Hydrocephalus is an accumulation of cerebrospinal fluid (CSF) within the brain’s ventricles. This excess fluid can lead to increased pressure on the brain, causing damage and symptoms. A common treatment for hydrocephalus is the surgical placement of a shunt.
Understanding Hydrocephalus and Shunts
Cerebrospinal fluid (CSF) cushions the brain and spinal cord, delivers nutrients, and removes waste. Normally, CSF circulates through the brain’s ventricles and around the brain and spinal cord, then absorbs into the bloodstream. Hydrocephalus occurs when this balance is disrupted, leading to overproduction, flow blockage, or absorption problems. The resulting fluid buildup enlarges ventricles and exerts pressure on the brain.
A shunt is a surgically implanted tube system diverting excess CSF to alleviate pressure. It consists of three main components: a proximal catheter, a valve, and a distal catheter. The proximal catheter collects fluid from a brain ventricle. The valve regulates CSF flow, and the distal catheter carries fluid to another body part for natural absorption.
How Shunts Function
The proximal catheter, positioned in a brain ventricle, collects accumulated CSF. This fluid then travels down the catheter to a valve, usually located under the skin, often behind the ear.
The valve regulates the one-way flow of CSF, preventing excessive (over-drainage) or insufficient (under-drainage) flow. It opens when pressure within the brain’s ventricles reaches a certain threshold, allowing fluid to pass through. From the valve, the distal catheter tunnels under the skin to a drainage site, commonly the abdominal cavity or a heart chamber. There, the diverted CSF is reabsorbed into the body’s circulatory system.
Types of Shunt Systems
Shunt systems are categorized by the body cavity where the distal catheter drains CSF. The most common is the ventriculoperitoneal (VP) shunt, diverting CSF from brain ventricles to the peritoneal cavity (abdomen). Its large surface area efficiently absorbs CSF. VP shunts are widely used for all ages.
Another type is the ventriculoatrial (VA) shunt, channeling CSF from brain ventricles directly into a heart chamber, usually the right atrium. Here, CSF mixes with blood for absorption. VA shunts are generally considered when a VP shunt is not feasible, such as in cases of abdominal complications or previous shunt failures. Less commonly, lumboperitoneal (LP) shunts drain CSF from the lumbar spinal canal into the peritoneal cavity. LP shunts are often employed for conditions like idiopathic intracranial hypertension rather than typical hydrocephalus.
Shunt systems also vary by valve type. Fixed-pressure valves are pre-set during manufacturing to open at a specific pressure level and cannot be adjusted after implantation without surgery. Programmable (adjustable) valves allow non-invasive changes to drainage settings via an external magnetic device. This offers flexibility for evolving patient needs, potentially reducing additional surgeries.
Recognizing Shunt Issues
While effective, shunts can malfunction or become infected, requiring prompt medical attention. Recognizing shunt issues is important. Symptoms often arise from a return of increased pressure within the brain.
Common indications of a shunt malfunction include:
Severe headaches, nausea, or vomiting.
Excessive tiredness or difficulty staying awake.
Changes in vision, such as blurriness or double vision.
In younger children, a bulging soft spot on the head or increased head size.
Behavioral changes, irritability, or a decline in school or job performance.
Infection signs often overlap with malfunction symptoms but may include fever, redness, or tenderness along the shunt’s pathway. Swelling along the shunt tract or abdominal pain (if drained into the abdomen) can also occur. Any of these symptoms warrant immediate medical evaluation, as untreated shunt complications can lead to serious health concerns.