When shunts go bad: complications experienced with shunt systems

X-ray images of a 20-month old hydrocephalus patient
experiencing shunt malfunction. As a result, the child
experienced sutural diastasis.

Hydrocephalus can be treated with a shunt system, however, this treatment often results in complications. Research has shown that an estimated fifty percent (50%) of shunts in pediatric patients fail within two (2) years often requiring repeated neurosurgery. The most commonly seen of these complications are: infection and malfunction (emphasis added).

I. Common complications

Shunt malfunction

A shunt malfunction involves either a partial or complete blockage (of the tubing) causing the shunt to function intermittently or not at all. As a result of the blockage cerebrospinal fluid (CF) accumulates and, as illustrated in the image at right, can result in diastasis where a fracture line traverses one (or more) sutures of the skull resulting in a widening of the suture.

The blockage can result from blood cells, tissue, or bacteria and occur in any part of the shunt. Both the ventricular catheter (the portion of the system placed in the brain) and the distal catheter (the portion of the system that drains CSF to other part of the body) can become blocked by tissue from the choroid plexus (which produces CSF) or ventricles. In adults, the blockage occurs most commonly in the distal portion of the shunt system.

Shunts - by their very nature - are very durable, but their components can become disengaged or fractured as a result of wear or as a child grows. In rare cases valve failure can occur due to a mechanical malfunction.

Shunt infection

Typically a shunt infection occurs because of the person's own bacteria and isn't acquired from someone else who is ill. The most common infection to occur in a shunt system is Staphylococcus Epidermidis which is know for attacking indwelling medical devices such as a shunt. which is normally found both on the surface of a person's skin as well as in the sweat glands. Normally a shunt infection occurs with a one (1) to three (3) month window following shunt implant surgery, but has been known to occur up to six (6) months following the surgery. Research has shown that patients receiving a ventriculoperitoneal (VP) shunt are statistically at the highest risk for developing a shunt infection secondary to abdominal infection.

II. Less common complications

Over drainage

CT scan shows hydroceplaus
patient with SVS.

This complication causes ventricles to decrease in size causing slit-like ventricles due to the brain and its meninges pulling away from the skull. Known as slit-ventricle syndrome or SVS for short (pictured at right) , it is most commonly seen in young adults (ages 20 - 39) who were shunted as a child. One symptom that is unique to SVS is the severe intermittent headache that can be relieved by lying down. In order to confirm a diagnosis of SVS, imaging must be completed that shows the smaller size ventricles.

Under drainage

Results in the exact opposite problem as over drainage and that is an increase in the size of ventricles as well as the inability to relieve the symptoms associated with the hydrocephalus. In some cases, to restore a balanced flow of CSF, it might be necessary to implant a new shunt with a more accurate pressure valve. In patient's with a programmable shunt, it is possible to restore a balanced flow by simply re-setting the opening pressure.

Subdural hematoma

Control unit of a programmable shunt.

This is generally seen in older adults (ages 60 - 80) and is caused when blood from a broken vessel in the meninges becomes trapped between the skull and the brain. Surgical intervention is required to correct this complication.

Multiloculated hydrocephalus

This condition occurs when a located (isolated) compartment in the ventricular system becomes enlarged and not in communication with the normal ventricle. There a numerous documented causes including: neonatal intraventricular hemorrhage, trauma that occurs at birth, ventriculitis (inflammation of the ventricles), or shunt-related infection. Typically it can be difficult to identify due to the fact that it is most often seen in infants and children who might be neurologically compromised.

 
For additional information: Complications of shunt systems