Journal of Clinical Neurophysiology最新文献

Purpose: Bereitschaftspotential (BP) or readiness potential in people with functional movement disorders can aid diagnostic workup. We evaluated the diagnostic value of BP as an interictal EEG marker in people with functional seizures (FS).

Methods: We recorded and analyzed BP interictal before intended movements in 17 adults with FS and 17 controls with alternative diagnoses. We evaluated the signals for the presence of BP, latency, amplitude, and early versus late BP.

Results: Bereitschaftspotential was present in all except one person with FS. We found no significant differences in the latency and amplitude of BP between participants with FS and controls. The early BP showed the most significant variance in amplitude, latency, and presence.

Conclusions: We found interictal typical BP values in participants with FS and variable semiology, while earlier research found interictal no BP in functional movement disorders. These findings do not support the use of BP as an interictal diagnostic tool for FS. Differences in early BP and focus on FS with pure motor semiology are starting points for further research evaluating potential interictal markers in people with FS.

Purpose: Anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis is an autoimmune reaction involving Immunoglobulin G antibodies against GluN1 subunit of NMDAR. Absence of biomarkers for early diagnosis and prognosis poses a challenge. Several small case-control studies have emphasized the prospect of quantitative EEG measurements. This study aimed to analyze and identify novel scalp quantitative EEG biomarkers and their implications on outcome of NMDRA encephalitis compared with a control group.

Methods: Retrospective (2012-2021) case-control study of patients with NMDRA encephalitis and with acute/subacute encephalitis from other causes. Clinical variables and outcomes were assessed with modified Rankin Scale at admission, discharge, and follow-up. All patients underwent extensive diagnostic workup, including scalp EEG within 72 hours of admission. Quantitative EEG was calculated for Renyi, Tsalis entropy, Hjorth complexity, mean energy, and spectral power of the following frequency bands and ratios: delta (0.5-4 Hz), theta (5-8 Hz), alpha (9-14 Hz), beta (15-30 Hz), gamma (31-45 Hz), gamma-beta, beta/alpha, beta/theta, and beta/delta. Descriptive statistics, power frequency bands, complexity measures, and Wilcoxon rank sum test were used.

Results: Patients with anti-NMDAR encephalitis had significantly higher delta frequency peak power, higher beta/alpha and gamma/beta frequency ratios, lower alpha and beta peak power, and lower beta/delta frequency ratio than the control group. In patients with anti-NMDAR encephalitis, higher delta and alpha peak power had the worst clinical outcome, at discharge and follow-up, and patients with higher gamma peak power had better outcomes.

Conclusions: Quantitative EEG is a valuable tool to differentiate anti-NMDAR encephalitis from other inflammatory encephalitis and predict outcomes in patients with anti-NMDAR encephalitis.

Purpose: This pilot study tests the contribution of fluctuating lower motor neuron excitability to motor evoked potential (MEP) variability.

Methods: In six pediatric patients with idiopathic scoliosis and normal neurologic examination, cascades of 30 intraoperative H-reflexes (HRs) and MEPs were evoked in the soleus muscle using constant-current stimulators and recorded through surface electrodes with a 20-second interstimulus interval. First, HRs were obtained with an intensity capable of evoking the maximum response. Subsequently, MEPs were obtained with double trains and an intensity of 700 to 900 mA. Coefficients of variation (CVs) of amplitude and area under the curve from HRs and MEPs were compared using a paired two-tailed Student t test. Coefficients of correlation between the mean CVs of HR and MEP parameters were also assessed.

Results: Pooling the results from the six patients, the mean CV of amplitude from the MEP (24.6 ± 3) was significantly higher than that from the HR (3.5 ± 4.4) ( P = 0.000091). The mean CV of the MEP area under the curve (21.8 ± 4.8) was also statistically significantly higher than that from the HR area under the curve (3.4 ± 4.5) ( P = 0.00091). The coefficients of correlation of the mean CV of the HR amplitude and area under the curve compared with the corresponding values of the MEP were low ( r = 0.29) and very low ( r = 0.03), respectively.

Conclusions: Our results suggest that fluctuations in lower motor neuron excitability may be less important than previously thought to explain the magnitude of MEP variability. The efficacy of corticospinal volleys to recruit a larger and more stable lower motor neuron population would be critical to obtain reproducible MEPs.

Purpose: We demonstrate that different regions of the cerebral cortex have different diurnal rhythms of spontaneously occurring high-frequency oscillations (HFOs).

Methods: High-frequency oscillations were assessed with standard-of-care stereotactic electroencephalography in patients with drug-resistant epilepsy. To ensure generalizability of our findings beyond patients with drug-resistant epilepsy, we excluded stereotactic electroencephalography electrode contacts lying within seizure-onset zones, epileptogenic lesions, having frequent epileptiform activity, and excessive artifact. For each patient, we evaluated twenty-four 5-minute stereotactic electroencephalography epochs, sampled hourly throughout the day, and obtained the HFO rate (number of HFOs/minute) in every stereotactic electroencephalography channel. We analyzed diurnal rhythms of the HFO rates with the cosinor model and clustered neuroanatomic parcels in a standard brain space based on similarity of their cosinor parameters. Finally, we compared overlap among resting-state networks, described in the neuroimaging literature, and chronobiological spatial clusters discovered by us.

Results: We found five clusters that localized predominantly or exclusively to the left perisylvian, left perirolandic and left temporal, right perisylvian and right parietal, right frontal, and right insular-opercular cortices, respectively. These clusters were characterized by similarity of the HFO rates according to the time of the day. Also, these chronobiological spatial clusters preferentially overlapped with specific resting-state networks, particularly default mode network (clusters 1 and 3), frontoparietal network (cluster 1), visual network (cluster 1), and mesial temporal network (cluster 2).

Conclusions: This is probably the first human study to report clusters of cortical regions with similar diurnal rhythms of electrographic activity. Overlap with resting-state networks attests to their functional significance and has implications for understanding cognitive functions and epilepsy-related mortality.

Purpose: Ictal high-frequency oscillations (HFOs) are a reliable indicator of a seizure onset zone for intracranial EEG recordings. Interictal HFOs often are also observed and may be a useful biomarker to supplement ictal data, but distinguishing pathologic from physiologic HFOs continues to be a challenging task. We present a method of classifying HFOs based on morphologic contrast to the background.

Methods: We retrospectively screened 31 consecutive patients who underwent intracranial recordings for epilepsy at Stanford Medical Center during a 2-year period, and 13 patients met the criteria for inclusion. Interictal EEG data were analyzed using an automated event detector followed by morphologic feature extraction and k-means clustering. Instead of only using event features, the algorithm also incorporated features of the background adjacent to the events. High-frequency oscillations with higher morphologic contrast to the background were labeled as pathologic, and "hotspots" with the most active pathologic HFOs were identified and compared with clinically determined seizure onset zones.

Results: Clustering with contrast features produced groups with better separation and more consistent boundaries. Eleven of the 13 patients proceeded to surgery, and patients whose hotspots matched seizure onset zones had better outcomes, with 4 out of 5 "match" patients having no disabling seizures at 1+ year postoperatively (Engel I or International League Against Epilepsy Class 1-2), while all "mismatch" patients continued to have disabling seizures (Fisher exact test P -value = 0.015).

Conclusions: High-frequency oscillations with higher contrast to background more likely represent paroxysmal bursts of pathologic activity. Patients with HFO hotspots outside of identified seizure onset zones may not respond as well to surgery.

Purpose: Sleep is an essential physiologic process, which is frequently disrupted in children with illness and/or injury. Accurate identification and quantification of sleep may provide insights to improve long-term clinical outcomes. Traditionally, however, the identification of sleep stages has relied on the resource-intensive and time-consuming gold standard polysomnogram. We sought to use limited EEG data, converted into density spectrum array EEG, to accurately identify sleep stages in a clinical pediatric population.

Methods: We reviewed 87 clinically indicated pediatric polysomnographic studies with concurrent full montage EEG, between March 2017 and June 2020, of which 11 had normal polysomnogram and EEG interpretations. We then converted the EEG data of those normal studies into density spectral array EEG trends and had five blinded raters classify sleep stage (wakefulness, nonrapid eye movement [NREM] 1, NREM 2, NREM 3, and rapid eye movement) in 5-minute epochs. We compared the classified sleep stages from density spectral array EEG to the gold standard polysomnogram.

Results: Inter-rater reliability was highest ( κ = 0.745, P < 0.0001) when classifying state into wakefulness, NREM sleep, and rapid eye movement sleep. Agreement between group classification and polysomnogram was highest ( κ = 0.873, [0.819, 0.926], P < 0.0001) when state was classified into wakefulness and sleep and was lowest ( κ = 0.674 [0.645, 0.703], P < 0.0001) when classified into wakefulness, NREM 1, NREM 2, NREM 3, and rapid eye movement. The most common error that raters made was overscoring of NREM 1.

Conclusions: Density spectral array EEG can be used to identify sleep stages in clinical pediatric patients without relying on traditional polysomnography.

Summary: This case report presents two illustrative cases of cyclic alternating pattern of encephalopathy, showcasing its distinct quantitative EEG signature alongside observed correlations with cardiorespiratory fluctuations. Recognizing cyclic alternating pattern encephalopathy patterns may provide clinicians with an actionable marker, guiding timely interventions and potentially improving outcomes in critically ill patients.

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: Electrophysiologic changes in early Guillain-Barré Syndrome (GBS) can be nondiagnostic. Improved testing paradigms may improve hyperacute treatment.

Methods: This work prospectively evaluated consecutive patients admitted to a metropolitan teaching hospital in Melbourne, Australia, with suspected acute GBS. We performed extensive neurophysiology at three different time points. Novel tests, including cutaneous silent periods, long latency reflexes, and contraction-induced H reflexes, were assessed.

Results: Twenty-three participants were studied, including 13 cases of acute GBS. In total, 69% of acute cases of GBS were accurately diagnosed on the first nerve conduction study using published neurophysiologic criteria, with serial studies rarely altering the GBS subtype classification. Antidromic and orthodromic upper limb sensory studies were diagnostically equivalent. A sural sparing pattern was seen in 77% of cases of GBS at the first test. Long latency reflexes and contraction-induced H reflexes testing were abnormal in most participants but were limited by muscle weakness in some. Cutaneous silent periods testing was unobtainable in approximately 50% of cases because of weakness and did not discriminate from mimic disorders.

Conclusions: Abnormalities of long latency reflexes and contraction-induced H reflexes may be helpful where initial electrophysiology is nondiagnostic but are nonspecific. Cutaneous silent periods testing seems of limited value. Comprehensive testing provides diagnostic certainty in most cases of GBS from the very first study.