The purported underutilization of magnetoencephalography (MEG) among the USA epilepsy centers has never been studied, and any evidence-based understanding of its magnitude is lacking.
Two hundred ...twenty-five National Association of Epilepsy Centers centers (2016) were invited to participate anonymously in a 13-question web-based survey of clinical practice focused on MEG use.
On average, centers (N = 70; 61 of which were level 4) reported <6 epileptologists, >7 dedicated epilepsy monitoring unit beds, 206 phase 1 studies, 15 phase 2 studies, 10 direct resections, and 9 indirect resections; 27% owned MEG. On average, 11.2 MEGs per year were ordered for epilepsy localization and 7.6 for any presurgical mapping modalities. Wada test aka the intracarotid sodium amobarbital procedure (ISAP) (43%) and functional MRI (29%) were preferred over MEG (4%) for language mapping. The number of epileptologists and the number of epilepsy monitoring unit beds correlated positively with the most clinical volumes. The centers who own a MEG had surgical volumes significantly higher than those without. The number and complexity of patients as well as the proximity of a MEG were perceived as significant contributors/obstacles to increased MEG use.
Only the centers with larger surgical volumes incorporate MEG regularly in presurgical evaluation of patients with drug-resistant epilepsy. A reversal of the pervasive underutilization of epilepsy surgery can benefit from MEG, but this requires a sustained concerted promotion by the epilepsy and MEG communities.
Broader utilization of magnetoencephalography (MEG) and optimization of clinical practice remain strategic goals of the American Clinical Magnetoencephalography Society. Despite the implementation of ...the first MEG Clinical Practice Guidelines, clinical adoption has been less than expected, prompting a reassessment.
Twenty-five clinical MEG centers were invited to participate anonymously in a survey of clinical practice.
Centers (N = 18) mostly operated within an academic medical center (10/18), were owned by the "hospital" (10/18), associated with a level 4 National Association of Epilepsy center (15/18), and directed by neurologists (10/18). A total of 873 (median 59) epilepsy studies, 1,179 evoked fields (of all types), and 1,607 (median 30) research MEG studies were reported. Fourteen of 17 centers serve children (median 35%), but only 5 of 14 sedate children for MEG. All (N = 14) centers record EEG simultaneous with MEG, and 57% used dipole source localization. The median reporting time for epilepsy studies was 12 and 10 days for presurgical mapping studies. Most (12/14) were favorable toward the Clinical Practice Guidelines and "formalized certification" but were against mandating the latter.
A plateau in MEG volumes suggests that MEG has not become a part of the standard of care, and correspondingly, the Clinical Practice Guidelines appeared to have had little impact on clinical practice. The American Clinical Magnetoencephalography Society must continue to engage magnetoencephalographers, potential referrers, and vendors.
According to the latest operational 2017 ILAE classification of epileptic seizures, the generalized epileptic seizure is still conceptualized as "originating at some point within and rapidly ...engaging, bilaterally distributed networks." In contrast, the focal epileptic seizure is defined as "
." Hence, one of the main concepts of "generalized" and "focal" epilepsy comes from EEG descriptions before the era of source localization, and a presumed simultaneous bilateral onset and bi-synchrony of epileptiform discharges remains a hallmark for generalized seizures. Current literature on the pathophysiology of generalized epilepsy supports the concept of a cortical epileptogenic focus triggering rapidly generalized epileptic discharges involving intact corticothalamic and corticocortical networks, known as the
. Likewise, focal epilepsy with rich connectivity can give rise to generalized spike and wave discharges resulting from widespread bilateral synchronization. Therefore, making this key distinction between generalized and focal epilepsy may be challenging in some cases, and for the first time, a combined generalized and focal epilepsy is categorized in the 2017 ILAE classification. Nevertheless, treatment options, such as the choice of antiseizure medications or surgical treatment, are the reason behind the importance of accurate epilepsy classification. Over the past several decades, plentiful scientific research on the pathophysiology of generalized epilepsy has been conducted using non-invasive neuroimaging and postprocessing of the electromagnetic neural signal by measuring the spatiotemporal and interhemispheric latency of bi-synchronous or generalized epileptiform discharges as well as network analysis to identify diagnostic and prognostic biomarkers for accurate diagnosis of the two major types of epilepsy. Among all the advanced techniques, magnetoencephalography (MEG) and multiple other methods provide excellent temporal and spatial resolution, inherently suited to analyzing and visualizing the propagation of generalized EEG activities. This article aims to provide a comprehensive literature review of recent innovations in MEG methodology using source localization and network analysis techniques that contributed to the literature of idiopathic generalized epilepsy in terms of pathophysiology and clinical prognosis, thus further blurring the boundary between focal and generalized epilepsy.
•Hippocampal spindles and barques occur equally often in temporal lobe epilepsy (TLE) and non-TLE by both noninvasive and intracranial EEG criteria.•In patients with seizure-free surgical outcome, ...barques were more prominent in extra-temporal TLE.•The presence of barques may signify lack of epileptogenic properties in the underlying hippocampus.
To assess whether hippocampal spindles and barques are markers of epileptogenicity.
Focal epilepsy patients that underwent stereo-electroencephalography implantation with at least one electrode in their hippocampus were selected (n = 75). The occurrence of spindles and barques in the hippocampus was evaluated in each patient. We created pairs of pathologic and pathology-free groups according to two sets of criteria: 1. Non-invasive diagnostic criteria (patients grouped according to focal epilepsy classification). 2. Intracranial neurophysiological criteria (patient’s hippocampi grouped according to their seizure onset involvement).
Hippocampal spindles and barques appear equally often in both pathologic and pathology-free groups, both for non-invasive (Pspindles = 0.73; Pbarques = 0.46) and intracranial criteria (Pspindles = 0.08; Pbarques = 0.26). In Engel Class I patients, spindles occurred with similar incidence both within the non-invasive (P = 0.67) and the intracranial criteria group (P = 0.20). Barques were significantly more frequent in extra-temporal lobe epilepsy defined by either non-invasive (P = 0.01) or intracranial (P = 0.01) criteria.
Both spindles and barques are normal entities of the hippocampal intracranial electroencephalogram. The presence of barques may also signify lack of epileptogenic properties in the hippocampus.
Understanding that hippocampal spindles and barques do not reflect epileptogenicity is critical for correct interpretation of epilepsy surgery evaluations and appropriate surgical treatment selection.
•VNS therapy titration to a target output current of 1.5 mA is achievable in most patients in <3 months.•Use of more tolerable stimulation parameters during titration delays achievement of a ...therapeutic dose.•VNS therapy is generally well tolerated and associated with improvements in mood.
Vagus Nerve Stimulation (VNS) therapy is widely understood to provide clinically meaningful improvements in seizure control to patients with drug-resistant epilepsy, and has been a staple in the clinical armamentaria available to epileptologists for over 25 years. Despite the long history of evidence-based reviews by neurology professional societies, there is still evidence of a practice gap in VNS titration and dosing that aims to maximize clinical benefit. Recent retrospective analyses have strongly argued for a more consistent application of a population-wide target dose of VNS, and further argued the importance of quickly achieving this target dose to hasten the onset of clinical benefits; however, these analyses failed to provide evidence for practical implementation. Herein, we describe a randomized controlled trial assessing the impact of titrating VNS according to three different protocols to achieve the target dose of 1.5 mA at 500µsec, for a 20-Hz signal frequency. The study was registered as NCT02385526 on March 11, 2015. Sixty-two patients were randomized into treatment groups that followed different titration protocols. One protocol (Group A) was designed to align with currently accepted professional guidance for VNS titration and the manufacturer’s labeling for VNS in epilepsy (Heck et al., 2002), while the other two protocols were derived from VNS applications in other therapeutic areas. Group A participants were most likely to achieve the target dose parameters in 12 weeks or less (81.8%), with a median time-until-achievement of the target dose of 8.1 weeks, while less than 60% of patients in other groups were able to achieve the same endpoint. Participants in all groups experienced low levels of transient tolerability concerns and adverse events, suggesting titration to the target dose in 12 weeks or less following the Group A protocol is generally acceptable to most patients. These findings indicate that patients receiving VNS for epilepsy can achieve the manufacturer-recommended dose range in 12 weeks or less. A wider implementation of the approach will likely improve the clinical impact of VNS on seizure control and prevent undertreatment.
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