Ventricular Peritoneal Shunt

Normal Anatomy

The cerebrospinal fluid (CSF) bathes the brain and spinal cord. Most of the CSF is located in the ventricles of the brain, which are large cavities in the brain that produce the CSF.

In hydrocephalus, the ventricles of the brain become enlarged with cerebrospinal fluid. This condition causes the brain tissue to compress against the skull, causing serious neurological problems.

There are numerous causes for hydrocephalus depending on the age group. In adults, common causes including bleeding inside the ventricles, infection (eg. meningitis), tumour causing obstruction, etc. In children, there are other rarer congenital causes. In the elderly, a condition called normal pressure hydrocephalus may require a ventricular peritoneal (VP) shunt.

Procedure

• Shunting, also called ventriculo-peritoneal shunting, is necessary in order to drain the excess fluid and relieve pressure in the brain
• A catheter is inserted into the brain to drain CSF from the ventricular system into the abdominal cavity while the patient is deep asleep under general anaesthesia

Risk Factors

The operation is generally safe with low surgical risk. Some of the risks encountered are as follows:

• Ileus
• Infection
• Obstruction
• Malplacement
• Wound breakdown with exposed shunt tubing

Rare but potentially more serious complications are listed below:

• Subdural hematoma
• Intracranial hematoma
• Bowel injury

Ileus

As the abdominal cavity is entered during operation, some patients may have slow gastric and bowel movement post operation and may experience feelings of nausea and vomiting. They may not tolerate full meals immediately post operation. These symptoms usually resolve spontaneously over time.

Infection

• Post operation symptoms and signs would include fever, vomiting, neck stiffness, redness along the shunt tract
• Most common organisms are S. epidermidis and S. aureus
• Treatment would be intravenous antibiotics, external ventricular drainage and removal of shunt

Obstruction

• Most often due to the head tip is obstructed with cells, choroid plexus, or debris. Diagnosis is based on recurrent signs of headache, vomiting and drowsiness confirmed by a computed tomography (CT) scan of the head or lumbar puncture
• Treatment usually entails revision of shunt

Malplacement

This occurs when the ventricular or peritoneal end of the shunt tubing is in a position which does not facilitate free flow of CSF. The result is poor CSF drainage and hydrocephalus does not resolve.

Wound breakdown/shunt tube exposure

This can occur when the wound does not heal well or the overlying skin is thin with minimal subcutaneous tissue layer resulting in wound breakdown.

Some risk factors include malnourishment, debilitated condition and prolonged steroid usage.

After the Operation

• The patient’s vital signs and neurological status are closely monitored. Medication is given for pain. Intravenous fluids and antibiotics are given. The patient is monitored closely to ensure that the shunt is functioning properly
• Often, imaging studies such as CT scans are done after the surgery to confirm good positioning of the shunt and resolution of the hydrocephalus

Expectation after Surgery

• The outcome from the actual surgery is good. Hydrocephalus is often associated with other conditions such as brain tumours, meningitis or bleeding. These conditions would influence the patient's prognosis
• The degree of hydrocephalus prior to surgery will also affect the outcome

When

• When the shunt is infected, blocked, broken, exposed or if it is in a suboptimal position
• When the pressure valve is unsuitable resulting in either residual hydrocephalus or intracranial hypotension
• Some of the symptoms and signs to look out for include fever, headache, nausea and/or vomiting, CSF leukocytosis/hyperproteinemia/hypoglycemia, raised intracranial pressure, hydrocephalus on CT scan or collapsed ventricles with postural headache

What does it involve?

• If infected, the entire shunt tubing is removed and a temporary external ventricular drain is inserted. A permanent shunt is reinserted once the infection has cleared with antibiotics
• If blocked, the respective tubing will be replaced, either ventricular or peritoneal
• If valve is suspected to be unsuitable, a new valve with the appropriate setting is chosen and inserted