Cerebral shunt

In cases of hydrocephalus (a birth defect), a plastic tube called a shunt is used to drain excess cerebrospinal fluid from the brain and carry it to other parts of the body. This tube goes from the affected area of the brain, connects to a one-way valve which sits outside the skull, but beneath the skin, somewhere behind the ear. It then travels down the neck, and into either the abdominal cavity (most common), the pleural cavity (surrounding the lungs) (alternative), or into the atrium of the heart (quite rare). Enough tubing is left in the area it drains to, so that it can uncoil as the child grows.

Although a shunt generally works well, it may stop working if it disconnects, becomes blocked, or it is outgrown. If this happens the cerebrospinal fluid will begin to accumulate again and a number of physical symptoms will develop. These symptoms may include: listlessness, headaches, irritability, light sensitivity, sound sensitivity, nausea, vomiting, dizziness, vertigo, migraines, seizures, a change in personality, weakness in the arms or legs, excessive head growth (seen infants, children under age 2), strabismus, and double vision. Signs of an infected shunt will be similar to those of a blocked shunt, but they will also have a fever and an elevated white blood cell count. If either of these are suspected, medical attention is needed immediately.

The shunt failure rate is also relatively high and it is not uncommon for patients to have multiple shunt revisions within their lifetime. By 2-3 years of age, approximately half of shunts that have been inserted have failed and been replaced.

The diagnosis of cerebrospinal fluid buildup is complex and requires expertise. This happens by neuroimaging studies: ultrasonography in the prenatal period (before birth) and in infancy, and computed tomography (CT) or magnetic resonance imaging (MRI) in older children.

Spitz-Holter
A common pediatric shunt is the Spitz-Holter shunt. It is a tiny one-way valve that releases controlled amounts of CSF from the brain to the heart. Spitz refers to the American neurosurgeon Eugene B. Spitz. Holter refers to the designer of the valve, John Holter, who was unable to save his son Casey from hydrocephalus, but his design, the Spitz-Holter valve/shunt, has helped millions around the world since the late 1950s.

Shunts may be either programmable or non-programmable. Programmable shunts allow ICP to be adjusted without invasive neurosurgery. The setting of a programmable shunt may be adjusted by a neurosurgeon or other qualified medical professional with the aid of a powerful magnet (designed especially for the type of shunt that the patient has), being comparable to the strength of the magnet in an MRI. This type of adjustment usually causes minimal discomfort.

Programmable shunts' settings cannot usually be affected by ordinary household magnets. The type of shunt used depends on the patient's medical history and anatomy, as well as the discretion of the neurosurgeon. Other types of shunts: Medtronic (programmable)