Long-term air-exposed functioning hydrocephalus valve with no infection.

Abstract: One of the reasons for shunt infection is valve erosion through the skin. In such cases, it is common practice to instantly relocate the shunt to avoid infection. We present a 77-year-old female patient with a 15-month history of hydrocephalus valve extrusion. Despite her poor mental status, clinical condition and hygiene, and the prolonged extrusion period, she developed neither a local nor a cerebrospinal fluid (CSF) infection. The patient was ultimately treated with shunt removal and repositioning. An extensive literature review revealed no previous report of such a case. This case indicates that under rare conditions, central nervous system (CNS) implantable devices might not become contaminated and may remain functional, even if they remain exposed for prolonged periods.

Key Words: hydrocephalus, long-term valve extrusion, shunt complications

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Even though cerebrospinal fluid (CSF) shunt surgery for hydrocephalus is considered a simple operation, it has the highest failure rate among neurosurgical procedures and a variety of complications, mainly obstruction and infection, with the latter being potentially fatal if not treated properly.

According to several reports, (1,2) shunts become infected mainly by bacterial organisms indigenous to the patient's skin flora. Hence, in some cases, the shunt will erode the skin and extrude, at which point infection almost always occurs, unless the entire apparatus is removed and placed elsewhere. (3) We present a patient with a long-term extruded valve through the occipital incision, without signs of infection, meningitis or shunt malfunction. A review of available literature revealed no other similar reports.

Case Report

This 77-year-old female underwent ventriculoatrial shunting (Delta 1.0, Medtronic, Athens, Greece) for a normal-pressure hydrocephalus at another hospital. She initially showed improvement in her mental status, but remained bed bound. One month later, she presented with skin ulceration over the shunt and finally developed an eschar. The ulceration was treated conservatively at home with local application of iodine-based antiseptics and plain dressings, but despite treatment, it caused skin erosion. At that time, due to the patient's poor clinical status, the family stopped local antiseptics and decided not to seek further treatment. Fifteen months later she sought medical advice at our hospital because the shunt had almost totally explanted.

On clinical examination, she was found to be undernourished and underweight, with a nasogastric feeding tube and a urinary catheter in situ. She was afebrile and had no nuchal rigidity. According to relatives, during the past year she had developed no symptoms or signs that could be attributed to a CNS infection. She was prescribed amoxicillin for approximately two weeks on two separate occasions; for a respiratory illness (750 mg in 3 daily doses of 250 mg orally) and a urinary tract infection (1,500 mg in 3 daily doses of 500 mg IM), respectively.

The valve was totally exposed in the occipital region, filled with clear CSF and surrounded by granulomatous tissue with no signs of inflammation (Fig.). The reservoir was placed in the center of a curvilinear incision. Finger pumping showed flashing of clear fluid through the valve. Gram stains and cultures retrieved via shunt tab were negative for CSF infection. WBC count, ESR, CRP and serum biochemistry were normal. A brain CT scan showed the shunt catheter in place. The patient was prescribed IV antibiotics (ceftriaxone 2 g/d) and underwent shunt replacement with a frontal ventricular approach on the opposite side. Intraoperative CSF and shunt cultures were negative. At the last follow up a year later, the frontal shunt was fully functional, but the patient showed no alteration in her mental status.

Discussion

Shunt infections occur with an incidence of 5 to 15% (4) and lead to prolonged hospital stay, increased morbidity, mortality and cost. The mechanism leading to infection remains poorly understood. The primary source of infection is believed to be skin bacteria introduced during surgery. There have been numerous reports suggesting that organisms isolated from shunt infections were present on the skin adjacent to the wound before surgery and a relationship between skin flora and subsequent shunt infection cultures has been identified. (5-7) Pople et al (5) reported that the skin bacterial density adjacent to the surgical incision correlated with the incidence of valve infection.

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Infections of CNS shunts are dominated by coagulase-negative Staphylococci, with Staphylococcus epidermidis accounting for 50 to 75% of infections, followed by Staphylococcus aureus, Gram negative enteric bacteria and anaerobic diphtheroids. (7) Some of these organisms demonstrate unique features that facilitate colonization and subsequent shunt infection.

Colonization starts at implantation. At first, the shunt is rapidly covered with a film of soluble connective tissue containing fibronectin, fibrinogen, collagen, or other proteins. (8) This covering contains binding sites for bacteria and allows irreversible bacterial adhesion. S. epidermidis has the capability of synthesizing and secreting a polysaccharide intercellular adhesin consisting of 2 forms, polysaccharide I and II. Polysaccharide I is a linear b-1,6-linked glycosaminoglycan mainly composed of 2-deoxy-2-amino-D-glucopyranosyl residues of which 80 to 85% are N-acetylated, and polysaccharide II is structurally related to polysaccharide I, but with a lower content of non-N-acetylated glucosaminyl residues. (9) Slime production facilitates colonization by enabling organisms to adhere together, forming large cell clusters, and carrying out substance exchange. (8) Furthermore, it acts as a mechanical barrier protecting bacteria from host defense mechanisms, systemic antibiotics and endogenous bactericidal compounds such as lysozyme. According to clinical experience, Staphylococcal infections of implantable material require device replacement. That is not the case with some nonadherent bacteria that are unable to produce this slime, thus making such infections significantly more likely to respond to treatment with antibiotics alone, without the need for removal of the colonized device. (10)

In the reported patient, the mechanism leading to extrusion was maintenance of the supine position over the surgical wound. This patient had a dearth of subcutaneous tissue, and insertion of the valve reservoir in the occiput resulted in stretching and continuous compression of the skin against the shunt reservoir and skull, thus leading to impairment of the blood supply, necrosis and ulceration. In addition, the curvilinear incision led to skin flap vascularization compromise, which, along with poor local hygiene and impaired healing due to poor nutrition, led to skin breakdown. (11,12)

It was surprising that a bed-bound elderly person developed neither local sepsis nor CSF infection after such an extended period of valve extrusion, especially since the occipital skin area in debilitated patients is usually colonized by a high microbial burden acquired during prolonged hospital stay, often resistant to several antibiotics. The local application of the iodine-based antiseptic was thought to have helped in the prevention of infection, even though Bayston et al (1) reported that locally applied iodine is lethal to surface bacteria, but may fail to reach the entire resident flora lying deep in the hair follicles.

Another factor that would advocate toward infection was that this patient was both undernourished and underweight. Beisel (13) has directly associated malnutrition and immune dysfunction, while Sullivan et al (14) clearly demonstrated that disturbances in the immune system, secondary to malnutrition, predispose patients to infection. The exact mechanism that prevented infection was not clear and we can only assume that the development of granular tissue around the burr hole sealed any communication of the skin flora with the CSF.

A careful review of a clinical series of patients with shunt infection revealed that those treated with antibiotics alone demonstrated a lower cure and a higher mortality rate, in contrast to treatment with shunt removal and antibiotic administration. (15,16) It is clear though that the appropriate course of action is dictated by the specifics of the individual situation. Our patient had not developed shunt or CNS infection and the fact that she was a high-risk, poor surgical candidate made decision making difficult. An initial thought was to perform a simple skin flap under local anesthesia and cover the shunt, supplementing this with aggressive antimicrobial chemotherapy. However, the long-term exposure of the valve to skin flora led us to the conclusion that infection would eventually occur, since antimicrobial chemotherapy could reduce but not eradicate the microorganisms within the biofilm. So, despite the fact that this was a high-risk surgical candidate, the morbidity and mortality associated with surgical treatment were weighed against the risks of nonsurgical management and the decision was made for shunt replacement.

Conclusion

Infection represents the most frequent complication of CSF shunting procedures. Even though there has been a large amount of literature concerning techniques and protocols for reducing the incidence of shunt infection, this report shows that, under rare conditions, CSF shunts might not get infected, even if they remain exposed for a long period of time (15 months). This is a unique case and, although it is in contrast with previously reported cases in which infection developed after a short period of extrusion, it does not disprove them, since this patient represents an exception and not the rule.

References

1. Bayston R, Lari J. A study of the sources of infection in colonised shunts. Dev Med Child Neurol 1974;16 (6 Suppl 32):16-22.

2. Faillace WJ. A no-touch technique protocol to diminish cerebrospinal fluid shunt infection. Surg Neurol 1995;43:344-350.

3. Scott MR. Shunt complications. In: Wilkins R, Rengachary S, eds. Neurosurgery. Vol 3. New York, McGraw-Hill Companies, 1996, 3655-3664.

4. Choux M, Genitori L, Lang D, et al. Shunt implantation: reducing the incidence of shunt infection. J Neurosurg 1992;77:875-880.

5. Pople IK, Bayston R, Hayward RD. Infection of cerebrospinal fluid shunts in infants: a study of etiological factors. J Neurosurg 1992;77:29-36.

6. Schoenbaum SC, Gardner P, Shillito J. Infections of cerebrospinal fluid shunts: epidemiology, clinical manifestations, and therapy. J Infect Dis 1975;131:543-552.

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

8. Peters G, Schumacher-Perdreau F, Jansen B, et al. Biology of Staphylococcus epidermidis extracellular slime. Zentralbl Bakt 1987;Suppl 16:15-32.

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

10. Diaz-Mitoma F, Harding GK, Hoban DJ, et al. Clinical significance of a test for slime production in ventriculo-peritoneal shunt infections caused by coagulase-negative staphylococci. J Infect Dis 1987;156:555-560.

11. Vercellotti GM, McCarthy JB, Lindholm P, et al. Extracellular matrix proteins (fibronectin, laminin and type IV collagen) bind and aggregate bacteria. Am J Pathol 1985;120:13-21.

12. Johnson GM, Lee, DA, Regelmann WE, et al. Interference with granulocyte function by Staphylococcus epidermidis slime. Infect Immun 1986;54:13-20.

13. Beisel WR. Nutrition in pediatric HIV infection: setting the research agenda: nutrition and immune function: overview. J Nutr 1996;126(Suppl 10):2611S-2615S.

14. Sullivan PB, Lambert B, Rose M, et al. Prevalence and severity of spasticity and nutritional problems in children with neurological impairment: Oxford feeding study. Dev Med Child Neurol 2000;42:674-680.

15. James HE, Walsh JW, Wilson HD, et al. Prospective randomized study of therapy in cerebrospinal fluid shunt infection. Neurosurgery 1980;7:459-463.

16. 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.

Andreas T. Kouyialis, MD, George Stranjalis, MD, Stefanos Korfias, MD, and Damianos E. Sakas, MD

From the Department of Neurosurgery, University of Athens Medical School, Evangelismos General Hospital, Athens, Greece.

Reprint requests to Andreas T. Kouyialis, Neurosurgeon, Flat 27 A Buttermere, University Hospital Aintrees. Lower Lane, Fazakerly, Liverpool, L9 7AL, United Kingdom. Email: [e-mail]

Accepted April 19, 2006.

RELATED ARTICLE: Key Points

* Shunt surgery is considered simple but has the highest failure rate among all neurosurgical procedures.

* Among shunt surgery-related complications, infection remains the foremost problem and is fatal if not treated properly.

* Central nervous system shunt infections are dominated by organisms with features that facilitate the colonization and subsequent infection of the shunt.

* Patients with shunt infection have a lower cure and a higher mortality rate when treated with antibiotics alone, in contrast to treatment with shunt removal and antibiotic administration.

* Under rare conditions, cerebrospinal fluid shunts might not get infected, even if they remain exposed for a long period of time.