Lack of spontaneous typical seizures during intracranial monitoring with stereo-electroencephalography.

OBJECTIVE: In the presurgical evaluation of patients with drug-resistant epilepsy (DRE), occasionally, patients do not experience spontaneous typical seizures (STS) during a stereo-electroencephalography (SEEG) study, which limits its effectiveness. We sought to identify risk factors for patients who did not have STS during SEEG and to analyze the clinical outcomes for this particular set of patients. METHODS: We conducted a retrospective analysis of all patients with DRE who underwent depth electrode implantation and SEEG recordings between January 2013 and December 2018. RESULTS: SEEG was performed in 155 cases during this period. 11 (7.2%) did not experience any clinical seizures (non-STS group), while 143 experienced at least one patient-typical seizure during admission (STS group). No significant differences were found between STS and non-STS groups in terms of patient demographics, lesional/non-lesional epilepsy ratio, pre-SEEG seizure frequency, number of ASMs used, electrographic seizures or postoperative seizure outcome in those who underwent resective surgery. Statistically significant differences were found in the average number of electrodes implanted (7.0 in the non-STS group vs. 10.2 in STS), days in Epilepsy Monitoring Unit (21.8 vs. 12.8 days) and the number of cases that underwent resective surgery following SEEG (27.3% vs. 60.8%), respectively. The three non-STS patients (30%) who underwent surgery, all had their typical seizures triggered during ECS studies. Three cases were found to have psychogenic non-epileptic seizures. None of the patients in the non-STS group were offered neurostimulation devices. Five of the non-STS patients experienced transient seizure improvement following SEEG. SIGNIFICANCE: We were unable to identify any factors that predicted lack of seizures during SEEG recordings. Resective surgery was only offered in cases where ECS studies replicated patient-typical seizures. Larger datasets are required to be able to identify factors that predict which patients will fail to develop seizures during SEEG.

Auditory verbal hallucinations as ictal phenomena in a patient with drug-resistant epilepsy.

PURPOSE: The presence of verbal auditory hallucinations is often associated with psychotic disorders and rarely is considered as an ictal phenomena. The aim of this paper is to describe the anatomical structures involved in the genesis of this ictal symptom during epileptic seizures and direct cortical stimulation using stereo encephalography (SEEG). METHOD: The case is of a 31-year-old right-handed female, bilateral speech representation, schizophrenia and with drug-resistant epilepsy and focal aware sensory seizures characterized by ictal verbal auditory hallucinations. She was implanted with depth electrodes, and she was monitored using SEEG recordings. RESULTS: She had focal aware sensory seizures characterized by verbal auditory hallucinations, with the following features: hearing numerous voices (both male and/or female), talking at the same time (not able to distinguish how many). The voices were inside her head, consisted of negative content, and lasted up to two minutes. Some of her focal aware sensory seizures evolved to focal motor seizures and rarely progressed to bilateral tonic clonic seizures. Her neurological examination, her brain MRI and her interictal SPECT were unremarkable. Her PET scan identified mild hypo metabolism over the right temporal and right frontal lobes. Her neuropsychological evaluation showed language laterality undetermined but her functional MRI showed bilateral language representation. On her video-EEG, three seizures were captured with a right posterior temporal onset. A subsequent SEEG showed thirteen typical seizures originating from the posterior temporal neocortical region. The cortical stimulation of the right posterior temporo-parietal neocortical region and right amygdala triggered her typical phenomena, which was multiple voices, inside her head, speaking in the second person, negative content, unable to identify gender, in English, and no side lateralization. CONCLUSION: Verbal auditory hallucinations should be analyzed carefully because they can be part of the seizure presentation. Our case supports the localization of these hallucinations in the right posterior neocortical temporal regions.

Extraoperative electrical stimulation mapping in epilepsy presurgical evaluation: a proposal and review of the literature.

BACKGROUND: Electrical stimulation mapping (ESM) is an important tool for the localization of the seizure onset zone (SOZ) in patients with medically resistant epilepsy (MRE). ESM is the gold standard for the identification of eloquent cortex in epilepsy surgery candidates. However, there is no standard protocol outlining how to perform ESM, to obtain the most useful information possible. The objective of this study, after reviewing the literature concerning ESM, is to propose a unifying technique to validate reliable data across different centers. METHODS: In this manuscript we summarize this technique from its origin to present, and review protocols used in other centers. We also describe a protocol that has been used in our institution, which utilizes depth electrodes. RESULTS: The most common type of ESM uses a "close-loop" system, bipolar and high frequency stimulation (50 Hz). We propose to use a pulse width of 300 µs, current spanning 1-6 mA in depth electrodes and 1-11 mA in subdural-grids. Stimulation time of 5 s maximum and at least 10 s break in between the stimulations. CONCLUSIONS: ESM is a useful tool for understanding eloquent cortex as well as the epilepsy network, although there is no clear consensus regarding how it should be performed.

Role of resective surgery in patients older than 60 years with therapy-resistant epilepsy.

OBJECTIVE: Epilepsy surgery for older adults is controversial owing to their longer duration of epilepsy and perceived higher surgical risk. However, because of an aging population and documented benefit of epilepsy surgery, surgery is considered more frequently for these patients. The authors' objective was to analyze the role of resective surgery in patients older than 60 years and to assess outcomes and safety. METHODS: The authors conducted a retrospective analysis of 595 patients who underwent resective epilepsy surgery at their center from 1999 to 2018. Thirty-one patients aged 60 years or older were identified. Sixty patients younger than 60 years were randomly selected as controls. Population characteristics, results of presurgical evaluations, outcomes, and complications were analyzed. RESULTS: No significant differences were found between the groups in terms of hemisphere dominance, side of surgery, presence of a lesion, and incidence of temporal lobe epilepsy. Epilepsy duration was greater in the older cohort (p = 0.019), and invasive EEG was more commonly employed in younger patients (p = 0.030). The rates of Engel class I outcome at 6 months, 1 year, and 2 years were 89.7%, 96.2%, and 94.7% for the older group and 75% (p = 0.159), 67.3% (p = 0.004), and 75.8% (p = 0.130) for the younger group, respectively. The proportion of seizure-free patients was greatest among those with temporal lobe epilepsy, particularly in the older group. Neurological complication rates did not differ significantly between groups, however medical and other minor complications occurred more frequently in the older group. CONCLUSIONS: Patients older than 60 years had equal or better outcomes at 1 year after epilepsy surgery than younger patients. A trend toward a greater proportion of patients with lesional temporal lobe epilepsy was found in the older group. These results suggest that good seizure outcomes can be obtained in older patients despite longer duration of epilepsy.

Intracranial Electroencephalographic Monitoring: From Subdural to Depth Electrodes.

At the London Health Sciences Centre Epilepsy Program, stereotactically implanted depth electrodes have largely replaced subdural electrodes in the presurgical investigation of patients with drug-resistant epilepsy over the past 4 years. The rationale for this paradigm shift was more experience with, and improved surgical techniques for, stereoelectroencephalography, a possible lower-risk profile for depth electrodes, better patient tolerability, shorter operative time, as well as increased recognition of potential surgical targets that are not accessible to subdural electrodes.

Coprolalia as a manifestation of epileptic seizures.

OBJECTIVE: The aim of this study was to investigate the lateralizing and localizing value of ictal coprolalia and brain areas involved in its production. METHODS: A retrospective search for patients manifesting ictal coprolalia was conducted in our EMU database. Continuous video-EEG recordings were reviewed, and EEG activity before and during coprolalia was analyzed using independent component analysis (ICA) technique and was compared to the seizures without coprolalia among the same patients. RESULTS: Nine patients were evaluated (five women), eight with intracranial video-EEG recordings (icVEEG). Four had frontal or temporal lesions, and five had normal MRIs. Six patients showed impairment in the language functions and five in the frontal executive tasks. Two hundred six seizures were reviewed (60.7% from icVEEG). Ictal coprolalia occurred in 46.6% of them, always associated with limbic auras or automatisms. They arose from the nondominant hemisphere in five patients, dominant hemisphere in three, and independently from the right and left hippocampus-parahippocampus in one. Electroencephalographic activity always involved orbitofrontal and/or mesial temporal regions of the nondominant hemisphere when coprolalia occurred. Independent component analysis of 31 seizures in seven patients showed a higher number of independent components in the nondominant hippocampus-parahippocampus before and during coprolalia and in the dominant lateral temporal region in those seizures without coprolalia (p=0.009). Five patients underwent surgery, and all five had an ILAE class 1 outcome. SIGNIFICANCE: Ictal coprolalia occurs in both males and females with temporal or orbitofrontal epilepsy and has a limited lateralizing value to the nondominant hemisphere but can be triggered by seizures from either hemisphere. It involves activation of the paralimbic temporal-orbitofrontal network.

Prevalence of benign epileptiform variants.

OBJECTIVE: There are numerous distinctive benign electroencephalographic (EEG) patterns which are morphologically epileptiform but are non-epileptic. The aim of this study was to determine the prevalence of different benign epileptiform variants (BEVs) among subjects who underwent routine EEG recordings in a large EEG laboratory over 35 years. METHODS: We retrospectively studied the prevalence of BEVs among 35,249 individuals who underwent outpatient EEG recordings at London Health Sciences Centre in London, Ontario, Canada between January 1, 1972 and December 31, 2007. The definitions of the Committee on Terminology of the International Federation of Societies for EEG and Clinical Neurophysiology (IFSECN) were used to delineate epileptiform patterns (Chatrian et al. A glossary of terms most commonly used by clinical electroencephlographers. Electroenceph Clin Neurophysiol 1974;37:538-48) and the descriptions of Klass and Westmoreland [Klass DW, Westmoreland BF. Nonepileptogenic epileptiform electroenephalographic activity. Ann Neurol 1985;18:627-35] were used to categorize the BEVs. RESULTS: BEVs were identified in 1183 out of 35,249 subjects (3.4%). The distribution of individual BEVs were as follows: benign sporadic sleep spikes 1.85%, wicket waves 0.03%, 14 and 6 Hz positive spikes 0.52%, 6 Hz spike-and-waves 1.02%, rhythmic temporal theta bursts of drowsiness 0.12%, and subclinical rhythmic electrographic discharge of adults in 0.07%. CONCLUSION: The prevalence of six types of BEVs was relatively low among the Canadian subjects when compared to the reports from other countries. SIGNIFICANCE: BEVs are relatively uncommon incidental EEG findings. Unlike focal epileptic spikes and generalized spike-and-waves, BEVs do not predict the occurrence of epilepsy. Accurate identification of the BEVs can avoid misdiagnosis and unnecessary investigations.