below you will read about hydrocephalus,the use of shunts,vp and lp shunts,surgeries,diagnosis,symptoms of shunt malfuctions.
Hydrocephalus is excessive accumulation of cerebrospinal
fluid within the cranium. If persistent and progressive ,it is treated by shunt insertion. Recently other methods of treatment
were introduced and these will be discussed in the appropriate section.
About 30 years ago before shunts were available
children with hydrocephalus, either died or left with severe disability. With the introduction of shunts procedures, hydrocephalic
child can lead a reasonable normal life and normal life expectancy.
Hydrocephalus is described either as obstructive
or noncommunicating and non-obstructive or communicating. This relates to the level of obstruction and whether CSF exits from
the foramina in the roof of the 4th ventricle or is fully trapped within the ventricular system. Hydrocephalus is also classified
as acquired when it is caused by acquired causes or congenital. In congenital hydrocephalus it is caused by either excessive
production of CSF, blockage to the CSF drainage or reduced excretion into the venous channels.
ANATOMY & PHYSIOLOGY OF CEREBROSPINAL
The CSF is clear colourless fluid which has minimal content of protein. It is contained in the ventricular system
as well as the subarachnoid spaces surrounding the brain and the spinal cord. The CSF is in hydrostatic equilibrium with the
interstitial tissue of the brain and can permeate across the brain tissue in both directions. It is expected that the brain
tissue and the CSF would have the same hydrostatic pressure in any part of the brain. As much as the brain tissue is protected
by a blood brain barrier from changes outside the central nervous system, the CSF has the same protection and does not change
biochemically as a result of changes in the systemic circulation. These barriers are at the level of the endothelium of brain
capillaries, at the level of the epithelium of the choroid plexuses and the outer layers of arachnoid matter. These barriers
protect the brain and the subarachnoid spaces from damaging influences outside the brain.
CEREBROSPINAL FLUID VOLUME & DISTRIBUTION
fluid fills the cavity of the ventricles and the subarachnoid spaces. The subarachnoid spaces are wide in certain areas and
these are called cisterns. At the cerebellomedullary area the cistern is called cisterna magna. We have also the pre-pontine
cistern surrounding the basilar artery and the interpeduncular cistern surrounding the circle of Willis. The subarachnoid
space extends caudally around the spinal cord and ends in lumbar -sacral dural sac where it surrounds the cauda equina.
average volume of intracranial cerebrospinal fluid is 125 mls with 89 mls in the subarachnoid space The volume of CSF in the
lumbar sac is about 30 mls.
The majority of CSF is produced by the choroid plexuses, there are assumptions that some CSF is formed
outside the choroid plexuses, from the brain substance. This is estimated to be about 10 to 15% of the whole volume of CSF.
is believed that CSF is formed at a rate of .5 ml per minute. It is believed that there is a persistent and steady production
of CSF irrespective of systemic changes. It is independent of the mean arterial blood pressure until this is reduced below
60 mms/mercury. However it is believed that the perfusion pressure influenced the production of CSF i.e. CSF production is
reduced at a higher threshold of systemic blood pressure when the CSF pressure is raised. Reduction of perfusion pressure
might act by diminishing choroid plexus blood flow and the supply of necessary material for CSF secretion.
CSF CIRCULATION AND DRAINAGE
From the lateral ventricles CSF passes through the foramen
of Munro to the 3rd ventricle(fig 1). From there it passes through the aqueduct of the Sylvius to the 4th ventricle. With
the CSF formed by the choroid plexus in the 4th ventricle it exits through the roof of the 4th ventricle. From there it passes
along the outer surface of the cerebellum and through the basal cisterns. It passes through the hiatus of the tent to the
Sylvian fissures and from there to the para-sagittal area. It is excreted by the arachnoid villi into the venous sinus, mainly
the sagittal sinus. It is believed that CSF takes one to two hours to reach the basal cisterns, 3 to 4 hours to reach the
sylvian fissure and 10 to 12 hours to spread over the cerebral subarachnoid space. By 24 hours it started to be cleared into
the superior sagittal sinus. The mechanism by which the CSF is secreted through the arachnoid villi is still not clear.
NORMAL CSF PRESSURE
In children and babies CSF pressure is low.
In infants it is estimated to be 40 to 50 mms of water and in children from 40 - 100 mms of water. In older age group it remains
constant of about 150 mms of water or 15 mm of Mercury. Pressures above 200 mms mms of water or 20 mms of Mercury are considered
The cerebral spinal fluid pressure is dependent on intracranial venous pressure, it is usually about 40 to
50 mms of water above the intracranial venous pressure. The difference in pressure is related to the continuous production
of CSF and resistance to its secretion.
There are fluctuations in the CSF pressure, these are influenced by ventilation
and cardiac contraction .CSF pressure falls with inspiration and rises during expiration, a variation of about 40 mms of water.
cardiac contraction there is a variation of about 20 mms of water with ventricular systole.
Hydrocephalus is classified into:
or obstructive hydrocephalus where there is no communication between the ventricular system and the subarachnoid space. The commonest cause of this category is aqueduct blockage.
or non-obstructive hydrocephalus where there is communication between the ventricular system and the subarachnoid space. The commonest cause of this group is post-infective and post-haemorrhagic hydrocephalus.
Causes of hydrocephalus
This is grouped into 3 main causes:
secretion of CSF by the choroid plexus as in cases of choroid plexus papilloma or carcinoma.
This is a rare cause.
Choroid plexus papilloma
to CSF circulation. This could be at any level of the CSF circulation. It could be at the level of the foramen of Monro where we have either unilateral or bilateral coverage
of the foramen of Monro giving dilatation of one or both lateral ventricles. This
is commonly seen in the colloid cyst and tumours of the third ventricle. Also in suprasellar lesion as suprasellar arachnoid
cyst or hypothalamic tumours. The commonest cause of obstructive hydrocephalus
is congenital aqueduct stenosis. There is narrowing or complete blockage of the
aqueduct. The child presents at an early age with dilated ventricles and large
Posterior fossa tumours
are a common cause of obstructive hydrocephalus due to blockage of the 4th ventricle. Medulloblastoma, cystic astrocytoma and ependymoma can all lead to obstructive hydrocephalus.
Third ventricle tumour causing hydrocephalus
A common cause of obstructive
hydrocephalus is Dandy Walker Syndrome where there is blockage of foramina of the 4th ventricle. This is a congenital condition associated with agenesis of the cerebellar vermis.
Obstruction to CSF
circulation can occur in the subarachnoid spaces after meningitis and scarring of the subarachnoid space or subarachnoid haemorrhage-causing
blockage of the subarachnoid spaces.
secretion of CSF into the venous sinuses caused by scarring of the arachnoid villi and is commonly seen after meningitis or
CLINICAL FEATURES OF HYDROCEPHALUS
is very important that Hydrocephalus is diagnosed early to minimise morbidity and mortality.
The common clinical presentation
in a child is increasing head size, irritability, failure to feed and vomiting. Motor and general developmental delay ,failure
to make appropriate visual and social contact is among the commonest neurological problems found in children with hydrocephalus.
In about 40% of cases there is excessive rate of head growth, fullness of anterior fontanelle in 40%, splayed sutures in 20%
and scalp vein dilatation in 15%.
Sunset eye sign and loss of upward gaze is found in about 14% with reduced conscious
level in 12%. papilloedema is unusual and found only in 7% of children. It is important to inquire about child responsiveness
and motor and intellectual milestones. An important sign is progressive increase in head size.
Sunset eye sign includes
upper eye lid retraction with defect of upward gaze and downward rotation of the globes. With open fontanelles, papilloedema
is not usually seen but optic nerve can progress to atrophy.
Delayed motor development can occur with children with
hydrocephalus due to raise intracranial pressure. This can present with increased tone and brisk tendon reflexes, especially
in the lower limbs and at later stages in the upper limbs.
Intellectual function would be difficult to assess in an
irritable or drowsy child.
In babies and infants ultrasound is sufficient to visualise the intracranial structures and ventricles.
In older children a CT scan or MRI could be performed. This would assist in visualising underlying causes if there are any.
Skull X-ray can show separation of sutures and copper beaten
appearance . However it should be noted that the copper beaten appearance is not always indicative of raising intracranial
MANAGEMENT OF HYDROCEPHALUS
CSF - DIVERSION AND ALTERNATIVE TREATMENTS
treatment of hydrocephalus started with the development of the valved shunt system by Halter and the application by Nelsen
Muslin bandages firmly applied to the head, adhesive plaster or rubber bandages were also used to compress
the head. This method was restarted by Epstein. The theory behind this method of treatment is to raise the intracranial pressure
which will increase Tran ependymal absorption of CSF ,or the reopening of compromised CSF pathways. However the method was
relegated to oblivion.
It would be ideal if we to design a drug which reduces the
CSF secretion ,allowing ventricular pressure and size to stabilise. Acetazolamide which is a carbonic anhydrase inhibitor
was initially shown to reduce CSF production by the choroid plexus. In a series of hydrocephalus in immature infants the drug
was used and success was claimed. It was claimed that ventricular shunt was avoided in 50% of cases.
plexectomy was tried but found unsuccessful.
These procedures were done in cases of obstructive hydrocephalus where the subarachnoid
spaces are still patent.
a. Third ventriculostomy.
Although this procedure was first devised by Dandy as an open
intracranial procedure, it had very high mortality and morbidity. However improved endoscopic techniques the procedure could
be done with minimal morbidity. The endoscope is passed through a burr hole to the third ventricle where the floor is fenestrated
just anterior to mamillary bodies. The hole is enlarged after that by introducing the endoscope or by introducing an inflatable
balloon. This operation is indicated in obstructive hydrocephalus with patent subarachnoid spaces.
shunt tubing is introduced in the posterior part of the lateral ventricle to the cisterna magna. This operation is not used
any more and it has high morbidity and mortality.
In this procedure the CSF is diverted from the ventricular system, usually the lateral
ventricle into another body cavity. The preferred site is the peritoneal cavity. Other sites used is the right atrium and
occasionally pleural cavity. The aim of the procedure is to normalise the intracranial pressure by draining the appropriate
amount of cerebrospinal fluid .This is achieved by creating appropriate CSF flow through a specially designed shunt valve
with the appropriate rate of flow and pressure. The shunts are made of medical grade silicon which is well tolerated by the
body. It causes minimal or no tissue reaction or intravascular thrombosis. The shunt system is either made of one unit or
several parts. An essential components of the shunt system is the shunt chamber which houses the valve which opens at a certain
pressure to regulate the CSF flow in a unidirectional way. The shunt chamber is proximally attached to ventricular catheter
which passes to the lateral ventricle .Distally it is attached to a catheter which leads the CSF into a body cavity. The flow
of CSF across the valve depends on the differential pressure between the inlet and the outlet.
standard shunt valve
programmable shunt system
TYPES OF SHUNT DRAINAGE
Currently ventriculo- atrial, ventriculo -peritoneal
and lumbar -peritoneal shunts are commonly used. The majority of surgeons prefer using the ventriculo peritoneal shunt. The
problem with the ventricular atrial shunt is that it would need repeated revision which becomes difficult as the child grows
older and venous access becomes more difficult. It also has a higher rate of complications. While the peritoneal cavity plenty
of tubing is left inside the peritoneum to accommodate for the child’s growth. Lumbo-peritoneal shunts have limited
indications. In ventriculo-peritoneal? shunts about 30cms is left in the peritoneal cavity.
Ventricular catheter is introduced through a burr hole just
below the right parietal eminence. The dura is opened and the catheter introduced into the right lateral ventricle. Ideally
the tip of catheter should be located in the anterior horn away from the choroid plexus. Our routine is to inject some air
and take an X-ray to verify that the catheter tip is located in the appropriate position. Endoscopic insertion of the ventricular
catheter can be used but usually it is not necessary in young children with large ventricles. The shunt chamber with the appropriate
differential pressure is connected to the ventricular catheter and inserted under the lower edge of the scalp incision. Following
that the peritoneal cavity is opened through a small mid-line supraumbilical incision ,through the linear alba to avoid cutting
through the abdominal muscles. The peritoneum is opened and the catheter is introduced. The ?peritoneal catheter can also
be introduced percutaneously, using a trocar and cannula. Following that the catheter is tunnelled under the skin using a
long introducer which is virtually a large trocar and cannula. The introducers can be tunnelled up to the scalp incision without
the necessity of intervening the skin incisions. Following that the parts of the catheter are tied together. In uni-catheters
the same procedure is used but the introducer is put through the scalp incision.
In atrial catheter a small neck incision
is made just below the angle of the jaw anterior to the anterior border of the sternomastoid muscle. The common facial vein
is isolated. The cardiac catheter is introduced into the common facial vein to the internal jugular vein to the right atrium.
It is important to locate the catheter in the middle of the right atrium, this would prevent thrombosis and clot formation
around the tip of the catheter. The position of the catheter is verified using X-ray after injecting dye into the catheter.
The lumbar peritoneal shunt is inserted by making a mid-line lumbar incision. The spinal catheter is introduced through
a trocar and cannula up to about 10cms within the thecal sac and then tunnelled under the abdominal wall to be introduced
into the peritoneum cavity either by an open incision or using percutaneous method using trocar and cannula.
hydrocephalus due to occlusion of aqueduct by
COMPLICATIONS OF SHUNT INSERTION
There are several
complications of shunt insertion such as disconnection of shunt components, fracture of a catheter, erosion of the shunt through
the skin, or viscera, loss of the ventricular catheter into the ventricle, particulate matter within the shunt, over and under
shunting and formation of subdural haematoma.
Complications be grouped into two main areas:
This could be in the form of under drainage of over drainage, blockage of the proximal or distal catheter or
failure of the shunt valve system. Failure related to surgical technique could be due to improper placement of the ventricular
catheter, distal catheter or migration of the shunt system.
It is estimated that the highest incidence of shunt failure
occurs in the first few months after surgery, this varies from 25 to 40% after one year follow up. Later on the risk of failure
would be 4 to 5 %.
is estimated that 50% of mechanical shunt failure is due to shunt blockage. this is usually highest in the immediate post
becomes occluded if brain debris or parts of choroid plexus become attached to the pores of the proximal catheter. The location
of the catheter is a significant factor. Ideally the catheter should lie in an area away from the choroid plexus and not in
close proximity to the ventricular wall, the anterior horn of the lateral ventricle fulfils such description.
Shunt valve blockage
This is related to deposition of brain debris
or blood clots within the valve system. In addition it could be due to failure of the valve system mechanism.
This occurs less frequently than the proximal
obstruction. The blockage could be related to accumulation of particles in the distal end of the catheter blocking the distal
opening of the catheter . Blockage can occur if the catheter has become encysted or isolated in one area of the peritoneal
cavity with diminished peritoneal absorption. We should also think of the possibility of the catheter migrating outside the
peritoneal cavity either into a viscus or the abdominal wall.
Catheters can also be disconnected , after a long time
within the tissues they could become brittle and fracture.
Infection is a regular complication of shunt operation
and may result in further risk of intellectual impairment. The average rate of infection is reported to be about 5% however
infection rate of .5%-1% has been reported. The rate of infection increases with the child in maturity. CSF examination and
positive bacterial culture would be an equivocal evidence of shunt infection. CSF should be obtained by shunt tap.
About 40% of shunt infections are caused
by staphylococcus epidermidis and about 20% by staph aureus. Other organisms are less frequent as streptococci and gram negative
features of shunt infection
Shunt infections usually present early after shunt insertion within eight to ten
weeks. The patient would present with fever, malaise, headache and irritability with some neck stiffness. Peritonitis is less
common. Patients with Staph epidermis may look remarkably well and the only sign of infection is intermittent fever or irritability.
can be diagnosed by blood culture, routine blood examination and CSF examination from the shunt chamber.
Treatment of shunt infection
methods of treatment were recommended:
1 Removal of shunt and the external ventricular drainage plus antibiotics.
Removal of a shunt and immediate reinsertion of shunt plus antibiotics.
3 Treatment with antibiotics alone.
was found that the highest rate of cure is achieved in the first group where the shunt is removed and external ventricular
drainage is instituted, the lowest rate of cure is by antibiotics alone.
The question of antibiotic prophylaxis is
controversial however it was found that intraoperative antibiotics or antibiotics for the first 24 hours gives the best results.
complications are less common, these are subdural collection from over drainage .slit ventricle syndrome ,also due to over
drainage. Disconnection of shunt parts or fracture of shunt tubing can also occur.
Hydrocephalus that is present at birth
is probably caused by environmental and genetic factors. When the condition develops after birth it is usually the result
of a disease (such as meningitis), injury to the head, tumors, cysts or bleeding inside the chambers of the brain.
A doctor may order the following procedures
to diagnose the condition accurately:
- Skull X-rays. In addition to the enlargement
of the skull caused by hydrocephalus, X-rays can reveal the distinctive appearance of the bones that shows an increase in
the pressure inside the skull over a period of time.
- Ultrasound. This is helpful in showing
whether or not there is bleeding inside the skull and the chambers of the brain.
- Computed tomography (CT) scans. These
will show the size of the chambers inside the brain and possibly where a blockage is that prevents the flow of fluid around
the brain and spinal cord. A CT scan will show cysts, tumors or an enlarged brain, if they are present.
- Magnetic resonance imaging
- Blood tests. These will help identify
if there is an infection present, including infections that may be present at birth from viruses such as rubella or herpes.
- Electroencephalogram (EEG). This test
may be helpful if there are seizures.
- Microscopic examination of the spinal
lp shunt stands for lumbarperitoneal
shunt stands for ventriculoperitoneal shunt
MY LIFE WITH HYDROCEPHALUS.
I had my first shunt put in when I was 4 mo's old.
I got a virual infection and I was too small to take antibiotics so the virual infection caused my right ventricle to close
off,so the Doctor had to put a vp shunt in.I went 16 yrs with my first vp shunt,not cause it was doing good,it was cause the
test wouldnt show anything but the symptoms were there.When my new Doctor finally did explore surgery on me,my shunt had fell
apart and a piece of it got lodge'd in my brain.About 17 hours later,I had 3 grandma and 2 petamal seizures.From Jan. of 2001
to december of 2003,i have had over 200 surgeries,it got so bad I had to have a iv implanted inside me.During 2001,I had to
have A Lumbar shunt put it and Then i was Diagnosed with Slit Ventricle Syndrome.In 2003 I had a piece of bone took out of
my skull to relief brain pressure.I didnt get to finish school cause i missed so much from being sick.The Doctors pulled me
out when i went into the 10th grade.The first Two years of my life,I stayed in the hospital,I was there so much,I had my own
room,fixed up with toys and baby bed and a bed for my mom.In feb.1983 I setup a shunt infection and the doctors would
come in and shoot antibiotics with a needle straight through my shunt(in my head).It has been a rough road but I think it
is getting better,atleast I hope.
Thanks for stopping by,I hope I helped you out and answered some questions for you,feel free to email me if you have questions
or just want to talk.my email address is Kingmstr531@aim.com
check out these links for more info on hydrocephalus and vp shunts...