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Gelfoam obstruction of endoscopic third ventriculostomy

Case illustration

Richard J. Edwards and Peter B. Dirks

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Pediatric brainstem hemorrhages after traumatic brain injury

Report of 2 cases

Alexandra D. Beier and Peter B. Dirks

Traumatic brain injuries afflict a large number of pediatric patients. The most severe injuries lead to increased intracranial pressure and herniation, with resultant changes in the brainstem. Traumatic brainstem hemorrhages have previously been associated with poor neurological outcome and fatality. However, this report discusses 2 pediatric patients who sustained severe head trauma with subsequent brainstem hemorrhages, and yet experienced good neurological outcome; the possible mechanism is described.

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Large vascular malformation in a child presenting with vascular steal phenomenon managed with pial synangiosis

Case report

Michael J. Ellis, Derek Armstrong, and Peter B. Dirks

The management of large and giant arteriovenous malformations (AVMs) in patients presenting with nonhemorrhagic neurological deficits secondary to vascular steal phenomenon is challenging and controversial. In many cases, large AVMs cannot be completely excised or cured, leaving patients with residual or partially treated AVMs, the natural history of which is unknown. Additionally, large, diffuse vascular malformations with multiple, small feeders, slow flow, or so-called cerebral proliferative angiopathy represent a related but distinct clinical and angiographic entity that may require a different therapeutic approach than traditional brain AVMs. The current management of children with other conditions of chronic cerebral hypoperfusion, such as moyamoya disease, involves consideration of surgical revascularization to enhance blood flow to the compromised hemisphere. Here, the authors present the case of a young child with a large thalamic vascular malformation who presented with clinical and radiological features of vascular steal and ischemia. In an effort to augment flow to the hypoperfused brain and protect against future ischemia, the authors treated the child with unilateral pial synangiosis. At 12 months, postoperative angiography demonstrated robust neovascularization, and the child has not sustained any further ischemic events. The authors discuss concept of vascular malformation–related hypoperfusion and the utility of indirect revascularization for inoperable vascular malformations presenting with ischemic symptoms.

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Relative contributions of the middle meningeal artery and superficial temporal artery in revascularization surgery for moyamoya syndrome in children: the results of superselective angiography

Clinical article

James A. J. King, Derek Armstrong, Shobhan Vachhrajani, and Peter B. Dirks

Object

The authors used postoperative superselective angiography to assess the relative contributions of the middle meningeal artery (MMA) and the superficial temporal artery (STA) to revascularization following surgery for moyamoya syndrome in children.

Methods

Using the neurosurgical database at the Hospital for Sick Children, the authors reviewed the clinical and pre- and postoperative angiographic records obtained in patients with moyamoya syndrome undergoing superselective angiography. Patients were 16 years of age or younger and were undergoing revascularization surgery for moyamoya syndrome during the study period. Lateral internal carotid artery, external carotid artery, STA, and MMA angiograms were analyzed in the late arterial phase to assess the relative contributions of the STA and MMA to overall revascularization as determined by the external carotid artery injection.

Results

The total moyamoya surgical revascularization experience at the Hospital for Sick Children over a 12-year period (May 1996–December 2008) comprised 33 patients (20 girls and 13 boys) undergoing a total of 50 craniotomies. A decision was made in 2001 to perform superselective angiography postoperatively in patients with moyamoya syndrome. Superselective angiography was identified to have been performed postoperatively in 12 patients and 18 treated hemispheres, and it demonstrated that the MMA contributed more significantly than the STA in 11 (61%) of the 18 hemispheres.

Seven patients were Asian, 3 patients had neurofibromatosis Type 1, 1 had Down syndrome, and 2 had no apparent risk factors (1 patient was Asian and had neurofibromatosis Type 1). Stroke had occurred in 58% of patients and transient ischemic attacks in 50% prior to surgery. Within the first 30 days of surgery, there were 2 episodes of stroke (11.7% per surgically treated hemisphere and 18.2% per patient). Seventy-eight percent of hemispheres surgically treated exhibited excellent revascularization (Matsushima Grade A) on follow-up angiography, and there were no strokes documented in any patients more than 1 month after surgery, in a long-term follow-up of mean 4.1 years.

Conclusions

The contributions of the MMA to revascularization after pial synangiosis for moyamoya syndrome are significant and may frequently exceed the contribution of the STA when surgery is performed with preservation of dural vasculature and dural inversion.

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Neurosurgical management of intracranial epidermoid tumors in children

Clinical article

Ibrahim Ahmed, Kurtis I. Auguste, Shobhan Vachhrajani, Peter B. Dirks, James M. Drake, and James T. Rutka

Object

Epidermoid tumors are benign lesions representing 1% of all intracranial tumors. There have been few pediatric series of intracranial epidermoid tumors reported previously. The authors present their experience in the management of these lesions.

Methods

The neurosurgical database at the Hospital for Sick Children was searched for children with surgically managed intracranial epidermoid tumors. The patients' charts were reviewed for demographic data, details of clinical presentation, surgical therapy, and follow-up. Ethics board approval was obtained for this study.

Results

Seven children, all girls, were identified who met the inclusion criteria between 1980 and 2007. The average age at surgery was 11.2 years (range 8–15 years), and the mean maximal tumor diameter was 2.1 cm. Headache was the most common presenting symptom, and 1 tumor was found incidentally. Most patients had normal neurological examinations, but meningism was found in 2 cases. There were 3 cerebellopontine angle lesions, 1 pontomedullary lesion, and 3 supratentorial tumors. Hydrocephalus developed in 1 patient after aseptic meningitis, and she underwent shunt placement. There were no operative deaths. Complete resection could be performed in 2 patients. One patient experienced a small recurrence that did not require a repeated operation, while 1 subtotally resected lesion recurred and the patient underwent a second operation.

Conclusions

Intracranial epidermoid tumors are rare in the pediatric population. Total resection is desirable to minimize the risk of postoperative aseptic meningitis, hydrocephalus, and tumor recurrence. Aggressive neurosurgical resection may be associated with cranial nerve or ischemic deficits, however. In these cases, neurosurgical judgment at the time of surgery is warranted to ensure maximum resection while minimizing postoperative neurological deficits.

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Imaging correlates of successful endoscopic third ventriculostomy

Abhaya V. Kulkarni, James M. Drake, Derek C. Armstrong, and Peter B. Dirks

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.

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Corticospinal tract mapping in children with ruptured arteriovenous malformations using functionally guided diffusion-tensor imaging

Report of 3 cases

Michael J. Ellis, James T. Rutka, Abhaya V. Kulkarni, Peter B. Dirks, and Elysa Widjaja

Arteriovenous malformations (AVMs) can lead to distortion or reorganization of functional brain anatomy, making localization of eloquent white matter tracts challenging. To improve the accuracy of corticospinal tract (CST) mapping, recent studies have examined the use of functional imaging techniques to help localize cortical motor activations and use these as seed points to reconstruct CSTs using diffusion-tensor imaging (DTI). The authors examined the role of pretreatment functionally guided DTI CST mapping in 3 children with ruptured AVMs. In 2 patients, magnetoencephalography motor activations were adjacent to the nidus and/or hemorrhagic cavity. However, in 1 child, functional MRI motor activations were detected in both hemispheres, suggestive of partial transfer of cortical motor function. In all children, quantitative analysis showed that fractional anisotropy values and fiber density indices were reduced in the CSTs of the hemisphere harboring the AVM compared with the unaffected side. In 2 children, CST caliber was slightly diminished, corresponding to no motor deficit in 1 patient and a temporary motor deficit in the other. In contrast, 1 child demonstrated marked reduction and displacement of the CSTs, correlating with severe motor deficit. Preoperative motor tractography data were loaded onto the intraoperative neuronavigation platform to guide complete resection of the AVM in 2 cases without permanent neurological deficits. These preliminary results confirm the feasibility of CST mapping in children with ruptured AVMs using functionally guided DTI tractography. Prospective studies are needed to assess the full value of this technique in the risk stratification, prognosis, and multimodality management of pediatric AVMs.

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Neurosurgical implications of osteogenesis imperfecta in children

Report of 4 cases

Deanna Sasaki-Adams, Abhaya Kulkarni, James Rutka, Peter Dirks, Michael Taylor, and James M. Drake

✓Osteogenesis imperfecta (OI) is a rare genetic disorder characterized by disruption of normal collagen formation resulting in varying degrees of skeletal vulnerability, ligamentous laxity, and scleral discoloration. Children with OI may suffer from complex neurosurgical problems affecting the brain and spine. The authors sought to determine the neurosurgical implications of OI in a cohort of patients treated at a quaternary care center for pediatrics.

The authors reviewed the case histories of 10 children with OI treated by the neurosurgical service at the Hospital for Sick Children in Toronto between January 1988 and March 2007. The cases of 4 of these children are highlighted in the article. The most common neurosurgical conditions encountered in this cohort included macrocephaly in 5 patients, subdural hematoma in 3 patients, epidural hematoma in 2 patients, and hydrocephalus in 3 patients. Basilar invagination and spinal fractures were observed in 20% of the cohort. Although some patients could be treated nonoperatively, several required craniotomy for clot evacuation, decompression, and spinal fixation for fracture or basilar invagination, and cerebrospinal fluid shunt insertion.

Neurosurgical conditions affecting patients with OI include macrocephaly, the development of an acute intracranial hematoma after often minimal trauma, the development of chronic subdural fluid collections that may require drainage, hydrocephalus (both communicating and noncommunicating), basilar invagination, and subaxial spinal fractures. Surgery may be complicated in some children because of the underlying bone fragility and bleeding diathesis commonly observed in patients with OI.

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Role of glial filaments in cells and tumors of glial origin: a review

James T. Rutka, Masaji Murakami, Peter B. Dirks, Sherri Lynn Hubbard, Laurence E. Becker, Kozo Fukuyama, Shin Jung, and Kazuhito Matsuzawa

In the adult human brain, normal astrocytes constitute nearly 40% of the total central nervous system (CNS) cell population and may assume a star-shaped configuration resembling epithelial cells insofar as the astrocytes remain intimately associated, through their cytoplasmic extensions, with the basement membrane of the capillary endothelial cells and the basal lamina of the glial limitans externa. Although their exact function remains unknown, in the past, astrocytes were thought to subserve an important supportive role for neurons, providing a favorable ionic environment, modulating extracellular levels of neurotransmitters, and serving as spacers that organize neurons. In immunohistochemical preparations, normal, reactive, and neoplastic astrocytes may be positively identified and distinguished from other CNS cell types by the expression of the astrocyte-specific intermediate filament glial fibrillary acidic protein (GFAP). This GFAP is a 50-kD intracytoplasmic filamentous protein that constitutes a portion of, and is specific for, the cytoskeleton of the astrocyte. This protein has proved to be the most specific marker for cells of astrocytic origin under normal and pathological conditions. Interestingly, with increasing astrocytic malignancy, there is progressive loss of GFAP production. As the human gene for GFAP has now been cloned and sequenced, this review begins with a summary of the molecular biology of GFAP including the proven utility of the GFAP promoter in targeting genes of interest to the CNS in transgenic animals. Based on the data provided the authors argue cogently for an expanded role of GFAP in complex cellular events such as cytoskeletal reorganization, maintenance of myelination, cell adhesion, and signaling pathways. As such, GFAP may not represent a mere mechanical integrator of cellular space, as has been previously thought. Rather, GFAP may provide docking sites for important kinases that recognize key cellular substrates that enable GFAP to form a dynamic continuum with microfilaments, integrin receptors, and the extracellular matrix.

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Role of glial filaments in cells and tumors of glial origin: a review

James T. Rutka, Masaji Murakami, Peter B. Dirks, Sherri Lynn Hubbard, Laurence E. Becker, Kozo Fukuyama, Shin Jung, Atsushi Tsugu, and Kazuhito Matsuzawa

✓ In the adult human brain, normal astrocytes constitute nearly 40% of the total central nervous system (CNS) cell population and may assume a star-shaped configuration resembling epithelial cells insofar as the astrocytes remain intimately associated, through their cytoplasmic extensions, with the basement membrane of the capillary endothelial cells and the basal lamina of the glial limitans externa. Although their exact function remains unknown, in the past, astrocytes were thought to subserve an important supportive role for neurons, providing a favorable ionic environment, modulating extracellular levels of neurotransmitters, and serving as spacers that organize neurons. In immunohistochemical preparations, normal, reactive, and neoplastic astrocytes may be positively identified and distinguished from other CNS cell types by the expression of the astrocyte-specific intermediate filament glial fibrillary acidic protein (GFAP). Glial fibrillary acidic protein is a 50-kD intracytoplasmic filamentous protein that constitutes a portion of, and is specific for, the cytoskeleton of the astrocyte. This protein has proved to be the most specific marker for cells of astrocytic origin under normal and pathological conditions. Interestingly, with increasing astrocytic malignancy, there is progressive loss of GFAP production. As the human gene for GFAP has now been cloned and sequenced, this review begins with a summary of the molecular biology of GFAP including the proven utility of the GFAP promoter in targeting genes of interest to the CNS in transgenic animals. Based on the data provided the authors argue cogently for an expanded role of GFAP in complex cellular events such as cytoskeletal reorganization, maintenance of myelination, cell adhesion, and signaling pathways. As such, GFAP may not represent a mere mechanical integrator of cellular space, as has been previously thought. Rather, GFAP may provide docking sites for important kinases that recognize key cellular substrates that enable GFAP to form a dynamic continuum with microfilaments, integrin receptors, and the extracellular matrix.