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Biomedical subjects

J M Drake

Publications and source records attributed to J M Drake.

At least 55 records · Page 3Linked to original sources
PubMed1996

Supratentorial primitive neuroectodermal tumors in children.

A retrospective review of 36 children diagnosed with a supratentorial primitive neuroectodermal tumor (PNET) at the Hospital for Sick Children was performed for the period 1970-1995. All children but one received their initial treatment at our institution. There were 18 males and 18 females and the median age at diagnosis was 35 months. Twenty-two PNETs were lobar, 3 were deep in the hemisphere, and 10 were located in the pineal region. One child presented with intracranial leptomeningeal disseminated disease. The tumors were mostly undifferentiated although 22 had some evidence of differentiation along one or more neuroepithelial lines. Five children had a biopsy, 24 had subtotal resection, and 7 had gross total resection. Twenty-six children had adjuvant radiotherapy and 13 had chemotherapy. At last follow-up 30 patients were dead and 6 were alive. The median survival was 23 months and the 2, 3, and 5 year survivals were 50%, 34%, and 18% respectively. All of the survivors received craniospinal radiation and 4 received chemotherapy. There was a statistically significantly worse survival in young children. There was a trend to better survival in children treated since 1984, and in children undergoing gross total resection. Because of the extremely poor survival, we recommended that all children undergo gross total resection followed by chemotherapy. For children older than 3 years of age craniospinal radiation should also be given.

Antineoplastic Agents↗
PubMed1996

Rationale and methodology of the multicenter pediatric cerebrospinal fluid shunt design trial. Pediatric Hydrocephalus Treatment Evaluation Group.

Cerebrospinal fluid shunt failure remains a common and at times overwhelming problem in pediatric patients with hydrocephalus. Two new shunt valve designs, the Orbis-Sigma (Cordis Corporation, Miami, Florida) and the Delta valve (PS Medical, Goletta, California), have flow/pressure characteristics dramatically different from those of standard differential pressure valves which have been used for over three decades. Both new designs reduce the siphoning effect in the upright position, and have been reported to reduce shunt failure rates in uncontrolled series, allegedly due to reduction in shunt overdrainage. Most mechanical shunt failure in the first 2 years after implantation is due to proximal shunt obstruction, overdrainage, and loculated ventricles. By reducing the incidence of slit ventricles associated with standard valves, both new designs could be envisioned as reducing the early mechanical complications. The improved results with both new valves could, however, also be to a large extent due to other confounding effects of shunt surgery, including patient selection, surgical technique, and specific configuration of the components of the shunt other than the valve. There are also theoretical reasons why these valve designs might be worse than their predecessors, including the narrow orifice and high resistance of the Orbis-Sigma, and the flexible membrane of the siphon control portion of the Delta valve, which may increase the ventricular pressure in the upright position or become blocked by encasing scar tissue. For this reason a randomized trial is required to determine efficacy, and a standard differential pressure valve is required as the control design. A significant reduction in early shunt failure would dramatically improve the morbidity and mortality of pediatric hydrocephalic patients, as well as providing substantial savings to the health care system. Failure to determine any difference would focus attention on other issues surrounding shunt surgery, such as patient characteristics or surgical technique.

Cerebrospinal Fluid Shunts↗
PubMed1996

The diagnosis of Neospora abortions in cattle.

An indirect immunofluorescent antibody test (IFAT) and an enzyme-linked immunosorbent assay (ELISA) for specific anti-Neospora antibodies in bovine sera and foetal fluids were compared with histological examination results on aborted foetal material. The agreement between serological and histological examination results was poor, while the two serological tests showed a high degree of agreement. Serological testing of diagnostic serum samples and foetal fluids suggests that the prevalence of anti-Neospora antibodies in cattle which recently aborted is around 40%, in line with previous estimates of the number of abortions in dairy cattle caused by Neospora sp. A sero-epidemiological approach to the diagnosis of Neospora abortions in cattle may be suggested from these data.

Journal Article↗
PubMed1996

Choices in the 1990s for the management of pediatric cerebral arteriovenous malformations.

A retrospective 45-year analysis of the management of 160 children with intracranial arteriovenous malformations at The Hospital for Sick Children, Toronto, reveals substantially improving outcomes which relate to more efficient diagnoses and treatments. 80% of children will declare their malformation by means of spontaneous intracranial hemorrhage. For those children who present with hemorrhage or epilepsy, 80% will require an operation. The overall mortality rate has declined to 12% since 1975 and that for the cerebellar lesions from 67 to 42%. 53% of the patients operated upon will be neurologically normal. Endovascular embolization of a child's AVM is a customized, partial solution for a limited number of children. Stereotactic radiosurgery will be used increasingly to obliterate those small lesions in children which are unassociated with hemorrhage or are the residua of an operation. As many as 10% of children (15/160) with diagnosed AVMs cannot be helped with operative or other interventional therapies. The recognition of the pediatric stroke syndromes, the early triage and diagnosis of a child's cerebral hemorrhage, the operative and anaesthetic technologies and the adjunct therapies - choices of the nineties - have resulted in a 66% decline in the overall mortality from this vascular lesion as well as greater assuredness that for most the lesion can be permanently obliterated.

Adolescent↗
PubMed1996

Shunt infections.

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Bacterial Infections↗
PubMed1995

Reduced local cerebral blood flow in periventricular white matter in experimental neonatal hydrocephalus-restoration with CSF shunting.

The extent to which the reduction in CBF occurring in hydrocephalus is a primary or secondary event in the pathogenesis of the brain injury that ensues has not been clearly established. This is particularly true in neonatal hydrocephalus, where the disorder is most common, and where timing of the treatment of the developing nervous system is so important. We investigated the changes in local CBF (lCBF) in an animal model of severe progressive neonatal hydrocephalus before and after CSF shunting. Hydrocephalus was induced in 27 1-week-old kittens by percutaneous injection of 0.05 ml of 25% kaolin into the cisterna magna. Fourteen littermates acted as controls. The lCBF was measured by 14C-iodoantipyrine quantitative autoradiography after 1 week in 15 animals (8 hydrocephalic, 7 controls) and after 3 weeks in 26 animals (19 hydrocephalic, 7 controls) following induction of hydrocephalus. Twelve of the 3-week hydrocephalic group received a ventriculoperitoneal shunt 10 days following kaolin injection. At 1 week following induction of hydrocephalus, lCBF was globally reduced in cortical gray matter and white matter as well as deep subcortical structures. The maximum reduction was in the parietal white matter, to 37% of control levels. At 3 weeks a significant reduction in lCBF persisted only in the white matter (parietal, occipital, and corpus callosum; average, 42% of control levels), whereas cortical gray and deep subcortical structures had returned to normal levels spontaneously.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

The detection and management of intracranial hypertension after initial suture release and decompression for craniofacial dysostosis syndromes.

We performed a retrospective study of 107 consecutive patients with syndromic forms of craniosynostosis (craniofacial dysostosis) seen by the craniofacial team at the Hospital for Sick Children between 1986 and 1992. There were 51 patients with Crouzon's syndrome, 33 with Apert's syndrome, 8 with Pfeiffer syndrome, 11 with Saethre-Chotzen syndrome, and 4 with kleeblättschadel anomaly. Six patients developed raised intracranial pressure (ICP) after initial suture release and decompression (Apert's syndrome, three patients; Pfeiffer syndrome, one patient; Saethre-Chotzen syndrome, two patients). Raised ICP was considered in those children who returned with a bulging fontanelle, progressive frontal bone protrusion, intermittent headaches, irritability, and vomiting. The diagnosis of raised ICP was based on papilledema (four patients), progressive macrocephaly (one patient), and ICP monitoring (one patient). No child in this group had hydrocephalus requiring cerebrospinal fluid diversion. Once raised ICP was detected in these children, a second operation was immediately performed to reduce the ICP with the intention of expanding the volume of the cranial cavity. The second procedures included: anterior cranial vault and upper orbital reshaping (four patients), posterior cranial vault reshaping (one patient), and total cranial vault reshaping (one patient). There were no perioperative complications in these patients, although one patient showed subsequent recurrence of raised ICP requiring further cranial vault re-expansion. At follow-up, ranging from 3 to 7 years, all six patients were asymptomatic without evidence of raised ICP. In our series, raised ICP occurred in 6% of the children with a craniofacial dysostosis syndrome after initial suture release and decompression.(ABSTRACT TRUNCATED AT 250 WORDS)

Child, Preschool↗
PubMed1995

Use of frameless stereotaxy with location of electroencephalographic electrodes on three-dimensional computed tomographic images in epilepsy surgery.

Epileptiform activity corresponding to structural lesions was identified by three-dimensional (3D) imaging using computed tomographic (CT) scan data concurrently with scalp EEG electrodes. The electrodes, placed according to the international 10-20 system, were used to record interictal and ictal epileptogenic foci in eight patients. Electrodes placed where marked or moderate epileptiform activity was detected were replaced with markers detectable on CT. Scans with these markers on the skin were obtained and the data transferred to a 3D imaging system, and correlated with underlying cerebral structures. The reformatted images were used to assess the relation among intracranial lesions, brain surface structures, and epileptogenic zones depicted by the markers. The images help the surgeon plan a craniotomy with enough space for both lesionectomy and resection of the epileptogenic zone. In the central regions where crucial motor functions are located, the markers indicate the central fissure or postcentral gyrus. An intraoperative 3D frameless stereotactic pointing device helps in directing further examination of the epileptogenic zone. This system improves on the precision available through intraoperative electrocorticographic recording in the extratemporal lobes, thus avoiding only approximate excision of lesion and epileptogenic zone and enabling the neurosurgeon to perform epilepsy surgery with greater confidence.

Adolescent↗
PubMed1994

Benign cerebellar astrocytoma in childhood: experience at the Hospital for Sick Children 1980-1992.

Between 1 January 1980, and 31 December 1992, 66 patients with cerebellar astrocytoma were diagnosed and treated at The Hospital for Sick Children in Toronto. These patients ranged in age between 1 and 18 years, with a mean age of 7.3 years. Thirty-eight patients were male and 28 were female. Total removal was possible in 61 patients and no recurrence occurred in these 61 patients. In the 5 patients in whom an incomplete resection was carried out, regrowth occurred between 1 and 8 years following resection.

Adolescent↗
PubMed1994

Acute and chronic cerebral white matter damage in neonatal hydrocephalus.

The neonatal cat model of kaolin-induced hydrocephalus is associated with progressive and severe ventriculomegaly. In this experiment we studied the evolution of the histopathological changes in hydrocephalic (n = 23) cats from 5-168 days after the induction of hydrocephalus along with age-matched controls (n = 10). In the periventricular white matter, extracellular edema and axonal damage were present within days of the onset of hydrocephalus. This was followed by reactive gliosis, white matter atrophy, and in some animals gross cavitation of the white matter. Even in the chronic, apparently compensated state there was ongoing glial cell death. Six cats were shunted an average of 23.6 +/- 6.5 days after the induction of hydrocephalus because they were no longer able to feed independently. In spite of clinical improvement the white matter changes persisted. Overt cortical changes were minimal except where areas of white matter destruction encroached upon the deep layers. The white matter changes are very similar to those seen in periventricular leukomalacia and suggest that ischemia plays a role in neonatal brain injury caused by hydrocephalus.

Animals↗
PubMed1994

Frameless stereotaxy in children.

Frameless stereotaxy provides stereotactic localization without a standard stereotactic frame. Other reference points on the patient are linked to radiographic images by means of a three-dimensional (3D) digitizer. We report the use of a frameless stereotactic system to assist in 53 procedures in 52 children using the ISG Viewing Wand system (ISG Technologies, Missasauga, Ont.). This device uses surface landmarks as well as random surface points as the reference system. The three-dimensional digitizer consists of a six-jointed articulated arm to which pointers, a rigid ventriculoscope, or stereotactic biopsy probe guide can be attached. Image reconstruction is performed on standard CT or MRI (3D volume acquisition) images, with typically 3-mm slice thickness. The tip of the probe can be displayed on 3D surfaced objects which can be cut away to reveal reformatted gray scale displayed on the cut surface, or in a triorthogonal view where simultaneous reformatted coronal and sagital views at the level of the tip of the probe are displayed. Cases for which the viewing wand was used included craniotomies for tumor (30), vascular malformation (6), epilepsy surgery (5), other lesions (3), rigid ventriculoscopy (9), and stereotactic biopsy (2). The accuracy of the system was measured by placing 20 fiducial markers on a plastic head of which 3-mm thickness CT images had been made. The average error using 4 fiducials as reference points was 1.5 mm when the fiducials were distributed around the circumference of the head. Using random surface points of 10, 20 and 40 in number gave average errors of 2.3, 1.6, 1.5 mm, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Biopsy↗
PubMed1994

Computer modeling of siphoning for CSF shunt design evaluation.

A computer model of the cerebrospinal fluid (CSF) compartment and various shunt designs was developed to simulate CSF dynamics, particularly in the upright position in which siphoning is known to occur. This novel mathematical model of the CSF compartment incorporates negative pressure and volume components that permit simulation of siphoning. The model was tested with data from a previously reported animal experiment. The correspondence between the model simulation and the reported intracranial pressure and CSF shunt flow rate was very good. A simulation of a shunted hydrocephalic patient in the recumbent and upright position was then carried out to examine the effects of a standard shunt valve, an externally adjustable valve, a variable resistance valve, and an antisiphon device. The resulting pressure profiles, which conformed to previously reported data, indicate that this model would be useful for the evaluation of current and future shunt designs.

Brain↗
PubMed1994

Anaerobic glycolysis preceding white-matter destruction in experimental neonatal hydrocephalus.

The metabolic changes in neonatal hydrocephalus that lead to permanent brain injury are not clearly defined, nor is the extent to which these changes can be prevented by a cerebrospinal fluid shunt. To clarify these processes, cerebral glucose utilization was examined using [14C]2-deoxyglucose autoradiography in 1-month-old kittens, kaolin-induced hydrocephalic littermates, and hydrocephalic kittens in which a ventriculoperitoneal shunt had been inserted 10 days after kaolin injection. The hydrocephalic kittens showed thinning of the cerebral mantle and an anterior-to-posterior gradient of enlargement of the ventricular system, with a ventricle:brain ratio of 24% for the frontal and 35% for the occipital horns compared with control (< 0.5%) and shunted (< 5%) animals. White matter in hydrocephalic animals was edematous. Myelination was delayed in the periventricular region and in the cores of the cerebral gyri. Glucose utilization in hydrocephalic and shunted animals was unchanged from control animals in all gray-matter regions examined. However, in hydrocephalic animals, the frontal white matter exhibited a significant increase in glucose utilization (25 mumol.100 gm-1.min-1) in the cores of gyri compared with normal surrounding white-matter values (14.8 mumol.100 gm-1.min-1). Very low values (mean 4 mumol.100 gm-1.min-1) were found in areas corresponding to severe white-matter edema, and these areas were surrounded by a halo of increased activity (24 mumol.100 gm-1.min-1). In contrast, cytochrome oxidase activity in white matter was homogeneous. Shunting resulted in restoration of the cerebral mantle thickness, a return to normal levels of glucose utilization in the white matter, and an improvement in myelination. It is suggested that the areas of increased glucose utilization seen in the white matter represent anaerobic glycolysis which, if untreated, progresses to infarction. The pattern of this increased glucose utilization matches that of expected myelination and, during this period of high energy demand, white matter may be susceptible to the hypoperfusion associated with hydrocephalus.

Anaerobiosis↗
PubMed1994

High-energy phosphate metabolism in a neonatal model of hydrocephalus before and after shunting.

The authors studied the effects of hydrocephalus on the high-energy phosphate metabolism of the brain and the impact of ventriculoperitoneal (VP) shunting on these changes in an experimental model of hydrocephalus. High-energy phosphate metabolism was analyzed using in vivo magnetic resonance (MR) imaging and 31P MR spectroscopy. Hydrocephalus was produced in 34 1-week-old kittens by cisternal injection of 0.05 ml of a 25% kaolin solution. Sixteen litter mates were used as controls. A VP shunt with a distal slit valve was implanted in 17 of the 34 hydrocephalic animals 10 days after induction of hydrocephalus. Both MR imaging and 31P MR spectroscopy were obtained 1 and 3 weeks after either kaolin or distilled water injection. Untreated hydrocephalic animals had marked dilatation of the lateral ventricles and periventricular edema. Magnetic resonance spectroscopy showed a significant decrease in the energy index ratio of phosphocreatine (PCR): inorganic phosphate (PI) and an increase in the PI:adenosine triphosphate (ATP) ratio. There was a direct correlation between the decrease in the energy index and ventricular size. Compared with preoperative scans, shunted animals showed no periventricular edema, and the ventricles decreased in size. Also, PCR:PI and PI:ATP ratios were within the levels of controls. This study suggests that neonatal hydrocephalus results in a mild hypoxic/ischemic insult that is treatable by VP shunting.

Adenosine Triphosphate↗
PubMed1994

Development of anaplastic changes in low-grade astrocytomas of childhood.

The authors present their experience with six children who developed anaplastic astrocytomas after receiving treatment for low-grade astrocytomas. Five children were from a series of 55 children with optic chiasmatic-hypothalamic gliomas who have been studied since 1976. The sixth child initially had a low-grade astrocytoma of the thalamus. The mean age of the children at initial presentation was 5.3 years. Five children were treated with surgery and radiation therapy; one child with a chiasmatic-hypothalamic glioma received radiation therapy alone. The amount of external radiation therapy used in all children was 50-52.5 Gy delivered in standard fractionations over approximately 6 weeks to include the volume of the original tumor plus a margin of 2 cm. The time to anaplastic transformation varied between 2 and 10 years (mean, 6.4 years). At tumor recurrence, the children had seizures or symptoms and signs of raised intracranial pressure. The location of the second tumor in all patients was either at the primary site or within the field of radiation therapy. Five of the six children underwent a second craniotomy and subtotal resection of their malignant gliomas. One child had positive cerebrospinal fluid cytology and multiple intraspinal metastatic tumor nodules detected by magnetic resonance imaging. On histopathological examination, four children had anaplastic astrocytoma, and two had glioblastoma multiforme. Four of the six children have died of their anaplastic astrocytomas (mean time from diagnosis of anaplastic astrocytoma to death, 10 months). Two children underwent chemotherapy and spinal irradiation for their anaplastic astrocytomas, and are currently alive and undergoing treatment. The possible mechanisms by which anaplastic tumors have developed in children treated previously for low-grade astrocytomas is discussed. The data suggest that radiation therapy may have played an integral role in the genesis of anaplastic astrocytomas in these children.

Astrocytoma↗
PubMed1994

Intracranial nasal dermoid sinus cysts: computed tomographic scan findings and surgical results.

From July 1987 to January 1991, 14 patients, ages 1 to 19 years (mean 6 years), were seen with nasal dermoid sinus cysts, a congenital lesion with the potential for intracranial extension. Each patient was assessed clinically for cyst location, symptoms, associated craniofacial deformity, and other congenital anomalies. In 5 (36 percent) of the 14 patients, ages 4 to 48 months (mean 25 months), computed tomographic scans indicated indirect signs of intracranial extension, which were confirmed intraoperatively and histologically in all 5 patients. After neurosurgical consultation, a combined single-stage intracranial-extracranial approach was used to excise the lesion. No perioperative complications occurred. Clinical assessment (follow-up 20 to 40 months, mean 31 months), confirmed by postoperative CT scan 1 year after surgery, indicated no evidence of recurrence, residual skeletal contour defects, or deformity; forehead and nasal growth were qualitatively normal, and scar appearance was satisfactory. Our experience indicates that intracranial extension of nasal dermoid sinus cysts seen at a tertiary care referral center are not rare, that computed tomography scan permits accurate diagnosis, and that the single-stage intracranial-extracranial approach to resection is effective and results in minimal morbidity.

Adolescent↗
PubMed1993

A concerted effort to prevent shunt infection.

In an attempt to reduce the rate of shunt infection a new protocol for shunt surgery was introduced on July 1, 1988 at The Hospital for Sick Children in Toronto. The operations were done at the beginning of the day, operating room personnel were kept to a minimum, no visitors were allowed in the room, a staff neurosurgeon or neurosurgical fellow attended all operations and two doses of perioperative cloxacillin 50 mg/kg were given intravenously. From July 1, 1988 to June 30, 1989 there were 576 shunt procedures on the Neurosurgical Service and 22 (3.8%) of these resulted in a shunt infection. During the preceding year (July 1, 1987 to June 30, 1988) 581 shunt operations were performed, 75 (12.9%) of which resulted in an infection (chi 2 = 29.9, P < 0.001). It appears that the introduction of this protocol for shunt surgery has helped to reduce the risk of shunt infection from 12.9% to 3.8% (a reduction of 70.5%). The rate of infection occurring after shunt revisions was not significantly different from that occurring after new shunt insertions. When the individual factors in the protocol were analyzed, the use of antibiotics and a shorter duration of surgery appeared to be related to a lower shunt infection rate.

Anti-Bacterial Agents↗