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...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.
J Clin Neurophysiol
· 2026 Feb · PMID 40434071
·
Full text
PURPOSE: To improve EEG source localization results of interictal epileptic discharges (IED) by applying postprocessing step to electrical source imaging (ESI). METHODS: Localization error of ESI was evaluated in compari...PURPOSE: To improve EEG source localization results of interictal epileptic discharges (IED) by applying postprocessing step to electrical source imaging (ESI). METHODS: Localization error of ESI was evaluated in comparison to known sources of stimulation potentials (ESP) by recording simultaneous stereo-EEG/scalp EEG. Error vectors were defined as the offset of the ESI-dipole of ESP to the stereo-EEG contacts used for stimulation. The inverted error vector was applied to the ESI-dipole of IED (IED-dipole). RESULTS: Seven IED clusters were evaluated. Corrected IED-dipoles were located closer to IED-onset contacts on stereo-EEG than uncorrected IED-dipoles ( median [ IQR ]: 7.8 [2.5] versus 18.7 [10.7] mm, P = 0.02). Anatomically, for high skull conductivities, all corrected IED-dipoles were located in cortical structures or adjacent to epileptogenic lesion, whereas uncorrected IED-dipoles were located in white matter or CSF ( P = 0.02). Physiologically, cortical extent of IED generators estimated from corrected IED-dipoles was 16.5 cm 2 ( IQR = 10.4 cm 2 ) and 7.4 cm 2 (range 5.8-9.2 cm 2 ) in the group of anterior temporal IED and prefrontal IED, respectively; the former was concordant with the extent estimated by subdural electrodes. In addition, the relationship of stereo-EEG IED amplitude (a) drop with increasing distance (d) from corrected IED-dipole could be modeled as a negative power equation a(d)∝1/d b ( R2 = 0.87, P < 0.01), with b ranging from 0.79 to 2.3, median: 1.57, consistent with a simulation model of the sensitivity of intracerebral electrode. CONCLUSIONS: Application of inverted error vector reduces localization error and shifts IED-dipole to an anatomically and physiologically plausible location.
PURPOSE: Charcot-Marie-Tooth disease (CMT), the most common form of hereditary neuropathy causes varying disability. Valid and accessible tools are needed for clinical and research evaluation. Previous studies have shown...PURPOSE: Charcot-Marie-Tooth disease (CMT), the most common form of hereditary neuropathy causes varying disability. Valid and accessible tools are needed for clinical and research evaluation. Previous studies have shown sonographic muscle thickness correlates with clinical and electrophysiological findings in many neuromuscular disorders. This study examines the correlation between muscle thickness in CMT1A patients with disease progression and clinical parameters, including the CMT neuropathy scale. METHODS: Prospective study evaluating CMT1A patients between January and December 2023 at the neuromuscular unit in Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. Patients underwent comprehensive clinical evaluation including the CMT neuropathy scale, and quantitative sonographic evaluation of muscle thickness in eight limb muscles. RESULTS: Eight CMT1A patients were examined, five on two occasions. Sum muscle thickness measured by ultrasound strongly correlated with most clinical parameters, including the CMT neuropathy scale. However, disease progression showed strong correlation with CMT neuropathy scale only. CONCLUSIONS: In CMT1A patients, standardized quantitative sonographic muscle thickness assessment is a valid and promising tool for evaluating disease burden and, to a lesser extent, progression, showing strong correlations with key clinical parameters. Consistent with prior studies of other neuromuscular disorders.
PURPOSE: Outpatient seizure monitoring is crucial for optimizing treatment strategies in epilepsy; however, traditional approaches such as seizure diaries and wearables have limitations in accuracy and practicality. This...PURPOSE: Outpatient seizure monitoring is crucial for optimizing treatment strategies in epilepsy; however, traditional approaches such as seizure diaries and wearables have limitations in accuracy and practicality. This study evaluated the adherence and utility of an implanted subcutaneous EEG monitoring system in patients with focal temporal lobe epilepsy. METHODS: At a tertiary epilepsy center, patients with focal epilepsy received a subcutaneous two-channel EEG system for ultra-long-term monitoring. The system includes a subcutaneously implanted electrode for data recording and a behind-the-ear companion device for the power supply and data transmission. Patient adherence to the device was evaluated using generalized estimating equations, considering sex, daytime/nighttime periods, age, and temporal course of measurements. The correlations between adherence and electrographic or diary-recorded seizures were also assessed. RESULTS: Fifteen adult patients (mean age: 45.6 years, 6 females) were monitored for an average of 200.6 days, with 416 electrographic seizures confirmed in 13 patients. The median adherence was 89.3% (interquartile range, [75.6%, 93.4%]), with females showing significantly higher adherence than males ( β , -1.1600; P = 0.049). Seizure diary reporting sensitivity and precision were 20.8% and 56.4%, respectively, compared with confirmed electrographic seizures. Adherence correlated positively with confirmed electrographic seizures ( r , 0.40; P, 0.004), but not with diary reports ( r , -0.22; P, 0.13). CONCLUSIONS: Patients using the subcutaneous EEG system demonstrated high adherence and reliable seizure monitoring, suggesting that it could serve as a valuable tool for managing focal epilepsy in clinical practice.
PURPOSE: Rolandic epileptiform discharges with tangential dipole (T-dipole) configurations are associated with favorable prognosis. Whether the same is true for T-dipole epileptiform discharges in other brain regions is...PURPOSE: Rolandic epileptiform discharges with tangential dipole (T-dipole) configurations are associated with favorable prognosis. Whether the same is true for T-dipole epileptiform discharges in other brain regions is less established and is the objective of this study. METHODS: Over 20 years, patients with epileptiform discharges were identified as follows: frontal (F = 176), temporal (T = 196), central (C = 201), parietal (P = 120), and occipital (O = 205). T-dipoles were documented. Clinical features of children with and without T-dipole were compared both regardless of brain region and separately for each brain region. RESULTS: The prevalence of T-dipoles was 232/898 (25.8%) overall and within different regions as follows: T = 104 (53.1%), O = 51 (24.9%), P = 23 (19.2%), C = 35 (17.4%), and F = 19 (10.8%). Most had epilepsy (T-dipole: 193 [83.2%] and nondipole: 532 [79.9%]). Regardless of region, T-dipole was associated with less drug-resistant epilepsy (11 [4.7%] vs. 202 [30.3%], P < 0.001), developmental delay (57 [24.6%] vs. 436 [51.0%], P < 0.001), school performance difficulties (SPD) (101 [43.5%] vs. 410 [61.6%], P < 0.001), autism (30 [12.9%] vs. 127 [19.1%], P = 0.037), and abnormal examination (28 [12.1%] vs. 257 [38.6%], P < 0.001]). Within different brain regions, on logistic regression, T-dipole was associated with lower odds of drug-resistant epilepsy (F, T, C, P, and O), developmental delay (F, T, C, and P), SPD (F, T, and C), autism (F and T), abnormal examination (F, T, C, and O), and abnormal neuroimaging (T, C, P, and O). CONCLUSIONS: On routine EEG analysis, focal epileptiform discharges with T-dipoles, regardless of brain region, are associated with a more favorable clinical course.
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 incapacita...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.
Versive head turns, characterized by forced and involuntary head movements leading to sustained unnatural positioning, are consistently recognized as reliable indicators of contralateral hemisphere involvement. This stud...Versive head turns, characterized by forced and involuntary head movements leading to sustained unnatural positioning, are consistently recognized as reliable indicators of contralateral hemisphere involvement. This study presents a case demonstrating ictal semiology marked by the simultaneous onset of blurred vision, spinning, distorted voice, and an early left-versive head turn. The versive head turn semiology correlated with rapid ictal discharges in the ipsilateral posterior cingulate gyrus and was reproducible with direct cortical stimulation during stereoelectroencephalography evaluation. A comprehensive literature review (from 1994 to 2023) was conducted to investigate the relationship between early ictal head version semiology, either contralateral or ipsilateral, and localization of the ictal onset regions. Analysis of 105 patients revealed that 87% exhibited early contralateral head version noted from seizures originating from anterior regions (frontal lobe or anterior/midcingulate regions), compared with 56% in posterior regions (parietal, occipital, or posterior cingulate areas) and 44% in the temporal lobe. When comparing anterior to temporal regions, the anterior group had an eightfold higher likelihood of contralateral versive seizures (odds ratios = 8.1, 95% confidence interest, 1.72-38.35, P = 0.0038), indicating a significantly higher likelihood of ipsilateral early head version in temporal lobe seizures. There was no significant difference in the likelihood of ipsilateral head version between the anterior and posterior groups or between the posterior and temporal groups. These findings underscore the need for cautious interpretation of early head versive signs alone as indicators of contralateral hemisphere epileptogenic zone, advocating for consideration of ipsilateral hemisphere epileptogenic zone involvement in presurgical hypotheses, in selected patients.
PURPOSE: Single-fiber electromyography is the most sensitive tool for diagnosing neuromuscular diseases but is limited in differentiating between presynaptic and postsynaptic neuromuscular junction involvement with incre...PURPOSE: Single-fiber electromyography is the most sensitive tool for diagnosing neuromuscular diseases but is limited in differentiating between presynaptic and postsynaptic neuromuscular junction involvement with increased jitter. With rising botulinum toxin (BoNT) use for therapeutic and cosmetic applications, referrals for electromyography because of myasthenia-like symptoms have increased, complicating differential diagnosis. This study examines whether spike count measurements from single-use concentric needle electrodes can distinguish BoNT effects from neuromuscular junction diseases such as myasthenia gravis. METHODS: We analyzed 49 patients and 26 controls, assessing jitter and spike count with concentric needle electrodes in the frontalis muscle. Groups included those exposed to BoNT (>1 month and <1 month prior) and patients with myasthenia gravis, with normal jitter controls for comparison. Data were analyzed for jitter, spike count, and additional electrophysiologic parameters using standard statistical tests ( P < 0.05). RESULTS: Results showed that spike counts were significantly different across the groups. Higher spike counts with lower single spike frequency were found in patients with BoNT exposure >1 month, suggesting a differentiation point from primary neuromuscular involvement. In contrast, patients with myasthenia gravis exhibited increased jitter without increased spike counts. CONCLUSIONS: These findings indicate that spike count analysis with concentric needle electrodes may aid in differentiating iatrogenic BoNT effects from primary neuromuscular junction disorders, such as myasthenia gravis. However, further studies with larger sample sizes are necessary to validate these results.
Thalamic neuromodulation has emerged as a promising treatment for drug-resistant epilepsy, with deep brain stimulation of the anterior nucleus of the thalamus currently Food and Drug Administration approved for this purp...Thalamic neuromodulation has emerged as a promising treatment for drug-resistant epilepsy, with deep brain stimulation of the anterior nucleus of the thalamus currently Food and Drug Administration approved for this purpose. The Stimulation of the Anterior Nucleus of Thalamus for Epilepsy trial demonstrated that chronic anterior nucleus of the thalamus stimulation can significantly reduce seizure burden. In addition, the centromedian nucleus is gaining interest as a potential neuromodulation target among epilepsy experts, though its use remains off-label. Effective selection of neuromodulation targets requires reliable biomarkers, ideally with real-time feedback, yet studies on the acute effects of thalamic stimulation on epileptiform activity remain limited. Our cases provide novel evidence of acute suppression of epileptiform activity in the cerebral cortex-specifically, the cingulate and insular cortices-after anterior nucleus of the thalamus and centromedian nucleus stimulation, respectively, through stereoelectroencephalography electrodes. This finding enhances our understanding of cortical responses to thalamic stimulation and supports its therapeutic potential in both chronic and acute settings. Emerging research suggests that other thalamic nuclei may also play a role in managing epilepsy originating from different brain regions. We emphasize that routine stereoelectroencephalography implantation in thalamic nuclei may provide valuable clinical insights and aid in selecting the optimal target for stimulation. This case mini-series contributes to the growing evidence supporting the therapeutic potential of thalamic neuromodulation in epilepsy treatment.
PURPOSE: Continuous electroencephalography (cEEG) is used in the critical care setting for seizure detection and treatment, sedation management, and ischemia detection. Further evidence is needed to support whether early...PURPOSE: Continuous electroencephalography (cEEG) is used in the critical care setting for seizure detection and treatment, sedation management, and ischemia detection. Further evidence is needed to support whether early cEEG use can improve outcomes. We examined whether time from admission to cEEG initiation affects outcomes. METHODS: This is a single-center cohort study of critically ill adults (age > 18 years) who underwent cEEG monitoring within 7 days of admission from January to December 2019. Patients with anoxic brain injury were excluded. Time (hours) from admission to cEEG was recorded. Outcomes were in-hospital mortality and poor discharge modified Rankin Score (4-6). Results are reported as median [quartile range] and odds ratio (OR) [confidence intervals, CI]. RESULTS: In total, 464 patients met eligibility. Median time to cEEG was 23 hours [13, 52]. On multivariable analysis, increasing time to cEEG was associated with discharge mortality (OR, 1.006 [CI, 1.0002-1.013], 0.1%/hour [CI, 0.02-0.2]) and poor outcome (OR, 1.013 [CI, 1.005-1.020], 0.2%/hour [CI, 0.07-0.3]). Median time to cEEG initiation in patients with clinical concern for seizures/status at presentation ( n = 121) was 12 hours [6, 17] and in patients without clinical concern for seizures at presentation ( n = 343) was 31 hours [18, 66]. In patients without clinical concern for seizures/status epilepticus at presentation, time to cEEG continued to be associated with mortality (OR, 1.007 [CI, 1.001-1.014)] and poor outcome (OR, 1.012 [CI, 1.003-1.021]). CONCLUSIONS: Increasing time to cEEG initiation was associated with higher mortality and worse outcomes. We hypothesize earlier cEEG results in timely interventions including treatment escalation and de-escalation that may improve outcomes.
PURPOSE: The aim of this study is to develop an intraoperative olfactory monitoring system using olfactory evoked potential produced by electrical stimulation. Furthermore, the study seeks to ascertain the feasibility an...PURPOSE: The aim of this study is to develop an intraoperative olfactory monitoring system using olfactory evoked potential produced by electrical stimulation. Furthermore, the study seeks to ascertain the feasibility and safety of olfactory evoked potential. This study lays the groundwork for safeguarding olfactory function during surgical procedures. METHODS: We provided a detailed description of the procedure involving electrical stimulation of the olfactory mucosa to induce olfactory evoked potentials during endonasal endoscopic surgery under general anesthesia. This study enrolled 20 patients undergoing endonasal endoscopic surgery. Before surgery, all patients reported no olfactory complaints, and T&T olfactometry did not detect any olfactory disorders. Olfactory evoked potentials were recorded from various regions of the nasal mucosa and followed by analysis of waveform differentiation, latencies, and amplitudes. RESULTS: Typical "N1-P1-N2" three-phase waves, consistent with the waveforms of olfactory evoked potentials recorded in previous studies, were collected from the olfactory mucosa in each case. No significant alteration was observed in the patients' olfactory function pre- and postsurgery. The latencies of the "N1-P1-N2" waves recorded during the operation were 12.2 ± 6.9 ms, 28.9 ± 10.0 ms, and 47.1 ± 11.6 ms, respectively, whereas the amplitudes of the "N1-P1" and "P1-N2" waves measured 0.9 and 0.6 μV, respectively. CONCLUSIONS: Intraoperative olfactory monitoring through olfactory evoked potential produced by electrical stimulation is achievable and safe.
In the 18th century, Luigi Galvani proposed the hypothesis of animal electricity, which is produced by the brain and distributed through the nerves to the muscles. This was the cornerstone of what is known today as the m...In the 18th century, Luigi Galvani proposed the hypothesis of animal electricity, which is produced by the brain and distributed through the nerves to the muscles. This was the cornerstone of what is known today as the modern study of nerve function, earning him the title of the Father of Clinical Neurophysiology. The 19th century was subsequently marked by two major figures: Santiago Ramón y Cajal (Neuron Theory) and Hans Berger, known for describing cerebral electrical activity and recording the first electroencephalograms. In Mexico, Clinical Neurophysiology emerged in the late 19th century and consolidated itself in the first half of the 20th century. In the year of 1938, Dr. Clemente Robles and Teodoro Flores Covarrubias built the first electroencephalograph, marking the beginning of the era of Clinical Neurophysiology. Initially, this diagnostic tool was primarily applied to psychiatric patients, as there was no clear separation between psychiatry and neurology and patients were treated jointly at the largest psychiatric center of that time, "La Castañeda." In 1968, the Mexican Society of Electroencephalography A.C. was founded and later changed its name to the Mexican Society of Clinical Neurophysiology A.C. Simultaneously, its members achieved universal recognition of the medical specialty, which has become established in clinical practice and has shown progressive academic and scientific growth in Mexico.
J Clin Neurophysiol
· 2026 Jan · PMID 40102207
·
Full text
PURPOSE: Aim of the study was to examine the associations between abductor pollicis brevis (APB) muscle stiffness evaluated by shear wave elastography and electrodiagnostic study findings in patients with carpal tunnel s...PURPOSE: Aim of the study was to examine the associations between abductor pollicis brevis (APB) muscle stiffness evaluated by shear wave elastography and electrodiagnostic study findings in patients with carpal tunnel syndrome. The association between shear wave elastography and APB muscle echogenicity was also examined. METHODS: This prospective study included patients who were referred to electrodiagnostic studies because of upper limb symptoms. The electrodiagnostic studies consisted of nerve conduction studies and needle-electromyography. Abductor pollicis brevis muscle shear wave velocity was measured, and muscle echogenicity assessed using the Heckmatt grading scale. RESULTS: In total, 97 hands were included in the nerve conduction studies. Of these, 53 APB muscles were further examined with needle-electromyography. Shear wave velocity correlated positively with the neurophysiologic severity of carpal tunnel syndrome ( r = 0.449, P = 0.028, N = 26). Mean shear wave velocity was faster in the APB muscles with neurogenic findings (mean 2.72 m/second, ±SD 0.36) than muscles with normal findings (2.48 m/second, ±SD 0.34, P = 0.036). In receiver operating characteristic analysis, the best shear wave velocity cutoff value was 2.66 m/second. With this cutoff value, the sensitivity was 0.692, while the 1-specificity was 0.233. Only seven APB muscles showed increased echogenicity. CONCLUSIONS: Shear wave velocity of APB muscle is positively associated with the neurophysiologic severity of carpal tunnel syndrome. Carpal tunnel syndrome-related axonal damage also seems to increase shear wave velocity in APB muscle; however, according to the receiver operating characteristic analysis, the method is not yet suitable for clinical use to define muscle denervation. The findings of this study show that shear wave elastography has potential as an additional clinical tool in the diagnostics of carpal tunnel syndrome.