Anatomy - Hydrocephalus
Hydrocephalus is a condition in which excess
cerebrospinal fluid (CSF) builds up within the ventricles
(fluid-containing cavities) of the brain and may increase
pressure within the head. Although hydrocephalus is
often described as "water on the brain," the "water"
is actually CSF, a clear fluid surrounding the brain
and spinal cord. Cerebrospinal fluid (CSF) is formed
in a region of the brain known as the choroid plexus.
CSF has three crucial functions:
1) it acts as a "shock absorber" for the brain and spinal
2) it acts as a vehicle for delivering nutrients to
the brain and removing waste;
3) it flows between the cranium and spine to regulate
changes in pressure within the brain.
The average adult produces about half a litre of CSF
daily. When an injury or illness alters the circulation
of CSF, one or more of the ventricles becomes enlarged
as CSF accumulates. In an adult, the skull is rigid
and cannot expand, so the pressure in the brain may
increase profoundly. Hydrocephalus is a chronic condition.
It can be controlled, but usually not cured. With appropriate
early treatment, however, many people with hydrocephalus
lead normal lives with few limitations. Hydrocephalus
can occur at any age, but is most common in infants
and adults age 60 and older. It affects adult males
and females, as well as people of different races about
equally. Experts believe that normal pressure hydrocephalus
accounts for 5 to 6 percent of all cases of dementia.
The incidence is approximately 1 out of 1,000 people.
Hydrocephalus most often occurs in children, but may
also occur in adults and the elderly.
Hydrocephalus ex-vacuo occurs when a stroke or injury
damages the brain and brain matter actually shrinks.
The brain may shrink in older patients or those with
Alzheimer's disease, and CSF volume increases to fill
the extra space. In these instances, the ventricles
are enlarged, but the pressure is usually normal.
Normal Pressure Hydrocephalus (NPH)
NPH results from the gradual blockage of the CSF draining
pathways in the brain. The ventricles enlarge to handle
the increased volume of CSF, and the compression of
the brain from within by the fluid-filled ventricles
destroys or damages brain tissue. NPH owes its name
to the fact that the ventricles inside the brain become
enlarged with little or no increase in pressure. However,
the name can be misleading, as some patient's CSF pressure
does fluctuate from high to normal to low when monitored.
NPH can occur as the result of head injury, cranial
surgery, haemorrhage, meningitis or tumour. Unfortunately,
the cause of the majority of NPH cases is unknown, making
it difficult to diagnose and understand. Compounding
this difficulty is the fact that some of the symptoms
of NPH are similar to the effects of the aging process,
as well as diseases such as Alzheimer's and Parkinson's.
The majority of the NPH population is older than 60,
and many of these people believe their symptoms are
just part of the aging process. Unfortunately, many
cases go unrecognised, are never properly treated, or
What symptoms can
Symptoms vary depending on the cause of the obstruction
to CSF circulation, the age at which the problem develops,
and the extent of damage to brain tissue caused by the
Symptoms of Adult-Onset Hydrocephalus:
- Difficulty focusing the eyes
- Unsteady walk or gait
- Leg weakness
- Sudden falls
- Personality changes
Primary Symptoms of NPH:
- Gait disturbance (difficulty walking)
- Dementia or forgetfulness
- Bladder control problems (as the condition progresses)
The gait in many patients with NPH is very distinctive:
wide-based, short, slow and shuffling. People may have
trouble picking up their feet, as if their feet are
glued to the ground. They may have difficulty going
up and down stairs and curbs, and as a result, they
are frequently falling. Gait disturbance is often the
most obvious first symptom. These disturbances range
in severity, from mild imbalance to the inability to
stand or walk at all. The symptoms of NPH usually get
worse over time if the condition is left untreated.
Patients with untreated, advanced NPH may experience
seizures, which can get progressively worse. Dementia
and/or bladder control problems usually appear after
gait disturbances, as the condition progresses. Mild
dementia can be described as a loss of interest in daily
activities, forgetfulness, difficulty dealing with routine
tasks and short-term memory loss. Not everyone with
NPH develops an obvious mental impairment. Bladder control
problems usually involve urinary frequency and urgency
in mild cases. In severe cases, however, a complete
loss of bladder control (urinary incontinence) may result.
Urinary frequency is the need to urinate more than usual,
often as frequently as every one to two hours. Urinary
urgency is a strong, immediate physical need to urinate.
This urge is sometimes so strong that it cannot be controlled,
resulting in incontinence.
Patients presenting the three primary NPH symptoms
or a combination of the other symptoms should consult
a neurosurgeon as soon as possible. Before your doctor
can recommend a course of treatment, he or she will:
- Review your medical history, and perform a physical
- Perform a complete neurological examination including
diagnostic testing if needed
- Ask specific questions to determine if symptoms
are caused by hydrocephalus
The neurological examination will also help to determine
the severity of your condition. There are a wide variety
of diagnostic tests that can help pinpoint the cause
and severity of hydrocephalus.
- Computed tomography scan (CT or CAT scan): A diagnostic
image created after a computer reads x-rays; can show
if the ventricles are enlarged or if there is an obvious
- Magnetic resonance imaging (MRI): A diagnostic
test that produces three-dimensional images of body
structures using magnetic fields and computer technology;
can reveal if the ventricles are enlarged and evaluate
the CSF flow. The MRI provides more information than
the CT scan, so is the preferred test, in most cases.
- Isotopic cisternography: A test that involves injecting
a radioactive isotope into the lower back through
a spinal tap. This allows the absorption of CSF to
be monitored over a period of time (up to 4 days).
Isotopic cisternography is considerably more involved
than a CT scan or MRI, but can aid in the diagnosis
- Lumbar puncture (spinal tap): Under local anesthetic,
a thin needle is passed into the spinal fluid space
of the low back. Removal of up to 50 cc of CSF is
done to see if symptoms are temporarily relieved.
This test is used to measure CSF pressure and analyze
the fluid. This procedure may help determine whether
a shunt, the common treatment for hydrocephalus, will
work. If lumbar puncture improves symptoms even temporarily,
this can be an indication that a shunt will be successful.
There are patients, however, who show no improvement
that go on to have a successful shunt procedure.
- Intracranial pressure monitoring: Monitoring may
be able to detect an abnormal pressure or pattern
of pressure waves. Monitoring requires insertion of
a catheter or small fiber optic cable through the
skull into the brain. This procedure requires admission
to the hospital for 24 hours.
When Surgery is Necessary
Hydrocephalus can be treated in a variety of ways.
The problem area may be treated directly (by removing
the cause of CSF obstruction), or indirectly (by diverting
the fluid to somewhere else; typically to another body
cavity). Indirect treatment is performed by implanting
a device known as a shunt to divert the excess CSF away
from the brain. The body cavity in which the CSF is
diverted is usually the peritoneal cavity (the area
surrounding the abdominal organs).
In some cases, two procedures are performed, one to
divert the CSF, and another at a later stage to remove
the cause of obstruction (e.g., a brain tumor). Once
inserted, the shunt system usually remains in place
for the duration of a patient's life (although additional
operations to revise the shunt system are sometimes
needed). The shunt system continuously performs its
function of diverting the CSF away from the brain, thereby
keeping the intracranial pressure within normal limits.
An alternative operation called endoscopic third ventriculostomy
may be recommended. In this operation, a tiny burr hole
is made in the skull and a neuroendoscope (a small camera
which is attached to medical instrument) is utilised
to enter the brain. The neurosurgeon will then make
a small hole (several millimeters) in the floor of the
third ventricle, creating a new pathway through which
CSF can flow.
Your neurological function will be evaluated post surgery.
If any neurological problems persist, rehabilitation
may be required to further your improvement. However,
recovery may be limited by the extent of the damage
already caused by the hydrocephalus and by your brain's
ability to heal.
Because hydrocephalus is an ongoing condition, long-term
follow-up by a doctor is required. Follow-up diagnostic
tests including CT scans, MRIs and x-rays, are helpful
in determining if the shunt is working properly. Do
not hesitate to contact your physician if you experience
any of the following postoperative symptoms:
- Redness, tenderness, pain or swelling of the skin
along the length of the tube or incision
- Irritability or drowsiness
- Nausea, vomiting, headache or double vision
- Abdominal pain
- Return of preoperative neurological symptoms
The prognosis for hydrocephalus depends on the cause,
the extent of symptoms, and the timeliness of diagnosis
and treatment. Some patients show a dramatic improvement
with treatment while others do not. In some instances
of NPH, dementia can be reversed by shunt placement.
Other symptoms such as headaches may disappear almost
immediately if the symptoms are related to elevated
pressure. If the cause of NPH is known, the rate of
shunting success can be as high as 80 percent. In cases
in which the cause is unknown, the success rate varies
from 25 to 74 percent.
In general, the earlier hydrocephalus is diagnosed,
the better the chance for successful treatment. The
longer the symptoms have been present, the less likely
it is that treatment will be successful. Unfortunately,
there is no way to accurately predict how successful
surgery will be for each individual. Some patients will
improve dramatically while others will reach a plateau
or decline after a few months.
Shunt malfunction or failure may occur. The valve can
become clogged or the pressure in the shunt may not
match the needs of the patient, requiring additional
surgery. In the event of an infection, antibiotic therapy
may be needed. A shunt malfunction may be indicated
by headaches, vision problems, irritability, fatigue,
personality change, loss of coordination, difficulty
in waking up or staying awake, a return of walking difficulties,
mild dementia or incontinence. Fortunately, most complications
can be dealt with successfully.
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