Hydrocephalus
Definition
Hydrocephalus
is the buildup of fluid in the cavities (ventricles) deep within the brain. The
excess fluid increases the size of the ventricles and puts pressure on the
brain.
Cerebrospinal
fluid normally flows through the ventricles and bathes the brain and spinal
column. But the pressure of too much cerebrospinal fluid associated with
hydrocephalus can damage brain tissues and cause a large spectrum of
impairments in brain function.
Although
hydrocephalus can occur at any age, it's more common among infants and older
adults.
Surgical
treatment for hydrocephalus can restore and maintain normal cerebrospinal fluid
levels in the brain. A variety of interventions are often required to manage
symptoms or functional impairments resulting from hydrocephalus.
Causes
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 ("sunset eyes") (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.
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.
Type
The cause of hydrocephalus is not known
with certainty and is probably multifactorial. It may be caused by impaired cerebrospinal fluid (CSF) flow, reabsorption, or excessive
CSF production.
·
Obstruction to CSF flow hinders 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) secondary to tumors, hemorrhages, infections or congenital malformations) and can cause increases
in central nervous system pressure.
·
Hydrocephalus can also be caused by
overproduction of cerebrospinal fluid (relative obstruction) (e.g., Choroid plexus papilloma, villous
hypertrophy).
·
Bilateral ureteric obstruction is a
rare, but reported, cause of hydrocephalus.
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 reabsorption 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 arachnoidal
granulations (also
called arachnoid granulations or Pacchioni's granulations), which are located
along the superior sagittal sinus and is the site of cerebrospinal fluid
reabsorption back into the venous system. Various neurologic conditions may
result in communicating hydrocephalus, including subarachnoid/intraventricular
hemorrhage, meningitisand
congenital absence of arachnoid villi. 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.
·
Hydrocephalus ex vacuo also
refers to an enlargement of cerebral ventricles and subarachnoid spaces, and is
usually due to brain atrophy (as it occurs indementias),
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.
·
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 (e.g., Chiari malformation).
·
The foramina of Luschka and foramen of Magendie may be obstructed due to congenital
failure of opening (e.g., Dandy-Walker malformation).
Symptoms
The signs and symptoms of hydrocephalus vary generally by age
of onset.
Infants
Common signs and symptoms of hydrocephalus in infants
include:
Changes in the head
·
An
unusually large head
·
A
rapid increase in the size of the head
·
A
bulging or tense soft spot (fontanel) on the top of the head
Physical symptoms
·
Vomiting
·
Sleepiness
·
Irritability
·
Poor
feeding
·
Seizures
·
Eyes
fixed downward (sunsetting of the eyes)
·
Deficits
in muscle tone and strength, responsiveness to touch, and expected growth
Toddlers and older
children
Among toddlers and older children, signs and symptoms may
include:
Physical symptoms
·
Headache
·
Blurred
or double vision
Physical signs
·
Abnormal
enlargement of a toddler's head
·
Sleepiness
·
Difficulty
remaining awake or waking up
·
Nausea
or vomiting
·
Unstable
balance
·
Poor
coordination
·
Poor
appetite
·
Seizures
Behavioral and
cognitive changes
·
Irritability
·
Change
in personality
·
Problems
with attention
·
Decline
in school performance
·
Delays
or problems with previously acquired skills, such as walking or talking
Young and middle-aged
adults
Common signs and symptoms in this age group include:
·
Headache
·
Difficulty
in remaining awake or waking up
·
Loss
of coordination or balance
·
Loss
of bladder control or a frequent urge to urinate
·
Impaired
vision
·
Decline
in memory, concentration and other thinking skills that may affect job
performance
Older adults
Among adults 60 years of age and older, the more common signs
and symptoms of hydrocephalus are:
·
Loss
of bladder control or a frequent urge to urinate
·
Memory
loss
·
Progressive
loss of other thinking or reasoning skills
·
Difficulty
walking, often described as a shuffling gait or the feeling of the feet being
stuck
·
Poor
coordination or balance
·
Slower
than normal movements in general
Risk
factors
In many cases, the exact event leading to hydrocephalus is
unknown. However, a number of developmental or medical problems can contribute
to or trigger hydrocephalus.
Newborns
Hydrocephalus present at birth
(congenital) or shortly after birth may occur because of any of the following:
·
Abnormal development of the central
nervous system that can obstruct the flow of cerebral spinal fluid
·
Bleeding within the ventricles, a
possible complication of premature birth
·
Infection in the uterus during a
pregnancy, such as rubella or syphilis, that can cause inflammation in fetal
brain tissues
Other contributing
factors
Other factors that can contribute to hydrocephalus among any
age group include:
·
Lesions or tumors of the brain or spinal
cord
·
Central nervous system infections, such
as bacterial meningitis or mumps
·
Bleeding in the brain from stroke or
head injury
·
Other traumatic injury to the brain
Complications
Long-term complications of hydrocephalus
can vary widely and are often difficult to predict.
If hydrocephalus has progressed by the
time of birth, it may result in significant intellectual, developmental and
physical disabilities. Less severe cases, when treated appropriately, may have
few, if any, notable complications.
Adults who have experienced a significant
decline in memory or other thinking skills generally have poorer recoveries and
persistent symptoms after treatment of hydrocephalus.
The severity of
complications depends on:
·
Underlying medical or developmental
problems
·
Severity of initial symptoms
·
Timeliness of diagnosis and treatment
Tests and
diagnosis
A diagnosis of hydrocephalus is usually based on:
·
Your answers to the doctor's questions
about signs and symptoms
·
A general physical
·
A neurological exam
·
Brain imaging tests
Neurological exam
The type of neurological exam will depend on a person's age.
The neurologist may ask questions and conduct relatively simple tests in the
office to judge:
Muscle condition
·
Reflexes
·
Muscle
strength
·
Muscle
tone
Sensory status
·
Sense
of touch
·
Vision
and eye movement
·
Hearing
Movement status
·
Coordination
·
Balance
Psychiatric condition
·
Mental
status
·
Mood
Brain imaging
Brain imaging tests can show enlargement
of the ventricles caused by excess cerebrospinal fluid. They may also be used
to identify underlying causes of hydrocephalus or other conditions contributing
to the symptoms. Imaging tests may include:
·
Ultrasound. Ultrasound
imaging, which uses high-frequency sound waves to produce images, is often used
for an initial assessment for infants because it's a relatively simple,
low-risk procedure. The ultrasound device is placed over the soft spot
(fontanel) on the top of a baby's head. Ultrasound may also detect
hydrocephalus prior to birth when the procedure is used during routine prenatal
examinations.
·
Magnetic resonance imaging (MRI) uses
radio waves and a magnetic field to produce detailed 3-D or cross-sectional
images of the brain. This test is painless, but it is noisy and requires lying
still. Some MRI scans can take up to an hour and require mild sedation for
children. However, some hospitals may use a quick version of MRI that takes
about five minutes and doesn't require sedation.
·
Computerized tomography (CT) scan
is a specialized X-ray technology that can produce cross-sectional views of the
brain. Scanning is painless and takes about 20 minutes. This test also requires
lying still, so a child usually receives a mild sedative. CT scans for
hydrocephalus are usually used only for emergency exams.
Treatments and drugs
One of two surgical treatments may be used
to treat hydrocephalus.
Shunt
The most common treatment for
hydrocephalus is the surgical insertion of a drainage system, called a shunt.
It consists of a long, flexible tube with a valve that keeps fluid from the
brain flowing in the right direction and at the proper rate. One end of the
tubing is usually placed in one of the brain's ventricles. The tubing is then
tunneled under the skin to another part of the body where the excess
cerebrospinal fluid can be more easily absorbed — such as the abdomen or a
chamber in the heart.
People who have hydrocephalus usually need
a shunt system for the rest of their lives, and regular monitoring is required.
Endoscopic
third ventriculostomy
Endoscopic third ventriculostomy is a
surgical procedure that can be used for some people. In the procedure, your
surgeon uses a small video camera to have direct vision inside the brain and
makes a hole in the bottom of one of the ventricles or between the ventricles
to enable cerebrospinal fluid to flow out of the brain.
Complications
of surgery
Both surgical procedures can result in
complications. Shunt systems can stop draining cerebrospinal fluid or poorly
regulate drainage because of mechanical malfunctions, blockage or infections.
Complications of ventriculostomy include bleeding and infections.
Any failure requires prompt attention,
surgical revisions or other interventions. Signs and symptoms of problems may
include:
·
Fever
·
Irritability
·
Drowsiness
·
Nausea or vomiting
·
Headache
·
Vision problems
·
Redness, pain or tenderness of the skin
along the path of the shunt tube
·
Abdominal pain when the shunt valve is
in the abdomen
·
Recurrence of any of the initial
hydrocephalus symptoms
Other
treatments
Some people with hydrocephalus,
particularly children, may need additional treatment, depending on the severity
of long-term complications of hydrocephalus.
A care team for children may include a:
·
Pediatrician or physiatrist, who
oversees the treatment plan and medical care
·
Pediatric neurologist, who
specializes in the diagnosis and treatment of neurological disorders in
children
·
Occupational therapist, who
specializes in therapy to develop everyday skills
·
Developmental therapist, who
specializes in therapy to help your child develop age-appropriate behaviors,
social skills and interpersonal skills
·
Mental health provider, such
as a psychologist or psychiatrist
·
Social worker, who
assists the family with accessing services and planning for transitions in care
·
Special education teacher, who
addresses learning disabilities, determines educational needs and identifies
appropriate educational resources
Adults with more severe complications also
may require the services of occupational therapists, social workers,
specialists in dementia care or other medical specialists.
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