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Cerebrospinal fluid (CSF), or ventricular, shunts are the predominant mode of therapy for children with hydrocephalus. Common causes of hydrocephalus in children include myelomeningocele, meningocele, obstructive or communicating hydrocephalus, intraventricular hemorrhage, congenital cyst, and central nervous system tumors.1 The majority of shunts are inserted in the perinatal period. The shunts divert CSF away from the ventricles, preventing increases in intracranial pressure that lead to neurologic sequelae. The typical CSF shunt has a proximal portion that enters the CSF space, an intermediate reservoir that lies outside the skull but underneath the skin, and a distal portion that terminates in either the peritoneal (ventriculoperioteal [VP] shunt), vascular (ventriculoatrial shunt; VA shunt), or pleural space (Figure 70–1).
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Infection develops in 5–15% of all CSF shunts;2,3 most infections occur within 6 months of shunt placement.3,4 Factors associated with CSF shunt infections include premature birth, young age, neuroendoscope use during shunt insertion, prior shunt infection, and hospital stay more than 3 days at the time of shunt insertion.1,5–7 Insertion of a VP shunt in a premature neonate (age <3 months) has been associated with a nearly five-fold increase in the risk of shunt infection. Patients younger than 1 year at the time of shunt placement also have a substantially higher risk of shunt infection than those older than 1 year at the time of shunt placement.8,9 Insertion of a shunt after a previous shunt infection is associated with a four-fold increase in the risk of shunt infection.
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The etiologic agents associated with CSF shunt infections are shown in Table 70–1.10 Staphylococcal species, especially coagulase-negative Staphylococcus and Staphylococcus aureus, account for almost two-thirds of all shunt infections.7,11 The remaining infections are produced by a wide variety of organisms, including gram-negative bacilli. Among 92 patients with VP shunts, prior S. aureus shunt infection (OR, 5.9; 95% CI: 1.4–25.9) independently increased the odds that S. aureus was the causal pathogen.5 Gram-negative organisms (e.g., Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa) tend to have a delayed onset, suggesting inoculation after surgery.1,10Propionibacterium acnes has been isolated more often in recent series of VP shunt infections; this bacterium generally causes low-grade, indolent infections.12 The apparent increase in P. acnes infection is probably a result of the more frequent use of anaerobic culture media and prolonged (up to 7 days) incubation times. Candida species should be considered in premature infants and other immunocompromised patients as well as in those patients receiving parenteral nutrition or prolonged corticosteroid therapy.13
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There are four common mechanisms of shunt infection: ...