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: 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: 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: 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.

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.

Purpose: Motor evoked potential (MEP) monitoring has been widely applied in various neurosurgical operations. This study aimed to assess the predictive value of MEP monitoring for postoperative motor deficit (PMD) in patients with insular gliomas.

Methods: Demographic and clinical data, MEP monitoring data, and follow-up data of 42 insular glioma patients were retrospectively reviewed, and 40 patients were finally enrolled. The value of MEP monitoring for predicting PMD was assessed with sensitivity, specificity, and false-positive/false-negative rates. Binary multivariate logistic regression analysis was performed to further identify the predictive value of MEP monitoring.

Results: Statistical analysis showed that irreversible MEP changes, but not all MEP changes, were more effective in predicting PMD. The sensitivity and specificity of irreversible MEP changes for predicting long-term PMD were 85.71 and 93.94%, whereas the false-positive and -negative rates were 25.00 and 3.12% respectively. In addition, irreversible MEP changes were identified as the only independent predictor for long-term PMD (odds ratio, 101.714; 95% confidence interval, 6.001-1724.122; p = 0.001).

Conclusions: MEP monitoring has been proven to be feasible in insular glioma surgery. Irreversible MEP changes showed good performance in predicting PMD. Their absence can offer an optimistic expectation for the long-term motor outcome. The findings can provide the surgical team with a more effective interpretation of MEP changes and contribute to exploring tailored MEP warning criteria.

Purpose: Intraoperative bulbocavernosus reflex neuromonitoring has been utilized to protect bowel, bladder, and sexual function, providing a continuous functional assessment of the somatic sacral nervous system during surgeries where it is at risk. Bulbocavernosus reflex data may also provide additional functional insight, including an evaluation for spinal shock, distinguishing upper versus lower motor neuron injury (conus vs. cauda syndromes) and prognosis for postoperative bowel and bladder function. Continuous intraoperative bulbocavernosus reflex monitoring has been utilized to provide the surgeon with an ongoing functional assessment of the anatomical elements involved in the S2-S4 mediated reflex arc including the conus, cauda equina and pudendal nerves. Intraoperative bulbocavernosus reflex monitoring typically includes the electrical activation of the dorsal nerves of the genitals to initiate the afferent component of the reflex, followed by recording the resulting muscle response using needle electromyography recordings from the external anal sphincter.

Methods: Herein we describe a complementary and novel technique that includes recording electromyography responses from the external urethral sphincter to monitor the external urethral sphincter reflex. Specialized foley catheters embedded with recording electrodes have recently become commercially available that provide the ability to perform intraoperative external urethral sphincter muscle recordings.

Results: We describe technical details and the potential utility of incorporating external urethral sphincter reflex recordings into existing sacral neuromonitoring paradigms to provide redundant yet complementary data streams.

Conclusions: We present two illustrative neurosurgical oncology cases to demonstrate the utility of the external urethral sphincter reflex technique in the setting of the necessary surgical sacrifice of sacral nerve roots.