ü WHAT IS HYDROCHEPALUS ?
ü HOW HYDROCHEPALUS HAPPEN ?
ü HOW TO TREAT HYDROCHEPALUS ?
Hydrochepalus 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 hydrochepalus, 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.
Hydrochepalus is described either as obstructive or non communicating 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. Hydrochepalus is also classified as acquired when it is caused by acquired causes or congenital. In congenital hydrochepalus it is caused by either excessive production of CFS, blockage to the CFS drainage or reduced excretion into the venous channels.
Hydrochepalus is classified into:
1. Non-communicating or obstructive hydrochepalus where there is no communication between the ventricular system and the subarachnoid space. The commonest cause of this category is aqueduct blockage.
2. Communicating or non-obstructive hydrochepalus where there is communication between the ventricular system and the subarachnoid space. The commonest cause of this group is post-infective and post-haemorrhagic hydrochepalus.
CAUSES OF HYDROCHEPALUS
This is grouped into 3 main causes:
1. Excessive secretion of CSF by the choroid plexus as in cases
of choroid plexus papilloma or carcinoma. This is a rare cause.
2. Blockage 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 hydrochepalus 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 head.
Posterior fossa tumours are a common cause of obstructive hydrochepalus due to blockage of the 4th ventricle. Medulloblastoma, cystic astrocytoma and ependymoma can all lead to obstructive hydrochepalus. A common cause of obstructive hydrochepalus 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.
3. Poor secretion of CSF into the venous sinuses caused by scarring of the arachnoid villi and is commonly seen after meningitis or haemorrhage.
CLINICAL FEATURES OF HYDROCHEPALUS
It is very important that Hydrochepalus 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 hydrochepalus. 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 hydrochepalus 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 pressure.
MANAGEMENT OF HYDROCHEPALUS
CSF - DIVERSION AND ALTERNATIVE TREATMENTS
The modern treatment of hydrochepalus started with the development of the valved shunt system by Halter and the application by Nelsen and Spitz.
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 hydrochepalus in immature infants the drug was used and success was claimed.
It was claimed that ventricular shunt was avoided in 50% of cases.
Endoscopic choroid plexectomy was tried but found unsuccessful.
Intracranial shunts :
These procedures were done in cases of obstructive hydrochepalus 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 hydrochepalus with patent subarachnoid spaces.
b. Ventriculocisternostomy The 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.
Extracranial shunt :
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. 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 30 cms 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
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.
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 :
a. Mechanical failure
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 %.
It is estimated that 50% of mechanical shunt failure is due
to shunt blockage. this is usually highest in the immediate post operative
This 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 organisms.
Clinical 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.
Infection can be diagnosed by blood culture, routine blood examination and CSF examination from the shunt chamber.
Treatment of shunt infection
Several methods of treatment were recommended :
1. Removal of shunt and the external ventricular drainage plus antibiotics.
2. Removal of a shunt and immediate reinsertion of shunt plus antibiotics.
3. Treatment with antibiotics alone.
It 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.
Other 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.