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Pranav Venkataraman, Samuel R. Browd and Barry R. Lutz

OBJECTIVE

The surgical placement of a shunt designed to resolve the brain's impaired ability to drain excess CSF is one of the most common treatments for hydrocephalus. The use of a dynamic testing platform is an important part of shunt testing that can faithfully reproduce the physiological environment of the implanted shunts.

METHODS

A simulation-based framework that serves as a proof of concept for enabling the application of virtual intracranial pressure (ICP) and CSF models to a physical shunt-testing system was engineered. This was achieved by designing hardware and software that enabled the application of dynamic model-driven inlet and outlet pressures to a shunt and the subsequent measurement of the resulting drainage rate.

RESULTS

A set of common physiological scenarios was simulated, including oscillations in ICP due to respiratory and cardiac cycles, changes in baseline ICP due to changes in patient posture, and transient ICP spikes caused by activities such as exercise, coughing, sneezing, and the Valsalva maneuver. The behavior of the Strata valve under a few of these physiological conditions is also demonstrated.

CONCLUSIONS

Testing shunts with dynamic ICP and CSF simulations can facilitate the optimization of shunts to be more failure resistant and better suited to patient physiology.

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Kenneth W. Feldman, Naomi F. Sugar and Samuel R. Browd

OBJECT

At presentation, children who have experienced abusive head trauma (AHT) often have subdural hemorrhage (SDH) that is acute, chronic, or both. Controversy exists whether the acute SDH associated with chronic SDH results from trauma or from spontaneous rebleeding. The authors compared the clinical presentations of children with AHT and acute SDH with those having acute and chronic SDH (acute/chronic SDH).

METHODS

The study was a multicenter retrospective review of children who had experienced AHT during 2004–2009. The authors compared the clinical and radiological characteristics of children with acute SDH to those of children with acute/chronic SDH.

RESULTS

The study included 383 children with AHT and either acute SDH (n = 291) or acute/chronic SDH (n = 92). The children with acute/chronic SDH were younger, had higher initial Glasgow Coma Scale scores, fewer deaths, fewer skull fractures, less parenchymal brain injury, and fewer acute noncranial fractures than did children with acute SDH. No between-group differences were found for the proportion with retinal hemorrhages, healing noncranial fractures, or acute abusive bruises. A similar proportion (approximately 80%) of children with acute/chronic SDH and with acute SDH had retinal hemorrhages or acute or healing extracranial injures. Of children with acute/chronic SDH, 20% were neurologically asymptomatic at presentation; almost half of these children were seen for macrocephaly, and for all of them, the acute SDH was completely within the area of the chronic SDH.

CONCLUSIONS

Overall, the presenting clinical and radiological characteristics of children with acute SDH and acute/chronic SDH caused by AHT did not differ, suggesting that repeated abuse, rather than spontaneous rebleeding, is the etiology of most acute SDH in children with chronic SDH. However, more severe neurological symptoms were more common among children with acute SDH. Children with acute/chronic SDH and asymptomatic macrocephaly have unique risks and distinct radiological and clinical characteristics.

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Abhaya V. Kulkarni, Jay Riva-Cambrin and Samuel R. Browd

Object

Published case series of endoscopic third ventriculostomy (ETV) for childhood hydrocephalus have reported widely varying success rates. The authors recently developed and internally validated the ETV Success Score (ETVSS); this is a simplified means of predicting the 6-month success rate of ETV for a child with hydrocephalus, based on age, etiology of hydrocephalus, and presence of a previous shunt. The authors hypothesized that the ETVSS would be able to predict with reasonable accuracy the actual ETV success rate reported among published case series.

Methods

A literature search was performed to identify published pediatric ETV papers that contained enough information with which to calculate an aggregate, mean predicted ETVSS for the cohort. This was then compared with the actual ETV success rate in the cohort. Data were extracted independently in triplicate, including by 2 individuals who were not involved with the development of the ETVSS.

Results

Fifteen papers reporting on 322 patients were included. Interrater reliability was very high in determining the predicted ETVSS (intraclass correlation coefficient 0.99). The predicted ETVSS for each paper agreed strongly with the actual ETV success rate reported in each paper (reliability intraclass correlation coefficient 0.81). There was no significant difference in the magnitude of the predicted ETVSS and the actual ETV success (p = 0.98, paired t-test). In a linear regression model, the predicted ETVSS explained 62% of the variation in actual ETV success. When the entire cohort was combined and analyzed together, the overall mean predicted ETVSS was 57.9%, which was nearly identical to the actual ETV success rate of 59.2%.

Conclusions

The ETVSS closely predicts the actual ETV success rate reported in selected papers published over the last 20 years and explains much of the variation.

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Samuel R. Browd, J. Steele McIntyre and Douglas Brockmeyer

Object

Normative morphological data pertaining to the development of the occipital condyle have not been reported. The first goal of this study was to establish normative data characterizing the shape of the occipital condyle in healthy children. The second objective of the study was to compare these data with measurements collected in patients with congenital occipitoatlantal instability (COI) or Down syndrome (DS). The effectiveness of CT and plain radiography data was also compared.

Methods

The authors retrospectively reviewed data obtained in 39 patients (14 with DS/COI and 25 age-matched controls). Patients underwent plain lateral radiography and CT scanning of the cervical spine. Normalized measurements of the occipital condyle were obtained for both groups using plain radiography and CT imaging techniques.

Results

The curvature of the occipital condyle in healthy children increased by 60% from infancy to adolescence. Comparison of condylar morphology on plain lateral radiographs and CT scans in patients with DS/COI and in age-matched controls demonstrated a significant difference in mean normalized depth/length ratios. Comparison of curvature data obtained using plain lateral cervical radiography with measurements obtained using cervical CT scanning demonstrated a correlation coefficient of 0.63. However, intra- and interobserver reliability for plain radiographic analysis of the occipital condyle was poor (r2 = 0.40 and 0.44, respectively).

Conclusions

Patient with DS/COI who have occipitoatlantal instability fail to develop the curved architecture in the occipital condyle that occurs in age-matched controls over time. Sagittal 2D CT reconstructions accurately determine the precise structure of the occipital condyle, although the indications for CT scanning are limited. Because of the poor intra- and interrater reliability on static plain radiographs, dynamic flexion/extension cervical spine radiographs remain the study of choice by which to directly evaluate occipitocervical motion.

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Samuel R. Browd, James T. Goodrich and Marion L. Walker

✓Craniopagus twins represent a rare phenomenon of congenital misfortune. Modern neurosurgical techniques have created opportunities for successful separation and the promise of a normal existence for these children, who in the past were often left as historical footnotes or put on display as oddities of nature. The authors document a brief history of conjoined twinning and discuss the modern science of craniopagus epidemiology, classification, and separation. In particular, the strategies used and the rationale for staged surgical separation are highlighted.

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Brian T. Ragel, Samuel R. Browd and Richard H. Schmidt

Object

Infection represents the most common serious complication of shunt surgery, and typically its incidence ranges between 5 and 15%, despite the use of systemic antibiotic agents. Because systemic antibiotic medications generally penetrate the cerebrospinal fluid (CSF) poorly, the authors investigated, in a controlled study, whether the addition of intraventricular antibiotic treatment decreases the incidence of perioperative infection in adult patients.

Methods

Data pertaining to all CSF shunt procedures conducted at the authors’ institution during an 11-year period were reviewed. Perioperative infection was defined as culture-positive CSF and the clinical presence of infection-related symptoms occurring within 90 days of surgery. All patients underwent intraoperative systemic antistaphylococcal antibiotic therapy. Before May 16, 1999, the senior author (R.H.S.) also administered 4 mg of gentamicin intraventricularly at surgery (Group I); thereafter, 10 mg of vancomycin was additionally administered (Group II). Other neurosurgeons at this institution did not use intraventricular antibiotic therapy, and their patients served as additional controls in identical time periods (Groups III and IV).

A total of 802 shunt procedures were performed in 534 patients. Control infection rates were 5.4% (eight of 147) in Group I; 6.2% (nine of 145) in Group III; and 6.7% (18 of 267) in Group IV. With the combination of systemic antibiotic and intraventricular gentamicin and vancomycin (Group II), the infection rate fell significantly to 0.4% (one of 243). No complications were noted in association with intraventricular antibiotic administration.

Conclusions

The combination of intraventricular gentamicin and vancomycin with systemic antibiotic therapy significantly decreased the incidence of perioperative shunt infection. It is presumed that intraventricular antibiotic therapy extends prophylactic antibiotic coverage into the CSF and prevents bacterial seeding.

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Brian W. Hanak, Emily F. Ross, Carolyn A. Harris, Samuel R. Browd and William Shain

OBJECTIVE

Shunt obstruction by cells and/or tissue is the most common cause of shunt failure. Ventricular catheter obstruction alone accounts for more than 50% of shunt failures in pediatric patients. The authors sought to systematically collect explanted ventricular catheters from the Seattle Children's Hospital with a focus on elucidating the cellular mechanisms underlying obstruction.

METHODS

In the operating room, explanted hardware was placed in 4% paraformaldehyde. Weekly, samples were transferred to buffer solution and stored at 4°C. After consent was obtained for their use, catheters were labeled using cell-specific markers for astrocytes (glial fibrillary acidic protein), microglia (ionized calcium-binding adapter molecule 1), and choroid plexus (transthyretin) in conjunction with a nuclear stain (Hoechst). Catheters were mounted in custom polycarbonate imaging chambers. Three-dimensional, multispectral, spinning-disk confocal microscopy was used to image catheter cerebrospinal fluid–intake holes (10× objective, 499.2-μm-thick z-stack, 2.4-μm step size, Olympus IX81 inverted microscope with motorized stage and charge-coupled device camera). Values are reported as the mean ± standard error of the mean and were compared using a 2-tailed Mann-Whitney U-test. Significance was defined at p < 0.05.

RESULTS

Thirty-six ventricular catheters have been imaged to date, resulting in the following observations: 1) Astrocytes and microglia are the dominant cell types bound directly to catheter surfaces; 2) cellular binding to catheters is ubiquitous even if no grossly visible tissue is apparent; and 3) immunohistochemical techniques are of limited utility when a catheter has been exposed to Bugbee wire electrocautery. Statistical analysis of 24 catheters was performed, after excluding 7 catheters exposed to Bugbee wire cautery, 3 that were poorly fixed, and 2 that demonstrated pronounced autofluorescence. This analysis revealed that catheters with a microglia-dominant cellular response tended to be implanted for shorter durations (24.7 ± 6.7 days) than those with an astrocyte-dominant response (1183 ± 642 days; p = 0.027).

CONCLUSIONS

Ventricular catheter occlusion remains a significant source of shunt morbidity in the pediatric population, and given their ability to intimately associate with catheter surfaces, astrocytes and microglia appear to be critical to this pathophysiology. Microglia tend to be the dominant cell type on catheters implanted for less than 2 months, while astrocytes tend to be the most prevalent cell type on catheters implanted for longer time courses and are noted to serve as an interface for the secondary attachment of ependymal cells and choroid plexus.

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Rohan Ramakrishna, Jeffrey C. Mai, Tanya Filardi, Samuel R. Browd and Richard G. Ellenbogen

This 18-year-old woman presented with symptoms of right upper-extremity ataxia and imaging evidence of syringomyelia and an acquired Chiari malformation after a previous suboccipital decompression for cerebellar hemorrhage. The patient underwent posterior fossa reexploration to detether any adhesions and release scar tissue in the fourth ventricular outlet. Her symptoms of syringomyelia resolved but she then developed symptoms of lethargy, confusion, and amnesia in addition to ataxia. Repeat neural axis imaging revealed resolution of the syrinx but prominent brainstem hypertrophy. Eventually, the placement of a ventriculoperitoneal shunt resulted in the resolution of both symptoms and brainstem hypertrophy. In the present article, the authors elaborate on this first reported case of a reversible brainstem hypertrophy responsive to CSF shunting.

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Mostafa El Khashab and Farideh Nejat

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Renee M. Reynolds, Ryan P. Morton, Marion L. Walker, Teresa L. Massagli and Samuel R. Browd

Selective dorsal rhizotomy may have a role in the management of spinal cord injury (SCI)–induced spasticity. Spasticity and spasms are common sequelae of SCI in children. Depending on the clinical scenario, treatments may include physical and occupational therapy, oral medications, chemodenervation, and neurosurgical interventions. Selective dorsal rhizotomy (SDR) is used in the management of spasticity in selected children with cerebral palsy, but, to the authors' knowledge, its use has not been reported in children with SCI. The authors describe the cases of 3 pediatric patients with SCI and associated spasticity treated with SDR. Two of the 3 patients have had significant long-term improvement in their preoperative spasticity. Although the third patient also experienced initial relief, his spasticity quickly returned to its preoperative severity, necessitating additional therapies. Selective dorsal rhizotomy may have a place in the treatment of selected children with spasticity due to SCI.