Transorbital penetrating head injury with a favorable outcome: illustrative case.

BACKGROUND: Transorbital penetrating head injuries (PHIs) are uncommon but can lead to substantial deficits, depending on intracranial involvement and the neuroanatomical structures affected. Complete recovery after such injuries is rare. OBSERVATIONS: A 7-year-old boy sustained a PHI when he fell onto a garden spike while climbing a fence. Initial imaging showed an orbital roof fracture, focal subarachnoid hemorrhage, and an intraparenchymal hemorrhage in the right frontal lobe with associated linear tract extending to the contralateral superior temporal gyrus. Relevant neuroanatomical structures, including the anterior cerebral arteries (ACAs) and the basal ganglia, were spared. This is in keeping with superior transorbital PHI caused by a garden spike, which had transgressed the skull entering from the right superior orbit. Clinically, he experienced some transient right-sided weakness and mild speech disturbance. Some questionable vasospasm of the ACAs observed on interim magnetic resonance imaging was absent in a repeat imaging study, followed by an unremarkable radiographic follow-up at 6 months after injury. At 18 months after injury, he is neurologically intact without deficit. LESSONS: Most PHIs bear serious lifelong consequences, but here was a case of a deep, penetrating object that managed to avoid all significant neuroanatomical pathways, leading to complete recovery in follow-up.

Predicting Maximal Costal Cartilage Graft Size for Laryngotracheal Reconstruction.

OBJECTIVES/HYPOTHESIS: Current methods of assessing rib cartilage dimensions for laryngotracheal reconstruction (LTR) are inexact, making surgical planning difficult. The purpose of this study was to determine the most appropriate rib for costal cartilage graft LTR to minimize the number of ribs harvested and improve surgical outcomes. STUDY DESIGN: Retrospective review. METHODS: Computed tomography imaging of chest scans in 25 children aged 1 to 18 years was evaluated. The lengths and widths of medial and lateral cartilaginous segments of ribs 4 to 7 were measured bilaterally. Right and left cartilaginous rib dimensions were compared using a two-sample t-test. Linear mixed-effect regression was performed to develop models quantifying the relationship between rib size and patient height, rib side, and rib number. RESULTS: Regression analysis established strong models for medial rib length (R2  = 0.89) and for medial and lateral rib width (R2  = 0.71, 0.77, respectively). There was no difference in rib dimensions across chest sides. Rib length and width increased with child height. Total cartilaginous rib length increased from superiorly to inferiorly, primarily due to an increase in the dimensions of the medial portion of each rib. CONCLUSION: Cartilaginous rib lengths and widths were associated with patient height, with taller children having longer ribs. Inferior ribs were longer than superior ribs, suggesting that inferior ribs may be preferred for LTR. There was no difference in cartilaginous rib length across chest side. Results may help surgeons with preoperative planning. LEVEL OF EVIDENCE: NA Laryngoscope, 132:1682-1686, 2022.

Connectomic Profiling Identifies Responders to Vagus Nerve Stimulation.

OBJECTIVE: Vagus nerve stimulation (VNS) is a common treatment for medically intractable epilepsy, but response rates are highly variable, with no preoperative means of identifying good candidates. This study aimed to predict VNS response using structural and functional connectomic profiling. METHODS: Fifty-six children, comprising discovery (n = 38) and validation (n = 18) cohorts, were recruited from 3 separate institutions. Diffusion tensor imaging was used to identify group differences in white matter microstructure, which in turn informed beamforming of resting-state magnetoencephalography recordings. The results were used to generate a support vector machine learning classifier, which was independently validated. This algorithm was compared to a second classifier generated using 31 clinical covariates. RESULTS: Treatment responders demonstrated greater fractional anisotropy in left thalamocortical, limbic, and association fibers, as well as greater connectivity in a functional network encompassing left thalamic, insular, and temporal nodes (p < 0.05). The resulting classifier demonstrated 89.5% accuracy and area under the receiver operating characteristic (ROC) curve of 0.93 on 10-fold cross-validation. In the external validation cohort, this model demonstrated an accuracy of 83.3%, with a sensitivity of 85.7% and specificity of 75.0%. This was significantly superior to predictions using clinical covariates alone, which exhibited an area under the ROC curve of 0.57 (p < 0.008). INTERPRETATION: This study provides the first multi-institutional, multimodal connectomic prediction algorithm for VNS, and provides new insights into its mechanism of action. Reliable identification of VNS responders is critical to mitigate surgical risks for children who may not benefit, and to ensure cost-effective allocation of health care resources. ANN NEUROL 2019;86:743-753.

Utility of depth electrode placement in the neurosurgical management of bottom-of-sulcus lesions: technical note.

OBJECTIVE: Small lesions at the depth of the sulcus, such as with bottom-of-sulcus focal cortical dysplasia, are not visible from the surface of the brain and can therefore be technically challenging to resect. In this technical note, the authors describe their method of using depth electrodes as landmarks for the subsequent resection of these exacting lesions. METHODS: A retrospective review was performed on pediatric patients who had undergone invasive electroencephalography with depth electrodes that were subsequently used as guides for resection in the period between July 2015 and June 2017. RESULTS: Ten patients (3-15 years old) met the criteria for this study. At the same time as invasive subdural grid and/or strip insertion, between 2 and 4 depth electrodes were placed using a hand-held frameless neuronavigation technique. Of the total 28 depth electrodes inserted, all were found within the targeted locations on postoperative imaging. There was 1 patient in whom an asymptomatic subarachnoid hemorrhage was demonstrated on postprocedural imaging. Depth electrodes aided in target identification in all 10 cases. CONCLUSIONS: Depth electrodes placed at the time of invasive intracranial electrode implantation can be used to help localize, target, and resect primary zones of epileptogenesis caused by bottom-of-sulcus lesions.

Easing anxiety in preparation for pediatric magnetic resonance imaging: a pilot study using animal-assisted therapy.

BACKGROUND: Children undergoing magnetic resonance imaging (MRI) can experience negative emotions both before and during their scan, causing them to move and often necessitating the use of procedural sedation. Several strategies to improve patient compliance have been attempted. OBJECTIVE: This study was designed to evaluate the effectiveness of a non-pharmacological intervention to reduce anxiety in pediatric patients preparing for MRI using animal-assisted therapy. MATERIALS AND METHODS: An animal intervention pilot study was performed in patients who agreed in advance to interact with a dog. Patients and caregivers filled out questionnaires, including questions designed to capture changes in patient emotion before and after the intervention. MRI diagnostic quality was compared to age- and gender-matched control groups with and without general anesthesia. RESULTS: The intervention in 21 patients comparing pre- and post-scan surveys demonstrated a statistically significant improvement in patient anxiety levels (P<0.01). Diagnostic MRI scans were achieved in 19/21 (90%), with no significant difference in exam quality or times compared against control groups. The majority of caregivers and staff members agreed strongly that patients benefited from the therapy dog's presence. CONCLUSION: The use of animal-assisted therapy in a pilot group in our MRI division resulted in a beneficial effect on patients' emotional status, easing anxiety in preparation for scheduled scans, without impacting MRI quality or duration. Further randomized studies will be needed to demonstrate its significance in reducing sedation rates in children undergoing MRI.

Practical considerations for establishing and maintaining a magnetic resonance imaging safety program in a pediatric practice.

Magnetic resonance imaging is a multipurpose imaging modality that is largely safe, given the lack of ionizing radiation. However there are electromagnetic and biological effects on human tissue when exposed to magnetic environments, and hence there is a risk of adverse events occurring with these exams. It is imperative to understand these risks and develop methods to minimize them and prevent consequent adverse events. Implementing these safety practices in pediatric MR imaging has been somewhat limited because of gaps in information and knowledge among the personnel who are closely involved in the MR environment. The American College of Radiology has provided guidelines on MR safety practices that are helpful in minimizing such adverse events. This article provides an overview of the issues related to MR safety and practical ways to implement them across different health care facilities.

Use and Safety of Gadolinium Based Contrast Agents in Pediatric MR Imaging.

Gadolinium-based contrast agents (GBCA) used for MR imaging are a valuable imaging resource that has benefited patient management over last three decades and largely have a high safety profile. However, recently, adverse effects related to GBCA like nephrogenic systemic fibrosis (NSF) and asymptomatic gadolinium deposition in tissues including brain are concerning. While NSF has largely stopped occurring due to precautions and guidelines to not use GBCA in patients with poor renal function, the long term effects of gadolinium deposition, especially in brain, are not known at this stage. Cautious approach needs to be taken with risk-benefit analysis in each patient to avoid its administration when not necessary. In this review, authors discuss basics of gadolinium, mechanism of enhancement, agents in clinical use and safety issues, and in the end, offer some solutions for safety concerns.

Remote MEG dipoles in focal cortical dysplasia at bottom of sulcus.

OBJECTIVE: To investigate whether the magnetoencephalography (MEG) single moving dipole (SMD) method could delineate the epileptic zone of focal cortical dysplasia (FCD) at the bottom of sulcus (FCDB). METHODS: We retrospectively analyzed 17 children (11 male; mean age 8.8 years, range 3-17 years) with FCD type II who underwent epilepsy surgery. We compared spatial congruence between the following: (1) MEG cluster and FCDB and (2) MEG cluster and FCD at the brain surface (FCDS). We measured the volume and depth of magnetic resonance imaging (MRI)-visible lesions to investigate whether they affect spatial congruence between MEG cluster and MRI-visible lesion. RESULTS: Eight children had FCDB and the other nine children had FCDS. The volume of MRI-visible lesions for FCDB ranged from 1,632 to 4,707 mm(3) (mean ± standard deviation [SD] 3,095 ± 1,211 mm(3) ). The depth of FCDB ranged from 19 to 33 mm (mean ± SD 26 ± 4 mm). The volume of MRI-visible lesion for FCDS ranged from 2,375 to 57,331 mm(3) (15,470 ± 18,455 mm(3) ). There was a tendency for a smaller volume of MRI-visible lesion for FCDB, relative to FCDS(p = 0.079). In FCDB, six children showed clusters of MEG dipoles and two children showed scattered MEG dipoles for interictal spikes. The spatial congruence between the MEG result and FCDB was partially overlapping in four children and discordant in another four children. In FCDS, eight children had MEG cluster and one child had MEG scatter alone. The spatial congruence between MEG result and FCDS was overlapping in eight of nine children (fully two; partially six) and discordant in one of nine children. Fifteen children (88%; FCDB eight; FCDS seven) became seizure-free after resective surgery. MEG spike dipole resection ratio in the cluster ranged from 4-100% (mean 67%) in 6 FCDB and 23-99% (mean 77%) in 8 FCDS. SIGNIFICANCE: The SMD method may drift MEG spike dipoles for FCDB. Lesionectomy can control seizures for four of eight patients in FCDB despite the remote MEG dipoles. The FCDB or FCDS partially overlapped with MEG cluster may have an extending/invisible epileptogenic zone consecutive to the MRI-visible lesion.

Utility of diffusion tensor imaging studies linked to neuronavigation and other modalities in repeat hemispherotomy for intractable epilepsy.

OBJECT Hemispherectomy for unilateral, medically refractory epilepsy is associated with excellent long-term seizure control. However, for patients with recurrent seizures following disconnection, workup and investigation can be challenging, and surgical options may be limited. Few studies have examined the role of repeat hemispherotomy in these patients. The authors hypothesized that residual fiber connections between the hemispheres could be the underlying cause of recurrent epilepsy in these patients. Diffusion tensor imaging (DTI) was used to test this hypothesis, and to target residual connections at reoperation using neuronavigation. METHODS The authors identified 8 patients with recurrent seizures following hemispherectomy who underwent surgery between 1995 and 2012. Prolonged video electroencephalography recordings documented persistent seizures arising from the affected hemisphere. In all patients, DTI demonstrated residual white matter association fibers connecting the hemispheres. A repeat craniotomy and neuronavigation-guided targeted disconnection of these residual fibers was performed. Engel class was used to determine outcome after surgery at a minimum of 2 years of follow-up. RESULTS Two patients underwent initial hemidecortication and 6 had periinsular hemispherotomy as their first procedures at a median age of 9.7 months. Initial pathologies included hemimegalencephaly (n = 4), multilobar cortical dysplasia (n = 3), and Rasmussen's encephalitis (n = 1). The mean duration of seizure freedom for the group after the initial procedure was 32.5 months (range 6-77 months). In all patients, DTI showed limited but definite residual connections between the 2 hemispheres, primarily across the rostrum/genu of the corpus callosum. The median age at reoperation was 6.8 years (range 1.3-14 years). The average time taken for reoperation was 3 hours (range 1.8-4.3 hours), with a mean blood loss of 150 ml (range 50-250 ml). One patient required a blood transfusion. Five patients are seizure free, and the remaining 3 patients are Engel Class II, with a minimum follow-up of 24 months for the group. CONCLUSIONS Repeat hemispherotomy is an option for consideration in patients with recurrent intractable epilepsy following failed surgery for catastrophic epilepsy. In conjunction with other modalities to establish seizure onset zones, advanced MRI and DTI sequences may be of value in identifying patients with residual connectivity between the affected and unaffected hemispheres. Targeted disconnection of these residual areas of connectivity using neuronavigation may result in improved seizure outcomes, with minimal and acceptable morbidity.

Functional hemispherectomy for catastrophic epilepsy in very young infants: technical considerations and complication avoidance.

PURPOSE: We report on our experience in performing peri-insular functional hemispherectomy (PIH) in very young infants with catastrophic epilepsy. METHODS: We retrospectively reviewed the medical charts of all infants with catastrophic epilepsy that underwent PIH under the age of 4 months at our institution. RESULTS: Four infants (three female, one male) were included (median age at time of surgery 2.9 months, range from 2.4 to 4.2 months; median patient's weight at time of surgery 5650 g, range from 4300 to 7500 g). None of the patients experienced hemodynamic instability during surgery. All four patients were given red blood cell replacement (median 435 ml, range from 230 to 800 ml), three of the four patients experienced coagulopathy during surgery and were given platelet cells transfusion in one (50 ml) and fresh frozen plasma in two patients (191 and 320 ml). Two patients experienced severe complications that, however, did not cause a permanent morbidity due to prompt diagnosis and correct management. After a median follow-up time of 4.3 years (range from 1.3 to 7.9 years), three of four patients are completely seizure free. The remaining patient is experiencing brief daily staring episodes. All of them have a hemiparesis but are fully ambulatory and have a useful upper limb function. CONCLUSION: In catastrophic epilepsy, PIH within the first months of life is feasible provided that an experienced multidisciplinary team is involved. Awareness of surgical challenges and potential complications is indispensible when the life-threatening nature of the epilepsy compels neurosurgeons to operate at this very young age.

Fibrous dysplasia of the temporal bone: A case from the Glen Williams Ossuary, Ontario, Canada.

This case is an example of fibrous dysplasia (FD) of bone in an adult male cranium. The Glen Williams Ossuary is a commingled sample composed of a minimum of 309 individuals from southern Ontario, Canada, dating to the 14th century, A.D., just prior to European contact. The site represents the outcome of a Feast of the Dead, a defining ceremony among Iroquoian speaking peoples of the region. The affected individual is represented by a partial adult cranium that possesses an enlarged left temporal bone. In the absence of changes affecting the texture and composition of the outer cortex, CT allows us to visualize the internal structure of the bone in multiple locations and orientations. This procedure revealed that pathological changes were restricted to the squamous portion. Three radiographic patterns associated with FD were noted in this individual: Pagetoid/ground glass appearance, sclerotic and cystic lesions. The unique pattern of radiographic findings and solitary nature of the lesion are strong evidence for the diagnosis of FD. Differential diagnoses include: Paget's disease, intraosseous meningeoma, giant cell tumor, osteochondroma and histiocytosis X.

The role of magnetoencephalography in children undergoing hemispherectomy.

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.

Neurosurgical management of intractable rolandic epilepsy in children: role of resection in eloquent cortex. Clinical article.

OBJECT: The authors undertook this study to review their experience with cortical resections in the rolandic region in children with intractable epilepsy. METHODS: The authors retrospectively reviewed the medical records obtained in 22 children with intractable epilepsy arising from the rolandic region. All patients underwent preoperative electroencephalography (EEG), MR imaging, prolonged video-EEG recordings, functional MR imaging, magnetoencephalography, and in some instances PET/SPECT studies. In 21 patients invasive subdural grid and depth electrode monitoring was performed. Resection of the epileptogenic zones in the rolandic region was undertaken in all cases. Seizure outcome was graded according to the Engel classification. Functional outcome was determined using validated outcome scores. RESULTS: There were 10 girls and 12 boys, whose mean age at seizure onset was 3.2 years. The mean age at surgery was 10 years. Seizure duration prior to surgery was a mean of 7.4 years. Nine patients had preoperative hemiparesis. Neuropsychological testing revealed impairment in some domains in 19 patients in whom evaluation was possible. Magnetic resonance imaging abnormalities were identified in 19 patients. Magnetoencephalography was performed in all patients and showed perirolandic spike clusters on the affected side in 20 patients. The mean duration of invasive monitoring was 4.2 days. The mean number of seizures during the period of invasive monitoring was 17. All patients underwent resection that involved primary motor and/or sensory cortex. The most common pathological entity encountered was cortical dysplasia, in 13 children. Immediately postoperatively, 20 patients had differing degrees of hemiparesis, from mild to severe. The hemiparesis improved in all affected patients by 3-6 months postoperatively. With a mean follow-up of 4.1 years (minimum 2 years), seizure outcome in 14 children (64%) was Engel Class I and seizure outcome in 4 (18%) was Engel Class II. In this series, seizure outcome following perirolandic resection was intimately related to the child's age at the time of surgery. By univariate logistic regression analysis, age at surgery was a statistically significant factor predicting seizure outcome (p < 0.024). CONCLUSIONS: Resection of rolandic cortex for intractable epilepsy is possible with expected morbidity. Accurate mapping of regions of functional cortex and epileptogenic zones may lead to improved seizure outcome in children with intractable rolandic epilepsy. It is important to counsel patients and families preoperatively to prepare them for possible worsened functional outcome involving motor, sensory and/or language pathways.

Presurgical localization of primary motor cortex in pediatric patients with brain lesions by the use of spatially filtered magnetoencephalography.

OBJECTIVE: The objective of this study was to confirm the efficacy of spatially filtered magnetoencephalography for the preoperative localization of primary motor cortex in pediatric patients with focal lesions in the region of the sensorimotor cortex. METHODS: We recorded movement-related magnetoencephalographic activity in 10 pediatric patients (age range, 7-18 years; mean age, 12.5 years) undergoing presurgical evaluation for focal brain lesion resection. Participants made transient movements of the right and left index finger in response to a visual cue. The premovement motor field component in the averaged brain response was localized with a newly developed beamformer spatial filter algorithm. Cortical mapping of motor cortex intraoperatively was conducted in 5 of the 10 patients. RESULTS: The motor field time-locked to electromyography onset was successfully localized to cortical areas corresponding to the hand region primary motor cortex in 95% of cases (9 of 10 from nonlesional hemisphere; 10 of 10 from lesional hemisphere). Intraoperative electrocortical stimulation activated the expected muscles at motor field coregistered cortical source locations in all cases tested (n = 5). Using these methods, we also found that displacement of the sensorimotor cortex by space-occupying tumors did not interfere with the localization of motor cortex. CONCLUSION: We conclude that noninvasive localization of the primary motor cortex can be reliably performed by using spatially filtered magnetoencephalography techniques, which provide a robust and accurate measurement of motor cortical function for the purpose of surgical guidance.

Subcortical alterations in tissue microstructure adjacent to focal cortical dysplasia: detection at diffusion-tensor MR imaging by using magnetoencephalographic dipole cluster localization.

PURPOSE: To determine whether changes at diffusion-tensor magnetic resonance (MR) imaging were present in children with intractable epilepsy and focal cortical dysplasia (FCD) in (a) subcortical white matter subjacent to MR imaging-visible areas of FCD, (b) subcortical white matter beyond the MR imaging-visible abnormality but subjacent to a magnetoencephalographic (MEG) dipole cluster, and (c) deep white matter tracts. MATERIALS AND METHODS: The study protocol had institutional research ethics board approval, and written informed consent was obtained. Fifteen children with FCD and intractable epilepsy (mean age, 11.6 years; range, 3.6-18.3 years) underwent diffusion-tensor MR imaging and MEG. Regions of interest were placed in (a) the subcortical white matter subjacent to the MR imaging-visible abnormality, as well as the contralateral side; (b) the subcortical white matter beyond the MR imaging-visible abnormality but subjacent to a MEG dipole cluster, as well as the contralateral side; and (c) deep white matter tracts projecting to or from the MR imaging-visible FCD, as well as the contralateral side. Fractional anisotropy (FA), mean diffusivity, and eigenvalues (lambda(1), lambda(2), lambda(3)) were evaluated. RESULTS: Eleven of 15 children had MEG dipole clusters, and four children had MEG scatter. There were significant differences in FA, mean diffusivity, lambda(2), and lambda(3) of the subcortical white matter subjacent to the MR imaging-visible FCD (P < .001 for all), as well as that beyond the MR imaging-visible FCD but subjacent to a MEG dipole cluster (P = .001, P = .036, P < .001, and P = .002, respectively), compared with the contralateral side. There were also significant differences in FA (P < .001), mean diffusivity (P = .008), lambda(2) (P < .001), and lambda(3) (P = .001) of the deep white matter tracts projecting to or from the MR imaging-visible FCD compared with the contralateral side. CONCLUSION: With use of MEG dipole clusters to localize the epileptogenic zone, diffusion-tensor imaging can help identify alterations in tissue microstructure beyond the MR imaging-visible FCD.

Magnetoencephalography using total intravenous anesthesia in pediatric patients with intractable epilepsy: lesional vs nonlesional epilepsy.

PURPOSE: Magnetoencephalography (MEG) provides source localization of interictal spikes. We use total intravenous anesthesia (TIVA) with propofol to immobilize uncooperative children. We evaluate the effect of TIVA on interictal spikes in children who have intractable epilepsy with or without MRI lesions. METHODS: We studied 28 children (3-14 years; mean, 6.6). We intravenously administered propofol (30-60 microg/kg/min) to record MEG with simultaneous EEG. We evaluated MEG spike sources (MEGSSs). We compared spikes on simultaneous EEG under TIVA with those on scalp video-EEG without TIVA. RESULTS: There was a significant decrease in frequent spikes (10 patients, 36%) on simultaneous EEG under TIVA compared to those (22 patients, 79%) on scalp video-EEG without TIVA (P<0.01). MEGSSs were present in 21 (75%) of 28 patients. Clustered MEGSSs occurred in 15 (83%) of 18 lesional patients but in 3 (30%) of 10 nonlesional patients (P<0.05). MEGSSs were more frequently absent in nonlesional (6 patients, 60%) than lesional (one patient, 5%) patients (P<0.01). Thirteen patients with MRI and/or histopathologically confirmed neuronal migration disorder most frequently showed clustered MEGSSs (11 patients, 85%) compared to those of other lesional and nonlesional patients. CONCLUSION: Propofol-based TIVA reduced interictal spikes on simultaneous EEG. TIVA for MEG still had utility in identifying spike sources in a subset of pediatric patients with intractable epilepsy who were uncooperative and surgical candidates. In lesional patients, MEG under TIVA frequently localized the clustered MEGSSs. Neuronal migration disorders were intrinsically epileptogenic and produced clustered MEGSSs under TIVA. Nonlesional patients often had no MEGSS under TIVA.

Somatosensory-evoked fields on magnetoencephalography for epilepsy infants younger than 4 years with total intravenous anesthesia.

OBJECTIVE: Patients must remain immobile for magnetoencephalography (MEG) and MRI recordings to allow precise localization of brain function for pre-surgical functional mapping. In young children with epilepsy, this is accomplished with recordings during sleep or with anesthesia. This paper demonstrates that MEG can detect, characterize and localize somatosensory-evoked fields (SEF) in infants younger than 4 years of age with or without total intravenous anesthesia (TIVA). METHODS: We investigated the latency, amplitude, residual error (RE) and location of the N20m of the SEF in 26 infants (mean age=2.6 years). Seventeen patients underwent TIVA and 9 patients were tested while asleep, without TIVA. RESULTS: MEG detected 44 reliable SEFs (77%) in 52 median nerve stimulations. We found 27 reliable SEFs (79%) with TIVA and 13 reliable SEFs (72%) without TIVA. TIVA effects included longer latencies (p<0.001) and lower RE (p<0.05) compared to those without TIVA. Older patients and larger head circumferences also showed significantly shorter latencies (p<0.01). CONCLUSIONS: TIVA resulted in reliable SEFs with lower RE and longer latencies. SIGNIFICANCE: MEG can detect reliable SEFs in infants younger than 4 years old. When infants require TIVA for MEG and MRI acquisition, SEFs can still be reliably observed.

Epileptic spasms in older pediatric patients: MEG and ictal high-frequency oscillations suggest focal-onset seizures in a subset of epileptic spasms.

OBJECTIVES: To elucidate the pathophysiology of intractable epileptic spasms in older children by describing the interictal magnetoencephalography spike sources (MEGSSs), intracranial EEG ictal-onset zones (IOZs) and their ictal high-frequency oscillations (HFOs) and surgical outcomes. METHODS: We studied five patients (4.5-14 years) who underwent surgery following intracranial video-EEG (VEEG) monitoring. We analyzed clinical profiles, MRIs, scalp and intracranial VEEGs, and MEGSSs. We localized ictal HFOs using a sampling rate of 1000 Hz and multiple band frequency analysis (MBFA). RESULTS: Seizure onset ranged from 0.4 to 8 years. Three patients presented with asymmetrical spasms. Interictal scalp VEEG recorded predominantly unilateral epileptiform discharges in four; generalized and multifocal in one. Ictal scalp VEEG showed generalized high-amplitude slow waves with superimposed fast waves in four patients; hemispheric electrodecremental episodes in one. MRI findings were normal in three, hemispheric polymicrogyria and periventricular heterotopia in one each. All patients had unilateral MEGSS clusters. Ictal HFOs, ranging from 150 to 250 Hz, localized over Rolandic and frontal regions in four, with one also having extensive temporo-occipital HFOs. After cortical resection, three patients were seizure free; one had >90% reduction in seizure frequency. One patient experienced residual seizures after resection of the hemispheric ictal HFO region. CONCLUSION: Unilateral clusters of MEGSSs overlapped regional IOZs in older patients with epileptic spasms. High spatio-temporal MBFA before and during spasms revealed the regional ictal HFOs. Seizure-free outcomes following resection of zone with MEGSS clusters and ictal HFOs suggested that a subset of epileptic spasms was focal-onset seizures.

Utility of magnetoencephalography in the evaluation of recurrent seizures after epilepsy surgery.

PURPOSE: To study the role of magnetoencephalography (MEG) in the surgical evaluation of children with recurrent seizures after epilepsy surgery. METHODS: We studied 17 children with recurrent seizures after epilepsy surgery using interictal and ictal scalp EEG, intracranial video EEG (IVEEG), MRI, and MEG. We analyzed the location and distribution of MEG spike sources (MEGSSs) and the relationship of MEGSSs to the margins of previous resections and surgical outcome. RESULTS: Clustered MEGSSs occurred at the margins of previous resections within two contiguous gyri in 10 patients (group A), extended spatially from a margin by < or =3 cm in three patients (group B), and were remote from a resection margin by >3 cm in six patients (group C). Two patients had concomitant group A and C clusters. Thirteen patients underwent second surgeries. IVEEG was used in four patients. Six of seven patients with group A MEGSS clusters did not require IVEEG for second surgeries. Follow-up periods ranged from 0.6 to 4.3 years (mean: 2.6 years). Eleven children, including eight who became seizure-free, achieved Engel class I or II. CONCLUSION: Our data demonstrate the utility of MEG for evaluating patients with recurrent seizures after epilepsy surgery. Specific MEGSS cluster patterns delineate epileptogenic zones. Removing cluster regions adjacent to the margins of previous resections, in addition to removing recurrent lesions, achieves favorable surgical outcome. Cluster location and extent identify which patients require IVEEG, potentially eliminating IVEEG for some. Patients with remotely located clusters require IVEEG for accurate assessment and localization of the entire epileptogenic zone.