A ventriculoperitoneal (VP) shunt is a device implanted by neurosurgeons to manage hydrocephalus, often described as “water on the brain.” This slender tube system drains excess cerebrospinal fluid (CSF) from the brain’s ventricles into the abdominal cavity, where it is safely absorbed into the bloodstream. The shunt’s primary function is to maintain stable pressure within the skull by diverting this fluid, preventing a dangerous buildup of pressure on brain tissue. A small valve within the system regulates the flow, ensuring drainage only occurs when pressure exceeds a set level.
Recognizing Signs of Shunt Malfunction
When a VP shunt stops functioning correctly, it fails to drain the excess CSF, leading to a rapid increase in pressure inside the head, which produces distinct symptoms. The manifestation of these signs depends heavily on the patient’s age, particularly whether the skull plates (fontanelles) have fused. Therefore, symptoms are typically categorized into those seen in infants and those in older children and adults.
Infants
In infants, whose skull bones have not yet fully fused, the primary indicators relate to the expansion of the head to accommodate the fluid buildup. Parents may observe a bulging or tense soft spot, known as the fontanelle, on the top of the baby’s head. Another measurable sign is an abnormally rapid increase in the circumference of the head compared to standard growth charts. The veins on the scalp may appear more prominent, and the eyes might display a downward gaze, sometimes referred to as “sunsetting.” Behavioral changes like unusual irritability, excessive sleepiness, or a decrease in feeding are also common signals.
Older Children and Adults
Symptoms in older children and adults are different because their fused skull prevents the head from expanding, leading to a more immediate and intense rise in pressure. The most frequent sign is a severe, persistent headache that may worsen upon waking and does not respond to typical pain relievers. This is often accompanied by nausea and projectile vomiting. Other neurological signs include vision changes, such as double vision or blurred sight, resulting from the pressure affecting the optic nerves. A significant change in mental state, including confusion, unusual lethargy, or difficulty waking up, indicates a serious malfunction that requires immediate attention.
Physical Assessment of the Shunt System
Beyond observing symptoms, some individuals or caregivers are taught specific, non-invasive ways to physically check the shunt system components located under the skin. The most accessible part of the shunt is the reservoir, a small, dome-shaped device usually placed just behind or above the ear. This reservoir is the site where neurosurgeons can access the CSF for diagnostic purposes.
A common assessment technique involves gently pressing on the reservoir, sometimes called “pumping,” to feel how quickly it compresses and how rapidly it refills with fluid. A reservoir that feels firm and is difficult to compress can suggest an obstruction in the tubing that drains the fluid away from the valve, known as a distal malfunction. Conversely, a reservoir that feels flat or is slow to refill after being gently compressed may suggest a blockage at the end of the tubing inside the brain, a proximal malfunction.
While this physical check is not a definitive diagnostic tool and is considered unreliable by many medical professionals, it can offer a preliminary idea of the shunt’s status. Excessive or forceful manipulation of the reservoir is advised against because it carries a risk of potentially damaging the shunt system. Any change in the feel of the reservoir, or visible signs of redness or swelling along the path of the tubing, should always prompt a conversation with the medical team.
Urgent Medical Evaluation
The suspicion of a VP shunt malfunction is always treated as a medical emergency because a delay in treatment can result in permanent neurological injury or death. If any of the signs of malfunction are observed, the individual or caregiver should immediately contact their neurosurgeon or proceed to the nearest emergency room. Medical professionals will not rely solely on symptoms or a physical check to confirm the diagnosis but will initiate a series of objective tests.
Diagnostic Imaging
One of the first steps involves obtaining imaging of the brain, typically a computed tomography (CT) scan or a magnetic resonance imaging (MRI) scan, to compare the current size of the brain’s ventricles to a previous baseline study. An increase in ventricle size often suggests that the shunt is failing to drain the CSF effectively. A “shunt series” of X-rays is also performed, which includes images of the head, neck, chest, and abdomen, to check the entire length of the implanted tubing for breaks, disconnections, or migration of the catheter.
Shunt Tap
In some cases, if the diagnosis remains uncertain or an infection is suspected, a neurosurgeon may perform a shunt tap. This involves inserting a thin needle into the reservoir under sterile conditions. This allows the physician to measure the internal pressure directly and collect a small sample of CSF for laboratory analysis to check for signs of infection or inflammation. These clinical evaluations provide the necessary information to determine the exact nature of the problem and guide surgical intervention.