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.

— L. Fleming Fallon, Jr., MD, PhD, DrPH

[New Latin, from Greek hudrokephalon : hudro-, hydro- + kephalē, head.]

For more information on hydrocephalus, visit Britannica.com.

Definition

The word hydrocephalus derives from the Greek words hydro, meaning water, and cephalus, meaning head. Hydrocephalus is the result of the excessive accumulation of fluid in the brain. Traditionally, hydrocephalus has been described as a disease characterized by increased intracranial pressure (ICP), increased cerebrospinal fluid (CSF) volume, and dilatation of the CSF spaces known as cerebral ventricles.

Description

Hydrocephalus is the result of an imbalance between the formation and drainage of cerebrospinal fluid. This imbalance appears when an injury or illness alters the circulation of CSF; one or more of the ventricles of the brain become enlarged as CSF accumulates. However, hydrocephalus is not a single disease entity, as a wide number of underlying diseases are responsible for causing retention of CSF, resulting in ventricular dilatation and increased intracranial pressure (ICP). In infants and children, for example, hydrocephalus usually results from a birth defect, viral infection, head injury, hemorrhage, meningitis, or tumor.

In adults, the causes of hydrocephalus include brain damage due to stroke or injury, Alzheimer's disease, or obstruction of the ventricles. Often, the cause is unknown. Conditions responsible for hydrocephalus in a fetus include infantile congenital (present at birth) hydrocephalus, hydrocephalus associated with encephalocele or myelomeningocele, posthemorrhagic hydrocephalus in newborns, and postmeningitic hydrocephalus. Conditions responsible for hydrocephalus in adults include hydrocephalus following subarachnoid hemorrhage, idiopathic adult hydrocephalus, and posttraumatic hydrocephalus. Tumors can also result in hydrocephalus in both children and adults. Based on the different kind of CSF circulation in the brain, hydrocephalus can be divided into two types: communicating and non-communicating. In communicating hydrocephalus, the CSF circulation pathways are competent from the ventricles inside of the brain to the fluid spaces just below the third ventricle. Non-communicating (obstructive) hydrocephalus refers to hydrocephalus that develops from a blockage of the normal circulation of CSF within the brain. In most cases, it refers to a blockage between the third and fourth ventricles.

Demographics

Overall incidence of infantile hydrocephalus is approximately one to two per 1,000 live births. The overall prevalence of hydrocephalus in the United States is about 0.5%. When cases of spina bifida are included, congenital hydrocephalus occurs in two to five births per 1,000 births. The incidence of acquired hydrocephalus in adults is not known because it occurs as a result of injury, illness, or environmental factors. Normal pressure hydrocephalus was found to be significantly more prevalent in males, and can occur in adults of any age group. The age distribution in children and teenagers is disputed.

Causes and symptoms

Approximately 16 oz (500 ml) of CSF are formed within the brain each day, by cells located on the wall of the four ventricles in the brain. Once formed, CSF circulates among all the ventricles before it is absorbed. The normal adult volume of circulating CSF is about 2 oz (150 ml). The CSF turnover rate is more than three times per day. Because production is independent of absorption, reduced absorption causes CSF to accumulate within the ventricles.

Hydrocephalus can be subdivided into three forms, involving the following:

• Disorders of cerebrospinal fluid circulation. Tumors, hemorrhages, congenital malformations, and infections can cause such obstructions in the circulation of cerebrospinal fluid.
• Disorders of cerebrospinal fluid absorption, resulting from diseases such as the superior vena cava syndrome and sinus thrombosis.
• Disorders of cerebrospinal fluid production: This is the less common form of hydrocephalus resulting from tumors that secrete cerebrospinal fluid in excess of its absorption.

Congenital hydrocephalus is thought to be caused by a complex interaction of genetic and environmental factors. The origin of hydrocephalus in congenital cases is unknown. Very few cases (less than 2%) are inherited (X-linked hydrocephalus). The most common causes of hydrocephalus in acquired cases are tumor obstruction, trauma, intracranial hemorrhage, and infection.

The two most common adult forms of hydrocephalus are hydrocephalus ex-vacuo and normal pressure hydrocephalus. Hydrocephalus ex-vacuo occurs when a stroke or injury damages the brain, yielding a brain substance. Although there is more CSF than usual, the CSF pressure may or may not be elevated. Normal pressure hydrocephalus is an abnormal increase of CSF in the brain's ventricles due to the gradual blockage of the CSF-draining pathways. This may result from a subarachnoid hemorrhage, head trauma, infection, tumor, or complications of surgery. The ventricles enlarge to handle the increased volume of the CSF, and the compression of the brain from within by the fluid-filled ventricles destroys or damages brain tissue. Fluctuation of CSF pressure from high to normal to low can also be present.

For congenital-onset hydrocephalus, early symptoms include enlargement of the head (increased head circumference), bulging fontanelles (soft spots) with or without enlargement of the head size, separation of sutures (the flexible and fibrous joints between the skull bones of an infant), and vomiting. Symptoms of continued hydrocephalus include irritability and muscle spasticity. Late symptoms of congenital-onset hydrocephalus seen in children up to five years of age include decreased mental function, delayed development, slow or restricted movement, difficulty feeding, lethargy, and delayed growth.

In children, symptoms depend on the amount of damage caused by ICP. Symptoms may be similar to many of those in infants or may include headache, vomiting, vision changes such as crossed eyes, uncontrolled eye movements, loss of coordination, poor gait (walking pattern), mental confusion, or psychosis. For adult-onset hydrocephalus, headaches and nausea are the most common symptoms. Other signs of the condition include difficulty focusing the eyes, unsteady gait, weakness of the legs, sudden falls, and a distinctive inability to walk forward. As hydrocephalus progresses, decreased mental activity appears, including lethargy, apathy, impaired memory, and speech problems. Urinary and bowel incontinence can also occur. During the final stage, dementia involving loss of movement, sensory functions, and cognitive abilities may result.

Diagnosis

Ultrasound can be used to diagnose prenatal hydrocephalus. Although fetal hydrocephalus may be an isolated finding, it is more frequently found along with other cerebral anomalies, including neural tube defects. Diagnosis after birth may be suggested by symptoms; however, imaging studies of the brain are the mainstay of diagnosis. Computed tomography (CT) and magnetic resonance imaging (MRI) reveal enlarged ventricles and may indicate a specific cause of hydrocephalus, such as a tumor or hemorrhage. The presence of papilledema (elevation or swelling of the optic disc) also indicates that hydrocephalus that is well developed. In rare cases, long-standing hydrocephalus causes blindness.

Small abnormalities that may not be seen with CT scanning, such as cysts and abscesses, are often seen with MRI. These studies can also help the neurosurgeon differentiate between communicating and non-communicating hydrocephalus. In cases of suspected normal pressure hydrocephalus, a lumbar puncture (spinal tap) may help determine CSF pressure. Also, a cisternagram can be useful to evaluate the dynamics of CSF flow in the brain and spinal chord. Cisternography can reveal CSF concentration, obstruction, leakage, and pressure. Also, certain biochemical markers in the blood have been described in the disease. They include increased neurofilament light protein (NFL) and tau protein, both markers of neuronal degeneration; increased myeline basic protein (a marker of demyelination; and albumin); and a marker of the blood-brain barrier function.

Treatment team

Treatment of hydrocephalus for children or adults will likely involve a neurologist, neurosurgeon, obstetrician, pediatrician, and specialty nurses and physical therapists.

Treatment

Medical treatment is first aimed at reducing intracranial pressure, while the need for a more permanent solution is determined. Reduction of fluid intake and administration of drugs such as mannitol, glycerol, urea (drugs with an osmotic effect), or furosemide (a diuretic) are able to reduce ICP and CSF production.

External drainage of the CSF is useful for urgent reduction of intracranial pressure, as well as of ventricular or subarachnoid hemorrhage. Complications include overdrainage, blocked tube, or bacterial contamination. The placement of a permanent ventricular shunt (internal shunting) is a common procedure. Around 33,000 shunts are placed in the United States each year; almost half of them to replace previous shunt devices. CSF from the ventricles in the brain is usually shunted to the peritoneum, pleura, ureter, bladder, or vascular spaces such as the jugular or subclavian veins. Most shunts are connected to the peritoneum. Some shunts operate according to intracranial pressure by using a valve system able to regulate the flow at a pressure close to the normal values of ICP. Others are programmable and can be adjusted to open at a given ICP. Complications include overdrainage that may cause intracranial hypotension, subdural hematoma, shunt occlusion, and infection. The risk of shunt failure is greater within the first year (between 25–40% of shunts must be replaced). The subsequent failure rate is around 5% for each year.

Other surgical procedures include, in some cases, choroid plexectomy, third ventriculostomy, and ventricular reservoir. Ventricular reservoir is basically a catheter inserted into a ventricle of the brain to draw CSF. This procedure is much simpler than placing a full shunt system and is used to provide temporary control of ICP until a full shunt can be placed.

Recovery and rehabilitation

Hydrocephalus is a chronic condition, and clinical symptoms are based on the time of insurgence of the disease. With appropriate, early treatment, a normal lifespan with few limitations can be reached. After surgery, specially trained medical professionals carefully monitor the patient. Some symptoms such as headaches may disappear immediately due to the release of excess pressure. The symptoms associated with normal pressure hydrocephalus (walking difficulties, mild dementia, poor bladder control) may improve quickly, or may take weeks to months to improve. In some patients, little or no improvement is also possible.

The length of the patient's hospital stay will be determined by the rate of recovery. If neurological problems persist, rehabilitation may be required to further the patient's improvement. However, recovery may be limited by the extent of the damage already caused by the hydrocephalus. Because hydrocephalus is an ongoing condition, patients do require long-term follow up. Follow-up diagnostic tests, including CT scans, MRI, and x rays, may be performed to determine if the shunt is working correctly.

Clinical trials

Ventricular shunts are the most common surgical treatment for hydrocephalus and appear to be the safest. It is possible that choroid plexectomy and third ventriculostomy may become more feasible in the future if better procedures and equipment are developed.

As of mid-2004, several clinical trials to study hydrocephalus were underway, including a trial to evaluate the efficacy and safety of endoscopic choroid plexus coagulation with third ventriculostomy in the treatment of idiopathic normal pressure hydrocephalus, sponsored by the Frenchay Hydrocephalus Research Fund. The National Institute of Neurological Disorders and Stroke is sponsoring a study to establish the physiology of syringomyelia. Updated information on these and other ongoing clinical trials may be found at the National Institutes of Health website for clinical trials at .

Prognosis

Untreated hydrocephalus has a survival rate of 40–50%, with the survivors having varying degrees of intellectual, physical, and neurological disabilities. Prognosis for treated hydrocephalus varies, depending on the cause. If the child survives for one year, more than 80% will have a fairly normal lifespan. Approximately one-third will have normal intellectual function, but neurological difficulties may persist. Hydrocephalus not associated with infection has the best prognosis, and hydrocephalus caused by tumors has a very poor prognosis. About 50% of all children who receive appropriate treatment and follow up will develop IQs in the near-normal or normal range.

Resources

BOOKS

Matsumoto, Satoshi. Hydrocephalus: Pathogenesis and Treatment. New York: Springer-Verlag, 1991.

The Official Parent's Sourcebook on Hydrocephalus: A Revised and Updated Directory for the Internet Age. San Diego: Icon Group International, 2002.

Toporek, Chuck, and Kellie Robinson. Hydrocephalus: A Guide for Patients, Families and Friends. Sebastopol, CA: Patient-Centered Guides, 1999.

PERIODICALS

Arriada, N., and J. Sotelo. "Review: Treatment of Hydrocephalus in Adults." Surg Neurol. (2002) Dec 58 (6): 377–84.

Davis, G. H. "Fetal Hydrocephalus." Clin Perinatol. (2003) Sep 30 (3): 531–9.

Meier, U., and C. Miethke. "Predictors of Outcome in Patients with Normal-Pressure Hydrocephalus." J Clin Neurosci. (2003) Jul 10 (4): 453–9.

OTHER

"NINDS Hydrocephalus Information Page." National Institute of Neurological Disorders and Stroke. May 15, 2004 (May 22, 2004). http://www.ninds.nih.gov/health_and_medical/disorders/hydrocephalus.htm.

"What is Hydrocephalus?" Hydrocephalus Foundation, Inc. May 15, 2004 (May 22, 2004). http://www.hydrocephalus.org/.

ORGANIZATIONS

Hydrocephalus Association. 870 Market Street, Suite 705, San Francisco, CA 94102. (415) 732-7040 or (888) 598-3789; Fax: (415) 732-7044. info@hydroassoc.org. http://www.hydroassoc.org.

National Hydrocephalus Foundation. 12413 Centralia Road, Lakewood, CA 90715-1623. (562) 402-3523 or (888) 857-3434; Fax: (562) 924-6666. hydrobrat@earthlink.net. http://nhfonline.org.

Antonio Farina, MD, PhD

Derived from the Greek for ‘water’ and ‘head’, hydrocephalus was recognized by Greek and Roman philosophers, including Hippocrates and Galen. Arabic medical scholars, like Albucasis, preserved and built upon the knowledge of the ancients, combining it with Arabic surgical expertise. One of the earliest illustrations of the condition, and a method of treating it, which involved opening the head and evacuating fluid, appeared in the fifteenth-century surgical manuscript by Sharaf ad Din. Nearly 200 years later, the Italian surgeon Marco Aurelio Severino depicted and described a case of infantile hydrocephalus in De Recondita Abscessuum Natura Libri VII (Seven Books on the Obscure Nature of Abscesses).

Hydrocephalus is sometimes called ‘water on the brain’, but the excess of fluid is in fact ‘in’ rather than ‘on’. There is normally cerebrospinal fluid filling the cerebral ventricles — the cavities deep inside the brain — and hydrocephalus describes an increase in its volume, and therefore of the size of the ventricles. Cerebrospinal fluid (CSF) is continually produced by transfer of a watery solution from the blood into the ventricles, flowing slowly through these cavities, and into the subarachnoid space, to bathe the outside of the brain and spinal cord; thence it is continually reabsorbed into the bloodstream. Hydrocephalus occurs if the rate of absorption does not keep pace with production.

Most often the problem is a mechanical obstruction. This may occur before birth, due to a malformation in the brain, resulting in an enlarged head which can pose problems during delivery. In other cases, although caused by a congenital defect — often associated with spina bifida — hydrocephalus may develop only later during infancy. Up to the age of two, when the bones of the skull begin to fuse, hydrocephalus results in overall enlargement in the size of the baby's head.

Later in life, at any age, a tumour may block a narrow part of the ventricular system, so that the system above this block expands; or there can be blockage in the surface spaces due to adhesions following meningitis or haemorrhage.

Obstructive forms of hydrocephalus occurring after fusion of the skull bones result in increasing intracranial pressure, with headache, vomiting, and danger to sight, with eventual death if unrelieved. The block can be located by imaging techniques (CT scan or MRI), which clearly show the shape and size of the ventricles. If it is not possible to remove the obstruction, the block may be bypassed by inserting a tube, with a one-way valve, leading from the ventricles either to the venous side of the heart or into the peritoneal cavity.

Hydrocephalus may result also from wasting away of the brain substance due to progressive disease such as Alzheimer's, or to sudden and massive insults such as those which lead to the vegetative state. There is no rise in pressure because the excess of ‘water’ simply takes up the space in and around the wasted brain.

— Karol K. Weaver, Bryan Jennett

Bibliography

• Lyons, A. E. (1995). Hydrocephalus first illustrated. Neurosurgery, 37, 511-3.
• Montagnani, C. A. (1986). Pediatric surgery in Islamic medicine from the Middle Ages to the Renaissance. Progress in Pediatric Surgery, 20, 39-51

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

Definition

Hydrocephalus is an abnormal expansion of cavities, called ventricles, within the brain, which is caused by an abnormally large accumulation of cerebrospinal fluid (CSF).

Description

Hydrocephalus is the result of an imbalance between the formation and drainage of CSF. There are four ventricles in the human brain. CSF is formed by structures within these ventricles. Once formed, CSF circulates among all the ventricles before it is absorbed and returned to the circulatory system. When the ventricles are obstructed, the CSF cannot circulate and be absorbed. An elevated level of CSF in the brain leads to pressure within the ventricles. This pressure pushes against the soft tissues of the brain, resulting in damage to these tissues.

There are three different types of hydrocephalus: communicating hydrocephalus, noncommunicating hydrocephalus, and normal pressure hydrocephalus. Communicating hydrocephalus is the most common type and exists when one or more passages connecting the ventricles become blocked. This blockage prevents the movement of CSF to its drainage sites in the subarachnoid space just inside the skull. In noncommunicating hydrocephalus, the tissue within the brain responsible for absorption of CSF is damaged. Normal pressure hydrocephalus is marked by ventricle enlargement without an apparent increase in CSF pressure. This type affects mainly the elderly and will not be discussed in this entry.

Hydrocephalus may be either congenital (present at birth) or acquired. An obstruction within the brain is the most frequent cause of congenital hydrocephalus. Acquired hydrocephalus may result from other birth defects such as spina bifida, conditions related to prematurity such as intraventricular hemorrhage (bleeding within the brain), infections such as meningitis, or other causes such as head trauma, tumors, and cysts.

Demographics

Hydrocephalus is believed to occur in approximately one to two of every 1,000 live births. It is not more prevalent in males or females, nor in any individual racial group.

Causes and Symptoms

Hydrocephalus has a variety of causes including the following:

• 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

Signs and symptoms of elevated-pressure hydrocephalus include the following:

• headache
• nausea and vomiting, especially in the morning
• lethargy
• disturbances in walking (gait)
• double vision
• subtle difficulties in learning and memory
• delay in achieving childhood 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, which leads to abnormal expansion of the skull.

Diagnosis

Imaging studies such as 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 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 are glycerol, digoxin, and isosorbide.

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.

Prevention

There is no known prevention of congenital hydrocephalus. Some cases of elevated pressure hydrocephalus may be avoided by preventing or treating the infectious diseases that precede them. Prenatal diagnosis of congenital brain malformation is often possible, offering the option of family planning.

Parental Concerns

Parents may be concerned about the intellectual development of a child with hydrocephalus. While nearly 50 percent of all children with hydrocephalus have average intelligence, many do not. Early intervention programs are important to the development of children with special needs and are available in most communities. In addition to developmental issues, many children with hydrocephalus require medical care. It is important for parents to prepare children for medical treatment and surgery. A healthcare team including a pediatrician, surgeon, and social worker is a valuable asset for parents and most children's hospitals can assist parents in finding the support and resources they need.

When to Call the Doctor

The most common treatment for hydrocephalus is the surgical installation of a shunt. If a child with a shunt has any of the following symptoms, parents should contact the child's doctor because the shunt may not be functioning properly. According to the Spina Bifida Association of America, nearly 40 percent of shunts malfunction and may need to be replaced within one year, 60 percent will require revision within five years, and 80 to 90 percent within ten years.

For this reason, parents need to be aware of the symptoms of shunt malfunction and contact their physician if they notice any of the following symptoms:

• headaches
• nausea
• vomiting
• seizures
• change in intellect or personality
• swallowing problems
• impaired muscle function, balance, or coordination

Resources

Books

Cinalli, G., et al. Hydrocephalus. New York: Springer, 2004.

Periodicals

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

Organizations

Hydrocephalus Foundation Inc. (HyFI). 910 Rear Broadway, Saugus, MA 01906. Web site: www.hydrocephalus.

Web Sites

"Hydrocephalus." American Association of Neurological Surgeons/Congress of Neurological Surgeons. Available online at www.neurosurgery.org/pubpages/patres/hydrobroch.html (accessed October 22, 2004).

"Hydrocephalus." Hyman-Newman Institute of Neurology and Neurosurgery. Available online at (accessed October 22, 2004).

[Article by: L. Fleming Fallon, MD, PhD, DrPH Deborah L. Nurmi, MS]

Resembling hydrocephalus.

Hydrocephalus
Classification and external resources
Hydrocephalus seen on a CT scan of the brain.
ICD-10	G91., Q03.
ICD-9	331.3, 331.4, 741.0, 742.3
DiseasesDB	6123
MedlinePlus	001571
eMedicine	neuro/161
MeSH	D006849

Hydrocephalus^[1] (pronounced /ˌhaɪdrɵˈsɛfələs/), also known as "water on the brain", is a medical condition. People with hydrocephalus have an abnormal accumulation of cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head, convulsion, and mental disability. Hydrocephalus can also cause death.

Contents 1 History 2 Epidemiology 3 Pathology 4 Classification 4.1 Communicating 4.2 Non-communicating 4.3 Congenital 4.4 Acquired 5 Symptoms 6 Effects 7 Treatment 7.1 Shunt complications 8 Shunts in Developing Countries 9 Exceptional case 10 See also 11 References 12 External links

History

Hydrocephalus was first described by the ancient Greek physician Hippocrates, but it remained an intractable condition until the 20th century, when shunts and other neurosurgical treatment modalities were developed. Although 1 million Americans suffer from hydrocephalus, it remains a lesser-known medical condition. Relatively small amounts of research are conducted to improve treatments for hydrocephalus, and to this day there remains no cure for the condition.

Epidemiology

Hydrocephalus affects both pediatric and adult patients. According to the NIH website, there are an estimated 700,000 children and adults living with hydrocephalus.

Pediatric hydrocephalus affects one in every 500 live births^[2], making it one of the most common developmental disabilities, more common than Down syndrome or deafness.^[3] . It is the leading cause of brain surgery for children in the United States. There are over 180 different causes of the condition, one of the most common acquired etiologies being brain hemorrhage associated with premature birth. Pediatric hydrocephalus may also be a heritable condition and runs in certain families mostly affecting boys.

One of the most performed treatments for hydrocephalus, the cerebral shunt, has not changed much since it was developed in 1960. The shunt must be implanted through neurosurgery into the patient's brain, a procedure which itself may cause brain damage. An estimated 50% of all shunts fail within two years, requiring further surgery to replace the shunts. In the past 25 years, death rates associated with hydrocephalus have decreased from 54% to 5% and the occurrence of intellectual disability has decreased from 62% to 30%.

In the United States, the healthcare cost for hydrocephalus has exceeded $1 billion per year, but is still much less funded than research on other diseases including juvenile diabetes.^[4]

Pathology

Hydrocephalus is usually due to blockage of CSF outflow in the ventricles or in the subarachnoid space over the brain. In a person without hydrocephalus, CSF continuously circulates through the brain, its ventricles and the spinal cord and is continuously drained away into the circulatory system. Alternatively, the condition may result from an overproduction of the CSF fluid, from a congenital malformation blocking normal drainage of the fluid, or from complications of head injuries or infections.^[5]

Compression of the brain by the accumulating fluid eventually may cause convulsions and mental retardation. These signs occur sooner in adults, whose skulls no longer are able to expand to accommodate the increasing fluid volume within. Fetuses, infants, and young children with hydrocephalus typically have an abnormally large head, excluding the face, because the pressure of the fluid causes the individual skull bones — which have yet to fuse — to bulge outward at their juncture points. Another medical sign, in infants, is a characteristic fixed downward gaze with whites of the eyes showing above the iris, as though the infant were trying to examine its own lower eyelids.^[6] Hydrocephalus occurs in about one out of every 500 live births^[2] and was routinely fatal until surgical techniques for shunting the excess fluid out of the central nervous system and into the blood or abdomen were developed. Hydrocephalus is detectable during prenatal ultrasound examinations.

Usually, hydrocephalus does not cause any intellectual disability if recognized and properly treated. A massive degree of hydrocephalus rarely exists in typically functioning people, though such a rarity may occur if onset is gradual rather than sudden.^[7]

Spontaneous intracerebral and intraventricular hemorrhage with hydrocephalus shown on CT scan^[8]

The elevated intracranial pressure may cause compression of the brain, leading to brain damage and other complications. Conditions among affected individuals vary widely. Children who have had hydrocephalus may have very small ventricles, and presented as the "normal case".

If the foramina (pl.) of the fourth ventricle or the cerebral aqueduct are blocked, cereobrospinal fluid (CSF) can accumulate within the ventricles. This condition is called internal hydrocephalus and it results in increased CSF pressure. The production of CSF continues, even when the passages that normally allow it to exit the brain are blocked. Consequently, fluid builds inside the brain causing pressure that compresses the nervous tissue and dilates the ventricles. Compression of the nervous tissue usually results in irreversible brain damage. If the skull bones are not completely ossified when the hydrocephalus occurs, the pressure may also severely enlarge the head. The cerebral aqueduct may be blocked at the time of birth or may become blocked later in life because of a tumor growing in the brainstem.

Internal hydrocephalus can be successfully treated by placing a drainage tube (shunt) between the brain ventricles and abdominal cavity to eliminate the high internal pressures. There is some risk of infection being introduced into the brain through these shunts, however, and the shunts must be replaced as the person grows. A subarachnoid hemorrhage may block the return of CSF to the circulation. If CSF accumulates in the subarachnoid space, the condition is called external hydrocephalus. In this condition, pressure is applied to the brain externally, compressing neural tissues and causing brain damage. Thus resulting in further damage of the brain tissue and leading to necrotization.

Classification

Hydrocephalus can be caused by impaired cerebrospinal fluid (CSF) flow, reabsorption, or excessive CSF production.

• The most common cause of hydrocephalus is CSF flow obstruction, hindering the free passage of cerebrospinal fluid through the ventricular system and subarachnoid space (e.g., stenosis of the cerebral aqueduct or obstruction of the interventricular foramina - foramina of Monro secondary to tumors, hemorrhages, infections or congenital malformations).
• Hydrocephalus can also be caused by overproduction of cerebrospinal fluid (relative obstruction) (e.g., papilloma of choroid plexus).

Based on its underlying mechanisms, hydrocephalus can be classified into communicating and non-communicating (obstructive). Both forms can be either congenital or acquired.

Communicating

Communicating hydrocephalus, also known as non-obstructive hydrocephalus, is caused by impaired cerebrospinal fluid resorption in the absence of any CSF-flow obstruction between the ventricles and subarachnoid space. It has been theorized that this is due to functional impairment of the arachnoid granulations, which are located along the superior sagittal sinus and is the site of cerebrospinal fluid resorption back into the venous system. Various neurologic conditions may result in communicating hydrocephalus, including subarachnoid/intraventricular hemorrhage, meningitis, Chiari malformation, and congenital absence of arachnoidal granulations (Pacchioni's granulations). Scarring and fibrosis of the subarachnoid space following infectious, inflammatory, or hemorrhagic events can also prevent resorption of CSF, causing diffuse ventricular dilatation.

• Normal pressure hydrocephalus (NPH) is a particular form of communicating hydrocephalus, characterized by enlarged cerebral ventricles, with only intermittently elevated cerebrospinal fluid pressure. The diagnosis of NPH can be established only with the help of continuous intraventricular pressure recordings (over 24 hours or even longer), since more often than not instant measurements yield normal pressure values. Dynamic compliance studies may be also helpful. Altered compliance (elasticity) of the ventricular walls, as well as increased viscosity of the cerebrospinal fluid, may play a role in the pathogenesis of normal pressure hydrocephalus.

Main article: normal pressure hydrocephalus

• Hydrocephalus ex vacuo also refers to an enlargement of cerebral ventricles and subarachnoid spaces, and is usually due to brain atrophy (as it occurs in dementias), post-traumatic brain injuries and even in some psychiatric disorders, such as schizophrenia. As opposed to hydrocephalus, this is a compensatory enlargement of the CSF-spaces in response to brain parenchyma loss - it is not the result of increased CSF pressure.

Non-communicating

Non-communicating hydrocephalus, or obstructive hydrocephalus, is caused by a CSF-flow obstruction ultimately preventing CSF from flowing into the subarachnoid space (either due to external compression or intraventricular mass lesions).

• Foramen of Monro obstruction may lead to dilation of one or, if large enough (e.g., in colloid cyst), both lateral ventricles.
• The aqueduct of Sylvius, normally narrow to begin with, may be obstructed by a number of genetically or acquired lesions (e.g., atresia, ependymitis, hemorrhage, tumor) and lead to dilation of both lateral ventricles as well as the third ventricle.
• Fourth ventricle obstruction will lead to dilatation of the aqueduct as well as the lateral and third ventricles.
• The foramina of Luschka and foramen of Magendie may be obstructed due to congenital failure of opening (e.g., Dandy-Walker malformation).

Congenital

Main articles: Arnold-Chiari malformation and Dandy-Walker malformation

The cranial bones fuse by the end of the third year of life. For head enlargement to occur, hydrocephalus must occur before then. The causes are usually genetic but can also be acquired and usually occur within the first few months of life, which include 1) intraventricular matrix hemorrhages in premature infants, 2) infections, 3) type II Arnold-Chiari malformation, 4) aqueduct atresia and stenosis, and 5) Dandy-Walker malformation.

In newborns and toddlers with hydrocephalus, the head circumference is enlarged rapidly and soon surpasses the 97th percentile. Since the skull bones have not yet firmly joined together, bulging, firm anterior and posterior fontanelles may be present even when the patient is in an upright position.

The infant exhibits fretfulness, poor feeding, and frequent vomiting. As the hydrocephalus progresses, torpor sets in, and the infant shows lack of interest in his surroundings. Later on, the upper eyelids become retracted and the eyes are turned downwards (due to hydrocephalic pressure on the mesencephalic tegmentum and paralysis of upward gaze). Movements become weak and the arms may become tremulous. Papilledema is absent but there may be reduction of vision. The head becomes so enlarged that the child may eventually be bedridden.

About 80-90% of fetuses or newborn infants with spina bifida—often associated with meningocele or myelomeningocele—develop hydrocephalus.^[9]

Acquired

This condition is acquired as a consequence of CNS infections, meningitis, brain tumors, head trauma, intracranial hemorrhage (subarachnoid or intraparenchymal) and is usually extremely painful.

Symptoms

Symptoms of increased intracranial pressure may include headaches, vomiting, nausea, papilledema, sleepiness, or coma. Elevated intracranial pressure may result in uncal and/or cerebellar tonsill herniation, with resulting life threatening brain stem compression. For details on other manifestations of increased intracranial pressure:

Main article: intracranial pressure

The triad (Hakim triad) of gait instability, urinary incontinence and dementia is a relatively typical manifestation of the distinct entity normal pressure hydrocephalus (NPH). Focal neurological deficits may also occur, such as abducens nerve palsy and vertical gaze palsy (Parinaud syndrome due to compression of the quadrigeminal plate, where the neural centers coordinating the conjugated vertical eye movement are located).

Main article: normal pressure hydrocephalus

Effects

Because hydrocephalus can injure the brain, thought and behavior may be adversely affected. Learning disabilities including short-term memory loss are common among those with hydrocephalus, who tend to score better on verbal IQ than on performance IQ, which is thought to reflect the distribution of nerve damage to the brain. However the severity of hydrocephalus can differ considerably between individuals and some are of average or above-average intelligence. Someone with hydrocephalus may have motion and visual problems, problems with coordination, or may be clumsy. They may reach puberty earlier than the average child (see precocious puberty). About one in four develops epilepsy.

Treatment

Hydrocephalus treatment is surgical. It involves the placement of a ventricular catheter (a tube made of silastic), into the cerebral ventricles to bypass the flow obstruction/malfunctioning arachnoidal granulations and drain the excess fluid into other body cavities, from where it can be resorbed. Most shunts drain the fluid into the peritoneal cavity (ventriculo-peritoneal shunt), but alternative sites include the right atrium (ventriculo-atrial shunt), pleural cavity (ventriculo-pleural shunt), and gallbladder. A shunt system can also be placed in the lumbar space of the spine and have the CSF redirected to the peritoneal cavity (Lumbar-peritoneal shunt). An alternative treatment for obstructive hydrocephalus in selected patients is the endoscopic third ventriculostomy (ETV), whereby a surgically created opening in the floor of the third ventricle allows the CSF to flow directly to the basal cisterns, thereby shortcutting any obstruction, as in aqueductal stenosis. This may or may not be appropriate based on individual anatomy.

Shunt complications

Examples of possible complications include shunt malfunction, shunt failure, and shunt infection. Although a shunt generally works well, it may stop working if it disconnects, becomes blocked (clogged), infected, or it is outgrown. If this happens the cerebrospinal fluid will begin to accumulate again and a number of physical symptoms will develop (headaches, nausea, vomiting, photophobia/light sensitivity), some extremely serious, like seizures. The shunt failure rate is also relatively high (of the 40,000 surgeries performed annually to treat hydrocephalus, only 30% are a patient's first surgery) ^[10] and it is not uncommon for patients to have multiple shunt revisions within their lifetime.

The diagnosis of cerebrospinal fluid buildup is complex and requires specialist expertise.

Another complication can occur when CSF drains more rapidly than it is produced by the choroid plexus, causing symptoms -listlessness, severe headaches, irritability, light sensitivity, auditory hyperesthesia (sound sensitivity), nausea, vomiting, dizziness, vertigo, migraines, seizures, a change in personality, weakness in the arms or legs, strabismus, and double vision - to appear when the patient is vertical. If the patient lies down, the symptoms usually vanish in a short amount of time. A CT scan may or may not show any change in ventricle size, particularly if the patient has a history of slit-like ventricles. Difficulty in diagnosing overdrainage can make treatment of this complication particularly frustrating for patients and their families.

Resistance to traditional analgesic pharmacological therapy may also be a sign of shunt overdrainage or failure. Diagnosis of the particular complication usually depends on when the symptoms appear - that is, whether symptoms occur when the patient is upright or in a prone position, with the head at roughly the same level as the feet.

Shunts in Developing Countries

Since the cost of shunt systems is beyond the reach of common people in developing countries, most people with hydrocephalus die without even getting a shunt. Worse is the rate of revision in shunt systems that adds to the cost of shunting many times. Looking at this point, a study done by Dr. Benjamin C. Warf compares different shunt systems and highlighting the role of low cost shunt systems in most of the developing countries. This study has been published in Journal of Neurosurgery: Pediatrics May 2005 issue. It is about comparing Chhabra shunt system to those of the shunt systems from developed countries. The study was done in Uganda and the shunts were donated by the International Federation for Spina Bifida and Hydrocephalus.

Exceptional case

One interesting case involving a person with past hydrocephalus was a 44-year old French man, whose brain had been reduced to little more than a thin sheet of actual brain tissue, due to the buildup of cerebrospinal fluid in his head. The man, who had had a shunt inserted into his head to drain away fluid (which was removed when he was 14), went to a hospital after he had been experiencing mild weakness in his left leg.

DWS: All of the black in the middle is cerebrospinal fluid and the brain matter is the rim of white along the outside of the skull. This is a screen shot from a Fox News report.

In July 2007, Fox News quoted Dr. Lionel Feuillet of Hôpital de la Timone in Marseille as saying: "The images were most unusual... the brain was virtually absent."^[11] When doctors learned of the man's medical history, they performed a computed tomography (CT) scan and magnetic resonance imaging (MRI) scan, and were astonished to see "massive enlargement" of the lateral ventricles in the skull. Intelligence tests showed the man had an IQ of 75, below the average score of 100. This would be considered "borderline intellectual functioning"- which is to say not quite mental retardation.

Remarkably, the man was a married father of two children, and worked as a civil servant, leading an at least superficially normal life, despite having enlarged ventricles with a decreased volume of brain tissue. "What I find amazing to this day is how the brain can deal with something which you think should not be compatible with life," commented Dr. Max Muenke, a pediatric brain defect specialist at the National Human Genome Research Institute. "If something happens very slowly over quite some time, maybe over decades, the different parts of the brain take up functions that would normally be done by the part that is pushed to the side."^[12][13]

See also

• Spina bifida
• Acquired hydrocephalus (causes of it)
  • CNS-infections
  • Brain tumors
  • Head trauma
  • Intracranial hemorrhage
• Arachnoid granulation
• Brain
• Cerebrospinal fluid
• Intracranial pressure
• Normal pressure hydrocephalus
• Cerebral shunt
• Subarachnoid space
• Ventricular system
• HEC syndrome

References

1. ^ From the Greek words ὑδρο- (hudro-) "water", and κέφαλος (kephalos) "head".
2. ^ ^{a b} http://www.ninds.nih.gov/disorders/hydrocephalus/detail_hydrocephalus.htm#131713125
3. ^ Eat your way to a better brain for your baby December 2005. Virtual Learning Environment (VLE)
4. ^ Need For Increased Federal Funding of Type 1 Diabetes Research JDRF
5. ^ "Hydrocephalus Fact Sheet", National Institute of Neurological Disorders and Stroke. (August 2005).
6. ^ Cabot, Richard C. (1919) Physical diagnosis , William Wood and company, New York, 7th edition, 527 pages, page 5. (Google Books)
7. ^ "Man with tiny brain shocks doctors", New Scientist (2007-07-20).
8. ^ Yadav YR, Mukerji G, Shenoy R, Basoor A, Jain G, Nelson A (2007). "Endoscopic management of hypertensive intraventricular haemorrhage with obstructive hydrocephalus". BMC Neurol 7: 1. doi:10.1186/1471-2377-7-1. PMID 17204141. PMC: 1780056. http://www.biomedcentral.com/1471-2377/7/1. 
9. ^ wwww.spinabifidamoms.com
10. ^ http://www.hydroassoc.org/media/stats
11. ^ "Man with Almost No Brain Has Led Normal Life", Fox News (2007-07-25). Also see "Man with tiny brain shocks doctors", NewScientist.com (2007-07-20); "Tiny Brain, Normal Life", ScienceDaily (2007-07-24).
12. ^ Man Lives Normal Life Despite Having Abnormal Brain
13. ^ Brain of a white-collar worker. Feuillet, L., Dufour, H. & Pelletier, J., et al. The Lancet, Volume 370, Issue 9583, Page 262, 21 July 2007

External links

• International Federation for Spina Bifida and Hydrocephalus (IF), the umbrella organisation for national spina bifida and hydrocephalus organisations
• Hydrocephalus Association at hydroassoc.org, US
• Hydrocephalus Clinical Research Network (HCRN) a multi-center clinical research network collaboration of several leading pediatric neurosurgeons in North America.
• Team Hydro a group affiliated with the Hydrocephalus Association in US, swimming for a cure

v • d • e Pathology of the nervous system, primarily CNS (G00–G47, 320–349) Brain/ encephalopathy Inflammatory Encephalitis (Viral encephalitis, Herpesviral encephalitis) · Cavernous sinus thrombosis · Brain abscess (Amoebic) Degenerative Extrapyramidal and movement disorders Basal ganglia disease: Parkinsonism (Parkinson's disease, Postencephalitic parkinsonism)  · Neuroleptic malignant syndrome  · Pantothenate kinase-associated neurodegeneration · Progressive supranuclear palsy · Striatonigral degeneration · Hemiballismus · Huntington's disease · Olivopontocerebellar atrophy Dyskinesia: Dystonia (Spasmodic torticollis, Meige's, Blepharospasm) · Chorea (Choreoathetosis)  · Myoclonus (Myoclonic epilepsy) Essential tremor  · Restless legs  · Stiff person Dementia Alzheimer's (Early-onset)  · Frontotemporal dementia/Frontotemporal lobar degeneration (Pick's, Dementia with Lewy bodies) · Multi-infarct dementia Mitochondrial disease Leigh's Demyelinating autoimmune (Multiple sclerosis, Neuromyelitis optica, Schilder's disease) · hereditary (Adrenoleukodystrophy, Alexander, Canavan, Krabbe, ML, Pelizaeus-Merzbacher, VWM, MFC, CAMFAK syndrome) · Central pontine myelinolysis · Marchiafava-Bignami disease  · Alpers' Episodic/ paroxysmal Seizure/epilepsy Focal  · Generalised  · Status epilepticus  · Myoclonic epilepsy Headache Migraine (Familial hemiplegic)  · Cluster  · Vascular  · Tension Vascular Transient ischemic attack (Amaurosis fugax, Transient global amnesia) Cerebrovascular disease  · Stroke (MCA, ACA, PCA, Foville's, Millard-Gubler, Lateral medullary, Weber's, Lacunar stroke) Sleep disorders Insomnia  · Hypersomnia  · Sleep apnea (Obstructive, Ondine's curse)  · Narcolepsy  · Cataplexy  · Kleine-Levin  · Circadian rhythm sleep  · Delayed sleep phase  · Advanced sleep phase CSF Intracranial hypertension (Hydrocephalus/Normal pressure, Idiopathic intracranial hypertension) · Cerebral edema · Intracranial hypotension Other Brain herniation · Reye's  · Hepatic encephalopathy  · Toxic encephalopathy Spinal cord/ myelopathy Inflammatory Myelitis: Poliomyelitis · Demyelinating disease (Transverse myelitis) · Tropical spastic paraparesis Other Syringomyelia · Syringobulbia · Morvan's syndrome · Vascular myelopathy (Foix-Alajouanine syndrome) · Spinal cord compression Both/either Inflammatory Encephalomyelitis (Acute disseminated) Meningitis/Arachnoiditis: Bacterial (Tuberculous, Haemophilus, Pneumococcal) · Viral (Herpesviral) · Fungal (Cryptococcal) · Aseptic (Drug-induced) Meningoencephalitis Systemic atrophies SA Friedreich's ataxia · Ataxia telangiectasia MND UMN only: PLS · PP · HSP LMN only: PMA · PBP (Fazio-Londe, Infantile progressive bulbar palsy) · SMA (SMN-linked, Kennedy disease, SMAX2, DSMA1) both: ALS central nervous system navs: anat/physio/dev, noncongen/congen/neoplasia, symptoms+signs/eponymous, proc

v • d • e Congenital malformations and deformations of nervous system (Q00-Q07, 740-742) Brain Neural tube defect Anencephaly (Acephaly, Acrania, Iniencephaly) · Encephalocele · Arnold-Chiari malformation Other Microcephaly · Congenital hydrocephalus (Dandy-Walker syndrome) other reduction deformities (Holoprosencephaly, Lissencephaly, Pachygyria, Hydranencephaly) Septo-optic dysplasia · Megalencephaly CNS cyst (Porencephaly, Schizencephaly) Polymicrogyria (Bilateral frontoparietal polymicrogyria) Spinal cord Neural tube defect Spina bifida · Rachischisis Other Currarino syndrome · Diastomatomyelia · Syringomyelia central nervous system navs: anat/physio/dev, noncongen/congen/neoplasia, symptoms+signs/eponymous, proc

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Dansk (Danish)
n. - vand i hovedet

Nederlands (Dutch)
waterhoofd

Français (French)
n. - hydrocéphalie

Deutsch (German)
n. - Hydrozephalus, Wasserkopf

Ελληνική (Greek)
n. - (παθολ., μτφ.) υδροκεφαλία

Italiano (Italian)
idrocefalo

Português (Portuguese)
n. - hidrocéfalo (m)

Русский (Russian)
водянка головного мозга

Español (Spanish)
n. - hidrocefalia, hidrocefalía

Svenska (Swedish)
n. - hydrocefalus (vattenskalle)

中文（简体）(Chinese (Simplified))
脑水肿, 脑积水

中文（繁體）(Chinese (Traditional))
n. - 腦水腫, 腦積水

한국어 (Korean)
n. - 뇌수종, 수두증

日本語 (Japanese)
n. - 脳水腫, 水頭

العربيه (Arabic)
‏(الاسم) استسقاء الرأس, مرض‏

עברית (Hebrew)
n. - ‮הידרקון הראש, מיימת הראש‬

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