Hydrocephalus is a build-up of fluid in the brain. The brain and spinal cord are surrounded by cerebrospinal fluid (CSF) which acts as a shock absorber, protecting the brain and spinal cord, as well as removing waste products from the brain and supplying nutrients to the brain. CSF is produced in fluid-filled cavities in the brain called ventricles. The CSF then flows out of the ventricles via small holes at the back of the brain. CSF is in a constant cycle of production, circulation and reabsorption. Usually, the production, circulation and reabsorption of fluid are balanced so that there is a constant amount of fluid around the brain and spinal cord. Anything that disrupts this balance can cause a build-up of CSF in the brain. This usually causes increased pressure which disrupts brain function and is known as hydrocephalus.
Hydrocephalus generally occurs if any one of the follows happens:
- too much CSF is produced (rare);
- the circulation of CSF is blocked (most common);
- not enough CSF is reabsorbed.
Hydrocephalus can affect all ages. The most common causes vary with age: developmental disorders, infection and bleeding in neonates; tumours in children and adolescents; bleeding and tumours in adults; and a condition called normal pressure hydrocephalus in the elderly.
Symptoms of hydrocephalus can vary depending on age and how the condition has developed. The pressure on the brain from hydrocephalus can cause a wide range of symptoms, including:
- nausea and vomiting;
- blurred vision and visual loss;
- urinary incontinence;
- drowsiness and confusion;
The diagnosis of hydrocephalus is confirmed by using brain imaging techniques such as CT and MRI scans. Other tests may be performed in adults in order to diagnose the condition which may include lumbar puncture, continuous lumbar CSF drainage, intracranial pressure (ICP) monitoring, measurement of cerebrospinal fluid outflow resistance, or isotopic cisternography.
Treatment for hydrocephalus is almost always surgical. In general, the aim is to increase the drainage of CSF from the ventricles inside brain. This reduces the pressure on the brain caused by the build-up of CSF. Surgical options include temporary external drainage (external ventricular drainage), permanent internal drainage (shunt or ventriculostomy) and / or removal of the underlying cause, e.g., if secondary to a tumour.
A shunt is soft, flexible tubing which diverts fluid from the brain to another area of the body, typically the abdomen. Most commonly, shunt tubing is inserted into one of the ventricles of the brain, attached to a valve (under the skin behind the ear) which drains via further tubing into the abdomen. This is known as a ventriculoperitoneal or VP shunt. When the fluid pressure in the brain increases, the valve opens and the fluid drains into the abdomen where it is absorbed, leaving the brain at normal pressure.
Endoscopic third ventriculostomy allows CSF to be rerouted without the need for a shunt. During this procedure, a new hole is made in the ventricle at the base of the brain. This allows CSF to flow out of the brain bypassing the obstruction which is causing hydrocephalus.