Journal of Clinical Neurophysiology最新文献

Purpose: Temporal encephaloceles are a cause of drug-resistant temporal lobe epilepsy; however, their relationship with epileptogenesis is unclear, and optimal surgical resection is uncertain. EEG source localization (ESL) may guide surgical decision-making.

Methods: We reviewed patients at Mayo Clinic Rochester with drug-resistant temporal lobe epilepsy and temporal encephaloceles, who underwent limited resection and had 1-year outcomes. EEG source localization was performed using standard density scalp EEG of ictal and interictal activity. Distance from dipole and standardized low-resolution brain electromagnetic tomography (sLORETA) solutions to the encephalocele were measured. Concordance of ESL with encephalocele and surgical resection was compared with 1-year surgical outcomes.

Results: Seventeen patients met criteria. The mean distances from ESL results to encephalocele center for dipole and sLORETA analyses were 23 mm (SD 9) and 22 mm (SD 11), respectively. Ten patients (55.6%) had Engel I outcomes at 1 year. Dipole-encephalocele distance and sLORETA-encephalocele distance were significantly longer in patients with Engel I outcome and patients whose encephalocele was contained by sLORETA had worse outcome as well; however, multiple logistic regression analysis found that only containment of encephalocele by the sLORETA current density was significant ( P < 0.05), odds ratio 0.12 (95% confidence interval [0.021, 0.71]).

Conclusions: EEG source localization of scalp EEG localizes near encephaloceles, however, typically not in the encephalocele itself; this may be due to scalp EEG sampling propagated activity or alternatively that the seizure onset zone extends beyond the herniated cortex. Surprisingly, we observed increased ESL to encephalocele distances in patients with excellent surgical outcomes. Larger cohort studies including intracranial EEG data are needed to further explore this finding.

Purpose: Motor evoked potential (MEP) amplitude and latency are acquired routinely during neuronavigated transcranial magnetic stimulation, a method of functional mapping of the motor cortex before epilepsy surgery. Although MEP amplitude is routinely used to generate a motor map, MEP latency in patients with focal epilepsy has not been studied systematically. Given that epilepsy may alter myelination, we tested whether intrinsic hand muscle MEPs obtained from the hemisphere containing a seizure focus differ in latency from MEPs collected from the opposite hemisphere.

Methods: Latencies of abductor pollicis brevis MEPs were obtained during routine motor mapping by neuronavigated transcranial magnetic stimulation in children with intractable, unihemispheric focal epilepsy. The primary motor cortex was stimulated bilaterally in all cases. Only data from patients without a lesion involving the corticospinal tract were included. We tested whether abductor pollicis brevis MEP latency varied as a function of seizure focus lateralization.

Results: In the 17 patients who met the inclusion criteria, the mean latency of MEPs with amplitudes in the top and bottom quartiles was shorter in the epileptic hemisphere. Interhemispheric latency difference was greater in patients with lesional epilepsy than in those with nonlesional epilepsy (0.7 ± 0.4 vs. 0.1 ± 0.6 milliseconds, P = 0.02).

Conclusions: Motor evoked potential latency was shortened in the epileptic hemisphere of children with focal epilepsy.

Background: Amblyopia is defined clinically as a difference in best-corrected visual acuity of two or more lines of acuity (0.2 logMAR) between the eyes. Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that can transiently alter the excitability of targeted brain areas in a polarity-specific manner.

Purpose: To detect the effect of tDCS on anisometropic amblyopia.

Methods: This is a randomized controlled trial conducted on 78 patients with anisometropic amblyopia from 4.5 to 12 years of age. All patients presented with monocular amblyopia. They were divided into three groups; each group received five sessions of tDCS (anodal tDCS, cathodal tDCS, and sham tDCS). The active electrode was placed over occipital midline and the reference over central midline. Pattern visual-evoked potentials and contrast sensitivity tests were conducted before, immediately after, and 1 week after tDCS.

Results: The amplitude of P100 was significantly decreased immediately after and 1 week after cathodal tDCS. The latency of P100 immediately after and 1 week after anodal tDCS was significantly decreased and increased significantly after cathodal tDCS. The amplitude of P100 and maximum and minimum contrast sensitivities were significantly increased immediately after and 1 week after anodal tDCS, and maximum contrast sensitivity was significantly decreased immediately after cathodal tDCS.

Conclusion: Anodal tDCS is a promising noninvasive modality for improvement of anisometropic amblyopia.

Purpose: Although the sensor-to-head distance is theoretically known to affect the signal strength in magnetoencephalography (MEG), these values have not been reported for a whole-head MEG system in a large population. We measured the distance and signal strength in 996 patients with epilepsy.

Methods: The MEG sensor array consisted of 102 measurement sites, each of which had two gradiometers and one magnetometer. The sensor-head distance was defined as the minimum distance between each site and a set of digitized scalp points. For the signal strength, we calculated the root-mean-square of the signal values in each sensor over a recording of 4 minutes. For analyses at the individual and sensor levels, these values were averaged over the sensors and patients, respectively. We evaluated the correlation between distance and signal strength at both individual and sensor levels. At the sensor level, we investigated regional differences in these measures.

Results: The individual-level analysis showed only a weak negative correlation between the sensor-head distance and the signal strength. The sensor-level analysis demonstrated a considerably negative correlation for both gradiometers and magnetometers. The sensor-head distances showed no significant differences between the regions, whereas the signal strength was higher in the temporal and occipital sensors than in the frontal and parietal sensors.

Conclusions: Sensor-head distance was not a definitive factor for determining the magnitude of MEG signals in individuals. Yet, the distance is important for the signal strength at a sensor level. Regional differences in signal strength may need to be considered in the analysis and interpretation of MEG.

Purpose: To evaluate the motor function of the lower extremity (LE), we used direct cortical stimulation motor-evoked potential (D-MEP) monitoring with a single six-contact subdural strip electrode placed in the interhemispheric fissure.

Methods: Intraoperative neuromonitoring using D-MEPs in the LE was performed in 18 cases (16 patients) for brain tumor surgery from December 2018 to April 2023 with a follow-up period of at least 3 months. After dural opening, a single six-contact subdural strip electrode was placed inside the interhemispheric fissure. To identify the central sulcus, phase reversal was recorded using somatosensory evoked potentials. Next, direct cortical stimulation was applied to the primary motor cortex. The baseline waveform was defined as a reproducible waveform of 30 µV or higher, and a significant decrease of ≥50% in the amplitude resulted in a warning during surgery.

Results: The success rate of central sulcus identification in the LE was 66.7% (12/18 cases). Direct cortical stimulation motor-evoked potential monitoring could record stable contralateral motor-evoked potentials of the tibialis anterior, gastrocnemius, and abductor hallucis in 16 of 18 cases (88.9%). The mean intensity of stimulation for D-MEPs was 20.5 ± 9.9 mA, and the 16 cases showed no significant reduction in amplitude. Seventeen cases showed no deterioration of motor function of the LE at 1 and 3 months postoperatively. In the remaining case with unsuccessful D-MEP, paralysis of the LE worsened at 1 and 3 months postoperatively.

Conclusions: The placement of electrodes in the interhemispheric fissure on the primary motor cortex of the LE enabled motor-function monitoring in the LE with D-MEPs, suggesting that D-MEP-based monitoring may be a reliable approach.

Purpose: To assess the agreement and consistency of absolute and relative stimulus-response curve (SRC) parameter estimates for upper extremity, lower extremity, and axial muscles.

Methods: Thirty (15 W, age: 27.0 ± 6.3 y, height: 171.9 ± 8.9 cm, weight: 80.2 ± 19.3 kg) healthy adults completed absolute (5% to 100% stimulator output) and relative (65% to 160% motor threshold) SRCs of the first dorsal interosseous, vastus lateralis, and rectus abdominis during submaximal isometric contractions. Mean motor-evoked potential amplitudes were fit with nonlinear regression to derive MEPmax, V50, and slope. Absolute agreement and consistency were assessed with ICCs, Cronbachs alphas, and Bland-Altman plots. Independent t-tests were used to examine differences in motor threshold, physical activity, strength, and muscle activity among participants with valid and invalid SRC parameters.

Results: Absolute and relative SRCs displayed good agreement and consistency for MEPmax and V50 but not slope. Motor thresholds were lower among participants with valid absolute SRCs for the rectus abdominis and vastus lateralis. Motor threshold, physical activity, strength, and muscle activity did not differ among those with valid and invalid parameters for all relative SRCs and absolute SRCs for the first dorsal interosseous.

Conclusions: Absolute and relative SRCs produce similar MEPmax and V50 estimates in the first dorsal interosseous, vastus lateralis, and rectus abdominis. The validity of absolute and relative SRC results may differ depending on individual characteristics and tested muscles.

Purpose: Electroencephalography (EEG) is a noninvasive diagnostic tool that can be of diagnostic value in patients with cognitive disorders. In recent years, increasing emphasis has been on quantitative EEG analysis, which is not easily accessible in clinical practice. The aim of this study was to assess the diagnostic and prognostic value of visual EEG assessment to distinguish different causes of cognitive disorders.

Methods: Patients with cognitive disorders from a specialized memory clinic cohort underwent routine workup including EEG, neuropsychological testing and brain imaging. Electroencephalography parameters including posterior dominant rhythm, background activity, and response to photic stimulation (intermittent photic stimulation) were visually scored. Final diagnosis was made by an expert panel.

Results: A total of 501 patients were included and underwent full diagnostic workup. One hundred eighty-three patients had dementia (111 Alzheimer disease, 30 vascular dementia, 15 frontotemporal dementia, and 9 dementia with Lewy bodies), 66 patients were classified as mild cognitive impairment, and in 176, no neurologic diagnosis was made. Electroencephalography was abnormal in 60% to 90% of patients with mild cognitive impairment and dementia, most profoundly in dementia with Lewy bodies and Alzheimer disease, while frontotemporal dementia had normal EEG relatively often. Only 30% of those without neurologic diagnosis had EEG abnormalities, mainly a diminished intermittent photic stimulation response. Odds ratio of conversion to dementia was 6.1 [1.5-24.7] for patients with mild cognitive impairment with abnormal background activity, compared with those with normal EEG.

Conclusions: Visual EEG assessment has diagnostic and prognostic value in clinical practice to distinguish patients with memory complaints without underlying neurologic disorder from patients with mild cognitive impairment or dementia.

Purpose: Scalp-EEG incompletely covers the frontal lobe cortex. Underrepresentation of frontobasal or frontomesial structures, fast ictal spreading, and false lateralization impede scalp-EEG interpretation. Hence, we investigated the significance of scalp-EEG in the presurgical workup of frontal lobe epilepsy.

Methods: Using descriptive statistical methods and Pearson chi-squared test for group comparisons, we retrospectively investigated postsurgical outcome, interictal epileptiform discharges (iiEDs), and electrographic seizure patterns on scalp-EEG in 81 consecutive patients undergoing resective epilepsy surgery within the margins of the frontal lobe.

Results: Postoperatively, patients with frontopolar iiEDs (n = 7) or concordant frontopolar iiED focus and seizure-onset (n = 2) were seizure free (n = 7/7, Engel Ia). MRI-positive patients with frontopolar iiEDs or frontopolar seizure-onset (n = 1/8 Engel Id, n = 7/8 Engel Ia) underwent surgery without stereo-EEG. Thirteen of 16 patients with frontolateral (n = 8/10, Engel Ia), or left frontobasal (n = 5/6, Engel Ia) seizure-onset undergoing further stereo-EEG, were seizure-free postoperatively. Seizure-onset prevalent over one electrode (n = 37/44 Engel I, p = 0.02), fast activity (FA)/flattening at seizure-onset (n = 29/33 Engel I, p = 0.02), FA/flattening during the seizure (n = 38/46 Engel I, p = 0.05), or focal rhythmic sharp-/spike-/polyspike-and-slow waves during the seizure (n = 24/31, Engel Ia, p = 0.05) were favorable prognostic markers. Interictal polyspike waves (p = 0.006 for Engel Ia) and interictal paroxysmal FA (p = 0.02 for Engel I) were unfavorable prognostic markers.

Conclusions: Frontopolar scalp-EEG findings serve as biomarkers for predicting favorable surgical outcome in lesional frontal lobe epilepsy. Consequently, careful analysis of scalp-EEG assists in bypassing stereo-EEG in these patients.

Purpose: The best possible outcomes in infantile epileptic spasms syndrome require electroclinical remission; however, determining electrographic remission is not straightforward. Although the determination of hypsarrhythmia has inadequate interrater reliability (IRR), the Burden of AmplitudeS and Epileptiform Discharges (BASED) score has shown promise for the reliable interictal assessment of infantile epileptic spasms syndrome. Our aim was to develop a BASED training program and assess the IRR among learners. We hypothesized moderate or better IRR for the final BASED score and the presence or absence of epileptic encephalopathy (+/-EE).

Methods: Using a web-based application, 31 learners assessed 12 unmarked EEGs (length 1-6 hours) from children with infantile epileptic spasms syndrome.

Results: For all readers, the IRR was good for the final BASED score (intraclass correlation coefficient 0.86) and +/-EE (Marginal Multirater Kappa 0.63). For all readers, the IRR was fair to good for all individual BASED score elements.

Conclusions: These findings support the use of our training program to quickly learn the BASED scoring method. The BASED score may be a valuable clinical and research tool. Given that the IRR for the determination of epileptic encephalopathy is not perfect, clinical acumen remains paramount. Additional experience with the BASED scoring technique among learners and advances in collaborative EEG evaluation platforms may improve IRR.