Cerebrospinal fluid shunts interfere with host defenses.

Despite advances in neurosurgical therapeutics, cerebrospinal fluid shunt infections have continued to complicate the management of patients with shunted hydrocephalus. Although various factors have been proposed to explain the pathogenesis of these infections, they have remained poorly understood. This in vitro study determined the ability of human neutrophils and monocytes to adhere to two types of shunt catheters and to phagocytose bacteria. These white blood cells failed to adhere in normal numbers to the catheters and failed to ingest fully a bacterial inoculum on the catheters' surfaces. While in contact with the shunt apparatus, the neutrophils also exocytosed myeloperoxidase, a major component of the intracellular microbicidal system. These observations suggest that the shunt apparatus may diminish the effectiveness of the hosts' defenses at the site of implantation.