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Hydrocephalus is an abnormal expansion of cavities (ventricles) within the brain that is caused by the accumulation of cerebrospinal fluid. Hydrocephalus comes from two Greek words: hydros means water and cephalus means head.
There are two main varieties of hydrocephalus: congenital and acquired. An obstruction of the cerebral aqueduct (aqueductal stenosis) is the most frequent cause of congenital hydrocephalus. Acquired hydrocephalus may result from spina bifida, intraventricular hemorrhage, meningitis, head trauma, tumors, and cysts.


Hydrocephalus is the result of an imbalance between the formation and drainage of cerebrospinal fluid (CSF). Approximately 500 milliliters (about a pint) of CSF is formed within the brain each day, by epidermal cells in structures collectively called the choroid plexus. These cells line chambers called ventricles that are located within the brain. There are four ventricles in a human brain. Once formed, CSF usually circulates among all the ventricles before it is absorbed and returned to the circulatory system. The normal adult volume of circulating CSF is 150 ml. The CSF turn-over rate is more than three times per day. Because production is independent of absorption, reduced absorption causes CSF to accumulate within the ventricles.
There are three different types of hydrocephalus. In the most common variety, reduced absorption occurs when one or more passages connecting the ventricles become blocked. This prevents the movement of CSF to its drainage sites in the subarachnoid space just inside the skull. This type of hydrocephalus is called "noncommunicating." In a second type, a reduction in the absorption rate is caused by damage to the absorptive tissue. This variety is called "communicating hydrocephalus."
Both of these types lead to an elevation of the CSF pressure within the brain. This increased pressure pushes aside the soft tissues of the brain. This squeezes and distorts them. This process also results in damage to these tissues. In infants whose skull bones have not yet fused, the intracranial pressure is partly relieved by expansion of the skull, so that symptoms may not be as dramatic. Both types of elevated-pressure hydrocephalus may occur from infancy to adulthood.
A third type of hydrocephalus, called "normal pressure hydrocephalus," is marked by ventricle enlargement without an apparent increase in CSF pressure. This type affects mainly the elderly.
Hydrocephalus has a variety of causes including:
  • congenital brain defects
  • hemorrhage, either into the ventricles or the subarachnoid space
  • infection of the central nervous system (syphilis, herpes, meningitis, encephalitis, or mumps)
  • tumor
Hydrocephalus is believed to occur in approximately one to two of every 1,000 live births. The incidence of adult onset hydrocephalus is not known. There is no known way to prevent hydrocephalus.

Causes and symptoms

Hydrocephalus that is congenital (present at birth) is thought to be caused by a complex interaction of genetic and environmental factors. Aqueductal stenosis, an obstruction of the cerebral aqueduct, is the most frequent cause of congenital hydrocephalus. As of 2001, the genetic factors are not well understood. According to the British Association for Spina Bifida and Hydrocephalus, in very rare circumstances, hydrocephalus is due to hereditary factors, which might affect future generations.
Signs and symptoms of elevated-pressure hydrocephalus include:
  • headache
  • nausea and vomiting, especially in the morning
  • lethargy
  • disturbances in walking (gait)
  • double vision
  • subtle difficulties in learning and memory
  • delay in children achieving developmental milestones
Irritability is the most common sign of hydrocephalus in infants. If this is not treated, it may lead to lethargy. Bulging of the fontanelles, or the soft spots between the skull bones, may also be an early sign. When hydrocephalus occurs in infants, fusion of the skull bones is prevented. This leads to abnormal expansion of the skull.
Symptoms of normal pressure hydrocephalus include dementia, gait abnormalities, and incontinence (involuntary urination or bowel movements).


Imaging studies—x ray, computed tomography scan (CT scan), ultrasound, and especially magnetic resonance imaging (MRI)—are used to assess the presence and location of obstructions, as well as changes in brain tissue that have occurred as a result of the hydrocephalus. Lumbar puncture (spinal tap) may be performed to aid in determining the cause when infection is suspected.


The primary method of treatment for both elevated and normal pressure hydrocephalus is surgical installation of a shunt. A shunt is a tube connecting the ventricles of the brain to an alternative drainage site, usually the abdominal cavity. A shunt contains a one-way valve to prevent reverse flow of fluid. In some cases of non-communicating hydrocephalus, a direct connection can be made between one of the ventricles and the subarachnoid space, allowing drainage without a shunt.
Installation of a shunt requires lifelong monitoring by the recipient or family members for signs of recurring hydrocephalus due to obstruction or failure of the shunt. Other than monitoring, no other management activity is usually required.
Some drugs may postpone the need for surgery by inhibiting the production of CSF. These include acetazolamide and furosemide. Other drugs that are used to delay surgery include glycerol, digoxin, and isosorbide.
Some cases of elevated pressure hydrocephalus may be avoided by preventing or treating the infectious diseases which precede them. Prenatal diagnosis of congenital brain malformation is often possible, offering the option of family planning.


The prognosis for elevated-pressure hydrocephalus depends on a wide variety of factors, including the cause, age of onset, and the timing of surgery. Studies indicate that about half of all children who receive appropriate treatment and follow-up will develop IQs greater than 85. Those with hydrocephalus at birth do better than those with later onset due to meningitis. For individuals with normal pressure hydrocephalus, approximately half will benefit by the installation of a shunt.



Toporek, Chuck, and Kellie Robinson. Hydrocephalus: A Guide for Patients, Families & Friends. Cambridge, Mass.: O'Reilly & Associates, 1999.


"Hydrocephalus." Review of Optometry 137, no. 8 (August 15, 2000): 56A.


Association for Spina Bifida and Hydrocephalus. 42 Park Rd., Peterborough, PE1 2UQ. UK 0173 355 5988. Fax: 017 3355 5985. postmaster@asbah.org. 〈http://www.asbah.demon.co.uk〉.
Hydrocephalus Foundation, Inc., (HyFI). 910 Rear Broadway, Saugus, MA 01906. (781) 942-1161. HyFI1@netscape.net. http://www.hydrocephalus.org.


"Hydrocephalus." American Association of Neurological Surgeons/Congress of Neurological Surgeons. 〈http://www.neurosurgery.org/pubpages/patres/hydrobroch.html〉.
"Hydrocephalus." Institute for Neurology and Neurosurgery. Beth Israel Medical Center, New York, NY. 〈http://nyneurosurgery.org/child/hydrocephalus/hydrocephalus.htm〉.
"Hydrocephalus." National Library of Medicine. MEDLINEplus. http://www.nlm.nih.gov/medlineplus/hydrocephalus.html.

Key terms

Cerebral ventricles — Spaces in the brain that are located between portions of the brain and filled with cerebrospinal fluid.
Cerebrospinal fluid — Fluid that circulates throughout the cerebral ventricles and around the spinal cord within the spinal canal.
Choroid plexus — Specialized cells located in the ventricles of the brain that produce cerebrospinal fluid.
Fontanelle — One of several "soft spots" on the skull where the developing bones of the skull have yet to fuse.
Shunt — A small tube placed in a ventricle of the brain to direct cerebrospinal fluid away from the blockage into another part of the body.
Stenosis — The constricting or narrowing of an opening or passageway.
Subarachnoid space — The space between two membranes surrounding the brain, the arachnoid and pia mater.
Gale Encyclopedia of Medicine. Copyright 2008 The Gale Group, Inc. All rights reserved.


a condition caused by enlargement of the cranium caused by abnormal accumulation of cerebrospinal fluid within the cerebral ventricular system; popularly known as water on the brain. Although it occurs occasionally in adults, it is usually associated with a congenital defect, usually a neural tube defect. adj., adj hydrocephal´ic.

There are two types of hydrocephalus, distinguished according to whether there is abnormal absorption of the cerebrospinal fluid or an obstruction to its flow. In communicating hydrocephalus there is some abnormality in the capacity to absorb fluid from the arachnoid space. There is no obstruction to the flow of fluid between the ventricles. In noncommunicating hydrocephalus there is an obstruction at some point in the ventricular system. The cause of noncommunicating hydrocephalus usually is a congenital abnormality, such as stenosis of the aqueduct of Sylvius, congenital atresia of the foramina of the fourth ventricle, or spina bifida cystica. Infections, intraventricular hemorrhage (a frequent problem in premature infants), trauma, and tumors can produce acquired communicating hydrocephalus.

Medical treatment has had only limited success in controlling the secretion of cerebrospinal fluid and relieving hydrocephalus. The most effective treatment is surgical correction employing a shunting technique. The basic components of the shunt are a ventricular catheter, a valve, and a distal catheter. Multiple perforations along the ventricular catheter permit the drainage of fluid from the ventricle. The valve is constructed so that fluid will flow in one direction only, and some valves have a pumping chamber to facilitate drainage. The distal catheter may be positioned at any of a number of sites, the most common being the peritoneal cavity (ventriculoperitoneal shunt) and the right atrium (ventriculoatrial shunt).
Patient Care. The child with hydrocephalus requires frequent and careful changing of position of the head as well as of the body. Pressure sores on the head are a constant threat because of the weight and size of the head and the child's inability to move it. The child should be picked up and held frequently, especially during feeding periods. Care must be taken that the head is well supported while the child is being held. An important aspect of care is preparation of the patient and family for discharge and care at home.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.


(hī'drō-sef'ă-lŭs), [MIM*236600]
A condition marked by an excessive accumulation of cerebrospinal fluid resulting in dilation of the cerebral ventricles and raised intracranial pressure; may also result in enlargement of the cranium and atrophy of the brain.
Synonym(s): hydrocephaly
[hydro- + G. kephalē, head]
Farlex Partner Medical Dictionary © Farlex 2012


(hī′drō-sĕf′ə-ləs) also


A usually congenital condition in which an abnormal accumulation of fluid in the cerebral ventricles causes enlargement of the skull and compression of the brain, destroying much of the neural tissue.

hy′dro·ce·phal′ic (-sə-făl′ĭk), hy′dro·ceph′a·loid′ (-loid′)(-ləs), hy′dro·ceph′a·lous (-ləs) adj.
The American Heritage® Medical Dictionary Copyright © 2007, 2004 by Houghton Mifflin Company. Published by Houghton Mifflin Company. All rights reserved.


The accumulation of an increased amount of fluid in the brain.

Medspeak-UK: pronounced, high droh KEFF uh less
Medspeak-US: pronounced, high droh SEFF uh less
Segen's Medical Dictionary. © 2012 Farlex, Inc. All rights reserved.


Water on the brain Neurology Distension of the cerebral ventricles due to an abnormal accumulation of CSF in the cerebral ventricles due to blockage of flow, ↑ production, or ↓ absorption; adult hydrocephlaus may be
1. ex vacuo, seen in severe cerebral atrophy, with loss of brain tissue, as in Pick's or Alzheimer's diseases, thus being hydrocephalus by default, as the production and absorption of cerebrospinal fluid are normal or.
2. normal pressure, occurring 2º to trauma or infection with reflux into the ventricles. See Obstructive hydrocephalus.
Hydrocephalus etiology
absorption, eg blockage by congenital malformations, obliteration of the aqueduct, hemorrhage, infection, neoplasms and trauma
production, an uncommon event; as the ventricle enlarges, the ependymal lining separates from the ventricles, permeability ↑, the brain becomes edematous and the gyri flatten; incomplete resolution results in chronic hydrocephalus; in infants with unclosed cranial sutures, the cranial circumference ↑, cerebral parenchyma is destroyed, gyri flatten, sulci are obliterated and the 'setting sun' sign appears, which is usually associated with a poor prognosis; treatment by ventriculo-peritoneal shunting is merely palliative
McGraw-Hill Concise Dictionary of Modern Medicine. © 2002 by The McGraw-Hill Companies, Inc.


A condition marked by an excessive accumulation of cerebrospinal fluid resulting in dilation of the cerebral ventricles and raised intracranial pressure; may also result in enlargement of the cranium and atrophy of the brain.
Synonym(s): hydrocephaly.
[hydro- + G. kephalē, head]
Medical Dictionary for the Health Professions and Nursing © Farlex 2012


’water on the brain’-an abnormal accumulation of cerebrospinal fluid within, and around, the brain. This occurs if the fluid, which is continuously secreted, cannot be normally reabsorbed, usually because of obstruction of the passages to the site of reabsorption, by a congenital abnormality or later acquired disease. In babies, the head becomes greatly enlarged, and if the cause cannot be removed, an artificial shunt, or bypass, must be inserted to carry the fluid down to the heart or the abdominal cavity. Unrelieved hydrocephalus causes brain damage by compression.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005


(hī'drō-sef'ă-lŭs) [MIM*236600]
Excessive accumulation of cerebrospinal fluid resulting in dilation of the cerebral ventricles and raised intracranial pressure; may also result in cranial enlargement and brain atrophy.
[hydro- + G. kephalē, head]
Medical Dictionary for the Dental Professions © Farlex 2012

Patient discussion about hydrocephalus

Q. i am 23 years old and i would like to know what are the risk in getting pregnent if i had Hydrocephalus? when i was 10 days old i was sick and there was a need for surgery in which they put in my head a shunt .i would like to know the connection between VP Shunt and pregnancy.is it dangerous?do u know about women that have shunt and were pregnant? thank u and happy new year

A. Dana, i'm not a doctor but i fail to see a connection. unless the hydrocephalus is the outcome of birth defects that also affect other parts of the body- there shouldn't be a problem. what was the reason for the hydrocephalus? from what you describes, it sounds like infection to me, no? if so- there shouldn't be a problem. but you give here small amount of details, it might be a good idea to look it you with your gynecologist just in case.

More discussions about hydrocephalus
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