the brain (ventricles) and/or between the inner and middle layers of tissues that cover the brain (the subarachnoid space). The extra fluid usually causes an enlarged head and developmental problems.

  • Hydrocephalus occurs when the fluid in the normal spaces in the brain (ventricles) cannot drain.

  • The fluid may accumulate for many reasons, such as a birth defect, bleeding within the brain, or a brain tumor.

  • Typical symptoms include an abnormally large head and abnormal development.

  • The diagnosis is based on computed tomography (CT), ultrasonography, or magnetic resonance imaging (MRI).

  • Surgery is needed to insert a drain (shunt) into the brain or to create an opening that allows fluid to drain.

The fluid surrounding the brain is called cerebrospinal fluid. This fluid is produced in spaces within the brain called ventricles. The fluid is constantly being produced and must drain to a different area, where it is absorbed into the blood. When the fluid cannot drain, it accumulates in the ventricles and/or subarachnoid space, causing hydrocephalus (water on the brain). Often, the pressure in the ventricles and within the brain increases, compressing brain tissue.

Infants can be born with hydrocephalus or it can occur during or after birth.

Symptoms of Hydrocephalus

An abnormally large head may be a sign of hydrocephalus.

When pressure in the brain is increased because of hydrocephalus, infants are irritable and listless, have a high-pitched cry, and vomit, and they may have seizures Seizures in Children Seizures are a periodic disturbance of the brain’s electrical activity, resulting in some degree of temporary brain dysfunction. When older infants or young children have seizures, they often... read more . Also, the soft spots between the skull bones (called the fontanelles) may bulge, causing a soft bump on the head. The eyes may not move together, sometimes making the child look cross-eyed (called strabismus Strabismus Strabismus is an intermittent or constant misalignment of an eye so that its line of vision is not pointed at the same object as the other eye. If untreated, strabismus can cause amblyopia ... read more Strabismus ).

Older children may have a headache, problems with vision, or both.

Other children develop normal intelligence.

Diagnosis of Hydrocephalus

  • Before birth, prenatal ultrasonography

  • After birth, computed tomography, magnetic resonance imaging, or ultrasonography of the head

After birth, doctors suspect the diagnosis in newborns based on symptoms noted during a routine physical examination. Doctors then do ultrasonography Ultrasonography Ultrasonography is a type of medical imaging that uses high-frequency sound (ultrasound) waves to produce images of internal organs and other tissues. During an ultrasound, a device called a... read more Ultrasonography of the head to confirm the diagnosis of hydrocephalus.

Once the diagnosis has been made, all children undergo CT or ultrasonography to monitor the hydrocephalus and determine whether it is worsening.

Treatment of Hydrocephalus

  • Sometimes spinal taps

  • For worsening hydrocephalus, a shunt or opening in the ventricles

The goal of treatment is

  • To keep pressure within the brain normal

Treatment of hydrocephalus depends on what is causing the disorder, how severe it is, and whether it is worsening.

If hydrocephalus is worsening, doctors place a ventricular shunt. The shunt is a plastic tube that creates a permanent alternate drainage path for cerebrospinal fluid. Draining the cerebrospinal fluid decreases the pressure and volume of the fluid inside the brain. Doctors place the shunt in the ventricles in the brain and run it under the skin from the head to another site, usually the abdomen (called a ventriculoperitoneal shunt, or VP shunt). The shunt contains a valve that allows fluid to leave the brain if the pressure becomes too high.

Although a few children can eventually do without the shunt as they get older, shunts are rarely removed because of the risk of bleeding and injury.

In some children, doctors do a ventriculostomy. In this procedure, doctors do not place a shunt and instead create an opening between a ventricle and the subarachnoid space in the brain. This opening allows excess fluid to drain and be absorbed as usual. Sometimes a shunt is still necessary if the ventriculostomy does not cure the hydrocephalus.

After placing a shunt or doing a ventriculostomy, doctors measure head circumference Head Circumference Physical growth refers to an increase in body size (length or height and weight) and in the size of organs. From birth to about age 1 or 2 years, children grow rapidly. After this rapid infant... read more and determine how the child is developing. Imaging tests (such as computed tomography or magnetic resonance imaging) are done periodically.

Complications of shunts

Shunts can become infected. Children who develop an infection are given antibiotics. Typically the shunt is then removed and replaced.

Shunts can break or become blocked and stop functioning correctly. To determine how a shunt is functioning, doctors take x-rays of the shunt and do imaging tests of the brain. A shunt that is not working correctly is typically removed and replaced.

More Information

The following English-language resource may be useful. Please note that THE MANUAL is not responsible for the content of this resource.

  • March of Dimes: An organization for pregnant people and babies that provides support and information about how to prevent maternal health risks, premature birth, and mother and infant deaths

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