Hydrocephalus is a condition in which abnormally widened (dilated) cerebral spaces in the brain (ventricles) inhibit the normal flow of cerebrospinal fluid (CSF). The cerebrospinal fluid accumulates in the skull and puts pressure on the brain tissue. An enlarged head in infants and increased cerebrospinal fluid pressure are frequent findings but are not necessary for the diagnosis of Hydrocephalus. There are several different forms of Hydrocephalus: communicating hydrocephalus, non-communicating hydrocephalus or obstructive hydrocephalus, internal hydrocephalus, normal pressure hydrocephalus, and benign hydrocephalus.
Hydrocephalus is characterized in children by an unusually large head (cephalomegaly); a thin, transparent scalp; a bulging forehead with prominent spaces between the bones of the skull (fontanelles); and a downward gaze. Other symptoms may include convulsions, abnormal reflexes, a slowed heartbeat and respiratory rate, headache, vomiting, irritability, weakness, and problems with vision. Blindness and continuing mental deterioration may occur if treatment is not administered.
When hydrocephalus begins in an adolescent or a young adult, the facial abnormalities are less obvious than in children with congenital or early onset hydrocephalus. Many of the other mental and physiologic symptoms are the same; however, previously acquired skills requiring coordinated movement (motor coordination) may be lost. Affected children and adolescents may also exhibit symptoms associated with diminished activity of the pituitary gland (hypopituitarism), such as delayed growth, obesity, and general weakness.
Hydrocephalus is subdivided according to the particular defect that exists in the brain and whether the cerebrospinal fluid pressure is high or normal.
In “communicating hydrocephalus”, there is no blockage (obstruction) in the cerebral spaces of the brain (ventricular system); the cerebrospinal fluid flows readily into the subarachnoid space (the space between the arachnoid and pia mater membranes in the brain), but the fluid is not absorbed readily, or perhaps produced in too great a quantity to be absorbed.
In “noncommunicating (obstructive) hydrocephalus”, the cerebrospinal fluid is blocked causing widening (dilation) of the pathways upstream of the block, leading to increased cerebrospinal fluid pressure in the skull.
“Normal-pressure hydrocephalus”, which affects middle-aged and older persons, is characterized by dilated ventricles but normal pressure within the spinal column (lumbar pressure). Other symptoms of normal-pressure hydrocephalus include loss of memory and intellectual capacity (dementia), loss of muscle coordination (ataxia), and loss of bladder control (urinary incontinence). Additional symptoms may include lack of emotions (apathy), memory disturbances, the slowing of mental and motor functions, and/or a lack of awareness or indifference to the affected sides of an affected individual’s body (anosognosia).
The cause of hydrocephalus is not known. Very few cases are caused by a birth defect; others can follow hemorrhage, viral infection, or meningitis. A genetic predisposition has been proposed, with transmission through autosomal recessive or X-linked genes.
Human traits, including the classic genetic diseases, are a product of the interaction of two genes, one received from the father and one from the mother.
In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If an individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease, but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is 25 percent. Fifty percent of their children risk being carriers of the disease, but generally will not show symptoms of the disorder. Twenty-five percent of their children may receive both normal genes, one from each parent, and will be genetically normal (for that particular trait). The risk is the same for each pregnancy.
X-linked recessive disorders are conditions which are coded on the X chromosome. Females have two X chromosomes, but males have one X chromosome and one Y chromosome. Therefore, in females, disease traits on the X chromosome can be masked by the normal gene on the other X chromosome. Since males only have one X chromosome, if they inherit a gene for a disease present on the X, it will be expressed. Men with X-linked disorders transmit the gene to all their daughters, who are carriers, but never to their sons. Women who are carriers of an X-linked disorder have a fifty percent risk of transmitting the carrier condition to their daughters, and a fifty percent risk of transmitting the disease to their sons.
Some cases of Hydrocephalus are believed to be caused by Dandy-Walker Cysts. (For more information on this disorder, choose “Dandy-Walker Malformation” as your search term in the Rare Disease Database.)
Most cases of Hydrocephalus are diagnosed in the first 2 years of life, but onset may occur at any age, depending on the cause. Most types of Hydrocephalus (with the exception of those caused by an X-linked genetic trait) seem to affect males and females equally.
The diagnosis of hydrocephalus may be confirmed based upon a thorough clinical evaluation, the identification of characteristic physical findings, a detailed patient history, and advanced imaging techniques, such as transillumination, an x-ray of the blood vessels using dye (angiogram), computerized tomography (CT scan), or magnetic resonance imaging (MRI). During CT scanning, a computer and x-rays are used to create a file showing cross-sectional images of internal structures such as the brain. During MRI, a magnetic field and radio waves are used to create cross-sectional images of certain structures.
In some cases, hydrocephalus may be diagnosed before birth (prenatally) using fetal ultrasonography to identify characteristic physical abnormalities. In fetal ultrasonography, an image of the developing fetus is created using sound waves.
Any one or more of several tests may be used to diagnose normal-pressure hydrocephalus (NPH). In addition to CT and MRI described above, such tests may include lumbar puncture or spinal tap, which permits the removal of up to 50 cc of spinal fluid and may temporarily relieve symptoms. Neurosurgeons often interpret even temporary relief as a result of a spinal tap to indicate that surgical treatment may be successful. The insertion of a lumbar catheter permits the continuous removal of spinal fluid and the continuous measurement of spinal fluid pressure. A positive response of patients to treatment by lumbar catheter is often interpreted as an indicator that the patient will respond to shunt surgery as well.
Intracranial pressure monitoring is done in the hospital and involves the insertion of a pressure monitor into the brain or a ventricle of the brain.
Central spinal fluid (CSF) outflow resistance is carried out only in a specialized hospital setting. Simultaneously, the brain is infused with artificial spinal fluid and the CSF pressure is recorded. The purpose of the test is to determine by how much the reabsorption of CSF back into the bloodstream is retarded.
Isotopic cisternography permits the clinician to monitor the CSF over a 4-day period by scanning how and where an isotope injected into one of the hollow spaces of the lower bac. is absorbed over the surface of the brain or retained in the hollows. This technique has lost favor over the past few years since it does not reliably predict how a patient will respond to shunt surgery.
Standard treatment for hydrocephalus is the insertion of a shunt or tube into the head cavity which drains the excess cerebrospinal fluid into a part of the body that can absorb it. In growing children, the shunt may have to be lengthened periodically. Complications may arise if the shunt becomes clogged or stops functioning. At times, a new shunt may have to be re-implanted.
Information on current clinical trials is posted on the Internet at www.clinicaltrials.gov. All studies receiving U.S. government funding, and some supported by private industry, are posted on this government web site.
For information about clinical trials being conducted at the NIH Clinical Center in Bethesda, MD, contact the NIH Patient Recruitment Office:
Tollfree: (800) 411-1222
TTY: (866) 411-1010
For information about clinical trials sponsored by private sources, contact:
As of December 2006, there were six clinical trials investigating various aspects of hydrocephalus listed on www.clinicaltrials.gov. These include a study, sponsored by Johns Hopkins University and Eli Lilly & Company, of the prevalence of hypopituitarism among adults with hydrocephalus. The purpose is to study the effect of hydrocephalus on anterior pituitary function. For information, contact Roberto Salvatori, MD, at (410) 955-3921 or firstname.lastname@example.org.
Other projects listed on the Clinical Trials web site at this time include two registries to collect data that may help in the understanding of hydrocephalus.
McKusick VA, ed. Online Mendelian Inheritance in Man (OMIM). Baltimore. MD: The Johns Hopkins University; Entry No: 307000; Last Update: 9/17/99.
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Hakim CA, Hakim R, Hakim S. Normal-pressure hydrocephalus. Neurosurg Clin N Am. 2001;12:761-73.
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Introductory Materials The Hydrocephalus Association publishes pamphlets, brochures and information sheets for non-medically trained people as well as for physicians. Among those used to prepare this report are:
Fudge RA, Ed. About Hydrocephalus, A Book for Families. Hydrocephalus Association, San Francisco, CA. 2000;36pp.
Fudge RA, Ed. Prenatal Hydrocephalus, A Book for Parents. Hydrocephalus Association, San Francisco, CA. 1999;16pp.
Fudge RA, Ed. About Normal Pressure Hydrocephalus, A Book for Adult and Their Families. Hydrocephalus Association, San Francisco, CA. 2000;24pp.
Information Sheet, Endoscopic Third Ventriculostomy. Hydrocephalus Association, San Francisco, CA. 1997:1-4.
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