Tatum, William O.

Summary: The responsive neurostimulator continuously monitors the electrocorticogram. It delivers short bursts of high-frequency electrical stimulation when personalized patterns are detected. Intracranial EEG recording including electrocorticography is susceptible to artifacts, albeit at a lesser frequency compared with scalp recording. The authors describe a novel case of a patient with focal epilepsy, bitemporal responsive neurostimulation, and seizures without self-awareness manifest as focal impaired awareness seizures adversely affecting memory. At follow-up evaluation, the patient reported being clinically seizure-free although a single long episode was detected using the Patient Data Management System over the course of 3 years. Initial review identified a left-sided rhythmic discharge with a bilateral spatial field of involvement. In response to detection, the responsive neurostimulation delivered a series of five electrical stimulations. On further review, the patient recalled undergoing cervical radiofrequency ablation, which coincided with the appearance of the “electrographic seizure.” Extrinsic electrical artifact involving monomorphic nonevolving waveforms confirmed electrical artifact identified and treated by responsive neurostimulation as an epileptic seizure. On rare occasion, implanted electrical devices may lead to misdiagnosis and mistreatment of patients because of intracranial artifact.

AbstractCorrectly diagnosing and classifying seizures and epilepsies is paramount to ensure the delivery of optimal care to patients with epilepsy. Focal seizures, defined as those that originate within networks limited to one hemisphere, are primarily subdivided into focal aware, focal impaired awareness, and focal to bilateral tonic–clonic seizures. Focal epilepsies account for most epilepsy cases both in children and adults. In children, focal epilepsies are typically subdivided in three groups: self‐limited focal epilepsy syndromes (e.g., self‐limited epilepsy with centrotemporal spikes), focal epilepsy of unknown cause but which do not meet criteria for a self‐limited focal epilepsy syndrome, and focal epilepsy of known cause (e.g., structural lesions—developmental or acquired). In adults, focal epilepsies are often acquired and may be caused by a structural lesion such as stroke, infection and traumatic brain injury, or brain tumors, vascular malformations, metabolic disorders, autoimmune, and/or genetic causes. In addition to seizure semiology, neuroimaging, neurophysiology, and neuropathology constitute the cornerstones of a diagnostic evaluation. Patients with focal epilepsy who become drug‐resistant should promptly undergo assessment in an epilepsy center. After excluding pseudo‐resistance, these patients should be considered for presurgical evaluation as a means to identify the location and extent of the epileptogenic zone and assess their candidacy for a surgical procedure. The goal of this seminar in epileptology is to summarize clinically relevant information concerning focal epilepsies. This contributes to the ILAE's mission to ensure that worldwide healthcare professionals, patients, and caregivers continue to have access to high‐quality educational resources concerning epilepsy.

AbstractNeuromodulation in epilepsy is a proven treatment for people with drug‐resistant focal epilepsy. Dual device therapies are increasingly utilized in people with drug‐resistant epilepsy. Vagus nerve stimulation (VNS) and deep brain stimulation (DBS) target the thalamus involving the primary neurobiological network in patients with genetic generalized epilepsy (GGE). We report a novel case of combined neuromodulation in a patient with drug‐resistant GGE who achieved a partial response with seizure reduction after VNS implantation yet following VNS‐DBS polyneurostimulation gradually achieved prolonged seizure freedom. We speculate that by combining the indirect activating effects of VNS with the direct inhibitory effects of DBS, this may provide synergy to thalamic modulated networks. We hypothesize a “rational polytherapy” may exist in some patients with GGE undergoing dual neuromodulation.

Purpose: Electroencephalogram is used for prognostication and diagnosis in critically ill patients and is vital in developing clinical management algorithms. Unique waveforms on EEG may distinguish neurological disorders and define a potential for seizures. To better characterize zeta waves, we sought to define their electroclinical spectrum. Methods: We performed a systematic review using MEDLINE, Embase, Cochrane Central Register of Controlled Trials and Cochrane Database of Systematic Review [through Ovid], Scopus, Science Citation Index Expanded and Emerging Sources Citation Index [through the Web of Science], and Epistemonikos. Grey literature resources were searched. Results: Five hundred thirty-seven articles were identified. After excluding duplicates and reviewing titles, abstracts, and bodies and bibliographies of articles, four studies reported 64 cases describing data from patients with zeta waves, with a prevalence of 3 to 4%. Various and often incomplete clinical, neuroimaging, and EEG data were available. 57 patients (89.1%) had a focal cerebral lesion concordant with the location of zeta waves on EEG. 26 patients (40.6%) had clinical seizures, all but one being focal onset. Thirteen patients (20%) had epileptiform activity on EEG. Typically, zeta waves were located in the frontal head regions, often with generalized, frontal, predominant, rhythmic delta activity and associated with focal EEG suppression. Conclusions: Zeta waves frequently represent an underlying focal structural lesion. Their presence suggests a heightened risk for seizures. The small number of retrospective cases series in the literature reporting zeta waves might be an underrepresentation. We suggest a need for prospective studies of cEEG in critically ill patients to determine their clinical significance.

OBJECTIVE The authors hypothesized that the proximity of deep brain stimulator contacts to the anterior thalamic nucleus–mammillothalamic tract (ANT-MMT) junction determines responsiveness to treatment with ANT deep brain stimulation (DBS) in drug-resistant epilepsy and conducted this study to test that hypothesis. METHODS This retrospective study evaluated patients who had undergone ANT DBS electrode implantation and whose devices were programmed to stimulate nearest the ANT-MMT junction based on direct MRI visualization. The proximity of the active electrode to the ANT and the ANT-MMT junction was compared between responders (≥ 50% reduction in seizure frequency) and nonresponders. Linear regression was performed to assess the percentage of seizure reduction and distance to both the ANT and the ANT-MMT junction. RESULTS Four (57.1%) of 7 patients had ≥ 50% reduction in seizures. All 4 responders had at least one contact within 1 mm of the ANT-MMT junction, whereas the 3 patients with < 50% seizure improvement did not have a contact within 1 mm of the ANT-MMT junction. Additionally, the 4 responders demonstrated contact positioning closer to the ANT-MMT junction than the 3 nonresponders (mean distance from MMT: 0.7 mm on the left and 0.6 mm on the right in responders vs 3.0 mm on the left and 2.3 mm on the right in nonresponders). However, proximity of the electrode contact to any point in the ANT nucleus did not correlate with seizure reduction. Greater seizure improvement was correlated with a contact position closer to the ANT-MMT junction (R2 = 0.62, p = 0.04). Seizure improvement was not significantly correlated with proximity of the contact to any ANT border (R2 = 0.24, p = 0.26). CONCLUSIONS Obtained using a combination of direct visualization and targeted programming of the ANT-MMT junction, data in this study support the hypothesis that proximity to the ANT alone does not correlate with seizure reduction in ANT DBS, whereas proximity to the ANT-MMT junction does. These findings support the importance of direct targeting in ANT DBS, as well as imaging-informed programming. Additionally, the authors provide supportive evidence for future prospective trials using ANT-MMT junction for direct surgical targeting.