Chapter 74: Cerebrospinal Fluid Shunt Infections

DEFINITIONS

Cerebrospinal fluid (CSF) shunts are the predominant mode of therapy for children with hydrocephalus. Shunt insertions and revisions are among the most commonly performed neurosurgical procedures. Common causes of hydrocephalus in children include intraventricular hemorrhage, myelomeningocele, central nervous system (CNS) tumors, aqueductal stenosis, communicating hydrocephalus, head injury, and infections. Most shunts are first inserted before 6 months of age.¹ The shunt apparatus diverts CSF away from the ventricles, preventing increases in intracranial pressure that may 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 [ventriculoperitoneal (VP) shunt], vascular [ventriculoatrial (VA) shunt], or pleural space [ventriculopleural (V-Pleural) shunt] (Figure 74-1).

EPIDEMIOLOGY

Infection develops in 5–15% of all CSF shunts at some point in the life of the shunt.^2,3 The use of different definitions across studies makes it challenging to determine the true incidence of CSF shunt infections. The most common definition, put forth by the Centers for Disease Control and Prevention National Healthcare Safety Network (CDC/NHSN), addresses postoperative (surgical site) infection, and does not attempt to address shunt infection specifically.⁴ Other definitions, such as that put forth by the Hydrocephalus Clinical Research Network (HCRN),⁵ focus solely on CSF shunts and the various ways infections are diagnosed.

Most infections occur within 6 months of initial shunt placement.^3,6 Factors associated with CSF shunt infections include a recent shunt insertion or revision, premature birth, young age, neuroendoscope use during shunt insertion, and prior shunt infection.^7–12 Insertion of a shunt after a previous shunt infection is associated with a 4-fold increase in the risk of shunt infection. A single revision surgery is associated with a 3–4-fold higher risk of infection, and two or more revision surgeries are associated with a 6–13-fold higher risk of infection.^11,12

The etiologic agents associated with CSF shunt infections are shown in Table 74-1.¹³ Staphylococcal species, especially coagulase-negative Staphylococcus and Staphylococcus aureus, account for almost two-thirds of all shunt infections.^10,14 The remaining infections are produced by a wide variety of organisms. Propionibacterium acnes has been isolated more often in recent series of VP shunt infections; this bacterium generally causes low-grade, indolent infections.¹⁵ The apparent increase in P. acnes infection is probably due to the more frequent use of anaerobic culture media and prolonged (≥10 days) incubation times, as recommended by the Infectious Diseases Society of America (IDSA).¹⁷ Candida species, while a rare cause of CSF shunt infection, should be considered in premature infants and ...