James M. Drake

Nosocomial Bacterial Meningitis

Nosocomial bacterial meningitis is most often related to either complicated head trauma or invasive procedures, such as craniotomy, placement of ventricular catheters, intrathecal infusion of medications, or spinal anesthesia. In addition, metastatic infection from hospital-acquired bacteremia occasionally leads to meningitis. The conditions are associated with different pathogenetic mechanisms and a different spectrum of microorganisms, and therefore the choice of empirical antimicrobial therapy will vary according to the condition.

CSF shunts 50 years on--past, present and future.

Abstractu2002Cerebrospinal fluid (CSF) shunts were invented almost 50 years ago. While their introduction revolutionized the treatment of hydrocephalus, their complications have become legendary, and the focus of much investigation and development of new devices. New devices have been based upon improved understanding of the pathophysiology of hydrocephalus or shunt complications. Despite the rational, or frequently ”more physiological,” functioning of these devices, all too often unexpected complications have ensued, and the initial enthusiasm for the devices has waned. Assessing the efficacy of the devices has been difficult, owing to the lack of properly conducted studies. Nevertheless, the overall impact of shunt design improvements has seemed very limited. A recent randomized trial of CSF shunt design, examining the failure rates of two new and widely used valves (the Cordis Orbis Sigma and the Medtronic PS Medical Delta valves) failed to find any advantage of these over standard valve designs, many of which have been used almost since the inception of CSF shunts. A search for risk factors for failure, in a post hoc analysis of the data, indicated only that the etiology of the hydrocephalus and the position and local environment of the ventricular catheter tip were probably important. Remarkably, the rate of change in the size of the ventricles and the final ventricular size were not different despite the substantial differences in flow characteristics of the two new valves. Shunt failure rates of less than 5% at 1 year, with infection rates of less than 1%, seem like reasonable goals for the next decade in the new millenium. This can be achieved through basic research into the pathophysiology of shunt failure with improved mathematical models, and perhaps animal models of shunt failure. Efficacy of new devices or treatments must be scrutinized scientifically so as not to waste valuable resources and time on unproven treatments. Uncontrolled series and testimonial assertions about new treatments or devices, especially from proponents with a vested interest, should be regarded with great skepticism. Nevertheless, our best efforts are likely to result in a major advance in the management of pediatric hydrocephalus, which now seems tantalizingly close.

Repeat Cerebrospinal Fluid Shunt Infection in Children

Background: In this study, we investigated the treatment of cerebrospinal fluid (CSF) shunt infection and the risk factors for repeat shunt infection (RSI) in a cohort of children treated at the Hospital for Sick Children, Toronto, Canada. Methods: Between 1996 and 2000, a total of 51 children were identified with shunt infection (mean age 5.8 years). The medical records of these children were reviewed to identify cases of RSI within 6 months of the initial shunt infection (ISI). Results: In the 51 ISIs, the infecting organisms were coagulase-negative Staphylococcus (43.1%), Staphylococcus aureus (37.3%) and others (19.6%). The initial mode of treatment of the shunt infection was using an external ventricular drain (EVD) with removal of the shunt apparatus (54.9%), externalization of the shunt (37.3%) or shunt removal only (7.8%). The mean number of days of external CSF drainage (either EVD or externalized shunt) was 11.2 days. Ten patients (19.6%) developed RSI. The actuarial risk of RSI plateaued after 90 days at 24.4%. The following variables were tested as risk factors for RSI using survival analysis, although none reached statistical significance: initial organism (p = 0.09), age (p = 0.42), etiology of hydrocephalus (p = 0.45), number of days of CSF drainage (p = 0.45), type of surgical treatment of the ISI (p = 0.58) and the presence of bacteriologically positive CSF at ISI (p = 0.85). Conclusions: The risk of RSI is substantial and greater effort needs to be directed towards understanding the risk factors. Such studies will need a greater sample size in order to obtain sufficient statistical power.

Results of endoscopic third ventriculostomy.

ETV is emerging as the treatment of choice for aqueductal stenosis caused by anatomic, inflammatory, and selected neoplastic etiologies. The technique has also proven useful in the pathologic diagnosis and treatment of these conditions. Long-term results of this procedure and comparison to standard shunting procedures are necessary to define indications for patients with pathologic findings in the intermediate response groups. Development of new studies for pre-operative assessment of CSF absorptive capacity and quantitative postoperative measures of ventriculostomy function would be invaluable additions to our ability to assess candidates for this procedure and their eventual outcome. Further study and technical refinements will, no doubt, lead to many more potential uses for these procedures in the treatment of hydrocephalus and its associated etiologies. The challenge for neuro-surgeons will be to define the operative indications and outcomes, while refining techniques for safely performing these useful procedures.

Cerebrospinal Fluid Shunt Infections

Despite recent reports of very low infection rates, cerebral spinal fluid shunt infection remains a persistent and devastating problem in most neurosurgical centers, occurring in 5–10% of procedures. Shunts are most commonly colonized by skin commensal organisms. Staphylococcus epider-midis accounts for 40% of shunt infections; 5. aureus accounts for 20%. Organisms like S. epidermidis produce an extracellular slime, or glycocalyx, which allows them to adhere to shunt material and inhibit the hosts defense mechanisms. Formation of a biolayer containing microcolonies of the organism on the prosthesis further inhibits attempts to eradicate the infection. Patients with shunt infections can have a wide variety of clinical symptoms, ranging from wound infection, meningitis, and peritonitis to more indolent symptoms like malaise or simple shunt obstruction. Growth of skin commensals only from shunt equipment cultured in broth media tends to considerably overestimate shunt infection. Removal of all the infected shunt equipment and interval external ventricular drainage produce the highest infection cure rate and lowest mortality rate. Antibiotic treatment alone is very effective for organisms, such as Hemophilus influenzae, that commonly cause meningitis in the general community, but has limited success and a high mortality rate with common shunt-infecting organisms. None of the procedures designed to prevent infection, including meticulous antisepsis and prophylactic antibiotic drugs, has been proven effective by randomized controlled trial. However, recent meta analysis of combined prophylactic antibiotic trials suggests that antibiotic prophylaxis is effective. Future efforts to prevent shunt infection will concentrate on new biomaterials, including those impregnated with antibiotic drugs.

Lack of benefit of endoscopic ventriculoperitoneal shunt insertion: a multicenter randomized trial.

OBJECTnEndoscopically assisted ventricular catheter placement has been reported to reduce shunt failure in uncontrolled series. The authors investigated the efficacy of this procedure in a prospective multicenter randomized trial.nnnMETHODSnChildren younger than 18 years old who were scheduled for their first ventriculoperitoneal (VP) shunt placement were randomized to undergo endoscopic or nonendoscopic insertion of a ventricular catheter. Eligibility and primary outcome (shunt failure) were decided in a blinded fashion. An intention-to-treat analysis was performed. The sample size offered 80% power to detect a 10 to 15% absolute reduction in the 1-year shunt failure rate. The authors studied 393 patients from 16 pediatric neurosurgery centers between May 1996 and November 1999. Median patient age at shunt insertion was 89 days. The baseline characteristics of patients within each group were similar: 54% of patients treated with endoscopy were male and 55% of patients treated without endoscopy were male; 30% of patients treated with and 26% of those without endoscopy had myelomeningocele; a differential pressure valve was used in 51% of patients with and 49% of those treated without endoscopy; a Delta valve was inserted in 38% of patients in each group; and a Sigma valve was placed in 9% of patients treated with and 12% of those treated without endoscopy. Median surgical time lasted 40 minutes in the group treated with and 35 minutes in the group treated without endoscopy. Ventricular catheters, which during surgery were thought to be situated away from the choroid plexus, were demonstrated to be in it on postoperative imaging in 67% of patients who had undergone endoscopic insertion and 61% of those who had undergone nonendoscopic shunt placements. The incidence of shunt failure at 1 year was 42% in the endoscopic insertion group and 34% in the nonendoscopic group. The time to first shunt failure was not different between the two groups (log rank = 2.92, p = 0.09).nnnCONCLUSIONSnEndoscopic insertion of the initial VP shunt in children suffering from hydrocephalus did not reduce the incidence of shunt failure.