Explainers

Hydrocephalus and Shunts


Hydrocephalus is a condition in the brain in which there is an accumulation of cerebrospinal fluid (CSF) in the ventricles, which then increases the intracranial pressure within the skull.

It can be the result of a variety of different diseases and injuries including those that cause disruptions to the absorption of CSF or an obstruction to the CSF flow (Koutoukidis et al. 2016).

There are different treatments available for those with hydrocephalus depending on many individual factors, but often can involve insertion of a shunt.

In the United States alone, every year 33,000 people are having shunts placed (Rinker et al. 2015).

A shunt allows the excess CSF to drain to a different part of the body. In the older patient with idiopathic normal pressure hydrocephalus, insertion of a VP shunt shows improvement rates in between 61-90% of patients presenting with this condition (Saehle et al. 2014). Idiopathic normal pressure hydrocephalus is often diagnosed in older adults and is characterised by gait disturbances, cognitive impairment and urinary incontinence (Saehle et al. 2014).

Hydrocephalus and Shunts

Different Types of Shunts

The different types of shunts used most commonly include ventriculoperitoneal (VP) shunts, ventriculoatrial (VA) shunts or a lumboperitoneal (LP) shunts (Koutoukidis et al. 2016).

Shunts will generally consist of three components:

  • An inflow catheter – This drains the CSF from the ventricles. It leaves the brain through a small hole in the skull, which then runs under the skin.
  • A valve mechanism – This regulates the pressure control through the shunt tubing. It is connected to the catheter and lies between the skin and the skull, usually on top of the head or behind the ear.
  • An outflow catheter – This runs under the skin and moves the CSF from the valve to the peritoneal cavity, heart or other drainage site.

(Hydrocephalus Association 2017).

As with any procedure, every shunt and every person with a shunt is different. So what works for one person may not necessary be ideal for the next. This is why some valves can be adjustable, which means that instead of having a fixed pressure valve at the same value for everyone, these adjustable valves can be readjusted by a clinician according to patient need (Hydrocephalus Association 2017).

VP shunts are the most common type of shunt for draining excess CSF. These shunts generally contain a pressure-sensitive valve that releases CSF once the pressure reaches a certain level (Rinker et al. 2015). In VP shunts, a catheter is inserted into the ventricle with tubing tunnelled subcutaneously down the thorax and then further tunnelled into the peritoneal cavity where the CSF is absorbed.

Hydrocephalus and Shunts

VA shunts are less common than VP shunts and the only difference between them is that rather than finishing in the peritoneal cavity, the VA shunt finishes in the right atrium of the heart and CSF is absorbed via our blood stream (Rinker et al. 2015).

An LP shunt consists of a catheter inserted between two lumbar vertebras into the thecal space, which is then tunnelled around the abdomen into the peritoneal cavity for absorption (Rinker et al. 2015).

Complications of Shunts

As with any surgery, the insertion of shunts doesn’t come without risks. These risks include mechanical obstruction of the shunt, infection, and subdural haematomas.

These complications can be divided into two categories as either arising from:

  1. A mechanical complication; or
  2. A biological complication.

Mechanical complications of a shunt include:

  • Malfunctions such as leaks, obstruction, migration or discontinuity.

Whereas the biological complications of a shunt include:

  • Infection
  • Abscess
  • Pseudocyst
  • Haemotoma; and
  • Peritonitis.

(Rinker et al. 2015)

The complication rates following insertion of a shunt tend to be high, with up to half of people experiencing some type of complication and needing shunt revisions. Generally with these complications there is often an overlap of both biological and mechanical factors that cause the problem (Rinker et al. 2015; Saehle et al. 2014).

To give you some statistics, shunt blockages occur in up to 31% of patients and over drainage occurs in about 3% of patients (Chari et al. 2014).

So what happens when there is an over drainage from the shunt?

Over drainage from the shunt can result in the ventricles decreasing in size and their meninges pulling away from the skull. This is a condition often called slit-ventricle syndrome. This complication is one that is more common in young adults who have had a shunt in place since childhood. The person with slit ventricle syndrome will often complain of severe but intermittent headaches that are often only relieved when lying down (Hydrocephalus Association 2017).

Under drainage of shunts has the opposite problem and will cause the ventricles to increase in their size. This will be in conjunction with the individual also not experiencing any relief of their previous symptoms of hydrocephalus. When this occurs, the patient may need a revision of their shunt, or if the person is able to adjust their pressure valves externally, they will need to be reviewed and readjusted (Hydrocephalus Association 2017).

Shunt infection tends to be one of the most common biological complications that occur in these individuals. They can be quite significant, as infection can have further implications and detrimental effects on the individual including abscess formation or shunt occlusion. If infection occurs, generally the shunt will need to be revised (Rinker et al. 2015).

Peritonitis can also occur with VP shunts where the individual displays general signs and symptoms of infection in conjunction with abdominal pain.

When the patient with a VP shunt complains of abdominal pain, the formation of an abdominal abscess also needs to be excluded. These abscesses can occur from many different ways including shunt contamination or from the shunt migrating into the bowel (Rinker et al. 2015).

A CSF pseudocyst is a rare complication of VP shunting and it is unclear as to what causes them. They will generally develop some time after the shunt has been placed – sometimes up to years down the track (Rinker et al. 2015).

VP shunts can also become obstructed. This may be due to the catheter disconnecting, migrating or even fracturing (Rinker et al. 2015). The shunt can become blocked in any part from the ventricular catheter in the brain, to the distal part of the catheter where it is draining (Hydrocephalus Association 2017).

Symptoms of a VP shunt obstruction are those seen with increased intracranial pressure, which could include: headache, vomiting, lethargy, irritability and confusion (Koutoukidis et al. 2016).

Nursing Care of a Patient with a Shunt

Nurses need to be monitoring the patient with a shunt for any of these complications. If they suspect any of these complications are occurring, they need to act immediately, as a delayed response can have dire consequences for the individual.

It is also important to note that some of these complications can occur any time. If your patient has had a shunt for five years, they can still be at risk of complications occurring. So, with your patient with a shunt, never stop monitoring for complications.

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