Shelly K Weiss

SickKids, Toronto, Ontario, Canada

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Publications (32)90.57 Total impact

  • Article: Neurosurgical management of frontal lobe epilepsy in children.
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    ABSTRACT: Pediatric frontal lobe epilepsy (FLE) remains a challenging condition for neurosurgeons and epileptologists to manage. Postoperative seizure outcomes remain far inferior to those observed in temporal lobe epilepsies, possibly due to inherent difficulties in delineating and subsequently completely resecting responsible epileptogenic regions. In this study, the authors review their institutional experience with the surgical management of FLE and attempt to find predictors that may help to improve seizure outcome in this population. All surgically treated cases of intractable FLE from 1990 to 2008 were reviewed. Demographic information, preoperative and intraoperative imaging and electrophysiological investigations, and follow-up seizure outcome were assessed. Inferential statistics were performed to look for potential predictors of seizure outcome. Forty patients (20 male, 20 female) underwent surgical management of FLE during the study period. Patients were an average of 5.6 years old at the time of FLE onset and 11.7 years at the time of surgery; patients were followed for a mean of 40.25 months. Most patients displayed typical FLE semiology. Twenty-eight patients had discrete lesions identified on MRI. Eight patients underwent 2 operations. Cortical dysplasia was the most common pathological diagnosis. Engel Class I outcome was obtained in 25 patients (62.5%), while Engel Class II outcome was observed in 5 patients (12.5%). No statistically significant predictors of outcome were found. Control of FLE remains a challenging problem. Favorable seizure outcome, obtained in 62% of patients in this series, is still not as easily obtained in FLE as it is in temporal lobe epilepsy. While no statistically significant predictors of seizure outcome were revealed in this study, patients with FLE continue to require extensive workup and investigation to arrive at a logical and comprehensive neurosurgical treatment plan. Future studies with improved neuroimaging and advanced invasive monitoring strategies may well help define factors for success in this form of epilepsy that is difficult to control.
    Journal of Neurosurgery Pediatrics 07/2012; 10(3):206-16. · 1.53 Impact Factor
  • Article: Focal resection of fast ripples on extraoperative intracranial EEG improves seizure outcome in pediatric epilepsy.
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    ABSTRACT: High-frequency oscillations (HFOs), termed ripples at 80-200 Hz and fast ripples (FRs) at >200/250 Hz, recorded by intracranial electroencephalography (EEG), may be a valuable surrogate marker for the localization of the epileptogenic zone. We evaluated the relationship of the resection of focal brain regions containing high-rate interictal HFOs and the seizure-onset zone (SOZ) determined by visual EEG analysis with the postsurgical seizure outcome, using extraoperative intracranial EEG monitoring in pediatric patients and automated HFO detection. We retrospectively analyzed 28 pediatric epilepsy patients who underwent extraoperative intracranial video-EEG monitoring prior to focal resection. Utilizing the automated analysis, we identified interictal HFOs during 20 min of sleep EEG and determined the brain regions containing high-rate HFOs. We investigated spatial relationships between regions with high-rate HFOs and SOZs. We compared the size of these regions, the surgical resection, and the amount of the regions with high-rate HFOs/SOZs within the resection area with seizure outcome. Ten patients were completely seizure-free and 18 were not at 2 years after surgery. The brain regions with high-rate ripples were larger than those with high-rate FRs (p = 0.0011) with partial overlap. More complete resection of the regions with high-rate FRs significantly correlated with a better seizure outcome (p = 0.046). More complete resection of the regions with high-rate ripples tended to improve seizure outcome (p = 0.091); however, the resection of SOZ did not influence seizure outcome (p = 0.18). The size of surgical resection was not associated with seizure outcome (p = 0.22-0.39). The interictal high-rate FRs are a possible surrogate marker of the epileptogenic zone. Interictal ripples are not as specific a marker of the epileptogenic zone as interictal FRs. Resection of the brain regions with high-rate interictal FRs in addition to the SOZ may achieve a better seizure outcome.
    Epilepsia 07/2011; 52(10):1802-11. · 3.96 Impact Factor
  • Article: Pharmacotherapy in pediatric sleep disorders.
    Shelly K Weiss, Andrea Garbutt
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    ABSTRACT: Sleep disorders are highly prevalent during childhood and adolescence. It is known that if left untreated, these problems can have significant impact on daytime function, including learning, memory, attention, and behavior. The approach to the treatment of these disorders (whether with or without pharmacotherapy) is dependent on a thorough evaluation of the sleep complaint and determination of an accurate diagnosis. Many pediatric sleep problems are due to insomnia. There is good evidence that young children with behaviorally based insomnia respond to appropriate behavioral interventions. There is less research evidence of the efficacy of these interventions in children who are either school age or adolescents; however, nonpharmacologic strategies are usually indicated initially in the approach to treatment. The indication for the use of pharmacotherapy in pediatric insomnia is not well understood; however, some general principles are described when medications may be considered. There are specific sleep disorders (other than insomnia) for which pharmacotherapy plus behavioral strategies are warranted. The research regarding pharmacotherapy in pediatric sleep disorders is limited; often, medications are used "off label" based on data extrapolated from adult studies. Clinicians who suggest over-the-counter treatments or prescribe medications for pediatric patients with sleep disorders should have an understanding of the classification of sleep disorders and the role of pharmacotherapy in the treatment of these disorders. In this chapter, the emphasis is on the pharmacologic treatment of sleep disorders in typically developing children and adolescents.
    Adolescent medicine: state of the art reviews 12/2010; 21(3):508-21, ix-x.
  • Article: Topographic movie of intracranial ictal high‐frequency oscillations with seizure semiology: Epileptic network in Jacksonian seizures
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    ABSTRACT: Purpose:  We developed a technique to produce images of dynamic changes in ictal high-frequency oscillations (HFOs) >40 Hz recorded on subdural electroencephalography (EEG) that are time-locked to the ictal EEG and ictal semiology video. We applied this technique to Jacksonian seizures to demonstrate ictal HFO propagation along the homunculus in the primary sensory-motor cortex to visualize the underlying epileptic network.Methods:  We analyzed intracranial ictal EEGs from two patients with intractable Jacksonian seizures who underwent epilepsy surgery. We calculated the degrees of increase in amplitude within 40–80, 80–200, and 200–300 Hz frequency bands compared to the interictal period and converted them into topographic movies projected onto the brain surface picture. We combined these data with the ictal EEGs and video of the patient demonstrating ictal semiology.Key Findings:  The ictal HFOs began in the sensory cortex and appeared concomitantly with the sensory aura. They then propagated to the motor cortex at the same time that focal motor symptoms evolved. As the seizure progressed, the ictal HFOs spread or reverberated in the rolandic region. However, even when the seizure became secondarily generalized, the ictal HFOs were confined to the rolandic region. In both cases, there was increased amplitude of higher frequency bands during seizure initiation compared to seizure progression.Significance:  This combined movie showed the ictal HFO propagation corresponding to the ictal semiology in Jacksonian seizures and revealed the epileptic network involved in seizure initiation and progression. This method may advance understanding of neural network activities relating to clinical seizure generation and propagation.
    Epilepsia 11/2010; 52(1):75 - 83. · 3.96 Impact Factor
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    Article: Topographic movie of intracranial ictal high-frequency oscillations with seizure semiology: epileptic network in Jacksonian seizures.
    [show abstract] [hide abstract]
    ABSTRACT: We developed a technique to produce images of dynamic changes in ictal high-frequency oscillations (HFOs) >40 Hz recorded on subdural electroencephalography (EEG) that are time-locked to the ictal EEG and ictal semiology video. We applied this technique to Jacksonian seizures to demonstrate ictal HFO propagation along the homunculus in the primary sensory-motor cortex to visualize the underlying epileptic network. We analyzed intracranial ictal EEGs from two patients with intractable Jacksonian seizures who underwent epilepsy surgery. We calculated the degrees of increase in amplitude within 40-80, 80-200, and 200-300 Hz frequency bands compared to the interictal period and converted them into topographic movies projected onto the brain surface picture. We combined these data with the ictal EEGs and video of the patient demonstrating ictal semiology. The ictal HFOs began in the sensory cortex and appeared concomitantly with the sensory aura. They then propagated to the motor cortex at the same time that focal motor symptoms evolved. As the seizure progressed, the ictal HFOs spread or reverberated in the rolandic region. However, even when the seizure became secondarily generalized, the ictal HFOs were confined to the rolandic region. In both cases, there was increased amplitude of higher frequency bands during seizure initiation compared to seizure progression. This combined movie showed the ictal HFO propagation corresponding to the ictal semiology in Jacksonian seizures and revealed the epileptic network involved in seizure initiation and progression. This method may advance understanding of neural network activities relating to clinical seizure generation and propagation.
    Epilepsia 11/2010; 52(1):75-83. · 3.96 Impact Factor
  • Article: Pathology type does not predict language lateralization in children with medically intractable epilepsy.
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    ABSTRACT: We examined potential differences in the effects of pathology type on language lateralization in pediatric epilepsy. We examined findings from intracarotid sodium amobarbital procedure (IAP/Wada) in a large consecutive sample of children with refractory epilepsy. Subjects were assigned to one of three pathology groups: developmental (n = 28), acquired (n = 26), and tumor (n = 20); groups were compared for language lateralization. Rates of atypical language lateralization did not differ across groups. Greater than half of the subjects with left hemisphere insults and seizure onset before 6 years of age had atypical language lateralization, independent of pathology type. Atypical language lateralization may occur in the context of developmental, acquired, and/or tumor pathology.
    Epilepsia 03/2009; 50(6):1498-504. · 3.96 Impact Factor
  • Article: Long-term seizure and social outcomes following temporal lobe surgery for intractable epilepsy during childhood.
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    ABSTRACT: Studies of adults who underwent temporal lobectomy for intractable temporal lobe epilepsy (TLE) demonstrated declining seizure free rates over time. Using seizure and social parameters, we followed patients who had temporal lobe surgery (TLS) in childhood to determine long-term outcomes. We identified 42 patients who underwent TLS for medically intractable epilepsy during childhood. Follow-up data were collected from 10 to 20 years after surgery (median, 12 years). We studied histopathology, seizure outcome, employment, school enrolment, and driver's licensing. Patients or parents graded their satisfaction with TLS. Number of Engel class I patients was 34 (81%) after 6 months; 32 (76%) after 1 year; 30 (71%) after 5 years; and 28 (67%) at last >or=10 years follow-up. Nineteen (79%) of 24 children with tumors or cavernous angioma achieved class I outcomes in contrast to 9 (50%) of 18 children with other pathologies (p<0.05). Ten (56%) of 18 recurrent seizure patients experienced seizures within the first year; 4 required reoperation for seizure freedom. More seizure free patients (24, 86%) than residual seizure patients (8, 57%) were employed or in school (p=0.05). Twelve (63%) of 19 eligible patients obtained driver's licenses. Twenty-three (82%) of 28 seizure free patients discontinued anticonvulsants. Surgery grading averaged "satisfied." Class I patients reported greater satisfaction than class III/IV patients (p<0.001). Two-thirds of children who underwent TLS achieved seizure freedom at >or=10 year follow-up. Children with tumors or cavernous angiomas achieved better long-term outcomes than those with other histopathologies. Long-term seizure free patients were most often satisfied with surgery and employed or in school.
    Epilepsy research 10/2008; 82(2-3):133-8. · 2.48 Impact Factor
  • Article: Contrast sensitivity is reduced in children with infantile spasms.
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    ABSTRACT: To investigate whether visual deficits in children with infantile spasm (IS) are the result of seizure activity or of treatment with the anticonvulsant drug vigabatrin (VGB). Vision function was determined in three experiments by determining peak contrast sensitivity (CS) and grating acuity (GA) with the sweep visual evoked potential. Cross-sectional study A: 34 children, including 11 patients with childhood epilepsy with exposure to VGB for at least 6 months, 10 with childhood epilepsy exposed to antiepileptic drugs other than VGB, and 13 normally developing children. Cross-sectional study B: 32 children, including 16 with IS naïve to VGB and 16 normally developing children. Longitudinal study: seven children with IS naïve to VGB, with subsequent follow-up 5 to 10 months after starting VGB. In cross-sectional study A, the median CS was reduced by 0.5 log units (P = 0.025) in children with epilepsy exposed to VGB compared with those exposed to other antiepileptic drugs and normally developing children. In cross-sectional study B, the median CS was reduced by 0.25 log units (P = 0.0015) in children with IS (VGB naïve) compared with normally developing children. Longitudinal assessment showed no decrease in CS in children with IS who were followed up 5 to 10 months after starting VGB. There was no difference in GA among groups in any of the experiments. Patients with IS have CS deficits, but a sparing of GA. This deficit is present before VGB treatment and does not worsen with treatment onset. Results suggest that visual dysfunction is largely the result of the seizures themselves.
    Investigative Ophthalmology &amp Visual Science 09/2007; 48(8):3610-5. · 3.60 Impact Factor
  • Article: Intrahemispheric reorganization of language in children with medically intractable epilepsy of the left hemisphere.
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    ABSTRACT: We investigated language representation in nine children (six male, three female; 5.6-17.7 years of age) who underwent surgical treatment of medically intractable epilepsy of the left hemisphere. Although interhemispheric reorganization has been previously documented in similar groups, this is the first study to systematically evaluate possible intrahemispheric effects of early insult. All cases had left hemisphere seizure foci and underwent extraoperative stimulation mapping (ESM) for language localization prior to receiving cortical resections. To compare ESM findings across subjects and to assess intrahemispheric reorganization, we developed a novel coregistration technique whereby independent raters plotted two-dimensional (2D) ESM findings in 3D standard space. Expressive language sites identified with ESM were compared with a structural probability map of pars opercularis, or Broca's area. The average difference between independent raters' estimates of 28 language sites was 3.9 mm (SD = 2.0), indicating excellent agreement; the coregistration procedure permitted assessment of 2D ESM findings in 3D standard space. We observed language sites in regions substantially anterior and superior to canonical Broca's area, possibly reflecting intrahemispheric reorganization. Findings suggest that left hemisphere insult in young children may result in anterior displacement of language within the frontal cortex.
    Journal of the International Neuropsychological Society 06/2007; 13(3):505-16. · 2.76 Impact Factor
  • Article: MEG predicts outcome following surgery for intractable epilepsy in children with normal or nonfocal MRI findings.
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    ABSTRACT: To identify the predictors of postsurgical seizure freedom in children with refractory epilepsy and normal or nonfocal MRI findings. We analyzed 22 children with normal or subtle and nonfocal MRI findings, who underwent surgery for intractable epilepsy following extraoperative intracranial EEG. We compared clinical profiles, neurophysiological data (scalp EEG, magnetoencephalography (MEG) and intracranial EEG), completeness of surgical resection and pathology to postoperative seizure outcomes. Seventeen children (77%) had a good postsurgical outcome (defined as Engel class IIIA or better), which included eight (36%) seizure-free children. All children with postsurgical seizure freedom had an MEG cluster in the final resection area. Postsurgical seizure freedom was obtained in none of the children who had bilateral MEG dipole clusters (3) or only scattered dipoles (1). All five children in whom ictal onset zones were confined to < or = 5 adjacent intracranial electrodes achieved seizure freedom compared to three of 17 children with ictal onset zones that extended over >5 electrodes (p = 0.002). None of six children with more than one type of seizure became seizure-free, compared to eight of 16 children with a single seizure type (p = 0.04). Complete resection of the preoperatively localized epileptogenic zone resulted in seizure remission in 63% (5/8) and incomplete resections, in 21% (3/14) (p = 0.06). Age of onset, duration of epilepsy, number of lobes involved in resection, and pathology failed to correlate with seizure freedom. Surgery for intractable epilepsy in children with normal MRI findings provided good postsurgical outcomes in the majority of our patients. As well, restricted ictal onset zone predicted postoperative seizure freedom. Postoperative seizure freedom was less likely to occur in children with bilateral MEG dipole clusters or only scattered dipoles, multiple seizure types and incomplete resection of the proposed epileptogenic zone. Seizure freedom was most likely to occur when there was concordance between EEG and MEG localization and least likely to occur when these results were divergent.
    Epilepsia 02/2007; 48(1):149-57. · 3.96 Impact Factor
  • Article: Temporal lobe surgery for intractable epilepsy in children: an analysis of outcomes in 126 children.
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    ABSTRACT: Temporal lobectomy is a well-established neurosurgical procedure for temporal lobe epilepsy. In this study, we conducted a retrospective review of children with drug-resistant temporal lobe epilepsy to evaluate seizure outcome after temporal lobe surgery. We reviewed the medical records of 126 children who had surgery for temporal lobe epilepsy at The Hospital for Sick Children between 1983 and 2003. The records were examined for preoperative and intraoperative factors that could predict patient outcome after surgery. The mean age at seizure onset was 5.9 years. The mean seizure duration before surgery was 5.6 years. All patients had preoperative computed tomographic scans, magnetic resonance imaging scans, or both. The mean age at the time of surgery was 13.5 years. Sixty-two patients underwent left temporal resections and 64 patients underwent right temporal resections. The histopathology of the temporal resections revealed low-grade brain tumors in 65 children (52%) and cavernous malformations in four children. Ganglioglioma and astrocytoma were the most common tumors encountered. Mesial temporal sclerosis was found in 16 patients (13%), astrogliosis in 15 patients (12%), and cortical dysplasia in eight patients (7%). Postoperative follow-up of at least 2 years was available for 106 patients and ranged up to 13.0 years. Seventy-four percent of patients had an Engel Class I or II outcome. Patients with temporal lobe lesions had better outcomes compared with those without lesions (P < 0.05). Patients without a history of secondary generalization of seizures also had a better outcome when compared with those with secondary generalization. Complications in the form of contralateral homonymous hemianopsia, dysphasia, and infection were found in 5% of patients. Twelve patients had a second temporal lobe procedure for intractable recurrent seizures. After a second procedure, seven patients returned to a seizure-free state. Temporal lobe resections for epilepsy in children are effective and safe procedures, with a favorable impact on seizure control. Repeat temporal resections for recurrent seizures may also be effective in restoring a seizure-free outcome to children.
    Neurosurgery 01/2007; 59(6):1203-13; discussion 1213-4. · 2.79 Impact Factor
  • Article: Topographic movie of ictal high-frequency oscillations on the brain surface using subdural EEG in neocortical epilepsy.
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    ABSTRACT: To understand the rapid dynamic changes of ictal intracranial high-frequency oscillations (HFOs) in neocortical epilepsy. We integrated multiple band frequency analysis and brain-surface topographic maps of HFOs from ictal subdural EEG (SDEEG) recordings. We used SDEEG to record partial seizures consisting of right-arm jerks with secondary generalization in a 17-year-old right-handed girl. We selected 20-s EEG sections that included preclinical seizure recordings. We averaged the HFO power between 60 and 120 Hz for 25 selected electrodes, made topographic maps from these averaged powers, and superimposed the maps on the brain-surface image. We filmed consecutive HFO maps at a 10-ms frame rate. Before clinical seizure onset, high-power HFOs emerged at the superior portion of the left precentral gyrus, then appeared in the middle of the left postcentral gyrus, and subsequently reverberated between both regions as well as the posterior portion of the left postcentral gyrus. Right-arm extension and facial grimacing started as the HFO power decreased. As generalized tonic-clonic seizures evolved, HFO power increased but remained within the central region. Topographic movies of intracranial HFOs on the brain surface allow visualization of the dynamic ictal changes in neocortical epilepsy.
    Epilepsia 12/2006; 47(11):1953-7. · 3.96 Impact Factor
  • Article: Topographic Movie of Ictal High‐Frequency Oscillations on the Brain Surface Using Subdural EEG in Neocortical Epilepsy
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    ABSTRACT:  Purpose: To understand the rapid dynamic changes of ictal intracranial high-frequency oscillations (HFOs) in neocortical epilepsy.Methods: We integrated multiple band frequency analysis and brain-surface topographic maps of HFOs from ictal subdural EEG (SDEEG) recordings. We used SDEEG to record partial seizures consisting of right-arm jerks with secondary generalization in a 17-year-old right-handed girl. We selected 20-s EEG sections that included preclinical seizure recordings. We averaged the HFO power between 60 and 120 Hz for 25 selected electrodes, made topographic maps from these averaged powers, and superimposed the maps on the brain-surface image. We filmed consecutive HFO maps at a 10-ms frame rate.Results: Before clinical seizure onset, high-power HFOs emerged at the superior portion of the left precentral gyrus, then appeared in the middle of the left postcentral gyrus, and subsequently reverberated between both regions as well as the posterior portion of the left postcentral gyrus. Right-arm extension and facial grimacing started as the HFO power decreased. As generalized tonic–clonic seizures evolved, HFO power increased but remained within the central region.Conclusions: Topographic movies of intracranial HFOs on the brain surface allow visualization of the dynamic ictal changes in neocortical epilepsy.
    Epilepsia 10/2006; 47(11):1953 - 1957. · 3.96 Impact Factor
  • Article: Preoperative simulation of intracerebral epileptiform discharges: synthetic aperture magnetometry virtual sensor analysis of interictal magnetoencephalography data.
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    ABSTRACT: Magnetoencephalography (MEG) has been used for the preoperative localization of epileptic equivalent current dipoles (ECDs) in neocortical epilepsy. Spatial filtering can be applied to MEG data by means of synthetic aperture magnetometry (SAM), and SAM virtual sensor analysis can be used to estimate the strength and temporal course of the epileptic source in the region of interest. To evaluate the clinical usefulness of this approach, the authors compare the results of SAM virtual sensor analysis to the results of ECD analysis, subdural electroencephalography (EEG) findings, and surgical outcomes in pediatric patients with neocortical epilepsy. Ten pediatric patients underwent MEG, invasive subdural EEG, and cortical resection for neocortical epilepsy. The authors compared the morphological characteristics, quantity, location, and distribution of the epileptiform discharges assessed using SAM and ECD analysis, and subdural EEG findings (interictal discharges and ictal onset zones). In nine patients, MEG revealed clustered ECDs. The region exhibiting the maximum percentage (> or = 70%) of spikes/sharp waves on SAM was colocalized to clustered ECDs in seven patients. In six patients, SAM demonstrated focal spikes; in two, diffuse spikes; and in two others, focal rhythmic sharp waves. These epileptiform discharges were similar to those recorded on subdural EEG. In nine patients, concordant regions containing the maximum percentage of spikes/sharp waves were revealed by SAM and subdural EEG data. The region of the maximum percentage of spikes/sharp waves as demonstrated by SAM was colocalized to the ictal onset zone identified by subdural EEG findings in seven patients and partially colocalized in two. The SAM virtual sensor analysis revealed morphological characteristics, location, and distribution of epileptiform discharges similar to those shown by subdural EEG recordings. By using SAM it is possible to predict intracerebral interictal epileptiform discharges in the region of interest from noninvasively collected preoperative MEG data. The maximum interictal discharge zone identified by SAM virtual sensors correlated to clustered ECDs and the ictal onset zone on subdural EEG findings. Complementary analyses of ECDs and SAM on three-dimensional MR images can improve delineation of epileptogenic zones and lesions in neocortical epilepsy.
    Journal of Neurosurgery 07/2006; 105(1 Suppl):41-9. · 2.96 Impact Factor
  • Article: Efficacy of dexamathasone on cerebral swelling and seizures during subdural grid EEG recording in children.
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    ABSTRACT: To evaluate the impact of steroid treatment on cerebral swelling and seizures during subdural grid EEG (SGEEG) monitoring. We reviewed data from 37 pediatric patients with intractable epilepsy who underwent SGEEG monitoring and divided the patients into those who received dexamethasone and those who did not. We then correlated administration of steroids to incidence of cerebral swelling on computed tomography (CT) scans and to frequency of seizures during SGEEG. Twenty-three patients received dexamethasone prophylactically every 6 hours (dosage range, 1-7.5 mg; mean, 3.2 mg) from the first day of SGEEG placement (group A); 14 patients received no dexamethasone (group B). Eight (21.6%) of 37 patients experienced cerebral swelling on CT: two (9%) were in group A, and six (42.9%) were in group B (p < 0.05). SGEEG monitoring time for recording habitual seizures that localized cortical areas for surgical excision was longer in group A (1-6 days; mean, 3.0) than it was in group B (1-3 days; mean, 2.2), (p < 0.05). Habitual seizures were recorded in 36 patients. One group A patient experienced obtundation due to cerebral swelling, and monitoring in this patient was discontinued. The prophylactic administration of steroids to pediatric patients during SGEEG monitoring is efficacious for reducing cerebral swelling. Although it decreases the frequency of habitual seizures and increases seizure-monitoring time, dexamethasone reduces the risk of complications from cerebral swelling during the SGEEG procedure.
    Epilepsia 02/2006; 47(1):176-80. · 3.96 Impact Factor
  • Article: Focal cortical high-frequency oscillations trigger epileptic spasms: confirmation by digital video subdural EEG.
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    ABSTRACT: To localize high-frequency oscillations (HFOs) on the cortex during epileptic spasms using video subdural EEG and Multiple Band Frequency Analysis (MBFA). Using video subdural EEG sampled at 1 kHz, we studied a 14-year-old boy with asymmetric epileptic spasms of possible left frontal origin. We identified HFOs, then analyzed and localized their distributions by MBFA. We correlated HFO distribution to clinical spasm intensity. Ictal subdural EEG recorded HFOs at 60-150 Hz lasting 0.3-4 s. MBFA showed extensive but noncontiguous distribution of HFOs predominantly over the left frontal and temporal regions. HFOs began and became quasiperiodic before manifestation of clinical spasms. As clinical spasms intensified, HFOs persisted in regions where they initiated subclinically but were of higher frequency and greater power than HFOs in other regions. We performed cortical resections over the left frontal and temporal regions with predominant HFOs. Six months after surgery, the patient remained seizure free. HFOs were present over the ictal onset zone during epileptic spasms. Periodic spasms in this patient had the characteristics of partial seizures. We show that HFOs occurred over the cerebral cortex during epileptic spasms, and we suggest that these focal cortical HFOs triggered the spasms.
    Clinical Neurophysiology 01/2006; 116(12):2819-25. · 3.41 Impact Factor
  • Article: Partial seizures triggering infantile spasms in the presence of a basal ganglia glioma.
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    ABSTRACT: Infantile spasms associated with brain tumors have been reported. A focal cortical lesion can induce infantile spasms by triggering the brainstem and basal ganglia in this vulnerable age group. We report the case of a female infant with a low-grade glioma in the right basal ganglia, spreading to the cortical area. She presented at the age of five months with left hemiparesis and partial seizures. She developed infantile spasms at the age of 12 months. This is the first video clip report of partial seizures triggering symmetrical spasms in series, secondary to a basal ganglia glioma extending to the cortex. [Published with video sequences].
    Epileptic disorders: international epilepsy journal with videotape 01/2006; 7(4):378-82. · 1.50 Impact Factor
  • Article: The prevalence of autistic spectrum disorder in children surveyed in a tertiary care epilepsy clinic.
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    ABSTRACT: It is well documented that children with autistic spectrum disorder (ASD) have an increased prevalence of seizures; however, studies have not been done to evaluate the prevalence of ASD in children with epilepsy. This comorbidity is important to define as early diagnosis and intervention in some children with ASD has been shown to improve outcome. Children with epilepsy seen in a tertiary care epilepsy clinic were evaluated using validated autism screening questionnaires (ASQ). In addition, questions about sleep-related disorders, behavior, seizure characteristics, antiepileptic agents, and body mass index (BMI) were requested. An attempt was then made to determine if there was a correlation between the factors identified and ASD. Of the 107 questionnaires returned, 97 ASQ's were properly completed and used in this study. Approximately 32% of children fit the ASQ criteria for having ASD. Most children had not been previously diagnosed. Worst behavior and daytime sleepiness was seen in those at greater risk (p < 0.01). Seizures also occurred earlier (approximately 2 years) in children at risk of having ASD. Though confirmatory diagnostic evaluations are needed, this questionnaire-based study suggests that children with epilepsy are at greater risk of having ASD, and illustrates the need for more clinical vigilance. Behavioral difficulties and daytime sleepiness identified in these children could potentially affect their ability to learn. It is of interest that the age of seizure onset identified in those at greater risk corresponds with the approximate age of regression identified in some children with ASD.
    Epilepsia 12/2005; 46(12):1970-7. · 3.96 Impact Factor
  • Article: Identifying the primary epileptogenic hemisphere from electroencephalographic (EEG) and magnetoencephalographic dipole lateralizations in children with intractable epilepsy.
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    ABSTRACT: We used electroencephalographic (EEG) and magnetoencephalographic dipole lateralizations to identify the primary epileptogenic hemisphere in 41 children with intractable localization-related epilepsy. We compared EEG and magnetoencephalographic dipole lateralizations, EEG ictal onsets, and magnetic resonance images (MRIs). Concordant lateralization of EEG and magnetoencephalographic dipoles (> 50% of each lateralizing to the same hemisphere) occurred in 34 patients, with EEG ictal onsets in the same hemisphere in 23 (68%) and concordant MRI lesions in 23 (68%). Focal resection in 16 of 20 patients resulted in a good surgical outcome. Of the seven children with nonconcordant magnetoencephalographic and EEG lateralizations, one (14%) had EEG ictal onset and one (14%) had MRI lesions that lateralized; none had surgery. The relationship between lateralized EEG and magnetoencephalographic dipoles forecasts surgical candidacy. Concordant lateralizations predict good seizure control after surgery by identifying the primary epileptogenic hemisphere. Discordant lateralizations signify an undetermined epileptogenic hemisphere and contraindicate surgery without further testing.
    Journal of Child Neurology 12/2005; 20(11):885-92. · 1.75 Impact Factor
  • Article: A reappraisal of rhythmic coma patterns in children.
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    ABSTRACT: This study was designed to determine the prevalence of rhythmic coma patterns in comatose children and to ascertain the prognostic significance of reactive rhythmic coma patterns. We retrospectively analyzed and classified electroencephalogram (EEGs) in comatose children between two months and 18 years of age during the period 1996 - 2003 according to modified Young's classification. Outcome at one-year was scored according to the Paediatric Cerebral and Overall Performance Category Scale. Outcomes were compared using Fisher's exact test and Mann-Whitney test. Analysis of 63 electroencephalogram (EEG) records in 38 patients showed rhythmic patterns in 19 records (30.2%; 9 alpha, 4 spindle, 4 theta and 2 beta coma patterns, total number of children = 14). Aetiology and outcome of alpha coma patterns and other rhythmic coma patterns were similar. In five children, one type of rhythmic pattern changed to another. Records with reactive rhythmic coma 66.7% (6/9), were associated with favourable outcome. Sixty percent of the records (6/10 records in seven children) with non-reactive pattern were associated with unfavourable outcome. This clinically significant difference did not reach statistical significance (lower Paediatric Cerebral and Overall Performance Category Scale score p= 0.14; favourable outcome p=0. 19). Rhythmic coma patterns in comatose children are not uncommon. Aetiology, reactivity and outcome of individual patterns are similar and thus make the rhythmic coma patterns distinct EEG signatures in comatose children. There was a clinically significant better outcome with reactive rhythmic coma patterns.
    The Canadian journal of neurological sciences. Le journal canadien des sciences neurologiques 12/2005; 32(4):518-23. · 0.97 Impact Factor

Institutions

  • 2002–2012
    • SickKids
      • • Division of Neurology
      • • Division of Neurosurgery
      Toronto, Ontario, Canada
  • 2010
    • KK Women's and Children's Hospital
      Singapore, Singapore
    • University of Toronto
      • Hospital for Sick Children
      Toronto, Ontario, Canada
  • 2005
    • The University of Tennessee Health Science Center
      • Department of Neurology
      Memphis, TN, USA