Management of neurosurgical implant-associated infections

With the technical developments in neurosurgery, increasing numbers of neurosurgical implants are used in an increasingly aged population of patients with several comorbidities. Consequently, the number of neurosurgical implant-associated infections is continuously raising, resulting in significant morbidity and mortality, including disfiguring skull deformities and lack of brain protection. In this article we review infections associated with craniotomy, cranioplasty, neurostimulators, internal cerebrospinal fluid shunts, and external ventricular and lumbar cerebrospinal fluid drainages. In all implant-associated infections biofilms are involved, which are difficult to eradicate. A low number of microorganisms is sufficient to form a biofilm on the implant surface. In most infections, microorganisms of the skin flora are involved. Microorganisms reach the implant during surgery or immediately thereafter as a result of wound healing disturbances. In about two thirds of patients, implant-associated infections manifest early (within the first month after surgery), whereas the remaining infections present later as a result of low-grade infections or by direct extension from adjacent infections (per continuitatem) to the implants due to soft tissue damage. Except for ventriculo-atrial cerebrospinal fluid shunts, neurosurgical implants are rarely infected by the haematogenous route. In this article we review established and clinically validated concepts for the management of biofilm-associated infections in orthopaedic and trauma surgery, which can be extrapolated to other surgical disciplines that use implants. However, the evidence for the success of this extrapolation to neurosurgical patients is sparse and has not been evaluated in large patient populations. For favourable outcome, an optimised microbiological diagnosis including sonication of removed implants and prolonged incubation of cultures is required. Furthermore, a combined surgical and antimicrobial management strategy is needed. Surgery includes an appropriate debridement with or without implant exchange or removal, depending on the age of the biofilm and the soft tissue condition. Antimicrobial treatment includes a prolonged biofilm-active therapy, typically for 4–12 weeks. This concept is attractive, because in selected patients, implants can be retained or exchanged in a one-stage surgical procedure, which improves not only quality of life, but also decreases morbidity because every additional neurosurgical intervention can lead to secondary complications, including intracerebral bleeding or ischemia.