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Hiroshi Otsubo, Atsushi Shirasawa, Shiro Chitoku, James T. Rutka, Scott B. Wilson and O. Carter Snead III

✓ The purpose of this paper is to describe the use of computerized brain-surface voltage topographic mapping to localize and identify epileptic discharges recorded on electrocorticographic (ECoG) studies in which a subdural grid was used during intracranial video electroencephalographic (IVEEG) monitoring. The authors studied 12 children who underwent surgery for intractable extrahippocampal epilepsy. Cortical surfaces and subdural grid electrodes were photographed during the initial surgery to create an electrode map that could be superimposed onto a picture of the brain surface. Spikes were selected from ictal discharges recorded at the beginning of clinically confirmed seizures and from interictal discharges seen on ECoG studies during IVEEG recording. A computer program was used to calculate the sequential amplitude of the spikes by using squared interpolation, and they were then superimposed onto the electrode map. Interictal discharges and high-amplitude spike complexes at seizure onset were plotted on the map. This mapping procedure depicted the ictal zone in nine patients and the interictal zone in 12, and proved to be an accurate and useful source of information for planning corrective surgery.

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Zulma S. Tovar-Spinoza, Ayako Ochi, James T. Rutka, Cristina Go and Hiroshi Otsubo

Epilepsy surgery requires the precise localization of the epileptogenic zone and the anatomical localization of eloquent cortex so that these areas can be preserved during cortical resection. Magnetoencephalography (MEG) is a technique that maps interictal magnetic dipole sources onto MR imaging to produce a magnetic source image. Magneto-encephalographic spike sources can be used to localize the epileptogenic zone and be part of the workup of the patient for epilepsy surgery in conjunction with data derived from an analysis of seizure semiology, scalp video electroencephalography, PET, functional MR imaging, and neuropsychological testing. In addition, magnetoencephalographic spike sources can be linked to neuronavigation platforms for use in the neurosurgical field. Finally, paradigms have been developed so that MEG can be used to identify functional areas of the cerebral cortex including the somatosensory, motor, language, and visual evoked fields.

The authors review the basic principles of MEG and the utility of MEG for presurgical planning as well as intra-operative mapping and discuss future applications of MEG technology.

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Harold J. Hoffman, Hiroshi Otsubo, E. Bruce Hendrick, Robin P. Humphreys, James M. Drake, Laurence E. Becker, Mark Greenberg and Derek Jenkin

✓ All patients with confirmed intracranial germ-cell tumors treated at the Hospital of Sick Children during the period January, 1952, to December, 1989, were reviewed. Of the 51 tumors reviewed, 16 were located in the suprasellar region, 32 in the pineal region, and three in both the pineal and the suprasellar regions. Forty-nine patients underwent surgical resection which was total in seven and partial in 20, and consisted of a biopsy in 22. Two patients were managed on the basis of serum and cerebrospinal fluid markers. Surgical tools such as the operating microscope, the ultrasonic surgical aspirator, and the laser beam allowed safe debulking and removal of the deep-seated tumors in the pineal region. There were no operative deaths in the 36 patients treated since 1972, who included 23 with pineal tumors. Twenty-five patients with germinomas received radiotherapy and had a 5-year survival rate of 85.1%. Thirteen patients with non-germinoma germ-cell tumors received radiotherapy and had a 5-year survival rate of 45.5%. On the basis of this review, the authors recommend resection of pineal and suprasellar germ-cell tumors in order to firmly establish an accurate histological diagnosis to guide the extent of adjuvant therapy. In the case of a pure germinoma without evidence of dissemination, adjuvant therapy consists only of local radiotherapy. On the other hand, for malignant non-germinoma germ-cell tumors, adjuvant therapy must include chemotherapy as well as craniospinal axis radiotherapy.

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Chusak Limotai, Cristina Y. Go, Shiro Baba, Kazuo Okanari, Ayako Ochi, James T. Rutka, O. Carter Snead III and Hiroshi Otsubo

Infants with Sturge-Weber syndrome (SWS) are considered for surgery if they develop seizures and the seizures prove medically refractory. The authors report on 2 infants (15 and 19 months old) with SWS who underwent scalp video electroencephalography (EEG) and subsequent functional hemispherotomy for intractable partial motor seizures due to extensive left hemispheric angiomatosis. They presented with similar interictal and ictal EEG findings. Ictal EEG showed abrupt high-amplitude delta slow waves, without evolution on the contralateral hemisphere before the build-up of ictal EEG changes on the lesional hemisphere. The patients became seizure free after hemispherotomy. The ictal contralateral slow waves were not a sign of an ictal hemisphere and may indicate prominent ischemic changes resulting from a steal phenomenon of hemispheric angiomatosis during seizure.

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Jeffrey P. Blount, Wayne Langburt, Hiroshi Otsubo, Shiro Chitoku, Ayako Ochi, Shelly Weiss, O. Carter Snead and James T. Rutka

Object. The technique involved in multiple subpial transections (MSTs) allows the surgeon treating patients with epilepsy the capability to make disconnective lesions in epileptogenic regions of eloquent cortex. Although there have been increasing numbers of reports in adults of the efficacy and relative safety of this technique, there are relatively few such reports in children. The authors present their experience in 30 children who underwent MSTs during the surgical management of the seizure disorder.

Methods. Thirty consecutive children who underwent MSTs with or without cortical excision form the basis of this retrospective review. An analysis of neurological adverse effects following MSTs and seizure outcome was performed.

Between 1996 and 2000, MSTs were performed either as stand-alone therapy (four patients) or in conjunction with planned cortical excisions (26 patients). Twenty-three children underwent invasive monitoring after placement of subdural grid electrodes, and in seven intraoperative electrocorticography alone was performed. The mean follow-up period for the group was 3.5 years (minimum 30 months in all cases). All 20 patients in whom MSTs were performed in the primary motor cortex experienced transient hemiparesis (mild in 12 and moderate in eight) lasting up to 6 weeks; however, no patient suffered a permanent motor deficit in the long-term follow-up period. In 26 patients who underwent cortical resections followed by MSTs, 12 (46%) were seizure free (Engel Class I) following surgery. Eleven patients (42%) (Engel Classes II and III) continued to suffer seizures but improvement in seizure control was adequate following surgery. In the 23 patients in whom subdural grids were placed to capture the ictal onset zone by invasive video-electroencephalography, MSTs comprised a mean of 37% of the surgically treated area under the grid.

Conclusions. The results of this series demonstrate that MSTs can be performed with acceptable morbidity in children undergoing epilepsy surgery. The precise role of MSTs in controlling seizure frequency and outcome, especially when combined with planned cortical resections, awaits further study.

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Çagatay Önal, Hiroshi Otsubo, Takashi Araki, Shiro Chitoku, Ayako Ochi, Shelly Weiss, William Logan, Irene Elliott, O. Carter Snead III and James T. Rutka

Object. This study was performed to evaluate the complications of invasive subdural grid monitoring during epilepsy surgery in children.

Methods. The authors retrospectively reviewed the records of 35 consecutive children with intractable localization-related epilepsy who underwent invasive video electroencephalography (EEG) with subdural grid electrodes at The Hospital for Sick Children between 1996 and 2001. After subdural grid monitoring and identification of the epileptic regions, cortical excisions and/or multiple subpial transections (MSTs) were performed. Complications after these procedures were then categorized as either surgical or neurological.

There were 17 male and 18 female patients whose mean age was 11.7 years. The duration of epilepsy before surgery ranged from 2 to 17 years (mean 8.3 years). Fifteen children (43%) had previously undergone surgical procedures for epilepsy. The number of electrodes on the grids ranged from 40 to 117 (mean 95). During invasive video EEG, cerebrospinal fluid leaks occurred in seven patients. Also, cerebral edema (five patients), subdural hematoma (five patients), and intracerebral hematoma (three patients) were observed on postprocedural imaging studies but did not require surgical intervention. Hypertrophic scars on the scalp were observed in nine patients. There were three infections, including one case of osteomyelitis and two superficial wound infections. Blood loss and the amounts of subsequent transfusions correlated directly with the size and number of electrodes on the grids (p < 0.001). Twenty-eight children derived significant benefit from cortical resections and MSTs, with a more than 50% reduction of seizures and a mean follow-up period of 30 months.

Conclusions. The results of this study indicate that carefully selected pediatric patients with intractable epilepsy can benefit from subdural invasive monitoring procedures that entail definite but acceptable risks.

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Koji Iida, Hiroshi Otsubo, Yuuri Matsumoto, Ayako Ochi, Makoto Oishi, Stephanie Holowka, Elizabeth Pang, Irene Elliott, Shelly K. Weiss, Sylvester H. Chuang, O. Carter Snead III and James T. Rutka

Object

The authors sought to validate magnetoencephalography spike sources (MEGSSs) in neuronavigation during epilepsy surgery in pediatric patients.

Methods

The distributions of MEGSSs in 16 children were defined and classified as clusters (Class I), greater than or equal to 20 MEGSSs with 1 cm or less between MEGSSs; small clusters (Class II), 6 to 19 with 1 cm or less between; and scatters (Class III), less than 6 or greater than 1 cm between spike sources. Using neuronavigation, the MEGSSs were correlated to epileptic zones from intra- and extraoperative electrocorticography (ECoG), surgical procedures, disease entities, and seizure outcomes.

Thirteen patients underwent MEGSSs: nine had clusters; two had small clusters, one with and one without clusters; and three had scatters alone. All 13 had scatters. Clusters localized within and extended from areas of cortical dysplasia and at margins of tumors or cystic lesions. All clusters were colocalized to ECoG-defined epileptic zones. Four of six patients with clusters and/or small clusters underwent complete excisions, and two underwent partial excision with or without multiple subpial transections. In the three patients with scatters alone, ECoG revealed epileptic zones buried within MEGSS areas; these regions of scatters were completely excised and treated with multiple subpial transections. Coexisting scatters were left untreated in nine of 10 patients. Postoperatively, nine of 13 patients were seizure free; the four patients with residual seizures had clusters in unresected eloquent cortex. Three patients in whom no MEGSSs were demonstrated underwent lesionectomies and were seizure free.

Conclusions

Magnetoencephalography spike source clusters indicate an epileptic zone requiring complete excision. Coexisting scatters remote from clusters are nonepileptogenic and do not require excision. Scatters alone, however, should be examined by ECoG; an epileptic zone may exist within these distributions.

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Hiroshi Hosoyama, Kazumi Matsuda, Tadahiro Mihara, Naotaka Usui, Koichi Baba, Yushi Inoue, Takayasu Tottori, Toshiaki Otsubo, Yumi Kashida, Koji Iida, Hirofumi Hirano, Ryosuke Hanaya and Kazunori Arita

OBJECTIVE

The aim of this study was to investigate the treatment outcomes and social engagement of patients who had undergone pediatric epilepsy surgery more than 10 years earlier.

METHODS

Between 1983 and 2005, 110 patients younger than 16 years underwent epilepsy surgery at the National Epilepsy Center, Shizuoka Institute of Epilepsy and Neurological Disorders. The authors sent a questionnaire to 103 patients who had undergone follow-up for more than 10 years after surgery; 85 patients (82.5%) responded. The survey contained 4 categories: seizure outcome, use of antiepileptic drugs, social participation, and general satisfaction with the surgical treatment (resection of the epileptic focus, including 4 hemispherectomies). The mean patient age at the time of surgery was 9.8 ± 4.2 (SD) years, and the mean duration of postoperative follow-up was 15.4 ± 5.0 years. Of the 85 patients, 79 (92.9%) presented with a lesional pathology, such as medial temporal sclerosis, developmental/neoplastic lesions, focal cortical dysplasia, and gliosis in a single lobe.

RESULTS

For 65 of the 85 responders (76.5%), the outcome was recorded as Engel Class I (including 15 [93.8%] of 16 patients with medial temporal sclerosis, 20 [80.0%] of 25 with developmental/neoplastic lesions, and 27 [73.0%] of 37 with focal cortical dysplasia). Of these, 29 (44.6%) were not taking antiepileptic drugs at the time of our survey, 29 (44.6%) held full-time jobs, and 33 of 59 patients (55.9%) eligible to drive had a driver's license. Among 73 patients who reported their degree of satisfaction, 58 (79.5%) were very satisfied with the treatment outcome.

CONCLUSIONS

The seizure outcome in patients who underwent resective surgery in childhood and underwent followup for more than 10 years was good. Of 85 respondents, 65 (76.5%) were classified in Engel Class I. The degree of social engagement was relatively high, and the satisfaction level with the treatment outcome was also high. From the perspective of seizure control and social adaptation, resective surgery yielded longitudinal benefits in children with intractable epilepsy, especially those with a lesional pathology in a single lobe.

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Koji Iida, Hiroshi Otsubo, Yuuri Matsumoto, Ayako Ochi, Makoto Oishi, Stephanie Holowka, Elizabeth Pang, Irene Elliott, Shelly K. Weiss, Sylvester H. Chuang, O. Carter Snead III and James T. Rutka

Object. The authors sought to validate magnetoencephalography spike sources (MEGSSs) in neuronavigation during epilepsy surgery in pediatric patients.

Methods. The distributions of MEGSSs in 16 children were defined and classified as clusters (Class I), greater than or equal to 20 MEGSSs with 1 cm or less between MEGSSs; small clusters (Class II), 6 to 19 with 1 cm or less between; and scatters (Class III), less than 6 or greater than 1 cm between spike sources. Using neuronavigation, the MEGSSs were correlated to epileptic zones from intra- and extraoperative electrocorticography (ECoG), surgical procedures, disease entities, and seizure outcomes.

Thirteen patients underwent MEGSSs: nine had clusters; two had small clusters, one with and one without clusters; and three had scatters alone. All 13 had scatters. Clusters localized within and extended from areas of cortical dysplasia and at margins of tumors or cystic lesions. All clusters were colocalized to ECoG-defined epileptic zones. Four of six patients with clusters and/or small clusters underwent complete excisions, and two underwent partial excision with or without multiple subpial transections. In the three patients with scatters alone, ECoG revealed epileptic zones buried within MEGSS areas; these regions of scatters were completely excised and treated with multiple subpial transections. Coexisting scatters were left untreated in nine of 10 patients. Postoperatively, nine of 13 patients were seizure free; the four patients with residual seizures had clusters in unresected eloquent cortex. Three patients in whom no MEGSSs were demonstrated underwent lesionectomies and were seizure free.

Conclusions. Magnetoencephalography spike source clusters indicate an epileptic zone requiring complete excision. Coexisting scatters remote from clusters are nonepileptogenic and do not require excision. Scatters alone, however, should be examined by ECoG; an epileptic zone may exist within these distributions.

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Cristina V. Torres, Aria Fallah, George M. Ibrahim, Samuel Cheshier, Hiroshi Otsubo, Ayako Ochi, Sylvester Chuang, O. Carter Snead, Stephanie Holowka and James T. Rutka

Object

Hemispherectomy is an established neurosurgical procedure for medication-resistant epilepsy in children. Despite the effectiveness of this technique, there are patients who do not achieve an optimum outcome after surgery; possible causes of suboptimal results include the presence of bilateral independent epileptogenic foci. Magnetoencephalography (MEG) is an emerging tool that has been found to be useful in the management of lesional and nonlesional epilepsy. The authors analyzed the relative contribution of MEG in patient selection for hemispherectomy.

Methods

The medical records of children undergoing hemispherectomy at the Hospital for Sick Children were reviewed. Those patients who underwent MEG as part of the presurgical evaluation were selected.

Results

Thirteen patients were included in the study. Nine patients were boys. The mean age at the time of surgery was 66 months (range 10–149 months). Seizure etiology was Rasmussen encephalitis in 6 patients, hemimegalencephaly in 2 patients, and cortical dysplasia in 4 patients. In 8 patients, video-EEG and MEG results were consistent to localize the primary epileptogenic hemisphere. In 2 patients, video-EEG lateralized the ictal onset, but MEG showed bilateral spikes. Two patients had bilateral video-EEG and MEG spikes. Engel Class I, II, and IV outcomes were seen in 10, 2, and 1 patients, respectively. In 2 of the patients who had an outcome other than Engel Class I, the MEG clusters were concentrated in the disconnected hemisphere. The third patient had bilateral clusters and potentially independent epileptogenic foci from bilateral cortical dysplasia.

Conclusions

The presence of unilateral MEG spike waves correlated with good outcomes following hemispherectomy. In some cases, MEG provides information that differs from that obtained from video-EEG and conventional MR imaging studies. Further studies with a greater number of patients are needed to assess the role of MEG in the preoperative assessment of candidates for hemispherectomy.