✓ A probabilistic model is used to estimate the cumulative risk to surgeons from human immunodeficiency virus (HIV). Recent data suggest that the probability of infection following percutaneous inoculation is about 1 in 250 cases. Several studies suggest that the frequency of percutaneous injury in surgery is at least 1 in 40 cases, for some as high as 1 in 20 cases. Assuming that on the average a surgeon will perform 350 operations per year and will practice for 30 years, the cumulative risk of HIV infection will depend on the prevalence of HIV infection in the surgical population. For HIV prevalences of 1 in 100 to 1 in 10, the cumulative risk per surgeon ranges from 1 in 100 to 1 in 5, respectively. Based on these risk estimates, it is crucial to decrease the frequency of percutaneous injury. The case is made for substantial improvements in barrier protection and modification of surgical technique.
Steven J. Schiff
Steven J. Schiff and Steven L. Weinstein
✓ The use of perioperative human recombinant erythropoietin is described in a Jehovah's Witness patient. Despite significant anemia, the child's hematocrit was sufficiently increased by the use of erythropoietin so that a two-stage hemispherectomy could be performed without blood transfusion.
Peter G. Aitken and Steven J. Schiff
✓ Hippocampal tissue slices in vitro were exposed to periods of hypoxia of different durations. Addition of pentobarbital to the perfusion medium significantly increased the duration of hypoxia that was survived by CA1 pyramidal cells.
Ira P. Weiss and Steven J. Schiff
✓ The variability of reflex responses during selective dorsal rhizotomy was studied in eight children between the ages of 3 and 7 years. For a given dorsal root or rootiet, the electrical reflex threshold and response varied considerably when observed over several minutes. Changes in electrode pressure, mechanical dissection of the root, and reflex spatial facilitation were all found to contribute to the variability. Even when electrode pressure was held constant, intrinsic spinal cord reflex variability substantially weakened the predictability of the intraoperative selection method used during this surgery.
Mallory Peterson, Benjamin C. Warf, and Steven J. Schiff
While there is a long history of interest in measuring brain growth, as of yet there is no definitive model for normative human brain volume growth. The goal of this study was to analyze a variety of candidate models for such growth and select the model that provides the most statistically applicable fit. The authors sought to optimize clinically applicable growth charts that would facilitate improved treatment and predictive management for conditions such as hydrocephalus.
The Weibull, two-term power law, West ontogenic, and Gompertz models were chosen as potential models. Normative brain volume data were compiled from the NIH MRI repository, and the data were fit using a nonlinear least squares regression algorithm. Appropriate statistical measures were analyzed for each model, and the best model was characterized with prediction bound curves to provide percentile estimates for clinical use.
Each model curve fit and the corresponding statistics were presented and analyzed. The Weibull fit had the best statistical results for both males and females, while the two-term power law generated the worst scores. The statistical measures and goodness of fit parameters for each model were provided to assure reproducibility.
The authors identified the Weibull model as the most effective growth curve fit for both males and females. Clinically usable growth charts were developed and provided to facilitate further clinical study of brain volume growth in conditions such as hydrocephalus. The authors note that the homogenous population from which the normative MRI data were compiled limits the study. Gaining a better understanding of the dynamics that underlie childhood brain growth would yield more predictive growth curves and improved neurosurgical management of hydrocephalus.
Steven J. Schiff, Brian K. Dunagan, and Robert M. Worth
Object. The authors examine the validity of single-unit neuronal recordings as a method of differentiating the globus pallidus internus (GPi) from the GP externus (GPe) in Parkinson Disease.
Methods. One hundred twenty-eight recordings of apparent single-unit activity used to help guide final electrode placement in eight patients who underwent pallidotomy were analyzed using sophisticated spike sorting methods, and 185 neurons were characterized for mean firing frequency and percent of firing within bursts. In addition, the total spectral power was calculated on the full measured waveform for each of 128 samples without spike sorting. No correlation was identified between these measures of neuronal activity and depth within the GP.
ConclusionsThese results call into question the validity of relying on single-unit activity and microelectrode recordings in the operating room to localize lesion or electrode placement within the GPi during stereotactic pallidal surgery.
Steven J. Schiff, Sylvia L. Ranjeva, Timothy D. Sauer, and Benjamin C. Warf
Hydrocephalus is one of the most common brain disorders in children throughout the world. The majority of infant hydrocephalus cases in East Africa appear to be postinfectious, related to preceding neonatal infections, and are thus preventable if the microbial origins and routes of infection can be characterized. In prior microbiological work, the authors noted evidence of seasonality in postinfectious hydrocephalus (PIH) cases.
The geographical address of 696 consecutive children with PIH who were treated over 6 years was fused with satellite rainfall data for the same time period. A comprehensive time series and spatiotemporal analysis of cases and rainfall was performed.
Four infection-onset peaks were found to straddle the twice-yearly rainy season peaks, demonstrating that the infections occurred at intermediate levels of rainfall.
The findings in this study reveal a previously unknown link between climate and a neurosurgical condition. Satellite-derived rainfall dynamics are an important factor in driving the infections that lead to PIH. Given prior microbial analysis, these findings point to the importance of environmental factors with respect to preventing the newborn infections that lead to PIH.
Jason G. Mandell, Jack W. Langelaan, Andrew G. Webb, and Steven J. Schiff
Accurate edge tracing segmentation remains an incompletely solved problem in brain image analysis. The authors propose a novel algorithm using a particle filter to follow the boundary of the brain in the style often used in autonomous air and ground vehicle navigation. Their goals were to create a versatile tool to segment brain and fluid in MRI and CT images of the developing brain, lay the foundation for an intelligent automated edge tracker that is modality independent, and segment normative data from MRI that can be applied to both MRI and CT.
Simulated MRI data sets were used to train and evaluate the particle filter segmentation algorithm. The method was then applied to produce normative growth curves for children and adolescents from 0 to 18 years of age for brain and fluid from MR images from the National Institutes of Health pediatric database and these data were compared to historical results. The authors further adapted this method for use with CT images of pediatric hydrocephalus and compared the results with hand-segmented data.
Segmentation of simulated MRI data with varied levels of noise (0%–9%) and spatial inhomogeneity (0%–40%) resulted in percent errors ranging from 0.06% to 5.38% for brain volume and 2.45% to 22.3% for fluid volume. The authors used this tool to create normal brain and CSF growth curves from MR images. The calculated growth curves showed excellent consistency with historical data. Additionally, compared with manual segmentation the particle filter accurately segmented brain and fluid volumes from CT scans of 5 pediatric patients with hydrocephalus (p < 0.001).
The authors have produced the first normative brain and CSF growth curves for children and adolescents 0–18 years of age. In addition, this study includes the first use of a particle filter as an edge tracker in image segmentation and offers a semiautomatic method to segment both pediatric and adult brain data from MR and CT images. The particle filter has the potential to be further automated toward a clinical rather than research tool with both of these modalities. Because of its modality independence, it has the capability to allow CT to be a more effective diagnostic tool for neurological disorders, a task of substantial importance in emergency settings and in developing countries where CT is often the only available method of brain imaging.
Benjamin C. Warf, Ariella R. Dagi, Brian Nsubuga Kaaya, and Steven J. Schiff
Neonatal infection is the most common cause of infant hydrocephalus in Uganda. Postinfectious hydrocephalus (PIH) is often accompanied by primary brain injury from the original infection. Since 2001, ETV (with or without choroid plexus cauterization) has been our primary treatment for PIH. The long-term outcome in these children is unknown.
We studied the 5-year outcome in a cohort of 149 infants treated for PIH from 2001 to 2005 and who lived in 4 districts close to the hospital. Survival analysis was performed using the Kaplan-Meier method. Statistical significance was determined using the Fisher, Breslow, and log-rank tests.
The patients' mean age at presentation was 9.5 months (median 3.0 months). Eighty-four patients (56.4%) were successfully treated without a shunt. Operative mortality was 1.2% for ETV and 4.4% for shunt placement (p = 0.3). Five-year survival was 72.8% in the non–shunt-treated group and 67.6% in the shunt-treated group, with no difference in survival (log rank p = 0.43, Breslow p = 0.46). Of 43 survivors assessed at 5–11 years, those with shunts had significantly worse functional outcomes (p = 0.003–0.035), probably reflecting treatment selection bias since those with the worst sequelae of ventriculitis were more likely to be treated with shunt placement.
Nearly one-third of treated infants died within 5 years, and at least one-third of the survivors were severely disabled. There was no survival advantage for non–shunt-treated patients at 5 years. A randomized trial of endoscopic third ventriculostomy versus shunt placement for treating PIH may be indicated. Public health measures that prevent these infections are urgently needed.
Jason G. Mandell, Abhaya V. Kulkarni, Benjamin C. Warf, and Steven J. Schiff
The evaluation of hydrocephalus remains focused on ventricular size, yet the goal of treatment is to allow for healthy brain development. It is likely that brain volume is more related to cognitive development than is fluid volume in children with hydrocephalus. This study tests this hypothesis by comparing brain and fluid volumes with neurocognitive outcome in pediatric patients with hydrocephalus.
Warf and colleagues previously acquired CT scans for pediatric patients in Uganda with myelomeningocele, measured frontal–occipital horn ratio (FOHR), and administered the modified Bayley Scales of Infant Development, third edition (BSID-III) to measure neurocognitive outcome that did not correlate with FOHR. In this present study, brain and fluid volumes were measured in 33 of these patients, 26 of whom required surgical treatment for hydrocephalus. Linear discrimination analysis (LDA) was used to test whether age-normalized brain and fluid volumes can discriminate neurocognitive outcome.
Hydrocephalic patients show normal to small brain volumes and substantially larger fluid volumes compared with normal values. FOHR correlates highly with fluid volume (r = 0.84, p < 0.001) and substantially less with brain volume (r = −0.37, p = 0.03), while brain and fluid volumes do not correlate with each other (p = 0.99). Brain and CSF volumes correlated best with fine motor (p = 0.03, p = 0.01), cognitive (p = 0.05, p = 0.09), and expressive communication (p = 0.08, p = 0.08) scores. A combination of these 3 scores was used as a multivariate measure of neurocognitive outcome. Brain volume alone, unlike fluid volume, could discriminate high from low cognitive outcome (by t-test and ANOVA). It was shown that a combination of age-normalized brain and fluid volumes can discriminate neurocognitive outcome by 2-way LDA (p < 0.01) and 3-way LDA (p < 0.01). The multivariate LDA demonstrated the contribution of large fluid volume to a decrement in cognition.
Hydrocephalus is treated by normalizing CSF, but normal brain development depends on brain growth. A combination of brain and CSF volumes appears to be significantly more powerful at predicting good versus poor neurocognitive outcomes in patients with hydrocephalus than either volume alone.