Infections of mechanical cerebrospinal fluid shunts.

In the United States approximately 16,000 CSF shunt operations are performed annually in the treatment of patients with hydrocephalus. Despite a reduction in the incidence of ventricular shunt infections from previous rates of 15 to 30 percent to rates of 5 to 10 percent in recent years, shunt infections remain the most important complication of the treatment of hydrocephalus and contribute significantly to excess morbidity and mortality. Skin flora organisms such as S. epidermidis, S. aureus, and Proprionibacterium are the most common infecting organisms, and the clustering of approximately 70 percent of infections within the 2-month postoperative period strongly suggests that colonization during shunt placement is an important initiating event. In infections caused by S. epidermidis the production of a glycocalyx slime appears to be an important pathogenetic factor. Clinical manifestations of shunt infections are often non-specific, and fever is the only consistent finding. Therefore, a high index of suspicion and a low threshold for diagnostic evaluation are indicated. Needle aspiration of the shunt reservoir or tubing is the single most reliable diagnostic step and is a procedure remarkably free of complications. The most effective treatment regimen is removal of the infected shunt, treatment with effective systemic antibiotics, and replacement of a new shunt in a new site after evidence of CSF inflammation has subsided. Recent preliminary experience combining systemic antibiotics, local instillation of antibiotics into the shunt reservoir or tubing, and revision of the distal shunt appears to offer hope of an effective alternative therapy without total shunt removal. Comparison of this approach to the previous "gold standard" in a well-designed prospective study is a high priority. In addition, attempts to reduce bacterial colonization of shunts by development of new shunt materials and the evaluation of newer antibiotics such as the quinolones in the prophylaxis and/or therapy of shunt infections should be encouraged.