John R. W. Kestle

Long-Term Follow-Up Data from the Shunt Design Trial

Background: A previously reported multicenter randomized trial assessed whether 2 new shunt valve designs would reduce shunt failure rates compared to differential pressure valves. The study did not show a significant difference in the time to first shunt failure. Patients entered the trial between October 1, 1993, and October 31, 1995. The primary results were based on the patients’ status as of October 31, 1996 (a minimum follow-up of 1 year). This report describes the late complications based on the patients’ most recent follow-up. Methods: Three hundred and forty-four hydrocephalic children at 12 North American and European centers were randomized to 1 of 3 valves: a standard differential pressure valve; a Delta valve (PS Medical-Medtronic) or a Sigma valve (NMT Cordis). Patients were followed until their first shunt failure. Shunt failure was defined as shunt surgery for obstruction, overdrainage, loculation or infection. If the shunt did not fail, follow-up was continued until August 31, 1999. Results: One hundred and seventy-seven patients had shunt failure. Shunt obstruction occurred in 131, overdrainage in 13, loculated ventricles in 2 and infection in 29. The overall shunt survival was 62% at 1 year, 52% at 2 years, 46% at 3 years, 41% at 4 years. The survival curves for the 3 valves were similar to those from the original trial and did not show a survival advantage for any particular valve. Conclusions: Prolonged follow-up to date does not alter the primary conclusions of the trial: there does not appear to be one valve that is clearly the best for the initial treatment of pediatric hydrocephalus.

Effect of hyperventilation on regional cerebral blood flow in head-injured children.

OBJECTIVES To study cerebral blood flow and cerebral oxygen consumption in severe head-injured children and also to assess the effect of hyperventilation on regional cerebral blood flow. DESIGN Prospective cohort study. SETTING Pediatric intensive care unit at a tertiary-level university childrens hospital. PATIENTS Twenty-three children with isolated severe brain injury, whose admission Glasgow Coma Scores were <8. INTERVENTIONS PaCO2 was adjusted by altering minute ventilation. Cerebral metabolic measurements were made at three levels of PaCO2 (>35, 25 to 35, and <25 torr [>4.7, 3.3 to 4.7, and <3.3 kPa]) after allowing 15 mins for equilibrium. MEASUREMENTS AND MAIN RESULTS Thirty-eight studies (each study consisting of three sets of measurements at different levels of PaCO2) were performed on 23 patients. At each level of PaCO2, the following measurements were made: xenon-enhanced computed tomography scans; cerebral blood flow; intracranial pressure; jugular venous bulb oxygen saturation; mean arterial pressure; and arterial oxygen saturation. Derived variables included: cerebral oxygen consumption; cerebral perfusion pressure; and oxygen extraction ratio. Cerebral blood flow decreased below normal after head injury (mean 49.6 +/- 14.6 mL/min/100 g). Cerebral oxygen consumption decreased out of proportion to the decrease in cerebral blood flow; cerebral oxygen consumption was only a third of the normal range (mean 1.02 +/- 0.59 mL/min/100 g). Neither cerebral blood flow nor cerebral oxygen consumption showed any relationship to time after injury, Glasgow Coma Score at the time of presentation, or intracranial pressure. The frequency of one or more regions of ischemia (defined as cerebral blood flow of <18 mL/min/100 g) was 28.9% during normocapnia. This value increased to 73.1% for PaCO2 at <25 torr. CONCLUSIONS Severe head injury in children produced a modest decrease in cerebral blood flow but a much larger decrease in cerebral oxygen consumption. Absolute hyperemia was uncommon at any time, but measured cerebral blood flow rates were still above the metabolic requirements of most children. The clear relationship between the frequency of cerebral ischemia and hypocarbia, combined with the rarity of hyperemia, suggests that hyperventilation should be used with caution and monitored carefully in children with severe head injuries.

Infection rates following initial cerebrospinal fluid shunt placement across pediatric hospitals in the United States: Clinical article

OBJECT Reported rates of CSF shunt infection vary widely across studies. The study objective was to determine the CSF shunt infection rates after initial shunt placement at multiple US pediatric hospitals. The authors hypothesized that infection rates between hospitals would vary widely even after adjustment for patient, hospital, and surgeon factors. METHODS This retrospective cohort study included children 0-18 years of age with uncomplicated initial CSF shunt placement performed between January 1, 2001, and December 31, 2005, and recorded in the Pediatric Health Information System (PHIS) longitudinal administrative database from 41 childrens hospitals. For each child with 24 months of follow-up, subsequent CSF shunt infections and procedures were determined. RESULTS The PHIS database included 7071 children with uncomplicated initial CSF shunt placement during this time period. During the 24 months of follow-up, these patients had a total of 825 shunt infections and 4434 subsequent shunt procedures. Overall unadjusted 24-month CSF shunt infection rates were 11.7% per patient and 7.2% per procedure. Unadjusted 24-month cumulative incidence rates for each hospital ranged from 4.1 to 20.5% per patient and 2.5-12.3% per procedure. Factors significantly associated with infection (p < 0.05) included young age, female sex, African-American race, public insurance, etiology of intraventricular hemorrhage, respiratory complex chronic condition, subsequent revision procedures, hospital volume, and surgeon case volume. Malignant lesions and trauma as etiologies were protective. Infection rates for each hospital adjusted for these factors decreased to 8.8-12.8% per patient and 1.4-5.3% per procedure. CONCLUSIONS Infections developed in > 11% of children who underwent uncomplicated initial CSF shunt placements within 24 months. Patient, hospital, and surgeon factors contributed somewhat to the wide variation in CSF shunt infection rates across hospitals. Additional factors may contribute to variation in CSF shunt infection rates between centers, but further study is needed. Benchmarking and future prospective multicenter studies of CSF shunt infection will need to incorporate these and other patient, hospital, and surgeon factors.

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

Abstract Cerebrospinal 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.

Simple Risk Predictions for Arteriovenous Malformation Hemorrhage

We present a simple risk prediction formula for arteriovenous malformation hemorrhage. Natural history studies have shown an annual risk of hemorrhage of 2 to 4% for patients with brain arteriovenous malformations. Although decision analysis programs and biostatistical models are available to predict long-term risks of hemorrhage, we hypothesized that there was varying knowledge regarding the use of such programs within the general neurosurgical community. To obtain information on the current use of risk data, we performed a survey of neurosurgeons at national meetings in 1988 and 1994. Neurosurgeons were asked to define the risk for arteriovenous malformation hemorrhage in the young adult patient over a 20- to 30-year period, given a 3 or 4% annual risk of hemorrhage. A wide range of answers was obtained (1-100% risk), and many different methods of calculation were used. The use of the multiplicative law of probability formula requires only knowledge of patient age and annual hemorrhage risk. Risk of hemorrhage = 1 - (risk of no hemorrhage) expected years of remaining life. The assumptions pertaining to this multiplicative formula include a constant yearly risk of hemorrhage and the independent behavior of all years of observation. We calculated the predictions of risk of hemorrhage across all age groups, as modified by published survival data. We think the use of this formula is justified by published natural history data across different ages and populations and that it is a simple and reasonable alternative to other methods of calculation.

Optic pathway gliomas: a review

Optic pathway gliomas represent approximately 3-5% of childhood intracranial tumors. They usually occur in children during the first decade of life and are seen in 11-30% of patients with neurofibromatosis Type 1 (NF1). Although these tumors are typically low-grade gliomas, the clinical course and natural history are highly variable, making treatment paradigms difficult. Overall, however, they are often indolent tumors that can be observed over time for progression without initial treatment, especially in patients with NF1. Chemotherapy is the first-line treatment for progressive tumors, and radiation therapy is reserved for patients with progressive disease who are older than 5-7 years. Surgery is reserved for large tumors causing mass effect or hydrocephalus and tumors confined to the orbit or unilateral optic nerve.

The influence of surgical operative experience on the duration of first ventriculoperitoneal shunt function and infection.

The relationship of surgeon experience, measured by operative volume, to the outcomes of ventricular shunt treatment of hydrocephalus in children is not clear. This paper explores this relationship based on first ventriculoperitoneal shunts (VPS) implanted in English-speaking Canada during the period from April 1989 to March 2001. Three thousand seven hundred and ninety-four first VPS insertions, performed by 254 surgeons, were reviewed. Surgical experience was represented by the number of shunt operations performed during the study period by each surgeon prior to the date of the operation. The 6-month shunt failure risk for less experienced surgeons was 38%, compared to 31% for more experienced surgeons. This difference decreased to 4% at 60 months and 3% at 120 months (p = 0.001). The infection rate for initial shunt insertions was 7% for patients treated by more experienced surgeons and 9.4% for those treated by less experienced surgeons (p = 0.006). A relationship between surgeon experience and shunt outcome that appears to be based on the operative experience that a surgeon brings to a procedure is in keeping with clinical experience. This observation has implications for public policy, service planning and surgical mentorship during the earlier years of a surgeon’s career.

The Surgical and Natural Morbidity of Aggressive Resection for Posterior Fossa Tumors in Childhood

The morbidity associated with gross total removal of pediatric posterior fossa tumors is well recognized although it is rarely isolated from other factors that comprise the management morbidity for these tumors. This study reviews (1) the operative and postoperative complications in 105 patients and (2) the neurological morbidity in a subset of 91 patients undergoing gross total removal of their tumor between 1982 and 1992. Gross total removal was achieved in 102 patients with a single procedure. Two patients with residual tumor underwent early repeat craniotomy for excision and 1 is being followed without repeat resection. Intra- and postoperative complications occurred in 33 patients and included hematoma requiring craniotomy (3), gastrointestinal hemorrhage (2), hydrocephalus requiring shunt placement (9), wound problems (4), and pseudomeningocele formation requiring additional treatment (5). Delayed onset hydrocephalus requiring shunting occurred in 2 patients and spinal deformity in 4 patients. Worsening of preoperative deficit (new cranial nerve palsies, worsening ataxia, bulbar dysfunction including apnea, mutism and seizures) occurred in 41% of patients operated on for primitive neuroectodermal tumors (PNET) (14/34), 53% of ependymomas (10/19), and 30% of astrocytomas (15/50). No patient who had a choroid plexus tumor was worsened by the procedure. Complete recovery of new postoperative deficits occurred in 14% of PNET (2/14), 50% of ependymoma (5/10) and 47% of astrocytoma (7/15), most often within 6 months of the procedure. Residual neurological morbidity, due to persistence of preoperative symptoms or due to deficits that occurred as the result of the surgical procedure, was assessed in a subgroup of 91 patients followed for an average of 48 months (2-147 months). This assessment did not include morbidity due to adjuvant therapy. Sixty-two percent of patients continued to exhibit abnormal cerebellar or bulbar signs. Forty-three percent of the total population exhibited limitation in function due to residual deficit. Only 38% of patients were both functionally normal and had a normal neurological examination at last follow-up.

A standardized protocol to reduce cerebrospinal fluid shunt infection: The Hydrocephalus Clinical Research Network Quality Improvement Initiative

OBJECT Quality improvement techniques are being implemented in many areas of medicine. In an effort to reduce the ventriculoperitoneal shunt infection rate, a standardized protocol was developed and implemented at 4 centers of the Hydrocephalus Clinical Research Network (HCRN). METHODS The protocol was developed sequentially by HCRN members using the current literature and prior institutional experience until consensus was obtained. The protocol was prospectively applied at each HCRN center to all children undergoing a shunt insertion or revision procedure. Infections were defined on the basis of CSF, wound, or pseudocyst cultures; wound breakdown; abdominal pseudocyst; or positive blood cultures in the presence of a ventriculoatrial shunt. Procedures and infections were measured before and after protocol implementation. RESULTS Twenty-one surgeons at 4 centers performed 1571 procedures between June 1, 2007, and February 28, 2009. The minimum follow-up was 6 months. The Network infection rate decreased from 8.8% prior to the protocol to 5.7% while using the protocol (p = 0.0028, absolute risk reduction 3.15%, relative risk reduction 36%). Three of 4 centers lowered their infection rate. Shunt surgery after external ventricular drainage (with or without prior infection) had the highest infection rate. Overall protocol compliance was 74.5% and improved over the course of the observation period. Based on logistic regression analysis, the use of BioGlide catheters (odds ratio [OR] 1.91, 95% CI 1.19-3.05; p = 0.007) and the use of antiseptic cream by any members of the surgical team (instead of a formal surgical scrub by all members of the surgical team; OR 4.53, 95% CI 1.43-14.41; p = 0.01) were associated with an increased risk of infection. CONCLUSIONS The standardized protocol for shunt surgery significantly reduced shunt infection across the HCRN. Overall protocol compliance was good. The protocol has established a common baseline within the Network, which will facilitate assessment of new treatments. Identification of factors associated with infection will allow further protocol refinement in the future.

The Treatment of Cerebrospinal Fluid Shunt Infections

It is our impression that the management strategy for infected cerebrospinal fluid (CSF) shunts varies significantly among pediatric neurosurgeons. The purpose of this paper is to present the results of a practice survey on the treatment of shunt infections which was distributed to all active members of the American Society of Pediatric Neurosurgeons (ASPN). Eighty-four of 129 ASPN members (65%) responded to the survey. Most ASPN members remove the shunt and place an external ventricular drain (EVD) to treat Staphylococcus epidermidis (59.5%), S. aureus (64.3%) and gram-negative rod infections (67.9%). The second most common method of treatment was externalization of the shunt (33.3, 29.8 and 25%, respectively). The duration of antibiotic treatment was extremely variable. When the shunt was removed and an EVD inserted, the duration of antibiotic treatment for S. epidermidis and S. aureus ranged from 5 to 21 total days (2–21 days of sterile cultures). For gram-negative rod infections treated with shunt removal and an EVD, the total duration of antibiotic therapy ranged from 5 to 24 days (2–37 days of sterile cultures). The majority of ASPN members remove the infected CSF shunt and place an EVD for the management of shunt infections. Significant variation exists in the duration of antibiotic therapy. Determining the most effective duration of antibiotic therapy in an effort to shorten hospitalization and minimize complications without sacrificing efficacy will require further study.