Hydrocephalus

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Diagnosis

Hydrocephalus may be suggested by symptoms; however, imaging studies of the brain are the mainstay of diagnosis. Computed tomography (CT scan) and magnetic resonance imaging (MRI scan) typically reveal enlarged ventricles and may indicate a specific cause. Abnormalities such as tumors and hemorrhages can also be detected.

Small abnormalities that may not be detected using CT scan, such as cysts and abscesses, are often seen with MRI. These studies can also help the neurosurgeon differentiate between communicating and noncommunicating hydrocephalus. In cases of suspected normal pressure hydrocephalus, a spinal tap may help determine CSF pressure.

A cisternagram evaluates the dynamics of CSF flow in the brain and spinal cord. In this procedure, a diagnostic dye is injected into the subarachnoid space around the brain. A series of pictures is taken once the dye has circulated through the entire CSF path. Cisternography can reveal CSF concentration, obstruction, leakage, and pressure.

In older people, pressure in the head can cause papilledema, swelling of the optic nerve. Papilledema can often be seen while examining the eyes. Unfortunately, it typically indicates hydrocephalus that is well developed. In rare cases, long standing hydrocephalus causes blindness.

Treatment

Treatment usually requires draining the excess fluid from the brain by diverting it to another place in the body.

Shunt
A shunt is a soft, flexible tube usually made of silicone rubber or plastic. Most shunts consist of a valve that promotes drainage and a catheter, a tube that connects the drainage site to the deposit site. If there is high intracranial pressure, a small sensor may be added near the valve. This sensor allows the neurosurgeon to monitor pressure levels.

The shunt used for treating hydrocephalus is usually permanent. The shunt is inserted with one tip in one of the ventricles of the brain and the other tip in the abdominal (peritoneal) cavity. This is known as a ventriculoperitoneal (VP) shunt. Less commonly used drainage sites include the right ventricle of the heart, the gall bladder, and the pleural space around the lungs. Depending on the location of the obstruction, fluid also may be drained from the subarachnoid space that surrounds the brain.

Although insertion and immediate operation of the shunt is usually uncomplicated, problems can arise.

• Abdominal problems:
  • Bowel twisting
  • Excess fluid collection
• Blockage of the shunt
• Brain injury:
  • Clots on brain surface
  • Loss of sensation
  • Memory loss
  • Paralysis
  • Seizures
  • Speech problems
• Headaches caused by overdraining
• Mechanical failure (e.g., separation of parts, valve failure)

Other complications include bleeding, problems with anesthesia, and infection. The body may react negatively to the shunt because it is made of foreign material.

Approximately 70% of shunts fail within 10 years of placement. To accommodate normal growth and to ensure long term function, shunts in infants and children are replaced frequently until adulthood. A child may require as many as five shunts during this period. A neurosurgeon periodically checks shunt function in adults.

Third Ventriculostomy
Third ventriculostomy involves entering the brain through the bones at the top of the skull. The neurosurgeon passes an endoscope (a thin telescopic instrument) through the lateral ventricle into the third ventricle and uses a laser to make a hole in its floor. Excess fluid drains through the hole into the subarachnoid space.

The overall success rate of third ventriculostomy is about 65%. When used to treat blockage caused by tumor or by aqueductal stenosis, success rates are slightly higher. In hydrocephalus caused by hemorrhaging or infection, they are slightly lower.

There are few risks associated with third ventriculostomy. CSF drains through a hole in the ventricle floor instead of a valve, so there is no risk of overdrainage. The absence of a tube eliminates the risk associated with a shunt.

Rarely, the basal artery near the third ventricle is injured during the procedure, which can cause life threatening hemorrhaging in the brain. However, use of the endoscope has lowered this risk.

Spinal Tap
In patients with normal pressure hydrocephalus, repeated spinal taps are performed to remove excess CSF. If this results in improvement, inserting a permanent shunt may be appropriate.

Prognosis
Hydrocephalus is usually a lifelong disorder. Prognosis depends on a number of factors, including the underlying condition that resulted in hydrocephalus, its duration and degree, as well as response to treatment.

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