Pediatric emergency medicine trisk 1165

TABLE 135.4
SIGNS AND SYMPTOMS OF SHUNT INFECTION IN PATIENTS
WITHOUT WOUND INFECTION
Change in sensorium
Irritability
Fever
Vomiting
Adbominal pain
Shunt obstruction
Adapted with permission from Odio C, McCracken GH, Nelson JD. CSF shunt infections in pediatrics: a
seven-year experience. Am J Dis Child 1984;138:1103–1108.

The peritoneal portion of the shunt may become infected through the shunt
mechanism or via a primary peritoneal infection. Peritoneal infection can result in
loculated, cystic pools of infection around the terminal portion of tubing
(pseudocysts). These infections may be indolent in their presentation, and the
shunt tap from the reservoir may not show evidence of infection.
Shunt nephritis is a rare but serious complication of ventricular–atrial shunts.
Renal deposition of antigen–antibody complexes leads to complement activation,
which damages the renal tissue.
Unfortunately, the child with an infected CSF shunt may present with
nonspecific signs and symptoms ( Table 135.4 ). Children commonly develop
symptoms of shunt malfunction, such as lethargy or irritability. Meningismus is
not often present. Infection may also manifest as abdominal complaints, such as
pain or vomiting, especially when the infection involves the distal catheter tip.
Fever is not always present in patients with shunt infections and is
uncommonly the only sign. As previously mentioned, infection is most common
within a few months of the shunting procedure, is uncommon after 6 months, and
is rare more than 1 year afterward. These rules are less applicable in patients with
gram-negative infections, which can occur later after shunt placement. Children
with gram-negative infections are more often bacteremic, if not septic appearing.

A wound infection overlying any portion of the shunt mechanism can manifest
as erythema and tenderness or swelling along the shunt tract or over the reservoir.
A reddened tract of skin paralleling the shunt tubing from the head to chest is
often detected and is virtually diagnostic of shunt infection.
In the absence of overlying infection, aspiration of a small amount of CSF from
the shunt system should be performed to identify the presence of a bacteriologic


cause of shunt infection. This procedure is usually performed by a neurosurgeon,
if possible. The results of this procedure are sometimes helpful but not always
determinate; the white blood cell (WBC) count can range from 0 to 2,600 if the
shunt is infected, and patients without infection can have up to 500 WBCs/mm3.
In the absence of a positive culture result, many clinicians use more than 50
WBCs/mm3 in the presence of fever, shunt malfunction, and neurologic or
abdominal symptoms to arrive at the diagnosis. Gram stain of the fluid may be
helpful in broadening antibiotic coverage if gram-negative organisms are present.
However, the Gram stain should not be used to narrow the usual antibiotic
coverage until the culture and sensitivities of the causative organisms are
obtained. Most neurosurgeons are reluctant to perform shunt taps in patients with
subtle neurologic complaints and vague infectious signs because of the purported
risk of “seeding” the shunt with skin flora. This risk has never been clearly
defined prospectively, but in a neurologically normal child, it is prudent to
perform a thorough fever workup for common infectious sources to avoid even a
small risk of causing a shunt infection.
Patients with ventriculoperitoneal shunt (VPS) who complain of abdominal
pain, with or without fever, may benefit from abdominal radiographs and
ultrasound to search for a loculated CSF collection or pseudocyst, or visceral
perforation.
Various permutations of medical and surgical therapy have been suggested for
the treatment of proximal CSF shunt infections. Medical therapy alone has been

found to have a relatively low success rate compared with a combined medical–
surgical approach. Potential surgical interventions include immediate shunt
replacement or the insertion of an extraventricular drainage (EVD) catheter,
followed by delayed shunt revision. The latter method improves the bacteriologic
cure rate significantly, although it must be performed in an institution that is
facile in managing and preventing infection of EVD catheters. Distal shunt
infections are treated with antibiotics and temporary externalization of the distal
shunt catheter.
Medical therapy provided in the ED for children with suspected CSF shunt
infections is limited to the administration of broad-spectrum IV antibiotics. The
antibiotics should be effective against S. epidermidis, S. aureus , and gramnegative organisms, as well as any organisms identified from previous infections,
and expanded to treat Pseudomonas aeruginosa infections in severely ill patients.
A reasonable choice of empiric therapy is cefepime followed by vancomycin.
Ciprofloxacin can be substituted for Cefepime in patients with documented


allergy. Eventually, antibiotic therapy may be narrowed on the basis of culture
and sensitivity results of the shunt fluid.
Overdrainage
Occasionally, children with CSF shunts experience symptoms related to the
system working too well, resulting in low ICP. Such overshunting is more
common in infants who have had initial shunting before 6 months of age. One
consequence is the slit ventricle syndrome, in which the ventricles collapse
around the proximal catheter port and block further drainage. The best means of
diagnosing intracranial hypotension is the patient’s history rather than physical
examination or radiographic analysis. Young infants may exhibit sunken
fontanels, microcephaly, or overriding parietal bones. Older children may exhibit
intermittent symptoms of headache, nausea, vomiting, and lethargy. The drainage
of CSF shunts increases when the patient is upright and decreases when supine. In
contrast to the classic timing of symptoms related to increased ICP, patients with

intracranial hypotension are often worse when in the standing position or after
they are awake for several hours. Lying supine for a few hours tends to relieve
symptoms of slit ventricle syndrome. Many patients with CSF shunts have CT
scans that reveal small ventricles; however, only a small proportion of these
patients have slit ventricle syndrome. Therefore, the CT scan is best used to
differentiate between shunt malfunction and other causes of symptoms rather than
to diagnose an overdrainage problem.
Chronic or recurrent episodes of slit ventricle syndrome can be addressed
surgically by upgrading the resistance of the valve or by insertion of an
antisiphon device. Oral analgesics may be helpful in managing mild cases.
Other Complications
Other complications related to CSF shunts deserve mention. The most common of
these complications is a benign postoperative leakage of CSF around the
proximal shunt tubing into the subgaleal space around the reservoir. The resulting
extracranial fluid collection resolves spontaneously, so drainage of this fluid
should be avoided. In non-postoperative patients, a new extracranial fluid
collection can suggest shunt malfunction, as the CSF takes the newest “path of
least resistance.”
Patients with CSF shunts have an increased risk of seizures compared with the
general population. These seizures often begin years after shunt placement and
are caused by epileptogenic scars. They are more common in patients with other


abnormalities correlated with seizures, such as porencephalic cyst or intracranial
hemorrhage.
Overdrainage can lead to shrinkage of brain tissue and concomitant subdural
accumulations (hematomas or CSF effusions referred to as hygromas). Similarly,
a decreased rate of head growth because of overdrainage can result in
craniosynostosis in the infant.
Some important, albeit rare, complications are related to specific types of CSF

shunts. The distal portions of a VPS can migrate and cause perforation of the
colon or genital tract. This section of tubing can act as a fulcrum for intestinal
volvulus. Ascites and abdominal cysts can form as a result of drainage of excess
fluid into the peritoneum. Increased intra-abdominal pressure can precipitate the
formation of an inguinal hernia through a patent processus vaginalis.
Ventricular–vascular shunts can be associated with an increased risk of
bacteremia. Shunt nephritis can result from complement activation and renal
deposition of immune complexes. Patients with ventriculoatrial shunts can
experience cardiac arrhythmias or atrial perforation, usually perioperatively.
Bacterial endocarditis, cardiac foreign body, and mural thrombus are rare but
notable complications of vascular shunts.
After ventriculoatrial shunt, the pleural cavity is the third most common site for
distal catheter placement. These can lead to pleural effusions and related
complications. Often, they are placed temporarily to allow “bowel rest” after
peritonitis but then revised to a standard VPS when the infectious peritoneal
issues have resolved.
Avoiding Pitfalls With New Endoscopic Technology
Neurosurgeons are increasingly using endoscopic techniques in the management
of pediatric hydrocephalus, particularly in obstructive hydrocephalus and the
treatment of intracranial cysts. Children who have previously been shuntdependent may undergo endoscopic third ventriculostomy (ETV), which is
effectively an internal shunt that bypasses a stenosed aqueduct of Sylvius. Parents
and emergency clinicians should be cognizant that these children are still subject
to the same manifestations of shunt failure; the presence of appropriate signs and
symptoms of raised ICP should initiate the same evaluation and criteria for
possible intervention outlined earlier in this section. It should be noted that while
not subject to the myriad malfunctions that befall patients with implanted
hardware such as infection, erosion, disconnection, and clogging, patients with
ETVs can suffer restenosis of their fenestration site, with reports of closure as late
as 8 years after the initial procedure.