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Gregory W. Albert, George M. Ibrahim, Hiroshi Otsubo, Ayako Ochi, Cristina Y. Go, O. Carter Snead III, James M. Drake, and James T. Rutka

Object

Resective surgery is increasingly used in the management of pediatric epilepsy. Frequently, invasive monitoring with subdural electrodes is required to adequately map the epileptogenic focus. The risks of invasive monitoring include the need for 2 operations, infection, and CSF leak. The aim of this study was to evaluate the feasibility and outcomes of resective epilepsy surgery guided by magnetoencephalography (MEG) in children who would have otherwise been candidates for electrode implantation.

Methods

The authors reviewed the records of patients undergoing resective epilepsy surgery at the Hospital for Sick Children between 2001 and 2010. They identified cases in which resections were based on MEG data and no intracranial recordings were performed. Each patient's chart was reviewed for presentation, MRI findings, MEG findings, surgical procedure, pathology, and surgical outcome.

Results

Sixteen patients qualified for the study. All patients had localized spike clusters on MEG and most had abnormal findings on MRI. Resection was carried out in each case based on the MEG data linked to neuronavigation and supplemented with intraoperative neuromonitoring. Overall, 62.5% of patients were seizure free following surgery, and 20% of patients experienced an improvement in seizures without attaining seizure freedom. In 2 cases, additional surgery was performed subsequently with intracranial monitoring in attempts to obtain seizure control.

Conclusions

MEG is a viable alternative to invasive monitoring with intracranial electrodes for planning of resective surgery in carefully selected pediatric patients with localization-related epilepsy. Good candidates for this approach include patients who have a well-delineated, localized spike cluster on MEG that is concordant with findings of other preoperative evaluations and patients with prior brain pathologies that make the implantation of subdural and depth electrodes somewhat problematic.

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Ibrahim H. Al-Ahmed, Mohamed Boughamoura, Peter Dirks, Abhaya V. Kulkarni, James T. Rutka, and James M. Drake

Object

Neurenteric cysts (NCs) are endothelium-lined structures of presumed endodermal origin. There have been few pediatric series of intracranial NCs reported previously. The authors present their experience in the management of these lesions.

Methods

A retrospective chart review of all cases of NCs identified between 1977 and 2007 was carried out. Demographics, details of clinical presentation, surgical therapy, and outcome data were extracted.

Results

Eleven cases were identified, involving 6 girls and 5 boys. The patients' average age was 4.6 years (range 1 day–14 years). Limb weakness was the most common presenting symptom. The location of the cysts was cervical in 2 cases, cervicothoracic in 4 cases, and thoracic in 3 cases. One cyst was anterior to the pons with extension to the left cerebellopontine angle and 1 cyst was at the craniocervical junction. Five patients had an apparently complete initial excision, with 1 recurrence. Four patients were initially treated with incomplete excision and/or cyst drainage, usually into an Ommaya reservoir. A neonate with a large cervicothoracic cyst died of multiple congenital anomalies without any intervention. All other patients were alive at last follow-up. One patient with a radiologically identified presumed cyst, which remained stable, was simply followed up. Several patients required multiple procedures and 1 patient developed hydrocephalus after aseptic meningitis and was treated with CSF shunting.

Conclusions

Neurenteric cysts are rare in the pediatric population. Total resection, if possible, provides the best long-term outcome. Incomplete excision may lead to multiple procedures, including cyst drainage, but can lead to long-term stability.

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George M. Ibrahim, Benjamin W. Barry, Aria Fallah, O. Carter Snead III, James M. Drake, James T. Rutka, and Mark Bernstein

Epilepsy is a common childhood condition associated with a considerable medical and psychosocial burden. Children in whom medical treatment fails to reduce seizure burden represent an especially vulnerable patient population because prolonged, uncontrolled seizures are associated with poor developmental and neurocognitive outcomes. Surgical treatment in the form of cortical resection, functional disconnection, or neuromodulation may alleviate or significantly reduce the disease burden for a subset of these patients. However, there remains a dichotomy between the perceived benefits of surgery and the implementation of surgical strategies in the management of medically intractable epilepsy. The current paper presents an analysis of the bioethical implications of existing inequities in access to pediatric epilepsy surgery that result from inconsistent referral practices and discrepant evaluation techniques. The authors provide a basic bioethical framework composed of 5 primary expectations to inform public, institutional, and personal policies toward the provision of epilepsy surgery to afflicted children.

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Sanjay Gupta, Shobhan Vachhrajani, Abhaya V. Kulkarni, Michael D. Taylor, Peter Dirks, James M. Drake, and James T. Rutka

Object

Extraaxial infections of the CNS, including subdural empyema and epidural abscess, are rare but potentially life-threatening conditions. Symptoms are usually progressive, and early diagnosis is therefore important. Early intervention with appropriate treatment offers the best opportunity for eradicating the infection and promoting maximal neurological recovery.

Methods

The medical records of children with extraaxial CNS infection over the last 24 years at the Hospital for Sick Children were analyzed. Only those patients with radiological and/or operative confirmation of the diagnosis of subdural empyema or epidural abscess were included in the study. Demographic and clinical data were collected to determine the outcomes after such infections and factors that predict for such outcomes.

Results

The authors identified 70 children who fulfilled the inclusion criteria. Sinusitis was the most common etiology and was seen in 38 patients. All of these patients were older than 7 years of age at diagnosis. Subdural empyemas were diagnosed in 13 patients following bacterial meningitis, and they were found primarily in infants within the 1st year of life. Other etiological factors included otogenic infection (4 cases), postneurosurgical infection (7 cases), and hematogenous spread of infection (7 cases including 6 cases of spinal epidural abscess). Streptococcus anginosus and Staphylococcus aureus were the most common pathogens identified. Sixty-four patients (91.4%) underwent at least 1 neurosurgical procedure. Seizures and cerebral edema from cortical vein thrombosis were the most common complications.

Conclusions

Due to variable etiology, identification of the responsible microorganism through neurosurgical drainage followed by long-term intravenous antibiotics remains the mainstay in treating extraaxial CNS infections. Optimal outcome is achieved with early diagnosis and therapy.

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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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Ichiro Sugiyama, Katsumi Imai, Yu Yamaguchi, Ayako Ochi, Yoko Akizuki, Cristina Go, Tomoyuki Akiyama, O. Carter Snead III, James T. Rutka, James M. Drake, Elysa Widjaja, Sylvester H. Chuang, Doug Cheyne, and Hiroshi Otsubo

Object

Magnetoencephalography (MEG) has been typically used to localize epileptic activity by modeling interictal activity as equivalent current dipoles (ECDs). Synthetic aperture magnetometry (SAM) is a recently developed adaptive spatial filtering algorithm for MEG that provides some advantages over the ECD approach. The SAM-kurtosis algorithm (also known as SAM[g2]) additionally provides automated temporal detection of spike sources by using excess kurtosis value (steepness of epileptic spike on virtual sensors). To evaluate the efficacy of the SAM(g2) method, the authors applied it to readings obtained in children with intractable epilepsy secondary to tuberous sclerosis complex (TSC), and compared them to localizations obtained with ECDs.

Methods

The authors studied 13 children with TSC (7 girls) whose ages ranged from 13 months to 16.3 years (mean 7.3 years). Video electroencephalography, MR imaging, and MEG studies were analyzed. A single ECD model was applied to localize ECD clusters. The SAM(g2) value was calculated at each SAM(g2) virtual voxel in the patient's MR imaging–defined brain volume. The authors defined the epileptic voxels of SAM(g2) (evSAM[g2]) as those with local peak kurtosis values higher than half of the maximum. A clustering of ECDs had to contain ≥ 6 ECDs within 1 cm of each other, and a grouping of evSAM(g2)s had to contain ≥ 3 evSAM(g2)s within 1 cm of each other. The authors then compared both ECD clusters and evSAM(g2) groups with the resection area and correlated these data with seizure outcome.

Results

Seizures started when patients were between 6 weeks and 8 years of age (median 6 months), and became intractable secondary to multiple tubers in all cases. Ictal onset on scalp video electroencephalography was lateralized in 8 patients (62%). The MEG studies showed multiple ECD clusters in 7 patients (54%). The SAM(g2) method showed multiple groups of epileptic voxels in 8 patients (62%). Colocalization of grouped evSAM(g2) with ECD clusters ranged from 20 to 100%, with a mean of 82%. Eight patients underwent resection of single (1 patient) and multiple (7 patients) lobes, with 6 patients achieving freedom from seizures. Of 8 patients who underwent surgery, in 7 the resection area covered ECD clusters and grouped evSAM(g2)s. In the remaining patient the resection area partially included the ECD cluster and grouped evSAM(g2)s. Six of the 7 patients became seizure free.

Conclusions

The combination of SAM(g2) and ECD analyses succeeded in localizing the complex epileptic zones in children with TSC who had intractable epilepsy secondary to multiple cortical tubers. For the subset of children with TSC who present with early-onset and nonlateralized seizures, MEG studies in which SAM(g2) and ECD are used might identify suitable candidates for resection to control seizures.

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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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Editorial

Achondroplasia

Arnold H. Menezes

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James A. J. King, Shobhan Vachhrajani, James M. Drake, and James T. Rutka

Object

Achondroplasia is the most common form of human short-limbed dwarfism. The pediatric neurosurgeon is frequently required to treat children with achondroplasia who have hydrocephalus, cervicomedullary compression (CMD), and spinal canal stenosis. Accordingly, the authors have reviewed the experience of neurosurgery in children with achondroplasia at The Hospital for Sick Children.

Methods

The medical records and neurosurgery database at The Hospital for Sick Children were searched to identify all children with achondroplasia who underwent at least 1 neurosurgical procedure between 1956 and the present.

Results

Twenty-nine children with achondroplasia underwent 85 surgical procedures: 52 for CSF diversion in 12 patients, 20 for CMD in 18 patients, 8 for spinal disorders in 4 patients, and 5 for miscellaneous purposes in 4 patients. The CSF shunts were placed almost exclusively before 1990 and were associated with a significant number of complications. Patients undergoing CMD did very well, with only 1 patient failing to improve clinically.

Conclusions

This review provides a historical perspective on the evolution of treatment of pediatric patients with achondroplasia. The use of CSF diversion procedures, formerly fraught with complications, is now rare following the realization of the natural history of CSF space enlargement in these patients. Cervicomedullary compression is more commonly recognized due to better imaging. Central apnea is now better detected by routine sleep studies. Spine surgery, although rare, requires evaluation of both spinal stenosis and instability. These patients are best evaluated by a multidisciplinary team.