Journal of Clinical Neurophysiology最新文献

Abstract: Peripheral nerve hyperexcitability syndromes are characterized by spontaneous motor discharges, fasciculations, and cramps. Morvan syndrome differs from Isaacs syndrome by its central nervous system involvement, autonomic dysfunction, and profound sleep disruption, often presenting as agrypnia excitata. We report two seropositive patients with cramps, fasciculations, insomnia, and autonomic dysfunction but without neuropsychiatric features. Case 1, a 49-year-old man, had LGI1 antibodies and presented with insomnia and autonomic symptoms. Video-polysomnography revealed severe insomnia with absent N3/REM sleep, reduced spindles and K-complexes, and oneiric stupor behaviors. Case 2, a 25-year-old woman, had LGI1 and CASPR2 antibodies, neuropathic pain, and fasciculations. Video-polysomnography demonstrated REM sleep without atonia, rapid N1-to-REM transitions, and microstructural abnormalities of N2 sleep. Tumor screening was negative in both; both improved with immunotherapy. A literature review confirms that video-polysomnography consistently reveals central involvement in Morvan syndrome, characterized by loss of sleep spindles, K-complexes, and pathological REM features, while Isaacs syndrome preserves normal sleep structure. Video-polysomnography is therefore an essential tool to detect subclinical central nervous system dysfunction in Morvan syndrome, especially when neuropsychiatric symptoms are absent, and helps distinguish it from Isaacs syndrome.

Purpose: Recent studies have challenged the assumption that brain activity is absent or only slow postictally, with reports of higher frequency activity. However, there are conflicting reports as to whether such activity is present under significant postictal suppression. To address this question, we performed a high-gain review combined with spectrographic analysis of postictal stereo-EEG suppression.

Methods: The postictal stereo-EEG of six focal to bilateral tonic-clonic seizures was reviewed both at standard gain (50-100 μV/mm) and at ultra-high gain (2-5 μV/mm). Time-frequency spectrographic analysis was performed of one channel in the seizure onset zone during the periictal period. Power of the gamma frequency band was quantified in the first 15 seconds postictally and compared with a preictal baseline.

Results: (1) Review at ultra-high gain identified an otherwise invisible evolving mixed-frequency background including high-frequency oscillatory activity, continuing ictal activity in one seizure, and early sharp activity (83.33%). (2) Activity was present despite significant suppression (18.46 μV in the seizure onset zone channel). (3) Time-frequency spectrogram revealed a steep drop of EEG power postictally, including gamma power, yet power was not completely absent.

Conclusions: (1) Although the stereo-EEG appeared suppressed postictally, the combination of direct review at ultra-high gain and spectrographic analysis identified otherwise invisible low-power activity. (2) We found intermittent high-frequency oscillatory activity, early postictal sharp activity, as well as the first report of persistent ictal discharges under apparent suppression. (3) Unmasking this activity could help explain postictal seizure-like behaviors and would challenge how the onset of the postictal state is declared.

Purpose: Prior research has suggested that select patients with refractory bilateral mesial temporal lobe epilepsy (MTLE) treated with responsive neurostimulation (RNS) may benefit from eventual resection of the more active side. However, there is little guidance regarding the role for continuing RNS therapy after unilateral resection. Our series aims to help define the utility of continued RNS therapy after resection and offer guiding principles for neurostimulation in this context.

Methods: Retrospective chart review was performed for patients who underwent RNS implant surgery for bilateral MTLE at our institution between the years 2015-2024.

Results: Five patients with RNS treating bilateral hippocampi ultimately underwent selective mesial temporal lobe resection on the primary side. After resection, 4/5 became seizure-free immediately; patient 4 had a 70% seizure reduction, with reemergence of seizures on the less active side. After reprogramming RNS to increase total number of daily stimulations, patient 4 became seizure-free. All patients continued RNS therapy after resection with the ipsilateral electrode used for monitoring, while the contralateral electrode monitored and delivered stimulation. Two patients had transient interruptions of RNS stimulation after resection associated with seizure relapse, followed by return to seizure freedom once stimulation was restored.

Conclusions: This series suggests that (1) unilateral remission in patients with bilateral MTLE being treated with RNS may be stimulation dependent; thus, stimulation should continue after unilateral resection; (2) unilateral seizure remission may depend on a particular threshold of number of stimulations per day.

Purpose: This study aimed to evaluate the diagnostic value of the second lumbrical-interosseous distal motor latency (2L-IO distal motor latency [DML]) difference in the diagnosis of carpal tunnel syndrome, and to assess its utility across different stages of the disease.

Methods: A total of 145 carpal tunnel syndrome-affected hands from 89 patients and 52 hands from 31 healthy volunteers were evaluated between January and August 2023. In addition to standard electrophysiologic tests, the DML difference between the 2L and interosseous muscles was recorded. Carpal tunnel syndrome severity was classified according to the Bland scale. The diagnostic sensitivity and specificity of the 2L-IO DML difference were analyzed using receiver operating characteristic analysis.

Results: The 2L-IO DML difference was significantly prolonged in the carpal tunnel syndrome group compared with healthy controls (1.85 ± 1.41 ms vs. 0.25 ± 0.28 ms; P < 0.001). With a cutoff value of 0.45 ms, the sensitivity and specificity of the method were calculated as 98.6 and 98.1%, respectively. Although the diagnostic accuracy of conventional tests was 84%, it increased to 98% with the 2L-IO DML difference. Diagnosis was achieved in 85% of early stage (Grade 0-1) cases and in 90% of advanced cases in which the abductor pollicis brevis response was absent.

Conclusions: The 2L-IO DML difference offers high diagnostic value in carpal tunnel syndrome, serving as a complementary test in early stages and a decisive tool in advanced stages. Preferentially recording from the 2L muscle instead of the abductor pollicis brevis may facilitate electrophysiologic evaluation, especially in challenging cases.

Introduction: Conventional EEG interpretation distinguishes spikes (20-70 ms) versus sharp waves (70-200 ms), but the rationale for this distinction is unclear. This preliminary study endeavors to correlate discharge duration with some clinical outcomes.

Methods: We measured spike and sharp wave duration for up to 10 discharges in 100 patients referred for routine, inpatient, or ambulatory EEGs. Excluded were generalized spikes, spike waves, polyspikes, seizures, or lateralized periodic discharges (LPDs).

Results: We measured 882 interictal discharges in 100 patients, comprising structural, genetic, autoimmune, and unknown etiologies. Epileptiform discharges, mainly temporal, were unilateral in 64 and bilateral or multifocal in 36 patients. Each record presented 3 to 10 discharges, with 74% having 10 or more. Mean discharge duration was 71.9 ± 31.4, range 15 to 200 ms. Most patients (87%) had mixed sharps and spikes, with 6% having only sharps and 7% having only spikes. Discharge durations within an individual patient were highly variable. Mean discharge duration and seizure frequency were poorly correlated ( r = -0.023, P = 0.82), as were discharge duration and number of antiseizure medications ( r = -0.027, P = 0.80).

Conclusions: In our series, discharge duration did not correlate with seizure frequency or number of antiseizures medicines. Only 13% of patients had exclusive spikes or sharp waves, suggesting that duration of an individual discharge is not a defining characteristic of that person's epilepsy. Although this study is small and preliminary, it suggests that the distinction between spike and sharp waves at 70 ms may not be clinically relevant and perhaps all epileptiform discharges could be called spikes.

Summary: The orbitofrontal cortex is central to decision making, reward valuation, emotional regulation, and goal-directed behavior. Although traditional cytoarchitectonic classifications, such as Brodmann map, identified multiple cortical areas within the orbitofrontal cortex, recent neuroimaging advancements such as the Human Connectome Project have refined our anatomical understanding in granular detail. This study characterizes the structural and functional connectivity of key orbitofrontal subregions, particularly Brodmann area 11, Brodmann area 13, Brodmann area 14, and Brodmann area 47, corresponding to Human Connectome Project areas 11L, 13L, orbitofrontal cortex (OFC)/polar orbitofrontal cortex, and 47m/47 s/a47r, respectively. Structural connectivity analyses reveal significant large white matter connections with the inferior frontal-occipital fasciculus, uncinate fasciculus, and pathways linking the OFC to the amygdala and temporal cortex. Functionally, 11L is involved in valuation and decision making, 13L contributes to emotion regulation, OFC/polar orbitofrontal cortex plays a key role in reward processing and self-referential cognition, and areas 47 m, 47 s, and a47r have a role in coordinating cognitive and emotional information, as well as language production and semantic processing. These subregions integrate sensory-affective information and support theory of mind and semantic processing. Disruptions in OFC connectivity contribute to neuropsychiatric and neurodegenerative disorders, inducing various symptoms of addiction, obesity, depression, Parkinson disease, and frontotemporal dementia, highlighting the relevance of our improved anatomical understanding of this region for targeted neuromodulation strategies. Importantly, this work leverages an anatomically precise nomenclature from the Human Connectome Project to refine our understanding of the OFC's connectivity, enabling more precise neuromodulatory targeting while improving the reproducibility and sharing of research findings of this region.

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.