hydrocephalus

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Hydrocephalus

 

Definition

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.

Description

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).

Diagnosis

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.

Treatment

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.

Prognosis

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.

Resources

Books

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

Periodicals

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

Organizations

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.

Other

"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.

hydrocephalus

 [hi″dro-sef´ah-lus]
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.

hy·dro·ceph·a·lus

(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]

hydrocephalus

/hy·dro·ceph·a·lus/ (-sef´ah-lus) a congenital or acquired condition marked by dilatation of the cerebral ventricles, usually occurring secondarily to obstruction of the cerebrospinal fluid pathways, and accompanied by an accumulation of cerebrospinal fluid within the skull; typically, there is enlargement of the head, prominence of the forehead, brain atrophy, mental deterioration, and convulsions.hydrocephal´ic
communicating hydrocephalus  that in which there is free access of fluid between the ventricles of the brain and the spinal canal.
noncommunicating hydrocephalus  obstructive h.
normal-pressure hydrocephalus , normal-pressure occult hydrocephalus dementia, ataxia, and urinary incontinence with enlarged ventricles associated with inadequacy of the subarachnoid spaces, but with normal cerebrospinal fluid pressure.
obstructive hydrocephalus  that due to obstruction of the flow of cerebrospinal fluid within the brain ventricles or through their exit foramina.
otitic hydrocephalus  that caused by spread of inflammation of otitis media to the cranial cavity.
posthemorrhagic hydrocephalus  hydrocephalus in an infant following intracranial hemorrhage that has distended the ventricles and obstructed normal pathways for cerebrospinal fluid.
hydrocephalus ex va´cuo  compensatory replacement by cerebrospinal fluid of the volume of tissue lost in atrophy of the brain.

hydrocephalus

(hī′drō-sĕf′ə-ləs) also

hydrocephaly

(-lē)
n.
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.

hydrocephalus

[-sef′ələs]
Etymology: Gk, hydor + kephale, head
a pathological condition characterized by an abnormal accumulation of cerebrospinal fluid, usually under increased pressure, within the cranial vault and subsequent dilation of the ventricles. Interference with the normal flow of cerebrospinal fluid may result from increased secretion of the fluid, obstruction within the ventricular system (noncommunicating or intraventricular hydrocephalus), or defective resorption from the cerebral subarachnoid space (communicating or extraventricular hydrocephalus). Hydrocephalus may be caused by developmental anomalies, infection, trauma, or brain tumors. Also called hydrocephaly. See also macrocephaly. hydrocephalic, adj., n.
observations The condition may be congenital, with rapid onset of symptoms, or it may progress slowly so that neurological manifestations do not appear until early to late childhood or even early adulthood. In infants the head grows at an abnormal rate with separation of the sutures, bulging fontanels, and dilated scalp veins. The face becomes disproportionately small, and the eyes appear depressed within the sockets. Typical behavior includes irritability with lethargy and vomiting, opisthotonos, lower extremity spasticity, and failure to perform normal reflex actions. If the condition progresses, lower brainstem function is disrupted; the skull becomes enormous; the cortex is destroyed; and the infant displays somnolence, seizures, and cardiopulmonary obstruction and usually does not survive the neonatal period. At later onset, after the cranial sutures have fused and the skull has formed, symptoms are primarily neurological and include headache, edema of the optic disc, strabismus, and loss of muscular coordination. Hydrocephalus in infants is suspected when head growth is observed to be in excess of the normal rate. In all age groups, diagnosis is confirmed by such procedures as cerebrospinal fluid examination, computed tomography, air encephalography, arteriography, and echoencephalography.
interventions Treatment consists almost exclusively of surgical intervention to correct the ventricular obstruction, reduce the production of cerebrospinal fluid, or shunt the excess fluid by ventricular bypass to the right atrium of the heart or to the peritoneal cavity. Surgically treated hydrocephalus with continued neurosurgical and medical management has a survival rate of approximately 80%, although prognosis depends largely on the cause of the condition. Hydrocephalus is frequently associated with myelomeningocele, in which case there is a less favorable prognosis.
nursing considerations Primary care of the child with hydrocephalus consists of maintaining adequate nutrition, proper positioning and support to prevent extra strain on the neck, and assistance with diagnostic evaluation and procedures. After surgery, in addition to routine care and observation to prevent complications, especially infection, the nurse gives support to the parents and teaches them how to care for a child with a functioning shunt, specifically how to recognize signs that indicate shunt malfunction or infection and how to pump the shunt.
enlarge picture
Fetus with pronounced hydrocephalus

hydrocephalus

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

Pronunciation
Medspeak-UK: pronounced, high droh KEFF uh less
Medspeak-US: pronounced, high droh SEFF uh less

hydrocephalus

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
.

hy·dro·ceph·a·lus

(hī'drō-sef'ă-lŭs)
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]

hydrocephalus

’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.

hydrocephalus

thinning of the skull, increase in head size and progressive reduction in brain function due to accumulation of cerebrospinal fluid

hydrocephalus,

n abnormal condition in which cerebrospinal fluid collects in the cranium, thus causing the ventricles to dilate. May be present at birth or may manifest in early adulthood. Caused by brain tumors, infection, trauma, or developmental anomalies. Also called
hydrocephaly.
Enlarge picture
Hydrocephalus.

hy·dro·ceph·a·lus

(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]

hydrocephalus (hī´drōsef´əlus),

n an abnormal accumulation of cerebrospinal fluid in the cranial vault, resulting in a disproportionately large cranium.

hydrocephalus

a condition characterized by abnormal accumulation of cerebrospinal fluid within the cerebral ventricular system. As a consequence, the ventricles are enlarged and the brain is diminutive. Called also water on the brain.
Although hydrocephalus occurs occasionally in adults, it is usually associated with a congenital defect in offspring.
There are two types of hydrocephalus, the distinction being based on 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, or congenital atresia of the foramina of the fourth ventricle. Infections, intraventricular hemorrhage, trauma and tumors can produce acquired communicating hydrocephalus.
There are three forms that occur in cattle: in one there is gross distention of the cranium with normal facial bones; in the second there is a similar enlargement of the cranium with an accompanying achondroplastic dishing of the face and foreshortening of the maxilla and a shortening of the limb bones—these are the classical 'bulldog' calves; in the third the cranium is normal in size but there is internal hydrocephalus and the calves are blind and imbecile. There are a number of inherited hydrocephalitides in cattle. The disease also occurs in pigs but the inheritance is complex in that it is exacerbated by a concurrent hypovitaminosis A.
In dogs and cats, hydrocephalus is common in some toy breeds such as the Chihuahua in which a domed cranium is a desirable feature of conformation. It also occurs less often in adults in association with brain tumors and from infections such as toxoplasmosis and feline infectious peritonitis.
Enlarge picture
Hydrocephalus in a calf. By permission from Parkinson TJ, England GCW, Arthur GH, Arthur's Veterinary Reproduction and Obstetrics, Saunders, 2001

compensatory hydrocephalus
cerebrospinal fluid occupies space vacated by brain parenchyma because of malformation or degeneration. Examples are seen in fetal infection by bluetongue virus or bovine virus diarrhea virus, severe polioencephalomalacia in cattle, and cerebral infarction in cats.
external hydrocephalus
the excess fluid is in the arachnoid space; rare in animals.
hypertensive hydrocephalus
accompanied by increased cerebrospinal fluid pressure.
internal hydrocephalus
the excess fluid is within the ventricular system; common in domestic animals and may be congenital or acquired.
normotensive hydrocephalus
accompanied by normal cerebrospinal fluid pressure.

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.

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