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Biomedical subjects

J M Drake

Publications and source records attributed to J M Drake.

At least 19 recordsLinked to original sources
PubMed2001

Spontaneous intraparenchymal hemorrhage in full-term neonates.

OBJECTIVE: Spontaneous intraparenchymal hemorrhage is extremely rare in full-term newborns. Reports to date have been limited to descriptions of individual cases, small groups within larger studies of intracranial hemorrhage, and one series of four patients. Structural lesions are rarely identified, and the majority of patients described have been managed without surgical intervention. METHODS: Analysis of a computerized database of pediatric neurosurgical patients from January 1960 to February 2000 identified full-term newborns younger than 3 months of age with nontraumatic intraparenchymal hemorrhages. Prenatal histories, labor and delivery histories, clinical presentations, imaging studies, management, and outcomes were reviewed. RESULTS: Eleven full-term newborns with spontaneous intraparenchymal hemorrhages were identified. The majority had normal prenatal courses. Most presented within the first 2 days of life (6 of 11 patients), and the most common presenting sign was seizure (7 of 11 patients). No cause was identified in 6 of 11 patients; the remainder were attributed to coagulopathy (n = 3), ruptured intracranial aneurysm (n = 1), or hemorrhagic infarction (n = 1). Eight patients underwent surgical hematoma evacuation on the basis of radiographic evidence of significant mass effect, evidence of signs of elevated intracranial pressure, or both. Three patients did not receive surgical intervention. There were no subsequent hemorrhages or deaths during a mean follow-up period of 4.5 years (range, 1-16 yr). Four patients had normal neurological outcomes, four had motor deficits (one of whom additionally demonstrated cognitive delay), and three had delayed speech. CONCLUSION: No cause is identified in most newborns with spontaneous intraparenchymal hemorrhage. Radiographic evidence of mass effect or signs of elevated intracranial pressure may necessitate surgical hematoma evacuation. Outcome varies widely and may be normal, even in patients with sizeable intraparenchymal hemorrhages.

Aneurysm, Ruptured↗
PubMed2001

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.

Adolescent↗
PubMed2001

Medulloblastoma in a child with Rubenstein-Taybi Syndrome: case report and review of the literature.

Although medulloblastoma is usually sporadic, there are a number of uncommon predisposing germline mutation syndromes, including: Gorlin's Syndrome, Turcot's Syndrome and Li-Fraumeni Syndrome. Patients with Rubenstein-Taybi Syndrome secondary to mutation/deletion of the CBP gene on chromosome 16 are predisposed to a variety of developmental anomalies as well as cancer. We report a child with Rubenstein-Taybi syndrome who developed a cerebellar medulloblastoma and review the literature on Rubenstein-Taybi Syndrome and pediatric medulloblastoma. As the product of the CBP gene functions in a variety of signaling pathways, we discuss the molecular implications of findings a medulloblastoma in a child with Rubenstein-Taybi Syndrome.

Abnormalities, Multiple↗
PubMed2001

Cerebrospinal fluid shunt infection: a prospective study of risk factors.

OBJECT: Hydrocephalus is a common condition of childhood that usually requires insertion of a cerebrospinal fluid (CSF) shunt. Infection is one of the most devastating complications that may arise from the presence of CSF shunts. In this study, the authors prospectively analyzed perioperative risk factors for CSF shunt infection in a cohort of children. METHODS: Between 1996 and 1999, 299 eligible patients underwent CSF shunt operations (insertions and revisions) that were observed by a research nurse at a tertiary care pediatric hospital. Several perioperative variables were recorded. All cases were followed postoperatively for 6 months to note any development of CSF shunt infection. A Cox proportional hazards model was used to analyze the relationship between the variables and the development of shunt infection. Thirty-one patients (10.4%) experienced shunt infection. Three perioperative variables were significantly associated with an increased risk of shunt infection: 1) the presence of a postoperative CSF leak (hazard ratio [HR] 19.16, 95% confidence interval [CI] 6.96-52.91); 2) patient prematurity (< 40 weeks' gestation at the time of shunt surgery: HR 4.72, 95% CI 1.71-13.06), and 3) the number of times the shunt system was inadvertently exposed to breached surgical gloves (HR 1.07, 95% CI 1.02-1.12). CONCLUSIONS: Three variables associated with an increased incidence of shunt infection have been identified. Changes in clinical practice should address these variables, as follows. 1) Great care should be taken intraoperatively to avoid a postoperative CSF leak. 2) Alternatives to placement of a CSF shunt in premature infants should be studied. 3) Surgeons should minimize manual contact with the shunt system and consider the use of double gloves.

Adolescent↗
PubMed2001

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.

Cerebrospinal Fluid Shunts↗
PubMed2001

Shunt malfunctions.

Shunt failure remains a disheartening complication of shunt surgery. The number of adjustable factors in attempting to reduce the rate is small. The clinical presentation and timing of shunt malfunction are well documented. Although the shunt design trials have been negative to date, valves have important effects that have not as yet been translated to improved outcome.

Cerebrospinal Fluid Shunts↗
PubMed2000

Familial posterior fossa brain tumors of infancy secondary to germline mutation of the hSNF5 gene.

We have identified a family afflicted over multiple generations with posterior fossa tumors of infancy, including central nervous system (CNS) malignant rhabdoid tumor (a subset of primitive neuroectodermal tumors, or PNET) and choroid plexus carcinoma. Various hereditary tumor syndromes, including Li-Fraumeni syndrome, Gorlin syndrome, and Turcot syndrome, have been linked to increased risk of developing CNS PNETs and choroid plexus tumors. Malignant rhabdoid tumors of the CNS and kidney show loss of heterozygosity at chromosome 22q11. The hSNF5 gene on chromosome 22q11 has recently been identified as a candidate tumor-suppressor gene in sporadic CNS and renal malignant rhabdoid tumors. We describe a family in which both affected and some unaffected family members were found to have a germline splice-site mutation of the hSNF5 gene, leading to exclusion of exon 7 from the mature cDNA and a subsequent frameshift. Tumor tissue shows loss of the wild-type hSNF5 allele, in keeping with a tumor-suppressor gene. These findings suggest that germline mutations in hSNF5 are associated with a novel autosomal dominant syndrome with incomplete penetrance that predisposes to malignant posterior fossa brain tumors in infancy.

Age of Onset↗
PubMed2000

Virtual tape measure for the operating microscope: system specifications and performance evaluation.

OBJECTIVE: The Virtual Tape Measure for the Operating Microscope (VTMOM) was created to assist surgeons in making accurate 3D measurements of anatomical structures seen in the surgical field under the operating microscope. The VTMOM employs augmented reality techniques by combining stereoscopic video images with stereoscopic computer graphics, and functions by relying on an operator's ability to align a 3D graphic pointer, which serves as the end-point of the virtual tape measure, with designated locations on the anatomical structure being measured. The VTMOM was evaluated for its baseline and application performances as well as its application efficacy. METHODS: Baseline performance was determined by measuring the mean error (bias) and standard deviation of error (imprecision) in measurements of non-anatomical objects. Application performance was determined by comparing the error in measuring the dimensions of aneurysm models with and without the VTMOM. Application efficacy was determined by comparing the error in selecting the appropriate aneurysm clip size with and without the VTMOM. RESULTS: Baseline performance indicated a bias of 0.3 mm and an imprecision of 0.6 mm. Application bias was 3.8 mm and imprecision was 2.8 mm for aneurysm diameter. The VTMOM did not improve aneurysm clip size selection accuracy. DISCUSSION AND CONCLUSION: The VTMOM is a potentially accurate tool for use under the operating microscope. However, its performance when measuring anatomical objects is highly dependent on complex visual features of the object surfaces.

Aneurysm↗
PubMed2000

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.

Animals↗
PubMed2000

Brain biomechanics: mathematical modeling of hydrocephalus.

The considerable amount of literature on mathematical models of hydrocephalus and other brain abnormalities is critically reviewed. These models have various degrees of mathematical sophistication, and have influenced not only the diagnosis of hydrocephalus, but also its treatment with CSF shunts. The mathematical models are classified into two classes, pressure-volume models, and consolidation models. Advantages and disadvantages of both types are pointed out with a view to removing the confusion frequently generated by the technical aspects of the subject. The conclusion is reached that, while none of the current models are good enough to be of immediate use to the neurosurgeon, mathematical models are likely in the future to be a powerful tool for the understanding and the treatment of hydrocephalus, as well as other conditions related to brain biomechanics. The amount of mathematics has been kept to the absolute minimum, but it is cited and appended for those who would like to dig further into this fascinating area of research.

Biomechanical Phenomena↗
PubMed2000

Ventriculoperitoneal shunt flow dependency on the number of patent holes in a ventricular catheter.

Minimally invasive recanalization of obstructed ventricular catheters is a new treatment modality currently under investigation. It has been shown that blocked ventricular catheters can be at least partly reopened with ultrasonic cavitation, fiberoptic delivery of laser energy and electrocautery. It is not known, however, how many of the holes must be reopened in order to establish acceptable pressure-flow characteristics. In this study, the pressure-flow relationship of partially obstructed ventricular catheters was determined using experimental and electrical circuit/computer models. It has been demonstrated in all cases that an additional pressure of no more than 0.5 cm of water is generated when only a single 500-microm-diameter hole in the ventricular catheter permits flow. Partial recanalization of a ventricular catheter provides acceptable CSF hydrodynamics.

Catheterization↗
PubMed2000

Imaging correlates of successful endoscopic third ventriculostomy.

OBJECT: The goal of this study was to determine and compare imaging correlates in pediatric patients who underwent successful or failed endoscopic third ventriculostomies (ETVs). To this end, the authors measured ventricular size changes and the presence of cerebrospinal fluid (CSF) flow void in both groups of children following ETV. METHODS: Images obtained in children with hydrocephalus immediately before and at least 30 days after having undergone ETV were reviewed by four independent observers (two blinded and two nonblinded). Each observer independently measured the frontal and occipital horn ratio ([FOR], a reliable and valid measure of ventricular size) and provided a subjective assessment of the presence of a flow void at the ETV site, the degree of periventricular edema, and the amount of CSF over the cerebral hemispheres. There were 29 children whose mean age was 6.6 years at the time of ETV and who had a mean postoperative follow-up period lasting 1.6 years. Postoperatively, the mean reduction in ventricular size (as measured using the FOR) was 7% (95% confidence interval [CI] 3-11%) in cases that were deemed failures (eight patients) and 16% (95% CI 12-20%) in clinically successful cases (21 patients). This reduction was significantly greater in cases of clinical success compared with those that were deemed failures (p = 0.03, t-test). There were no substantial differences between blinded and nonblinded assessments. Flow void was present in 94% of successes and absent in 75% of failures (p = 0.01, Fisher's exact test). The other subjective assessments were not significantly different between the groups of successes and failures. CONCLUSIONS: Ventricular size appears to be somewhat reduced in both groups of patients who underwent clinically successful and failed ETV; however, the reduction is significantly greater among clinically successful cases. The presence of a flow void also appears to correlate with clinical success and its absence with clinical failure.

Adolescent↗
PubMed1999

Noninvasive cerebrospinal fluid shunt flow measurement by Doppler ultrasound using ultrasonically excited bubbles: a feasibility study.

Because normal cerebrospinal fluid (CSF) has almost no natural Doppler scatterers, patency testing of ventriculoperitoneal cerebrospinal fluid shunts (small silastic tubing with lumen diameter of approximately 1 mm draining excessive CSF from the brain) cannot be performed by Doppler ultrasound. We have developed a low-frequency bubble excitation system that generates microbubble scatterers in both distilled water and CSF. Doppler ultrasound can then be used for flow measurement in a ventriculoperitoneal shunt. By using low duty-cycle (approximately 10%), low-frequency (approximately 30 kHz), and low-amplitude (approximately 30 kPa) ultrasound, a population of microbubbles can be maintained for sufficiently long times (>10 min) for Doppler ultrasound measurement, although bubble initiation is inconsistent. The minimum pressure needed for bubble maintenance was found to decrease with increasing burst length and duty cycle. It has been possible to detect the presence of CSF shunt flow down to a mean flow rate of 3 mL/h (mean velocity approximately 0.6 mm/s). The bubble maintenance scheme developed satisfies the safety parameters specified by the American Institute of Ultrasound in Medicine (AIUM) and the US Food and Drug Administration (FDA). Results from both in vitro and in vivo (externalized shunts) experiments indicate the feasibility of this scheme for determining realistic CSF shunt flows, though some practical problems remain before the technique will be ready for clinical use.

Child↗
PubMed1999

MR characteristics of malignant spinal cord astrocytomas in children.

OBJECTIVE: Malignant spinal cord astrocytomas are rare tumors and their specific MR characteristics have not been previously described. We present a detailed MR analysis of four children with malignant astrocytoma. METHODS: A review of the clinical database at the Hospital for Sick Children, Toronto revealed four patients with histologically-verified malignant spinal cord astrocytomas (WHO Grade 3 or 4) with pre-operative MR available for retrospective review. RESULTS: There were three boys and one girl with a mean age at presentation of four years (range 7 months-12 years). Mean duration of symptoms prior to presentation was six weeks (range 3 days-5 months). Pre-operative MR analysis revealed that all tumors were located in the cervical or cervico-thoracic regions and expanded the cord over an average of 6.5 vertebral levels. The signal was usually hypointense on T1-weighted and hyperintense or mixed intensity on T2-weighted images. In the three cases where gadolinium was given, all demonstrated enhancement (one rim enhancement with a discrete border and two with inhomogeneous central enhancement). One tumor appeared to be exophytic, one had a significant cystic component, and none showed evidence of hemorrhage. Pre-operative leptomeningeal spread of tumor was documented in two of four cases and involved intracranial spread in both cases. CONCLUSIONS: There did not appear to be any specific MR characteristics to help differentiate a malignant astrocytoma from a low-grade tumor, except for the high rate of leptomeningeal spread at presentation. It is recommended that full neuraxis MR imaging be performed pre-operatively in children in whom a rapidly progressive clinical course suggests a malignant lesion. This will likely have a high positive yield and provide valuable information prior to surgical intervention.

Astrocytoma↗
PubMed1999

Measurement of ventricular size: reliability of the frontal and occipital horn ratio compared to subjective assessment.

INTRODUCTION: The frontal and occipital horn ration (FOR) has recently been described as a simple, linear measurement of ventricular size that correlates very well with ventricular volume. This study further characterizes the measurement properties of the FOR by investigating its interobserver reliability and comparing it to a subjective assessment of ventricular size. METHODS: Axial images (CT and MR) of children with hydrocephalus taken before and after third ventriculostomy were reviewed by 4 independent observers. Two observers were blinded to patient identity and clinical status and 2 observers were nonblinded. Each observer independently recorded linear measurements from which the FOR was calculated for each image. Each reviewer also made a separate subjective assessment of the degree of hydrocephalus on a 9-point adjectival scale. Reliability was calculated using a repeated-measures analysis of variance (ANOVA) and an intraclass correlation coefficient (ICC) with random image and observer effects. RESULTS: There were 120 separate observations (4 observers, 30 images). The FOR ranged from 0.33 to 0.75 (mean 0.55, standard deviation 0.11). The reliability coefficient was 0.93 (95% confidence interval, CI 0.80-0.97) between the 2 blinded observers and 0.98 (95% CI, 0.95-0.99) between the 2 nonblinded observer. The overall interobserver reliability for all 4 observers was 0.95 (95% CI 0.92-0.98). The mean FOR for each observer was very similar, regardless of the observer's blinding status. However, the reliability of the observers' subjective assessment of the hydrocephalus was much lower (ICC = 0.77, 95% CI 0. 60-0.88). CONCLUSIONS: The FOR demonstrates excellent interobserver reliability (>0.9) and was superior to subjective assessments of hydrocephalus. In this study, excellent reliability was maintained regardless of the blinding status of the observers. This further demonstrates the properties of the FOR as a simple and reproducible measure of ventricular size. It is suitable for use in clinical studies, possibly even in situations in which observer blinding is not possible.

Cerebral Ventricles↗
PubMed1999

Primary Ewing's sarcoma of the skull in children. Utility of molecular diagnostics, surgery and adjuvant therapies.

Ewing's sarcoma (ES) of the skull is rare. Herein, we present 2 cases of ES that involved the cranium in young children. In one case, the lesion originated in the petrous temporal bone; in the other, the frontal bone. Both children were acutely compromised neurologically by signs and symptoms of raised intracranial pressure. In both cases, radiographs revealed massive tumors affecting the skull. Neurosurgical resection of the tumor was undertaken in both instances, and the diagnosis of ES was confirmed by immunohistochemistry, cytogenetic analysis (translocation 11;22), spectral karyotyping and RT-PCR (demonstration of a EWS/FLI1 fusion transcript). Following aggressive surgical resection, both children received intensive chemotherapy. No child has received radiation therapy. One child is alive and well 8 years after diagnosis without any evidence of residual disease. The other is currently undergoing chemotherapy for her tumor. The principles involved in the management of children with cranial-based ES are discussed. These 2 cases serve to illustrate the fact that even children with massive ES tumors of the cranium may be salvaged with aggressive combination therapy.

Acute Disease↗