Complications and malfunctions of shunt systems

Sadly, much of my inspiration for blogs on hydrocephalus come about because of a bad situation that occurs either to me or one of my friends with hydrocephalus. This is one of those occasions. Early Monday morning, one of my friends passed away after tubing from his shunt broke and came into contact with his brain stem. You might wonder how such a thing could happen. So named because of its stem-like appearance, the brain stem is where the base of the brain attaches to the spinal cord. (WebMD, 2016) it's main job is to control the flow of messages between the brain and the rest of the body; it is also controls basic body functions such as breathing, heart rate, and blood pressure.

What can go wrong?

Hydrocephalus is treated by surgically implanting a shunt into the patient's brain, however, complications can develop or the shunt can malfunction. Interestingly, in pediatric patients, there is a fifty percent (50%) shunt failure rate after only two (2) years. The exact cause for this is unclear.

Shunt malfunction

A partial or complete blockage of the shunt system is know as a shunt malfunction. (Hydrocephalus Association, 2014) When this occurs, cerebrospinal fluid builds up and causes symptoms similar to those seen with untreated hydrocephalus.

The blockage is caused by a build-up of blood cells, tissue, or bacteria and occur anywhere system. Both the proximal catheter (which is implanted in the brain) as well as the distal catheter (which can be implanted either in the ventricle of the heart, the peritoneal cavity of the abdomen, or, rarely, in the spine) can be blocked. These blockages originate in either the choroid plexus or the ventricles of the brain. Generally speaking, in adult hydrocephalus patient's, blockages occur with greater frequency in the distal catheter.

Generally, a shunt system is durable, however, components of the system (pictured below) can become disengaged or fractured as the result of normal wear -- particularly in children due to their growth spurts. Also, although rare, a valve can fail due to a mechanical malfunction.

Shunt infection

A shunt infection usually occurs as a result of the person's own bacterial organisms and isn't caused by be exposed to someone who is sick. The most common bacterium to cause an infection is Staphlococcus epidermis. which is normally present on a person's skin as well as in the hair follicles and in the sweat glands. This type of infection is typically seen one (1) to three (3) months after shunt implant surgery, but can occur up to six (6) months later. In persons with a ventriculoperitoneal (VP) shunt is a shunt infection that occurs secondarily to an abdominal infection. Lastly, in persons treated with a ventriculoatrial shunt (which empties into the right ventricle of the heart) a generalized infection can occur.

Other shunt complications

Over drainage causes the ventricles to decrease in size and become slit-like (see: What is slit ventricle syndrome (SVS)?) due to the brain and meninges pulling away from the skull. SVS is most common in young adults who have been shunted since early childhood. A telltale symptom of SVS is severe intermittent headache that improves when the person is laying down.

Under drainage does the exact opposite and causes the ventricles to swell. When this occurs, the shunt might not be able to relieve the hydrocephalus symptoms. In order to restore a balanced flow of CSF, it might be necessary to implant a new shunt with a more accurate pressure valve. If the person has a shunt with programmable valves, the balance of flow can be restored by resetting the opening pressure.

 Subdural hematoma (pictured at left) occurs when a broken blood vessel in the meninges becomes trapped between the skull and the brain. It is seen most commonly in adults with Normal pressure hydrocephalus (NPH) and requires surgical intervention to correct it.

Multiloculated hydrocephalus is located (isolated) CSF compartment in the ventricular system that is enlarged and not in communication with the normal ventricle. It can be the result of trauma at birth, neonatal intraventricular hemorrhage, Ventriculitis, over drainage, or other conditions. This complication might be difficult to identify because it is typically seen in infants and children who might be neurologically compromised. Treatment involves surgery to implant ventricular catheters, Craniotomy and fenestration (opening) of the intraventricular loculations. (John Hopkins Medical, N.D.)

Seizures can sometimes occur in people (both adults and children) with hydrocephalus. Medical research has shown there is NO CORRELATION (emphasis added) between the site a shunt implant (or the number of revisions a person has) and a increased risk of developing seizures. The one possible exception to this involves children who have significant cognitive delays or motor disabilities are at higher risk (italic emphasis added) are more likely to experience seizures compared to children without similar delays or disabilities. Research has also shown that seizures aren't likely to occur at the time a shunt malfunctions, and the more likely explanation for the occurrence of a seizure disorder is related to an associated malformation of the cerebral cortex.

Abdominal complications can also occur in patient's with hydrocephalus who are treated with a shunt. This is due to the fact the distal catheter of a ventriculoperitoneal (VP) shunt is placed in  the peritoneal cavity of the abdomen. Although complications associated with a VP shunt aren't less in frequency (when compared to a ventriculoatrial [VA] shunt), they tend to be less severe and have a lower mortality rate. These complications can include: peritoneal pseudocysts, loss of the distal catheter, bowel perforations, and hernias.

Bibliography

Hydrocephalus Association (2014). Complications of shunt systems. Retrieved on February 12, 2018 from https://www.hydroassoc.org/complications-of-shunt-systems/

John Hopkins Medicine (N.D.) Craniotomy. Retrieved on February 13, 2016 from https://www.hopkinsmedicine.org/healthlibrary/test_procedures/neurological/craniotomy_92,P08767

WebMD (2016). Medical definition of brain stem. Retrieved on February 12, 2018 from https://www.medicinenet.com/script/main/art.asp?articlekey=2517