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 treatment of cerebrospinal fluid shunt infections. Results from a practice survey of the American Society of Pediatric Neurosurgeons.

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.

Predicting shunt failure on the basis of clinical symptoms and signs in children.

OBJECT: In evaluating pediatric patients for shunt malfunction, predictive values for symptoms and signs are important in deciding which patients should undergo an imaging study, whereas determining clinical findings that correlate with a low probability of shunt failure could simplify management. METHODS: Data obtained during the recently completed Pediatric Shunt Design Trial (PSDT) were analyzed. Predictive values were calculated for symptoms and signs of shunt failure. To refine predictive capability, a shunt score based on a cluster of signs and symptoms was derived and validated using multivariate methods. Four hundred thirty-one patient encounters after recent shunt insertions were analyzed. For encounters that took place within 5 months after shunt insertion (early encounters), predictive values for symptoms and signs included the following: nausea and vomiting (positive predictive value [PPV] 79%, likelihood ratio [LR] 10.4), irritability (PPV 78%, LR 9.8), decreased level of consciousness (LOC) (PPV 100%), erythema (PPV 100%), and bulging fontanelle (PPV 92%, LR 33.1). Between 9 months and 2 years after shunt insertion (late encounters), only loss of developmental milestones (PPV 83%, LR 36.7) and decreased LOC (PPV 100%) were strongly associated with shunt failure. However, the absence of a symptom or sign still left a 15 to 29% (early encounter group) or 9 to 13% (late encounter group) chance of shunt failure. Using the shunt score developed for early encounters, which sums from 1 to 3 points according to the specific symptoms or signs present, patients with scores of 0, 1, 2, and 3 or greater had shunt failure rates of 4%, 50%, 75%, and 100%, respectively. Using the shunt score derived from late encounters, patients with scores of 0, 1, and 2 or greater had shunt failure rates of 8%, 38%, and 100%, respectively. CONCLUSIONS: In children, certain symptoms and signs that occur during the first several months following shunt insertion are strongly associated with shunt failure; however, the individual absence of these symptoms and signs offers the clinician only a limited ability to rule out a shunt malfunction. Combining them in a weighted scoring system improves the ability to predict shunt failure based on clinical findings.

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

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.

Clinical trials.

The randomized clinical trial (RCT) is often referred to as the gold standard for the assessment of treatment efficacy. RCTs are receiving greater attention in the literature and higher priority by funding agencies than they have in the past. In this paper, the basic principles of clinical trial design are reviewed using examples from the neurosurgical literature. The importance of designing the trial to answer one question well is emphasized.

Randomized trial of cerebrospinal fluid shunt valve design in pediatric hydrocephalus.

OBJECTIVE: Forty percent of standard cerebrospinal fluid shunts implanted for the treatment of pediatric hydrocephalus fail within the first year. Two new shunt valves designed to limit excess flow, particularly in upright positions, were studied to compare treatment failure rates with those for standard differential-pressure valves. METHODS: Three hundred-forty-four hydrocephalic children (age, birth to 18 yr) undergoing their first cerebrospinal fluid shunt insertion were randomized at 12 North American or European pediatric neurosurgical centers. Patients received one of three valves, i.e., a standard differential-pressure valve; a Delta valve (Medtronic PS Medical, Goleta, CA), which contains a siphon-control component designed to reduce siphoning in upright positions; or an Orbis-Sigma valve (Cordis, Miami, FL), with a variable-resistance, flow-limiting component. Patients were monitored for a minimum of 1 year. Endpoints were defined as shunt failure resulting from shunt obstruction, overdrainage, loculations of the cerebral ventricles, or infection. Outcome events were assessed by blinded independent case review. RESULTS: One hundred-fifty patients reached an endpoint; shunt obstruction occurred in 108 (31.4%), overdrainage in 12 (3.5%), loculated ventricles in 2 (0.6%), and infection in 28 (8.1%). Sixty-one percent were shunt failure-free at 1 year and 47% at 2 years, with a median shunt failure-free duration of 656 days. There was no difference in shunt failure-free duration among the three valves (P = 0.24). CONCLUSION: Cerebrospinal fluid shunt failure, predominantly from shunt obstruction and infection, remains a persistent problem in pediatric hydrocephalus. Two new valve designs did not significantly affect shunt failure rates.

Therapeutic electrical stimulation following selective posterior rhizotomy in children with spastic diplegic cerebral palsy: a randomized clinical trial.

A randomized controlled trial was carried out to determine the effectiveness of therapeutic electrical stimulation (TES) in improving the function of children with spastic cerebral palsy (CP), who had undergone selective posterior lumbosacral rhizotomy more than a year previously. Children were randomly assigned to groups to receive TES for 1 year, or to have no TES. The primary outcome was the change in the Gross Motor Function Measure (GMFM), a quantitative and validated measure for use in children with spastic CP. There was a statistically significant and clinically important improvement in outcome for the treated children, with the mean change in the GMFM score at one year being 5.5% compared with 1.9% in the untreated group (P = 0.001). TES was simple to use, had no significant complications, and was well accepted by the children and their caregivers, as indicated by an average compliance of 93% for the application of TES on a nightly basis over the course of the study. It was concluded that TES may be beneficial in children with spastic CP who have undergone a selective posterior rhizotomy procedure more than 1 year previously.

Variation between centers in electrophysiologic techniques used in lumbosacral selective dorsal rhizotomy for spastic cerebral palsy.

The extent of variation between centers in the electrophysiologic techniques used in lumbosacral selective dorsal rhizotomy (SDR) for spastic cerebral palsy was studied using a questionnaire survey. Nineteen centers completed the questionnaire, and the responses were analyzed for those 16 centers in which the extent of dorsal root section was guided by intraoperative electrophysiologic responses. Consistent techniques included: use of unipolar stimulating electrodes (11 of 15 responses); stimulation < 4 cm from the root exit foramen (14 of 16); separation of dorsal roots into three to eight rootlets each (14 of 16); tetanic stimulation frequency of 50 Hz (11 of 16); tetanic stimulation at 100% of threshold (13 of 16); recording from multiple lower limb muscles simultaneously (16 of 16), and using contralateral spread of the response as a major criterion of electrophysiologic abnormality (13 of 16). There was more variation (< 11 of 16 concurrence) with respect to the use of a constant current versus constant voltage stimulator; the location of the cathode of the stimulating electrode relative to the anode; the definition of the threshold for a response; whether threshold was determined from stimulation of a dorsal root, or individual rootlets; the type of recording electrodes (needle versus surface), and the relative importance of electrophysiologic versus clinical findings in determining how much of each dorsal root to cut. In 10 centers, SDR would proceed without the benefit of electrophysiologic guidance if the equipment should fail intraoperatively (only if quadriplegic in 4), and this had happened in 6. The results indicate significant variation in many aspects of electrophysiologically guided SDR.

Value of postoperative surveillance imaging in the management of children with some common brain tumors.

The rationale for obtaining surveillance computerized tomography (CT) scans or magnetic resonance (MR) images in pediatric patients with brain tumors is that early detection of recurrence may result in timely treatment and better outcome. The purpose of this study was to investigate the value of surveillance cranial images in a variety of common pediatric brain tumors managed at a tertiary care pediatric hospital. A retrospective chart review was performed of children with astrocytoma of the cerebral hemisphere, cerebellum, optic chiasm/hypothalamus, or thalamus; cerebellar or supratentorial high-grade glioma; supratentorial ganglioglioma; posterior fossa or supratentorial primitive neuroectodermal tumor (PNET); and posterior fossa ependymoma. Data were analyzed to determine the frequency with which recurrences were identified on a surveillance image and how the type of image at which recurrence was identified related to outcome. In 159 children, 17 of 44 recurrences were diagnosed by surveillance imaging. The percentage of recurrences identified by surveillance imaging was 64% for ependymoma, 50% for supratentorial PNET, 43% for optic/hypothalamic astrocytoma, and less than 30% for other tumors. The rate of diagnosis of recurrence per surveillance image varied from 0% to 11.8% for different tumor types. Only for ependymomas did there appear to be an improved outcome when recurrence was identified prior to symptoms. Our results indicate that, using the protocols outlined in this study, surveillance imaging was not valuable in identifying recurrence of cerebellar astrocytoma or supratentorial ganglioglioma during the study period, but was probably worthwhile in identifying recurrence of posterior fossa ependymoma and optic/hypothalamic astrocytoma and, possibly, medulloblastoma. Surveillance protocols could be made more effective by individualizing them for each type of tumor, based on current data on the patterns of recurrence.

The significance of bacteriologically positive ventriculoperitoneal shunt components in the absence of other signs of shunt infection.

The purpose of this study was to determine the significance of "asymptomatic bacteriological shunt contamination" (ABSC), defined as a positive bacteriological culture found on a ventricular shunt component in the absence of bacteria in the cerebrospinal fluid (CSF) culture and/or clinical evidence of infection. Of 174 ventriculoperitoneal shunt revisions, 19 cases of ABSC were identified and reviewed retrospectively. In all but one case, no antibiotic medications were instituted because of the positive bacteriological culture. The most common infecting organisms were coagulase-negative staphylococci (seven) and propionibacteria (eight). A comparison of the 19 study cases with the authors' overall shunt experience, as documented in the British Columbia's Children's Hospital shunt database for the time period of the study, lead the authors to suggest that ABSC was not of significance in causing the shunt failure at which contamination was identified and, more importantly, did not increase the risk of future shunt malfunction. The results of this study indicate that in the absence of clinical evidence of shunt infection or a positive bacteriological culture from CSF, bacteria in a shunt component removed at revision in a child almost always represents a contaminant that may be ignored. Therefore, the authors advise that routine culture of shunt components removed at revision of a shunt is not indicated.

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.

The natural history of cerebral cavernous malformations.

To determine the natural history of brain cavernous malformations, the authors entered patients referred to their center into a prospective registry between 1987 and 1993. All patients underwent magnetic resonance imaging, which showed the typical appearance of this lesion, and conservative management was recommended in all. Patients or their referring physicians were contacted for follow-up data. The purpose of the study was to define the rate of symptomatic hemorrhage and to determine the outcome in those patients who had suffered seizures. Follow-up data were available for 122 patients with a mean age at entry of 37 years (range 4-82 years). The malformation was located in the brainstem in 43 cases (35%), the basal ganglia/thalamus in 20 (17%), and a hemispheric area in 59 (48%). Fifty percent of patients had never had a symptomatic hemorrhage, 41% had one bleed, 7% had two, and 2% had three. Seizures were reported in 23% of patients and headaches in 15%. Lesions were solitary in 80% of patients and multiple in 20%. The retrospective annual hemorrhage rate (61 bleeds/4550.6 patient-years of life) was 1.3%. The mean prospective follow-up period was 34 months. There were nine bleeds during this time, six with new neurological deficits. In patients without a prior bleed, the prospective annual rate of hemorrhage was 0.6%. In contrast, patients with prior hemorrhage had an annual bleed rate of 4.5% (p = 0.028). Patient sex (p = 0.97) or the presence of seizures (p = 0.11), headaches (p = 0.06), or solitary versus multiple lesions (p = 0.15) were not significant predictors of later hemorrhage. There was no difference in the rate of bleeds between brain locations. Four patients with seizures became seizure-free and four patients without seizures later developed seizures; only one patient developed intractable seizures. Fourteen had radiosurgery. No patient died in the follow-up period. This study indicates that conservative versus operative management strategies may need to be redefined, especially in patients who present with hemorrhage and who appear to have a significantly increased risk of subsequent rehemorrhage.

Reduction of hemorrhage risk after stereotactic radiosurgery for cavernous malformations.

The benefits of radiosurgery for cavernous malformations are difficult to assess because of the unclear natural history of this vascular lesion, the inability to image malformation vessels, and the lack of an imaging technique that defines "cure." The authors selected for radiosurgery 47 patients who harbored a hemorrhagic malformation in a critical intraparenchymal location remote from a pial or ependymal surface. Of these, 44 patients had experienced at least two hemorrhages before radiosurgery. The mean patient age was 39 years; six patients had previously undergone attempted surgical removal. The malformation was located in the pons/midbrain in 24 cases, the medulla in three, the thalamus in nine, the basal ganglia in three, deep in a parietal lobe in four, and deep in a temporal lobe in four. Patients had sustained initial hemorrhages from 0.5 to 12 years prior to radiosurgery (mean 4.12 years). In these patients, who were not typical of the majority of patients with cavernous malformations, there were 109 bleeds before radiosurgery in 193 prior observation-years, for 56.5% annual hemorrhage rate (including the first hemorrhage), or an annual rate of 32% subsequent to the first hemorrhage. The mean follow-up period after radiosurgery was 3.6 years (range 0.33-6.4 years). The proportion of patients with hemorrhage after radiosurgery was significantly reduced (p < 0.0001), as was the mean number of hemorrhages per patient (p = 0.00004). In the first 2 years after radiosurgery, there were seven bleeds in 80 observation-years (8.8% annual hemorrhage rate). In the 2- to 6-year interval after radiosurgery, the annual rate decreased to 1.1% (one bleed). After radiosurgery, 12 patients (26%) sustained neurological worsening that correlated with imaging changes. In eight patients these deficits were temporary; two underwent surgical resection and died. Two patients had new permanent deficits (4%). A significant reduction was observed in the hemorrhage rate after radiosurgery in patients who had deep hemorrhagic cavernous malformations, especially after a 2-year latency interval. This evidence provides further support to the belief that radiosurgery is an effective strategy for cavernous malformations, especially when located within the parenchyma of the brainstem or diencephalon.

Relationship of intraoperative electrophysiological criteria to outcome after selective functional posterior rhizotomy.

At British Columbia's Children's Hospital, the criteria used in selective functional posterior rhizotomy (SFPR) evolved in three distinct phases. In Phase 1 the electrophysiological criteria for abnormality included a low threshold to a single stimulation, a sustained response to 50-Hz stimulation, and spread outside the segmental level being stimulated. In Phase 2 the electrophysiological criteria were unchanged, but fewer L3-4 nerve roots were cut. In Phase 3, fewer L3-4 nerve roots were cut, as in Phase 2, but based on the results of posterior nerve root stimulation in nonspastic controls, the only electrophysiological criterion used was contralateral and suprasegmental spread. The present study examined the relationship between the criteria used in each phase and patient outcome. The records of 77 consecutive children who underwent SFPR and had a minimum follow-up period of 1 year were reviewed, comprising 25, 19, and 33 patients in Phases 1, 2, and 3, respectively. Outcome parameters included quantitative assessments of lower-limb spasticity and range of motion, and qualitative assessments of lower-limb function. In Phase 3, 52% of the nerve roots were cut, compared to 66% in Phases 1 and 2. In all three phases there was a significant decrease in lower-limb spasticity and an increase in range of movement, with the smallest decrease in spasticity in Phase 3. Over 90% of children in each phase improved with respect to lower-limb function, and excluding independent walkers and quadriplegics confined to a wheelchair, improvement in the level of ambulation occurred in 87.5%, 71.4%, and 73.7% of patients, in Phases 1, 2, and 3, respectively.

Acute subdural hematoma associated with cerebral infarction in the full-term neonate.

Acute subdural hematomas in the full-term neonate are usually thought to be a manifestation of birth trauma. Most commonly, these hematomas are associated with a tentorial tear, and less frequently are secondary to damage to the occipital sinus accompanying occipital osteodiastasis, or to rupture of bridging superficial cerebral convexity veins. We report 6 cases of acute subdural hematoma associated with cerebral infarction (SDH/CI) in term neonates, an entity which has not been well-documented previously. This combination accounted for half the cases of neonatal acute subdural hematomas referred to a pediatric neurosurgical service. All children presented within 72 h of birth, usually after an uneventful delivery, and typically with seizures (5/6), apneic spells (3/6) and a full or bulging fontanel (5/6). Although the patients were referred to the neurosurgical servive for management of a convexity subdural hematoma, the CT scans showed a large associated cerebral infarct, which was hemorrhagic in 5 of the 6 cases, most commonly in the distribution of the middle cerebral artery. Craniotomy was performed in 4 patients, needle aspiration of the subdural hematoma in 1, and no surgical intervention in 1. The outcome in 3 patients, who have been followed for more than 1 year, has been good, with some mild focal neurologic deficits, but no seizure activity. The pathogenesis of this entity is unclear, but the acute subdural hematoma in these cases is probably secondary to the cerebral infarction. Recognition of SDH/CI as a specific entity in term neonates has significant management and possibly medicolegal implications.

Cost analysis of continuous intrathecal baclofen versus selective functional posterior rhizotomy in the treatment of spastic quadriplegia associated with cerebral palsy.

The purpose of the study was to analyze the relative cost of selective functional posterior rhizotomy (SFPR) and continuous intrathecal baclofen in the treatment of children with severe spastic quadriplegia related to cerebral palsy. No attempt was made to analyze the efficacy of the two types of treatment. Nine children with spastic quadriplegia secondary to cerebral palsy in whom continuous intrathecal baclofen was attempted were matched as closely as possible with a group of 10 patients with spastic quadriplegia out of a total of 100 children who had undergone SFPR in the same time period. Clinical care flow charts were created to identify the various points of contact with members of the health care team, so that cost points could be identified and costs calculated. The cost per patient up to 1 year a after treatment CDN$ 64,163.10 for patients with implanted pumps for continuous intrathecal baclofen versus CDN$ 16,913.54 for SFPR. When adjustments were made to exclude costs and savings associated with research protocols, the average for the baclofen group decreased to approximately CDN$ 63,000, with minimal change for the SFPR group. The higher cost per patient on baclofen was related to the cost associated with screening patients who did not go on to have implantation of a continuous infusion pump, and to additional hospitalization for complications in the baclofen group. It is cautioned that this cost analysis was based on the experience at British Columbia's Children's Hospital, and the results may not be generalizable to other institutions or to other patient populations.

The effect of single-application topical ophthalmic anesthesia in patients with trigeminal neuralgia. A randomized double-blind placebo-controlled trial.

To evaluate the reported benefit of ipsilateral single-application ophthalmic anesthetic eyedrops in patients with typical trigeminal neuralgia, a randomized double-blind placebo-controlled trial was performed. Forty-seven patients were randomly assigned to receive two drops of either proparacaine (25 cases) or saline placebo (22 cases). The experimental and placebo groups were equivalent in regard to patient age, distribution of trigeminal neuralgia pain, duration of pain, current medication regimens, and number of prior procedures performed. Pain response was assessed at 3, 10, and 30 days after instillation using two pain rating scales and a measure of pain frequency. Treatment failure was defined in advance as any of the following: a lack of clinical response, the need for an increase in medication, or the need for surgery. No significant difference in outcomes was found between the two groups either when using a verbal pain rating scale (p = 0.24) or when comparing overall pain status (unchanged, improved throughout the study period, or temporarily improved) (p = 0.98). No difference in the frequency of trigeminal neuralgia attacks between the two treatment groups (scaled within five levels of pain frequency) was detected (p = 0.09). During follow-up monitoring, 11 patients in the test drug group and 14 in the placebo group required surgery because of persistent pain (p = 0.24). The results of this study indicate that single-application topical ophthalmic anesthesia reduces neither the severity nor the frequency of pain in comparison to placebo administration. Although a simple and safe treatment, the single application of topical ophthalmic eyedrops provides no short- or long-term benefit to patients with trigeminal neuralgia.

Prevention of postshunting ventricular asymmetry by transseptal placement of ventricular catheters. A randomized study.

Ventricular asymmetry is common after ventricular shunting, and occasionally isolation of the contralateral ventricle necessitates a second shunt. The following study was performed to determine whether contralateral placement of the ventricular catheter via ultrasound-guided perforation of the septum pellucidum would decrease the incidence of postshunting ventricular asymmetry which might predispose to symptomatic isolation of a lateral ventricle. Fifty-eight children with hydrocephalus and an open fontanel, who were having a ventriculo-peritoneal shunt via a parieto-occipital approach, were randomized to have the ventricular catheter tip placed into either the ipsilateral or the contralateral frontal horn. Ventricular asymmetry occurred in 23% of the patients with contralateral versus 54% with ipsilateral placement (chi 2 = 5.53; p = 0.019). In 7 patients with contralateral placement, in whom a special catheter with two sets of holes was used, such that holes were located in both ventricles, no shunt-related ventricular asymmetry occurred. In 2 children with ipsilateral placement, a second shunt was required for a symptomatic isolated lateral ventricle. Perforation of the septum pellucidum with placement of the ventricular catheter in the contralateral ventricle, using a specially designed catheter with two sets of holes, may decrease the incidence of postshunting ventricular asymmetry and symptomatic isolation of a lateral ventricle.