Publications by authors named "Dirks P"

NrCAM, a member of the L1 family of cell adhesion molecules, serves important functions during the development of the nervous system, e.g. in adhesion-dependent processes such as neurite outgrowth and axonal pathfinding.

View Article and Find Full Text PDF

Object: The authors' aim in conducting this study was to investigate retrospectively the prognostic significance of angiogenic features in optic pathway/hypothalamic gliomas (OPHGs) in children.

Methods: Patients were identified in whom a diagnosis of OPHG was made using pathological analysis at the Toronto Hospital for Sick Children between 1985 and 2002. Tumor specimens were reviewed for diagnostic accuracy and adequacy of the specimen.

View Article and Find Full Text PDF

Two children with a new diagnosis of hemorrhagic type moyamoya disease experienced cerebral infarction after intraventricular hemorrhage. The patients developed ischemia 15 and 2 days after the initial diagnosis of hemorrhage. No provocative factor such as hypoperfusion was identified, but both patients exhibited signs of increased intracranial pressure on computed tomographic scan before infarction.

View Article and Find Full Text PDF

Aims: To review the ocular manifestations of crush head injuries in children.

Methods: Retrospective clinical and pathological reviews. Group 1: A total of 16 children admitted with crush head injuries from television tip over.

View Article and Find Full Text PDF

Object: Television tipover has recently been recognized as a significant cause of injury in children, and head injury accounts for most of the associated deaths. The authors reviewed their experience with children who sustained head injury from falling televisions.

Methods: Children admitted with the diagnosis of head injury related to falling televisions since 1992 were identified from the authors' trauma database, and a retrospective review of the medical records was performed.

View Article and Find Full Text PDF

Object: The ability to map cerebrovascular reactivity (CVR) at the tissue level in patients with moyamoya disease could have considerable impact on patient management, especially in guiding surgical intervention and assessing the effectiveness of surgical revascularization. This paper introduces a new noninvasive magnetic resonance (MR) imaging-based method to map CVR. Preoperative and postoperative results are reported in three cases to demonstrate the efficacy of this technique in assessing vascular reserve at the microvascular level.

View Article and Find Full Text PDF

Objectives: To review all cases of pediatric aneurysms, we treated and evaluated their characteristics. The objective of the study is to compare between surgical and endovascular approaches regarding treatment and outcome.

Methods: All cases of pediatric intracranial aneurysms diagnosed and managed by our team in the last 12 years were prospectively collected in our vascular malformation data base and reviewed.

View Article and Find Full Text PDF

Object: In the preceding article, the authors described the Hydrocephalus Outcome Questionnaire (HOQ), a simple, reliable, and valid measure of health status in children with hydrocephalus. In the present study, they present their initial experience in using the HOQ to quantify the health status in a typical cohort of children with hydrocephalus.

Methods: The mothers of children with hydrocephalus completed the HOQ and, with the child's attending surgeon, provided a global rating of their children's health.

View Article and Find Full Text PDF

Pilomyxoid astrocytoma (PMA), a recently described variant of low-grade astrocytoma is associated with a high rate of recurrence and a propensity for CSF seeding. While cases of PMA have been reported in infants and young children, there has been no report of PMA in patients with neurofibromatosis. The first reportable case of PMA occurring in a child with neurofibromatosis type 1 (NF1) is described.

View Article and Find Full Text PDF

The cancer stem cell (CSC) hypothesis suggests that neoplastic clones are maintained exclusively by a rare fraction of cells with stem cell properties. Although the existence of CSCs in human leukaemia is established, little evidence exists for CSCs in solid tumours, except for breast cancer. Recently, we prospectively isolated a CD133+ cell subpopulation from human brain tumours that exhibited stem cell properties in vitro.

View Article and Find Full Text PDF

Migratory birds can use a magnetic compass for orientation during their migratory journeys covering thousands of kilometers. But how do they sense the reference direction provided by the Earth's magnetic field? Behavioral evidence and theoretical considerations have suggested that radical-pair processes in differently oriented, light-sensitive molecules of the retina could enable migratory birds to perceive the magnetic field as visual patterns. The cryptochromes (CRYs) have been suggested as the most likely candidate class of molecules, but do CRYs exist in the retina of migratory birds? Here, we show that at least one CRY1 and one CRY2 exist in the retina of migratory garden warblers and that garden-warbler CRY1 (gwCRY1) is cytosolic.

View Article and Find Full Text PDF

Visual sensation in vertebrates starts with the isomerization of 11-cis retinaldehyde into all-trans retinaldehyde. Aldehyde dehydrogenases, present in the pigment epithelium and some retinal cells, convert all-trans retinaldehyde into all-trans retinoic acid (at-RA). Evidence in the retina and the hippocampus has accumulated, showing that at-RA, besides being a morphogenetic factor, also acts as a neuromodulator.

View Article and Find Full Text PDF

Most current research on human brain tumors is focused on the molecular and cellular analysis of the bulk tumor mass. However, evidence in leukemia and more recently in solid tumors such as breast cancer suggests that the tumor cell population is heterogeneous with respect to proliferation and differentiation. Recently, several groups have described the existence of a cancer stem cell population in human brain tumors of different phenotypes from both children and adults.

View Article and Find Full Text PDF

Malignancy is considered a contra-indication to organ donation, with a few possible exceptions. We present the case of a child with fatal intracranial hemorrhage from a primary brain tumor (PBT) whose organs were denied for transplant after recovery. We review the literature of organ donors with PBTs in the context of the current organ shortage and discuss the implications for the practicing oncologist.

View Article and Find Full Text PDF

We report a 14-year-old girl in whom a diagnosis of primary central nervous system lymphoma was confirmed while receiving growth hormone (GH) for GH deficiency, detected after presenting with short stature. MRI revealed an enhancing and thickened pituitary stalk with absence of the normal bright signal in the posterior pituitary. Regular MRI surveillance detected progression of the neurohypophyseal changes 13 months into GH treatment.

View Article and Find Full Text PDF

Patients And Methods: The clinical, radiological, surgical, and pathological findings of 16 children with a primary central nervous system (CNS) sarcoma are reported. There were 8 (50%) girls and 8 (50%) boys ranging in age from 4 months to 14 years (mean age 4.8 years).

View Article and Find Full Text PDF

We report the clinical and imaging findings in the cases of two children who initially presented with back pain related to epidural AVF in the cervicothoracic spine. Both lesions were of particular interest because of their exclusive epidural and paraspinal venous drainage and the presence of the prominent venous pouches in the epidural space. Angiography revealed that one was multifocal and of relatively slow flow.

View Article and Find Full Text PDF

Most current research on human brain tumors is focused on the molecular and cellular analysis of the bulk tumor mass. However, there is overwhelming evidence in some malignancies that the tumor clone is heterogeneous with respect to proliferation and differentiation. In human leukemia, the tumor clone is organized as a hierarchy that originates from rare leukemic stem cells that possess extensive proliferative and self-renewal potential, and are responsible for maintaining the tumor clone.

View Article and Find Full Text PDF

Aberrant receptor tyrosine kinase signaling plays an important role in the molecular pathogenesis of brain tumors. We have been studying a previously identified human glioblastoma-derived PDGFR-alpha mutant that has an in-frame deletion in the extracellular domain, causing loss of exons 8 and 9 (PDGFR-alpha(delta8,9)). In the primary tumor, this deletion mutant receptor was shown to be amplified and overexpressed.

View Article and Find Full Text PDF

We previously showed that the expression of p16(ink4a) (p16), in conjunction with retinoic acid (RA) treatment in the p16-deficient astrocytoma cell line, U343 MG-A, induced a potent cell cycle arrest in G(1) associated with changes in morphology. In this study, we investigated the effects of p16 expression and RA treatment on the expression and distribution of actin, glial fibrillary acidic protein (GFAP), and vimentin within the U343 MG-A astrocytoma cytoskeleton. Changes in expression and location of the small GTPase, rhoA, were also examined after p16 expression and RA treatment.

View Article and Find Full Text PDF

Neck injuries in children most commonly affect the upper cervical spine. Injuries of the transverse ligament and its attachments may result in C1-2 instability, but the optimum form of treatment is unknown. Three patients, who ranged in age from 5 to 11 years, sustained transverse atlantal ligament injuries with unilateral avulsion fracture of the osseous tubercle of C-1.

View Article and Find Full Text PDF

Choroid plexus tumors are papillary neoplasms originating from the epithelium of the choroid plexus within the cerebral ventricles. They may be highly proliferative tumors, but detailed studies confirming their proliferative potential are lacking. Accordingly, we performed a clinicopathological correlation study of neoplasms arising from the choroid plexus in children using immunohistochemistry to characterize both their proliferative potential and their degree of cell cycle dysregulation when compared to non-neoplastic choroid epithelium.

View Article and Find Full Text PDF

Neural stem cells have recently come to the forefront in neurobiology because of the possibilities for CNS repair by transplantation. Further understanding of the biology of these cells is critical for making their use in CNS repair possible. It is likely that these discoveries will also have spin-offs for neuro-oncology as primary brain tumors may arise from a CNS progenitor cell.

View Article and Find Full Text PDF