Exposed CSF shunts: the naked truth about shunt infections.

In the article entitled, "Long-term air-exposed functioning hydrocephalus valve with no infection," the authors describe an interesting case of an elderly patient whose ventriculoperitoneal shunt valve has eroded through the skin without a resulting shunt infection or malfunction. (1) For any practitioner who takes care of patients with cerebrospinal fluid (CSF) shunts, the very thought of shunt components being exposed to the external environment for fifteen months without significant morbidity arising is somewhat implausible given the relatively high rate of infection and malfunction even in young, healthy patients with no history of wound complications. The authors of this case report fittingly emphasize the rarity of this clinical entity. More importantly, however, they also remind the reader of the serious and often life-threatening difficulties of treating patients with hydrocephalus and indirectly bolster a recently developed therapeutic option for preventing infections in the future.

Despite improvement in surgical technique and consistent use of preoperative antibiotics before CSF shunt placement, roughly 1 in 10 implanted CSF shunts become infected in North America. (2) In pediatric populations, reduced IQ and school performance, psychomotor retardation, and increased risk of seizures have all been associated with such infections. (3-10) In addition, shunt infection is a common cause of shunt failure with its additional risk of morbidity and mortality. (11) The exact medical cost to society of such infections is not clear. However, given that CSF shunt placements, the majority of which are revision surgeries, have been estimated to account for greater than 100 million dollars (US) of national healthcare expenditures annually, (12) it is not unreasonable to conclude that shunt infections contribute significantly to these healthcare costs.

The majority of infections appear within the first six months postoperatively and likely result from direct inoculation of shunt components by nonpathogenic skin flora at the time of surgery. (2,13-16) Standard treatment of shunt infections involves IV antibiotics in combination with removal and/or replacement of the colonized hardware. IV antibiotics alone are often inadequate in eradicating such infections, (5) largely due to the production of bacterial "slime," which allows protection from host defense mechanisms and systemically administered antibiotics. (17) Thus, as with any type of microbial colonization of an implanted foreign material within the human body (shunts, cardiac valves, central venous catheters, urinary catheters, etc.), lone antimicrobial administration is often a secondary option behind removal of the foreign body when feasible. (5)

In this case report, the authors comment on possible reasons why this patient did not experience a shunt infection. In doing so, they highlight a potential mechanism by which practitioners may more successfully prevent infections in the future. First, they note that the exposed shunt components were continuously soaked in iodine, arguably creating a sterile wound and prohibiting shunt colonization. Secondly, the authors hypothesize that the chronic nature of the wound may have generated granular tissue around the burr hole, preventing communication of the skin flora with CSF. Both putative reasons deserve serious consideration since they both prevent microbial colonization of internalized shunt components.

In an effort to systematically decrease the progression of shunt contamination to colonization and infection in a similar fashion, antibiotic-impregnated shunt (AIS) systems have been developed. These systems are designed to release antibiotics over the course of several weeks after implantation, thus "sterilizing" any contamination that may have occurred during operative exposure to skin flora. Not surprisingly, introduction of such AIS systems into hydrocephalic patient populations have been shown to decrease the incidence of early shunt infections in a small number of studies. (7,18)

Although this patient did not possess an antibiotic-impregnated shunt, her internalized shunt components were likely never colonized by skin flora due to the nature of her wound and chronic sterilization with iodine. Despite the fortuitous outcome for this patient, treatment of an exposed shunt component with iodine dressings is not the treatment of choice; rather, such shunts should be removed and/or replaced in combination with antibiotics, as was done for this patient. Replacement of her shunt system with an antibiotic-impregnated one may have also been beneficial. The ability of such AIS systems to limit shunt colonization and infection affords the neurosurgeon an effective tool in treating patients with hydrocephalus, and for this reason, use of such components may soon become the standard of care.

References

1. Kouyialis AT, Stranjalis G, Korfias S, et al. Long-term air-exposed functioning hydrocephalus valve with no infection. South Med J 2006;99:1127-1129.

2. Gardner P, Leipzig T, Phillips P. Infections of central nervous system shunts. Med Clin North Am 1985;69:297-314.

3. Blount J, Campbell J, Haines S. Complications in ventricular cerebrospinal fluid shunting. Neurosurg Clin N Am 1993;4:633-656.

4. Chadduck W, Adametz J. Incidence of seizures in patients with myelomeningocele: a multifactorial analysis. Surg Neurol 1988;30:281-285.

5. Chapman P, Borges L. Shunt infections: prevention and treatment. Clin Neurosurg 1984;32:652-664.

6. Fan-Havard P, Nahata M. Treatment and prevention of infections of cerebrospinal fluid shunts. Clin Pharm 1987;6:866-880.

7. Govender S, Nathoo N, van Dellen J. Evaluation of an antibiotic-impregnated shunt system for the treatment of hydrocephalus. J Neurosurg 2003;99:831-839.

8. McGirt MJ, Leveque JC, Wellons JC 3rd, et al. Cerebrospinal fluid shunt survival and etiology of failures: a seven-year institutional experience. Pediatr Neurosurg 2002 36:248-255.

9. Walters BC, Goumnerova L, Hoffman HJ, et al. A randomized controlled trial of perioperative rifampin/trimethoprim in cerebrospinal fluid shunt surgery. Childs Nerv Syst 1992;8:253-257.

10. Walters BC, Hoffman HJ, Hendrick EB, et al. Cerebrospinal fluid shunt infection. Influences on initial management and subsequent outcome. J Neurosurg 1984;60:1014-1021.

11. Smith E, Butler W, Barker FG 2nd. In-hospital mortality rates after ventriculoperitoneal shunt procedures in the United States, 1998 to 2000: relation to hospital and surgeon volume of care. J Neurosurg 2004 100 (2 Suppl Pediatrics):90-97.

12. Bondurant CP, Jimenez DF. Epidemiology of cerebrospinal fluid shunting. Pediatr Neurosurg 1995;23:254-258; discussion 259.

13. Enger P, Svendsen F, Wester K. CSF shunt infections in children: experiences from a population-based study. Acta Neurochir (Wien) 2003;145:243-248; discussion 248.

14. George R, Leibrock L, Epstein M. Long-term analysis of cerebrospinal fluid shunt infections. A 25-year experience. J Neurosurg 1979 51:804-811.

15. Kanev P, Sheehan J. Reflections on shunt infection. Pediatr Neurosurg 2003;39:285-290.

16. Ronan A, Hogg G, Klug G. Cerebrospinal fluid shunt infections in children. Pediatr Infect Dis J 1995;14:782-786.

17. von Eiff C, Peters G, Heilmann C. Pathogenesis of infections due to coagulase-negative staphylococci. Lancet Infect Dis 2002;2:677-685.

18. Sciubba DM, Stuart RM, McGirt MJ, et al. Effect of antibiotic-impregnated shunt catheters in decreasing the incidence of shunt infection in the treatment of hydrocephalus. J Neurosurg 2005:103 (2 Suppl):131-136.

I have always depended on the kindness of strangers.
--Tennessee Williams

Daniel M. Sciubba, MD

From the Johns Hopkins University School of Medicine, Baltimore, MD.

Reprint requests to Daniel M. Sciubba, MD, Johns Hopkins University School of Medicine, 600 North Wolfe Street, Meyer 8-181, Baltimore, MD 21287. Email: [e-mail]

Accepted May 3, 2006.