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Many patients with medically refractory epilepsy now undergo successful surgery based on noninvasive diagnostic information, but intracranial electroencephalography (IEEG) continues to be used as increasingly complex cases are considered surgical candidates. The indications for IEEG and the modalities employed vary across epilepsy surgical centers; each modality has its advantages and limitations. IEEG can be performed in the same intraoperative setting, that is, intraoperative electrocorticography, or through an independent implantation procedure with chronic extraoperative recordings; the latter are not only resource intensive but also carry risk. A lack of understanding of IEEG limitations predisposes to data misinterpretation that can lead to denying surgery when indicated or, worse yet, incorrect resection with adverse outcomes. Given the lack of class 1 or 2 evidence on IEEG, a consensus-based expert recommendation on the diagnostic utility of IEEG is presented, with emphasis on the application of various modalities in specific substrates or locations, taking into account their relative efficacy, safety, ease, and incremental cost-benefit. These recommendations aim to curtail outlying indications that risk the over- or underutilization of IEEG, while retaining substantial flexibility in keeping with most standard practices at epilepsy centers and addressing some of the needs of resource-poor regions around the world.

SUMMARYThe International League Against Epilepsy (ILAE) Subcommittee for Pediatric Neuroimaging examined the usefulness of, and indications for, neuroimaging in the evaluation of children with newly diagnosed epilepsy. The retrospective and prospective published series with n ‡30 utilizing computed tomography (CT) and magnetic resonance imaging (MRI) (1.5 T) that evaluated children with new-onset seizure(s) were reviewed. Nearly 50% of individual imaging studies in children with localization-related new-onset seizure(s) were reported to be abnormal; 15-20% of imaging studies provided useful information on etiology or and seizure focus, and 2-4% provided information that potentially altered immediate medical management. A significant imaging abnormality in the absence of a history of a localization-related seizure, abnormal neurologic examination, or focal electroencephalography (EEG) is rare. Imaging studies in childhood absence epilepsy, juvenile absence epilepsy, juvenile myoclonic epilepsy, and benign childhood epilepsy with centrotemporal spikes (BECTS) do not identify significant structural abnormalities. Imaging provides important contributions to establishing etiology, providing prognostic information, and directing treatment in children with recently diagnosed epilepsy. Imaging is recommended when localization-related epilepsy is known or suspected, when the epilepsy classification is in doubt, or when an epilepsy syndrome with remote symptomatic cause is suspected. When available, MRI is preferred to CT because of its superior resolution, versatility, and lack of radiation.

SUMMARY Electroencephalographic source localization (ESL)by noninvasive means is an area of renewed interest in clinical epileptology. This has been driven by innovations in the computer-assisted modeling of dipolar and distributed sources for the investigation of focal epilepsy; a process fueled by the everincreasing computational power available to researchers for the analysis of scalp EEG recordings. However, demonstration of the validity and clinical utility of these mathematically derived source modeling techniques has struggled to keep pace. This review evaluates the current clinical "fitness" of ESL as applied to the focal epilepsies by examining some of the key studies performed in the field, with emphasis given to clinical work published in the last five years. In doing so, we discuss why ESL techniques have not made an impact on routine epilepsy practice, underlining some of the current problems and controversies in the field. We conclude by examining where ESL currently sits alongside magnetoencephalography and combined EEG-functional magnetic resonance imaging in the investigation of focal epilepsy. KEY WORDS: Source modeling, Dipole, Distributed, Electroencephalography, Magnetoencephalography, Functional magnetic resonance imaging. CONCEPTS AND CONTROVERSIESIn the last five years, research in the field of electroencephalographic source localization (ESL) produced more than 150 scientific papers on computer-assisted mathematical techniques for dipolar and distributed source modeling. By comparison, less than half of this number of publications addressed the clinical validation of such techniques for the investigation of focal epilepsy. Most clinical studies featured less than 20 subjects and few were conducted prospectively. Such an imbalance might be explained away by the relative efficiency with which ESL simulation studies yield publishable results, particularly in the view of the advancing computational power and data storage capacity of the modern PC processor. However, this explanation falls short of addressing the confusion, even cynicism, among neurologists and neurosurgeons as

Summary: Hypothalamic hamartomas may be associated with gelastic seizures, focal seizures, and a generalized epileptic encephalopathy, with severe seizures and cognitive and behavior decline. Despite earlier views to the contrary, good evidence now exists that all these clinical features are caused, directly or indirectly, by the hamartoma. Resection of these lesions was long regarded as too hazardous and unlikely to benefit seizure control. It is now clear that hypothalamic hamartomas can be effectively treated with a variety of surgical approaches with sustained seizure control and often seizure freedom. Qualitative observations suggest that behavior and cognition also improve with treatment, but quantitative validation is required. The specific approach should be tailored according to the surgical anatomy of the lesion and the experience of the surgeon. Choices include a transcallosal approach (good for intraventricular lesions), a pterional approach (useful for interpeduncular lesions), a transventricular endoscopic approach, or destruction of the lesion with radiofrequency probes or gamma knife radiosurgery. The previously dismal outlook for children with severe seizures associated with this lesion has now dramatically changed. These insights may have implications for other epileptic encephalopathies of childhood.The generalized epileptic encephalopathies of childhood, typified by the Lennox-Gastaut syndrome, are important and distressing disorders to treat. The association of damaging tonic and atonic seizures ("crash helmet epilepsy"), with frequent cognitive decline and behavioral abnormalities, is an all too familiar scenario for treating physicians. Complete, or even adequate, control of seizures is rarely achieved. The outcome in adult life is generally that of continuing seizures associated with intellectual and social disability. Such epileptic encephalopathies have a wide variety of causes including developmental abnormalities and perinatal and early childhood insults (1). Hypothalamic hamartoma is a rare cause (2), but provides singular insights into the pathophysiology of such epileptic encephalopathies (3).In the last few years, a paradigm shift has occurred in the understanding of the pathophysiology and management of epilepsy associated with these lesions. It is now clear that it is a treatable epileptic encephalopathy. Collation of clinical research results from centers around the world investigating this rare disorder at a recent meeting in Montreal suggested that the lessons learned from studying this remarkable epilepsy syndrome will lead to significant improvement in management. This has major implications for the relatively small numbers of children with this condition, but it also has wider implications for understanding the generalized epileptic encephalopathies. Strong evidence now exists that removal, destruction, or disconnection of the hamartoma leads to remarkable control of the seizures, as well as to improvement in behavior and probable cessation of cognitive decline. 969

In children with typical AS, we have confirmed a core network of structures involved in generalized epileptiform activity that includes the reticular structures of the brainstem. Furthermore, we have identified changes in parietal BOLD signal which precede the onset of epileptiform activity, suggesting the parietal cortex has a role in the initiation of epileptiform activity.

Gelastic seizures in hypothalamic hamartoma arise from the hamartoma itself; the interictal spike-wave does not. The evolution of EEG abnormalities, the development of generalized seizures years after onset of gelastic seizures, and the postoperative running down of interictal spike-wave and generalized seizures in these patients may reflect secondary epileptogenesis.

Summary Purpose:  Studies in adult and neonatal intensive care units (ICUs) report a high prevalence of epileptic seizures in comatose patients. The prevalence of seizures in pediatric ICUs is variably reported in a few retrospective studies using different electroencephalography (EEG) methods. We aimed to determine prospectively the prevalence of epileptic seizures (clinical and subclinical) in comatose children in the pediatric ICU using continuous video‐EEG (v‐EEG) monitoring. Methods:  We performed v‐EEG in consecutive children aged 2 months to 17 years admitted to the pediatric ICU with sustained depressed consciousness over a period of 15 months. Results:  We monitored 100 comatose children, 69% within 24 h of ICU admission. Median length of ICU stay was 5 days. Median duration of v‐EEG was 20 h. Epileptic seizures were identified in only seven patients, of whom six had a history of epilepsy with witnessed seizures immediately prior to v‐EEG. All epileptic seizures were recorded in the first 3 h of v‐EEG. Seizures were suspected by ICU staff in 18 monitored patients, only four of whom had confirmed epileptic seizures. Discussion:  The lower prevalence of epileptic seizures and the shorter length of ICU stay in children compared to adults and neonates suggest a different spectrum of disease and neurologic response. Short‐duration v‐EEG in patients with a history of prior seizures, epilepsy, or clinical events suspected to be seizures seems more appropriate than routine v‐EEG in all comatose children in the pediatric ICU.