CSF shunt complications

8.1 CSF shunt complications



Richard Lennon




Essentials



1 Emergency physicians should consider the possibility of a shunt complication in any child with a cerebrospinal fluid (CSF) shunt presenting to an ED because symptoms and signs of malfunction may be non-specific, subtle and of gradual onset.

2 The most common shunt complications are malfunction (undershunting and overshunting) and infection.

3 Shunt infection is much more likely to occur in the 6 months following insertion or revision.

4 CT scan and plain X-rays of shunt hardware (‘Shunt Series’) are the preferred imaging methods for detecting shunt malfunction; however, these tests are not 100% sensitive and patients should be referred to the neurosurgical service if clinical suspicion persists.

5 Before performing any procedure on a shunt, it is best to consult with the treating neurosurgeon.


Introduction


The intervention of cerebrospinal fluid (CSF) shunting for CSF accumulations has brought about long-term survival and avoidance of disabilities in children suffering from hydrocephalus. Unfortunately, the insertion of inert non-growing hardware in infants and children who are usually very active and can expect to grow 20 to 30 times their birth weight leads to a high rate of shunt complications. Some studies find that 60% or more shunts need revising after several years. The task of the Emergency Physician is to diagnose those complications, commence time critical treatments and refer to a neurosurgical service when appropriate.



Types of shunt


Many types of CSF shunt may be encountered in paediatric emergency practice. There are also many different types of shunt hardware; however, most have the same basic structure, which comprises a proximal tube that takes CSF, usually from the lateral ventricle, to the outer surface of the skull. At this point there is usually a subcutaneous one-way valve and possibly a pumping device. There may also be an antisiphoning device. The distal tubing is tunnelled under the skin to the drainage site, which is most commonly the peritoneal cavity. The distal catheter usually contains valves that prevent back flow. Variations on the positioning of the proximal tubing include placement in the subdural or subarachnoid space and placement in cystic malformations such as the Dandy Walker syndrome and also in the spinal canal as in lumbo-peritoneal shunts. Variations in the placement of the distal catheter include the right atrium, the pleural cavity and the gall bladder. By far the most common is the peritoneal cavity, with these alternatives only being used if the peritoneal site is contraindicated.


Shunt problems that may present to an emergency department (ED) are listed in Table 8.1.1.






Table 8.1.1 Complications of CSF shunts

• Infection

• Malfunction
Blocked proximal catheter

Blocked distal catheter

Loculation of lateral ventricle

Valve dysfunction

Overshunting/slit ventricle syndrome

Disconnection

• Abdominal pseudocyst

• Migration of distal catheter

• Invasion of abdominal organs (VP shunt)

• Peritonitis, ascites (VP shunt)

• Pulmonary emboli (VA shunt)

• Glomerulonephritis (VA shunts)

• Brain tumour metastases

• CSF ascites

• Pleural effusion (pleural shunts)


Clinical presentation


The developmental stage of the child with a CSF shunt can cause considerable variation in the clinical presentation of shunt complications. The most obvious is the presence of an open anterior fontanelle in infants up to the age of approximately 9 to 18 months. Simply looking and feeling the fontanelle allows an estimation of intracranial pressure. A bulging fontanelle is a highly specific but not very sensitive sign of under-shunting; a sunken fontanelle can be a sign of overshunting.


The cranial sutures in children are not fused and can undergo diastasis due to raised intracranial pressure. The older a child is, the longer and higher the intracranial pressure has to be to cause diastasis. This also means that the head circumference will rapidly increase when there is inadequate shunting. Therefore it is important to measure the occipitofrontal circumference and compare it with previous records if available and plot it on growth centile charts. A head circumference that is rapidly crossing centiles in an upward fashion or a head circumference that is in the very high centile range especially when the other parameters, weight and length, are not, is an indicator of undershunting. Another implication of unfused cranial sutures is that because this allows an increase in cranial volume it retards the rise in intracranial pressure. This may be the reason that small infants present with more non-specific signs and symptoms than older children.


The most common question an emergency physician will have to answer when confronted with a child who has a CSF shunt is ‘Should I refer this patient to the neurosurgical service?’ A recent study by Piatt et al1 attempted to quantify the power of various symptoms and sign to predict shunt malfunction or infection. Table 8.1.2 shows the strongly predictive signs and symptoms that allow referral to be made on the basis of that single finding. This may be done even before computerised tomography (CT) scanning, as the neurosurgeon may prefer to have the scan done locally to allow for easier comparison with previous scans (see discussion of CT scanning below). Table 8.1.3 shows the signs and symptoms with strong positive predictive power but not strong enough to warrant immediate referral if just one feature is present on its own. Thus in a patient with a ventriculoperitoneal shunt (VPS) who presents with fever alone, an initial general work up for a cause of the fever is warranted and then consideration for referral to neurosurgery made if no definite cause for the fever is found. However, fever with another feature listed in Table 8.1.3, such as headache, warrants early neurosurgical referral. The question of whether to send the child home is more difficult. The absence of any of the symptoms and signs listed in Tables 8.1.2 and 8.1.3 does not rule out shunt malfunction or infection. If concerned about shunt infection, this is much less likely if the patient is more than 6 months from the last shunt insertion or revision. However, this does not exclude shunt malfunction. Where a symptom or sign that is not of high predictive power is adequately explained by another diagnosis (e.g. vomiting with diarrhoea and recent contact with a case of gastroenteritis) CSF shunt complication is very unlikely. For cases where CSF shunt complications are neither ruled in or out on historical and examination findings, one must resort to investigations and/or observation and/or neurosurgical consultation.






Table 8.1.2 Signs and symptoms that on their own warrant immediate referral to neurosurgical service

Bulging fontanelle

Related posts:

Syncope Abdominal and pelvic trauma Default ThumbnailThyroid emergencies CNS infections: meningitis and encephalitis Default ThumbnailGeneral approach to poisoning Specific poisons

Stay updated, free articles. Join our Telegram channel
Tags:
Sep 7, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on CSF shunt complications

Full access? Get Clinical Tree

 Get Clinical Tree app for offline access