What is Hydrocephalus?
Hydrocephalus is a condition in which the primary characteristic is excessive
accumulation of fluid in the brain. Although hydrocephalus was once known as
“water on the brain,” the “water” is actually cerebrospinal fluid (CSF) — a clear
fluid surrounding the brain and spinal cord. The excessive accumulation of CSF
results in an abnormal dilation of the spaces in the brain called ventricles. This
dilation causes potentially harmful pressure on the tissues of the brain
Hydrocephalus may be congenital or acquired. Congenital hydrocephalus is
present at birth and may be caused by genetic abnormalities or developmental
disorders such as spina bifida and encephalocele. Acquired hydrocephalus
develops at the time of birth or at some point afterward and can affect
individuals of all ages. For example, hydrocephalus ex-vacuo occurs when
there is damage to the brain caused by stroke or traumatic injury. Normal
pressure hydrocephalus occurs most often among the elderly. It may result from
a subarachnoid hemorrhage, head trauma, infection, tumor, or complications of
surgery, although many people develop normal pressure hydrocephalus without
an obvious cause. Symptoms of hydrocephalus vary with age, disease
progression, and individual differences in tolerance to CSF[1];[2]. In infancy, the
most obvious indication of hydrocephalus is often the rapid increase in head
circumstance or an unusually large head size. In older children and
adults, symptoms may include headache followed by vomiting, nausea,
papilledema (swelling of the optic disk, which is part of the optic nerve),
downward deviation of the eyes (called “sunsetting”), problems with balance,
poor coordination, gait disturbance, urinary incontinence, slowing or loss of
development (in children), lethargy, drowsiness, irritability, or other changes in
personality or cognition, including memory loss. Hydrocephalus is diagnosed
through clinical neurological evaluation and by using cranial imaging
techniques such as ultrasonography, computer tomography (CT), magnetic
resonance imaging (MRI), or pressure-monitoring techniques[3].

Is there any treatment?
Hydrocephalus is most often treated with the surgical placement of a shunt
system. Thissystem diverts the flow of CSF from a site within the central
nervous system to another area of the body where it can be absorbed as part of
the circulatory process.A limited number of patients can be treated with an
alternative procedure called third ventriculostomy. In this procedure, a small
hole is made in the floor of the third ventricle, allowing the CSF to bypass the
obstruction and flow toward the site of resorption around the surface of the
brain.

What is the prognosis?
The prognosis for patients diagnosed with hydrocephalus is difficult to predict,
although there is some correlation between the specific cause of hydrocephalus and the
patient’s
outcome. Prognosis is further complicated by the presence of associated disorders, the
timeliness of diagnosis, and the success of treatment. The symptoms of normal pressure
hydrocephalus usually get worse over time if the condition is not treated, although some
people may experience temporary improvements. If left untreated, progressive
hydrocephalus is fatal, with rare exceptions. The parents of children with hydrocephalus
should be aware that hydrocephalus poses risks to both cognitive and physical
development. Treatment by an interdisciplinary team of medical professionals,
rehabilitation specialists, and educational experts is critical to a positive outcome. Many
children diagnosed with the disorder benefit from rehabilitation therapies and educational
interventions, and go on to lead normal lives with few limitations.
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. Note: in the initial description of
hydrocephalus the text says 1 in 1,000 live births have hydrocephalus, when the actual
value is 1 or 2 per 1,000 births (1/500). There are many sources to confirm this.[1].

Epidemiology
There is no cure for hydrocephalus.
Hydrocephalus affects one in every 1000 live births, making it one of the most common
developmental disabilities, more common than Down syndrome or deafness [4];[5].
According to the NIH website, there are an estimated 700,000 children and adults living
with hydrocephalus, and 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 being brain hemorrhage associated with premature birth.
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% [5].
Pathology

Spontaneous intracerebral and intraventricular hemorrhage with hydrocephalus shown on CT scan.

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,
cerebrospinal 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

aqueduct may be blocked at the time of birth or may become blocked later in life because
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
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[6].

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 [7]
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.
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 [7]
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
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 reduction of vision. The head becomes
so is absent but there may be 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.[7]
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[7].
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:

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).

Effects [8]
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
motivation 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.
Because the problem resides inside the head, doctors rely heavily on
computer tomography scanning (CT scans), which may be used frequently to evaluate
the condition of the disorder throughout the patient’s life. Each CT scan exposes the
patient to many times the level of x-ray radiation of a chest x-ray. See CT
radiation exposure.
Treatment [9]
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)
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 fluid in his skull. The man, who 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
rid of white along the outside of the skull. This is a screen shot from a Fox News
report.Dr.Lionel Feuillet of Hospital de la Timone in Marseille as saying: “The images
were most unusual… the brain was virtually absent.” [9] 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 but not considered mentally retarded or disabled, either.Remarkably, the man was a married father of two children, and worked as a civil servant, leading a normal life, despite having little 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.”[5]

What research is being done?
The NINDS conducts and supports a wide range of fundamental studies that explore the complex mechanisms of normal brain development. The knowledge gained from these studies provides the foundation for understanding how this process can go awry and, thus, offers hope for new means to treat and prevent developmental brain disorders such as congenital hydrocephalus [5].