What is a shunt?
A shunt is a hollow tube surgically placed in the brain (or occasionally in the spine) to help drain cerebrospinal fluid and redirect it to another location in the body where it can be reabsorbed.
Shunt procedures can address pressure on the brain caused by hydrocephalus and relieve its symptoms such as gait difficulty, mild dementia and lack of bladder control.
If the doctor finds that these problems improve after a lumbar puncture, it may mean that placing a shunt may be able to provide a longer-term benefit.
Different Kinds of Shunts
Different shunt systems re-route the excess fluid to:
- The abdomen (ventriculo-peritoneal or lumbo-peritoneal shunt)
- The lung (ventriculo-pleural shunt)
- The heart (ventriculo-atrial shunt)
The neurosurgeon will discuss the pros and cons of each approach with you.
Special Considerations for Ventriculo-Peritoneal (VP) Shunt
Notify your neurosurgery team before any abdominal surgery, so proper precautions can be discussed with your surgeon. Also, contact the team if you have an abdominal infection including appendicitis, peritonitis, diverticulitis or other condition that requires emergency surgery or antibiotic treatment.
Special Considerations for Ventriculo-Atrial (VA) Shunt
Be sure to take antibiotics 30 to 60 minutes before any surgical or dental procedure. Your doctor may recommend daily aspirin to prevent blood clots at the far end of the catheter.
About the Shunt Operation
The actual surgical procedure to implant a shunt typically requires about an hour in the operating room. Afterward, you will be carefully observed for 24 hours. Your stay in the hospital will generally be for two to four days total.
Follow-up visits will help the doctor ensure that the shunt is functioning properly and continuing to relieve hydrocephalus symptoms.
In addition, the care team may recommend physical therapy, occupational therapy and other rehabilitation strategies to help resolve symptoms as soon as possible.
How a Shunt Helps
Hydrocephalus symptoms may improve within days of shunt surgery, or may take weeks to months to get better.
Other neurological or medical conditions can affect recovery. If your symptoms are mostly due to normal pressure hydrocephalus as opposed to other conditions, the shunt is likely to help alleviate them.
About 10 percent of patients show some improvement soon after a shunt is placed, but show less of a long-term response. The reasons for this are not well understood.
Other patients may develop additional disorders of the brain that also affect gait and memory (such as some forms of dementia or Parkinson’s disease) that will not respond to drainage from the shunt.
About the Shunt Systems
Shunts can be programmable (externally adjustable by a magnetic device) or non-programmable.
Most surgeons will choose a programmable model, despite the fact that in clinical trials, both types perform comparably. Likewise, there are various manufacturers of programmable shunts, none of which has been clinically proven to be more effective than others.
To prevent over-drainage the surgeon may implant an anti-siphon device along with your shunt, which helps to prevent over-drainage in an upright position. Anti-siphon devices come in a range of strengths for your surgeon to choose from.
In general, a higher shunt setting means less fluid is being drained. A lower setting means more fluid is being drained. The settings vary for each manufacturer. The number does not correspond to intracranial pressures. Your shunt valve setting can be changed by your physician using a programming device, or it can be changed accidentally if you come close to a magnet, even ones found in headphones. Some of the newer types of shunts are not affected by magnets or magnetic fields, including MRIs. Always confirm with your physicians if the kind of shunt you have is affected by magnetic fields.
Have the care team confirm your shunt setting if:
You experience headache, persistent nausea, vomiting, drowsiness, weakness, seizures, slurred speech or worsening gait and balance.
You have an MRI for any reason (CT scans have no effect on the shunt). Contact your care provider before you schedule an MRI to arrange for the valve to be adjusted the same day.
Shunt Complications and Risks
Potential complications of shunt surgery include those related to the actual operation as well as those that may occur days to years later.
Each person’s situation is different, so it is important for individuals and their families to consider these potential complications carefully. You should discuss all your concerns with the doctor to ensure that the potential benefit of getting a shunt outweighs the risks.
Risks and complications may include:
Blockage (obstruction) is one of the most common problems. Blockages can often be fixed (sometimes with further surgery) and rarely result in serious harm.
Shunt malfunction may include over- or under-drainage. A shunt system that is not functioning properly requires immediate medical attention.
- Over-drainage: When the shunt allows cerebral fluid to drain from the brain’s ventricles more quickly than it is produced, the ventricles can collapse, tearing blood vessels and causing bleeding in the brain or blood clot, marked by severe headache, nausea, vomiting, seizure and other symptoms. This risk occurs in approximately 5 to 10 percent of people with shunts.
- Under-drainage occurs when CSF is not removed quickly enough. Pressure builds and the symptoms of hydrocephalus recur.
Infection at the site of the surgical wound, the shunt or in the cerebrospinal fluid itself (meningitis). Symptoms may include a low-grade fever, soreness of the neck or shoulder muscles, and redness or tenderness along the path of the shunt. Hydrocephalus symptoms may reappear as well. If you suspect an infection, call 911 and go to the nearest emergency room immediately.
It is difficult to predict how long shunts will last, but some practitioners note that about half of all shunts need to be revised or replaced after 6 years.