Shunt complications

Shunt infections

Occasionally, bacteria from the skin can infect the shunt, at the time of surgery. Bacteria live within layers of the skin, no matter how clean it is or how thoroughly the skin is prepared for surgery. The bacteria are harmless when on unbroken skin but can cause infections in other parts of the body. The bacteria are released into the surgical cut onto the underlying tissue.

Signs of shunt blockage develop very quickly for infected VP shunts, but infected VA shunts do not block, and may not result in any symptoms for several years after insertion. It is not possible for a shunt to become infected through day-to-day illnesses, such as colds, flu or dental problems.

You will not need antibiotic cover for dental work. However, VP shunts can become infected following abdominal infections, like a burst appendix, or bladder or bowel surgery. Ensure your surgeons know you have a VP shunt if these situations arise.

If it is suspected that your VP shunt is infected, it will usually block, and you will need to seek medical attention straight away. The shunt will be removed and sent for testing, and an External Ventricular Drain (EVD) system will be inserted. This will allow the infected CSF to be drained into a bag outside the body, whilst antibiotics are used to clear the infection. It is important that blood or protein present in the CSF are allowed to clear before the new shunt is fitted, as these can block the new valve. 

Shunt blockages

Shunts can block for a number of reasons.

Proximal

The tiny drainage holes in the proximal catheter may become clogged with healthy brain cells as the catheter is passed through the brain on its way to the ventricle.

This may be a repeated problem for some people, leading to a shunt’s blocking within a few days of being inserted, even with no infection present. Some people are more prone to this, and at the moment we don’t know why that is. The drainage holes can become blocked with choroid plexus, a tissue in the ventricles that produces CSF.

The shunt can move slightly so the tip is no longer in the ventricle but in the brain tissue itself. The valve can become blocked with protein or blood from haemorrhage, although this is rare.

Distal

The bottom end of a VP shunt can become blocked by the tissue covering the bowel, especially if there is a lot of scar tissue (adhesions) in the abdominal cavity, or infections or blood in the abdomen. 

Shunt revisions

If it is necessary to change part or all of your shunt, your neurosurgeon will aim to achieve this with the smallest risk of complications possible. Shunts may, over time, become attached to surrounding tissues, and it can be difficult to remove without causing complications. However, if the shunt is infected, it will usually be necessary to remove the whole shunt so that the infection can be treated effectively.

If the shunt needs changing for another reason, it may be possible to leave a non-functioning shunt in place and just add another shunt system, in another part of the head. If the proximal catheter is blocked but the distal catheter is working, it may be possible to just change the blocked component. Shunts which are under-or-over draining may be ‘tied off’ when another shunt is inserted, to stop them working.