What Is a Cerebrospinal Fluid Shunt?

A cerebrospinal fluid shunt is a medical device that allows drainage of cerebrospinal fluid. Having excess fluid is known as hydrocephalus, and though a variety of medical conditions cause it, it is most prominent in infants born with the condition. To ensure that the cerebrospinal fluid shunt does not expel too much cerebrospinal fluid, various shunt systems exist. For adults who develop hydrocephalus, a permanent shunt may be necessary to prevent against a recurring buildup of fluid.

Cerebrospinal fluid cushions and supports the brain within the skull. A buildup of fluid raises intracranial pressure and can cause brain damage if left unchecked. Various disorders including cancer can cause hydrocephalus in adults. In newborns, the condition causes an abnormally large head. When the condition develops in the womb, the fluid pushed against the still soft skull and causes it to grow out; it is generally diagnosed at birth.

Whether an infant or adult has hydrocephalus, a cerebrospinal fluid shunt is always the main course of treatment. Since the introduction of the cerebrospinal fluid shunt in the 1960s, the mortality rate of hydrocephalus has dropped by 90% and the chances of mental impairment has dropped by 50%. After a surgeon drills a small hole into the skull, the shunt is inserted into the brain at the area where the fluid is built up. If the cause of hydrocephalus is non-hereditary, the patient may only need a shunt for a short time. If a child is born with hereditary hydrocephalus, he or she will need a shunt for the rest of his or her life.

As they must remain in a patient's body, permanent shunts are more complicated that the ones surgeons use in the operating room. Permanent shunts developed in the past 25 years have the capability to drain only excess cerebrospinal fluid while maintaining a normal amount within the skull. Instead of draining fluid just outside the head, a long catheter within the body exits just beside the patient's navel. Generally, the release of fluid is so light that it rarely if ever bothers the patient. Yet despite these advances, inserting and maintaining a permanent shunt is not without risk.

Inserting a cerebrospinal fluid shunt, whether temporary or permanent, carries the risk of brain damage. Though when viewed in comparison to the brain damage caused by hydrocephalus, the risk is worth it to the vast majority of patients. Obstruction and infection can also occur with permanent shunts, the latter possibly life-threatening since the infection attacks the brain. Half of all patients who receive a permanent shunt should expect it to fail within two years. Many surgeries may be necessary over a patient's life to replace shunts.