Journal of Clinical Neurophysiology最新文献

Summary: Epilepsy neuromodulation treatment failure is a significant challenge, with multiple possible causes. The responsive neurostimulation (RNS) system delivers stimulation from a single current source, and the relative flow of the electrical current through each stimulating contact is inversely proportional to the relative impedance of each contact. Current shunting through low-impedance contacts (i.e., intraventricular contacts) can divert therapy away from the intended targets and may be a cause of treatment failure. We present a case of a patient with bitemporal epilepsy and bitemporal encephaloceles, with poor response to bilateral mesial temporal RNS, who completed stereotactic EEG (sEEG) monitoring to investigate the possible causes of treatment failure. The sEEG was safely completed without damaging the RNS device. The sEEG recorded independent bitemporal interictal epileptiform discharges and seizures, which did not arise from sampled encephalocele regions. The sEEG-recorded RNS stimulation artifact was reduced in the left mesial temporal region relative to the right, which suggested potential current shunting through the right-sided contacts. Impedance measurements confirmed several low-impedance contacts from the right lead, with associated intraventricular position on imaging. At last follow up, 161 days after replacement of the right lead, the patient experienced an additional 58% reduction in seizure burden. Effective therapy delivery by single-current-source neurostimulation systems, such as RNS, critically depends on relative electrode impedances. Current shunting through low-impedance contacts is an underappreciated potential cause of treatment failure. Routine impedance assessments and individualized stimulation programs are recommended to avoid unintended current diversion. Concurrent sEEG monitoring and active RNS are feasible and can characterize stimulation effects.

Summary: Mesial temporal lobe epilepsy (mTLE) is the most prevalent type of focal epilepsy, marked by significant comorbidities including memory impairment, depression, panic, and bipolar disorders, rendering it highly incapacitating. However, early diagnosis remains challenging due to a prolonged latent period, subtle prodromal symptoms, and scant scalp EEG manifestation of hippocampal epileptiform activity. Consequently, identification of early biomarkers for mTLE is crucial. Small sharp spikes (SSSs) have traditionally been considered benign EEG patterns as they are inconsistently correlated with epilepsy, almost equally occurring in patients with and without epilepsy. Recent studies, however, have demonstrated a time-locked association between SSS and hippocampal spikes in patients with mTLE, which strongly suggests that SSS represent pathologic EEG biomarkers of mTLE, challenging the prevailing belief that SSS are benign EEG patterns. Nonetheless, the clinical significance of SSS remains controversial, particularly in patients without a diagnosis of epilepsy. Considering that patients without a diagnosis of epilepsy displaying SSS often exhibit prodromal symptoms reminiscent of those seen in mTLE, prompting EEG investigation, which raises the possibility that these patients are likely in the latent period of mTLE and suspicious for epilepsy. Therefore, SSS might be early biomarkers for mTLE. A correlation between SSS and hippocampal spikes might also exist among these patients. The implication of SSS as early EEG biomarkers is profound, enabling early diagnosis and providing a window for antiseizure and disease-modifying interventions for patients with mTLE. Here, we critically reappraise the clinical significance of SSS and explore the perspectives of SSS as early pathologic EEG markers for mTLE.

Summary: The orbitofrontal cortex (OFC) plays a pivotal role in integrating sensory, emotional, and cognitive signals to support flexible, goal-directed behavior. This review synthesizes converging evidence from lesion studies, neuroimaging, intracranial recordings and stimulations to elucidate the OFC's contribution to emotional regulation, social behavior, and value-based decision making. Lesions in the OFC are associated with affective disturbances, social disinhibition, and impaired behavioral adaptation to feedback. The OFC evaluates the hedonic valence of stimuli across sensory modalities-visual, gustatory, olfactory, somatosensory, and auditory-thereby contributing to subjective affective experience. Intracranial and neuroimaging data further underscore the OFC's involvement in processing emotional facial expressions, tactile pleasure, and social cues such as attractiveness and vocal identity. Stimulation studies provide causal evidence for the OFC's role in modulating emotional perception and mood. Structural and functional alterations of the OFC are consistently observed across multiple neuropsychiatric conditions, including major depressive disorder, obsessive-compulsive disorder, borderline personality disorder, and addiction. These abnormalities manifest as impaired reward processing, increased impulsivity, and affective dysregulation, and may be ameliorated by targeted neuromodulatory interventions such as deep brain stimulation and repetitive transcranial magnetic stimulation. Collectively, findings highlight the OFC as a central hub for affective-cognitive integration and as a promising target for therapeutic modulation in psychiatric disorders.

Introduction: EEG source localization is an established technique for localizing scalp EEG in medically refractory epilepsy but has not been adequately studied with intracranial EEG (iEEG). Differences in sensor location and spatial sampling may affect the accuracy of EEG source localization with iEEG. Corticocortical evoked potentials can be used to evaluate EEG source localization algorithms for iEEG given the known source location.

Methods: We recorded 205 sets of corticocortical evoked potentials using low-frequency single-pulse electrical stimulation in four patients with iEEG. Averaged corticocortical evoked potentials were analyzed using 11 distributed source algorithms and compared using the Wilcoxon signed-rank test ( P < 0.05). We measured the localization error from stimulated electrodes and the spatial dispersion of each solution.

Results: Minimum norm, standard low-resolution electromagnetic tomography (sLORETA), LP Norm, sLORETA-weighted accurate minimum norm (SWARM), exact LORETA (eLORETA), standardized weighted LORETA (swLORETA), and standardized shrinking LORETA-FOCUSS (ssLOFO) had the least localization error (13.3-15.7 mm) and were superior to focal underdetermined system solver (FOCUSS), logistic autoregressive average (LAURA, and LORETA, 17.9-21.7, P < 0.001). The FOCUSS solution had the smallest spatial dispersion (7.4 mm), followed by minimum norm, L1 norm, LP norm, and SWARM (20.8-28.3 mm). Gray matter stimulations had less localization error than white matter (median differences 3.1-6.1 mm) across all algorithms except SWARM, LORETA, and logistic autoregressive average. A multivariate linear regression showed that distance from the source to sensors and gray/white matter stimulation had a significant effect on localization error for some algorithms but not SWARM, minimum norm, focal underdetermined system solver, logistic autoregressive average, and LORETA.

Conclusions: Our study demonstrated that minimum norm, L1 norm, LP norm, and SWARM localize iEEG corticocortical evoked potentials well with lower localization error and spatial dispersion. Larger studies are needed to confirm these findings.

Summary: The orbitofrontal cortex (OFC) is a highly interconnected region, cytoarchitectonically diverse. Seizures involving the OFC present significant diagnostic challenges because of their variable semiological features, which often overlap with those typically attributed to frontal and temporal epilepsies. Moreover, OFC seizures semiology is shaped by the epileptogenic zone network (EZN), involving either ictal propagation or reconfiguration of functional networks. We systematically reviewed 87 patients presenting seizures involving the OFC to analyze semiological profiles using the latest International League Against Epilepsy classification. We found that seizures with EZN restricted to the OFC displayed sparse semiology, including hyperkinetic behaviors, verbal automatisms, and frequent sleep association, while extended EZN seizures exhibited richer semiological profiles, varying according to EZN distribution. Temporal involvement correlated with more auras, oro-alimentary automatisms, and occurred more often with sleep, while frontal and insular participation involved hyperkinetic behaviors with more mimic and gestural automatisms. Semiological profiles of the OFC-restricted EZN seizures are concordant with propagation patterns that align with the functional connectivity of the OFC: lateral OFC seizures tend to propagate to the lateral and mesial frontal lobe while medial OFC seizures propagated to temporal lobe, either medial or polar. Despite population-level observations, semiological profiles alone seem insufficient for delimitation of extension or distribution of EZN. According to seizure semiology, "frontal" like profiles appear more frequent (∼2/3 of patients) while "temporal" like profiles were more associated with an extended EZN. These findings underscore the importance of comprehensive presurgical evaluations, to delineate EZN extension and distribution in seizures involving the OFC.

Summary: Orbitofrontal epilepsies (OFE) produce variable clinical semiologies and nonspecific electrographic patterns thereby being challenging to localize. Furthermore, systematic studies of the surgical management and outcomes in OFE are sparse. The authors review the current literature and discuss the intracranial electroencephalography, microsurgical techniques, and surgical outcomes of patients in the context of a 20-year surgical experience in treating 24 patients with OFE. The authors distinguish between purely orbitofrontal resections (OF-focal, n = 10) and those in whom additional brain regions were concurrently resected (OF-plus, n = 14). These two cohorts were similar with respect to age, duration of epilepsy, and presence of an OF lesion on MRI. Patients frequently reported no auras (OF-focal: 7 [70%], OF-plus: 8 [57%]); generalized tonic-clonic seizures were common (OF-focal: 6 [60%], OF-plus: 7 [50%]); and seizures were often nocturnal (OF-focal: 5 [50%], OF-plus: 8 [57%]). Surgical extensions among the OF-plus group included the prefrontal or frontal pole (67%), temporal pole (11%), and mesial temporal lobe (22%). Durable Engel I to II outcomes at last follow-up (median: 4 years, interquartile range [IQR]: 2-7) were achieved in 5 patients (50%) with OF-focal epilepsies and 8 (57%) patients with OF-plus epilepsies. Among nonlesional cases, 4 of 11 patients (36%) achieved seizure freedom, of whom 3 (75%) underwent OF-plus resection. The most common etiology was malformation of cortical development (58%). Surgical resection of the OFE carries the same seizure-free rates as other neocortical epilepsies and can be done safely with minimal cognitive or functional decline.

Introduction: Prior findings on direct intracranial electrical stimulation (iES) of the human orbitofrontal cortex (OFC), which includes the orbital and ventromedial prefrontal regions, have been mixed, with several reports lacking replication. We aimed to clarify the effects of iES in the OFC.

Methods: We analyzed data from 608 stimulations across 277 OFC site pairs (352 sites total) in 49 patients collected over 17 years of our practice.

Results: We found 24.4% of sites as responsive to iES, with subjects reporting visual and olfactory sensations. However, post hoc analysis revealed that these responses largely originated from the stimulation of nearby non-OFC optic and olfactory structures. After applying quality controls, stimulation of only 0.6% of OFC sites (2 sites, 2 patients) produced changes in subjective domain, while 99.4% had no reportable effects. Contrary to earlier studies, we found no evidence of valence lateralization or functional organization within the OFC.

Conclusions: Our findings suggest that the electrical perturbation of OFC is largely silent and does not lead to reportable change in the subjective state of the individual.

Significance: Orbitofrontal cortex is a higher transmodal cortical area. The variability and limited replicability of reported effects from prior publications and the inconsistencies in the extant literature about OFC stimulations can be attributed to methodological shortcomings.

Purpose: Delivering optimal care to patients with seizures and epilepsy requires all EEGs to be interpreted accurately and reliably. This study investigated neurology professionals' opinions on the ideal standards for EEG in clinical care.

Methods: We developed an anonymous e-survey targeting practicing and trainee neurologists focused on participants' demographics, clinical practice characteristics, and views on optimal EEG standards of care-including whether an EEG certification test is needed and whether postresidency/fellowship training in EEG/epilepsy is necessary for neurologists who interpret outpatient/routine EEGs in practice. The survey was hosted by the Neurology Clinical Practice-Practice Current, and it was distributed online through the American Academy of Neurology, American Epilepsy Society, American Clinical Neurophysiology Society, and International League Against Epilepsy, and through social media.

Results: Two hundred eighty-three responses were included: 119 from EEG/epilepsy-trained neurologists, 83 from non-EEG/epilepsy-trained neurologists, 75 from trainees, and 6 from advanced care providers. Most participants (78%) agreed that "an objective certification test of ability to interpret EEGs is needed for all those who interpret EEGs in clinical practice." Most participants (71%) believed that outpatient/routine EEGs may be read only by neurologists with EEG/epilepsy training; this opinion was more prevalent among EEG/epilepsy-trained (83%) versus non-EEG/epilepsy-trained neurologists (55%).

Conclusions: Our neurology community should discuss the need to develop and implement a certification test of ability for all neurologists who wish to interpret EEGs in clinical practice. In addition, it is imperative to improve in-residency EEG education to ensure that neurology graduates achieve EEG competence before entering the workforce.