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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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Michael J. Ellis, Abhaya V. Kulkarni, James M. Drake, James T. Rutka, Derek Armstrong and Peter B. Dirks

Object

Confirming the successful management of pediatric arteriovenous malformations (AVMs) requires high-quality postoperative digital subtraction angiography. Although the role of intraoperative angiography during the microsurgical removal of AVMs is well established in adults, the technique has several limitations including poor image quality, uniplanar image acquisition, and absent full heparin protection. Here, the authors report on their experience with high-quality intraoperative angiography during the surgical management of pediatric AVMs in their image-guided therapy (IGT) facility.

Methods

The authors retrospectively reviewed the demographic, clinical, and radiological characteristics of 22 patients who underwent the surgical management of AVMs at the Hospital for Sick Children in Toronto, with the aid of high-quality intraoperative or immediate postresection cerebral angiography via a transfemoral approach.

Results

Between January 2000 and August 2009, 18 children (mean age 13.05 ± 4.04 years, range 4–21 years) underwent both surgical management of an AVM and intraoperative cerebral angiography at an IGT facility. An additional 4 children underwent angiography immediately after surgery in the regular operating room while under the same anesthesia. The mean AVM size was 2.55 ± 1.43 cm (range 1–6 cm) with a mean Spetzler-Martin grade of 2.27 (range 1–4). Intraoperative angiography in 4 of the 18 patients demonstrated residual AVM requiring additional resection. One patient demonstrated residual AVM on immediate postoperative angiography and underwent immediate reoperation. Successful excision of the residual AVM was confirmed on angiography the following day in that case. Procedural complications occurred in connection with 1 (3.3%) of 30 angiograms, including asymptomatic transient nonfilling of an ophthalmic artery, which was resolved on follow-up angiography. Negative intraoperative angiograms were confirmed with follow-up angiograms in 15 (93.75%) of 16 patients at a mean of 9.93 ± 5.70 months. One patient with a negative intraoperative angiogram demonstrated a tiny residual AVM on follow-up angiography at 8 months (false-negative rate 6.25%), but had a negative preoperative angiogram 1 year later in the IGT facility. No patient with a negative intraoperative angiogram required further AVM-directed treatment.

Conclusions

Intraoperative angiography is a safe and effective adjunct to the surgical management of AVMs in children. This novel approach allows the pre-, intra-, and postoperative acquisition of high-quality images, which can help guide the resection of AVMs, especially those that are small, diffuse, or of a complex angioarchitecture.

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Ratan D. Bhardwaj, Kurtis I. Auguste, Abhaya V. Kulkarni, Peter B. Dirks, James M. Drake and James T. Rutka

Object

Because of their location and biological behavior, brainstem cavernous malformations (CMs) pose a formidable clinical challenge to the neurosurgeon. The optimal management of these lesions requires considerable neurosurgical judgment. Accordingly, the authors reviewed their experience with the management of pediatric brainstem CMs at the Hospital for Sick Children.

Methods

The authors performed a retrospective chart review of pediatric patients who had received diagnoses of a brainstem CM at the Hospital for Sick Children over the past 20 years.

Results

Twenty patients were diagnosed with brainstem CMs. The mean age at diagnosis was 10.1 ± 5.4 years, and the patients included 13 boys and 7 girls. The mean maximal diameter of the CM was 14.3 ± 11.2 mm. The lesions were evenly distributed on the right and left sides of the brainstem with 4 midbrain, 13 pontine, and 3 medullary lesions. Seven patients underwent surgery for the management of their CMs, with a mean age at presentation of 5.2 years, and a mean CM size of 21.0 mm. Of note from the surgical group, 2 patients had a family history of CMs, 2 lesions were medullary, the CM reached a pial surface in 6 of 7 patients, and 6 of 7 lesions were located on the right side. The mean age at presentation among the 13 patients in the nonsurgical group was 12.7 years, and the mean CM size was 10.6 mm. Seven of these patients had a prior history of radiation for tumor, and only 3 had lesions that reached a pial surface.

Conclusions

The management of brainstem CMs in children is influenced by multiple factors. The majority of patients received conservative management and tended to be asymptomatic with smaller lesions. Patients with larger lesions and direct pial contact, in whom symptoms arose at a younger age were more likely to undergo surgical management. A history of familial CM was also a predictor for receiving surgical treatment. No patients with a prior history of radiation therapy underwent surgery for CMs. The presence of multiple lesions seemed to have no impact on the type of management chosen. Patients who underwent surgery did suffer morbidity related to the procedure, and tended to improve clinically over time. Conservative management was associated with new deficits arising in children, some of which improved with time. Consideration of many clinical and radiological parameters is thus prudent when managing the care of children with brainstem CMs.

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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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Benjamin W. Y. Lo, Abhaya V. Kulkarni, James T. Rutka, Andrew Jea, James M. Drake, Maria Lamberti-Pasculli, Peter B. Dirks and Lehana Thabane

Object

Cephaloceles represent primary axial mesodermal defects, occurring in 0.8–4 per 10,000 live births. Prior studies have reported posterior location, hydrocephalus, microcephaly, seizure, and presence of brain tissue as poor prognostic markers for neurological outcome. However, these studies were small and the results were analyzed using univariate tests. The purpose of this study was to investigate the potential risk factors for the occurrence of developmental delay in patients with cephaloceles, using both univariate and multivariable regression techniques.

Methods

This is a retrospective cohort study of cephalocele cases treated at the Hospital for Sick Children between 1990 and 2006. Two independent investigators collected the data from the Hospital for Sick Children Encephalocele Database and hospital charts. Developmental assessments were made by general pediatricians and neuropsychologists. Both univariate analysis (α = 0.10) and multivariable logistic regression analysis (α = 0.05) were performed.

Results

Eighty-five cases of cephaloceles were identified. The patient group consisted of 48 boys and 37 girls. Sixty-eight lesions were encephaloceles and 17 were meningoceles. The distribution was as follows: frontal (40 lesions), occipital (33), and parietal (12). Associated conditions included hydrocephalus (23), seizure disorder (17), microcephaly (6), corpus callosal abnormalities (15), heterotopias (9), cerebral dysgenesis (11), and myelomeningocele (1). Evaluation of long-term development revealed that 41 patients (48%) had normal development, 9 (11%) had mild delay, 14 (16%) had moderate delay, and 21 (25%) had severe delay. Hydrocephalus, seizure disorder, microcephaly, presence of associated intracranial abnormalities, and presence of brain tissue were significantly associated with poor outcome on univariate analysis. Multivariable analysis revealed hydrocephalus and presence of intracranial abnormalities to be statistically significant predictors of developmental delay.

Conclusions

To the authors' knowledge, this is one of the largest North American cephalocele series documented. Unlike prior studies, location of the cephaloceles is not a significant predictor of outcome. The multivariable regression analysis demonstrates hydrocephalus and the presence of associated intracranial abnormalities as variables with cumulative predictive effects for developmental delay.

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Andrew Jea, Michael D. Taylor, Peter B. Dirks, Abhaya V. Kulkarni, James T. Rutka and James M. Drake

✓The authors describe the novel use of C-1 lateral mass screws in four children 8 years of age or younger, in whom occipitocervical or atlantoaxial fusion was performed for trauma or os odontoideum. The authors retrospectively reviewed the demographics and procedural data of four children, ranging in age from 2 to 8 years, who required and underwent surgical fixation. Although C1–2 screw/rod constructs involving individual C-1 lateral mass screws and C-2 pars interarticularis or pedicle screws have been widely applied in adults, only C1–2 transarticular screw fixation has been reported in children less than 8 years of age. This report demonstrates the successful results of rigid occipitocervical and atlantoaxial fusion in four children in whom C-1 lateral mass screws were placed as part of a screw/rod construct. There was one instance of a vertebral artery injury, and the lessons learned from this complication are discussed.

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Douglas L. Brockmeyer

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Abhaya V. Kulkarni, James M. Drake, Doron Rabin, Peter B. Dirks, Robin P. Humphreys and James T. Rutka

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. An exploratory analysis was performed using a multivariate analysis of variance (ANOVA) to determine which variables might be associated with worse health status.

The mothers of 80 children, ranging in age from 5 to 17 years, participated in the study. The mean HOQ Overall Health score was 0.68, a value estimated to be equivalent to a mean health utility score of 0.77. The global health ratings provided by the mothers and the surgeons were moderately correlated with the HOQ scores (Pearson correlations 0.58 and 0.57, respectively). Results of the multivariate ANOVA indicated that the presence of epilepsy was strongly associated with a worse health status (p < 0.0001, F-test).

Conclusions. The health status of a typical sample of children with hydrocephalus was measured using the HOQ. The only consistently significant association with health status found was the presence of epilepsy.

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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.

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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.