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  • 1
    Online Resource
    Online Resource
    A structured ICA-based process for removing auditory evoked potentials
    Springer Science and Business Media LLC ; 2022
    In:  Scientific Reports Vol. 12, No. 1 ( 2022-01-26)
    Details
    In: Scientific Reports, Springer Science and Business Media LLC, Vol. 12, No. 1 ( 2022-01-26)
    Abstract: Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs), recorded using electroencephalography (EEG), reflect a combination of TMS-induced cortical activity and multi-sensory responses to TMS. The auditory evoked potential (AEP) is a high-amplitude sensory potential—evoked by the “click” sound produced by every TMS pulse—that can dominate the TEP and obscure observation of other neural components. The AEP is peripherally evoked and therefore should not be stimulation site specific. We address the problem of disentangling the peripherally evoked AEP of the TEP from components evoked by cortical stimulation and ask whether removal of AEP enables more accurate isolation of TEP. We hypothesized that isolation of the AEP using Independent Components Analysis (ICA) would reveal features that are stimulation site specific and unique individual features. In order to improve the effectiveness of ICA for removal of AEP from the TEP, and thus more clearly separate the transcranial-evoked and non-specific TMS-modulated potentials, we merged sham and active TMS datasets representing multiple stimulation conditions, removed the resulting AEP component, and evaluated performance across different sham protocols and clinical populations using reduction in Global and Local Mean Field Power (GMFP/LMFP) and cosine similarity analysis. We show that removing AEPs significantly reduced GMFP and LMFP in the post-stimulation TEP (14 to 400 ms), driven by time windows consistent with the N100 and P200 temporal characteristics of AEPs. Cosine similarity analysis supports that removing AEPs reduces TEP similarity between subjects and reduces TEP similarity between stimulation conditions. Similarity is reduced most in a mid-latency window consistent with the N100 time-course, but nevertheless remains high in this time window. Residual TEP in this window has a time-course and topography unique from AEPs, which follow-up exploratory analyses suggest could be a modulation in the alpha band that is not stimulation site specific but is unique to individual subject. We show, using two datasets and two implementations of sham, evidence in cortical topography, TEP time-course, GMFP/LMFP and cosine similarity analyses that this procedure is effective and conservative in removing the AEP from TEP, and may thus better isolate TMS-evoked activity. We show TEP remaining in early, mid and late latencies. The early response is site and subject specific. Later response may be consistent with TMS-modulated alpha activity that is not site specific but is unique to the individual. TEP remaining after removal of AEP is unique and can provide insight into TMS-evoked potentials and other modulated oscillatory dynamics.
    Type of Medium: Online Resource
    ISSN: 2045-2322
    URL: Article
    DOI: 10.1038/s41598-022-05397-3
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2022
    detail.hit.zdb_id: 2615211-3
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  • 2
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    Neurophysiologic predictors of individual risk for post‐operative delirium after elective surgery
    Wiley ; 2023
    In:  Journal of the American Geriatrics Society Vol. 71, No. 1 ( 2023-01), p. 235-244
    Details
    In: Journal of the American Geriatrics Society, Wiley, Vol. 71, No. 1 ( 2023-01), p. 235-244
    Abstract: Post‐surgical delirium is associated with increased morbidity, lasting cognitive decline, and loss of functional independence. Within a conceptual framework that delirium is triggered by stressors when vulnerabilities exist in cerebral connectivity and plasticity, we previously suggested that neurophysiologic measures might identify individuals at risk for post‐surgical delirium. Here we demonstrate the feasibility of the approach and provide preliminary experimental evidence of the predictive value of such neurophysiologic measures for the risk of delirium in older persons undergoing elective surgery. Methods Electroencephalography (EEG) and transcranial magnetic stimulation (TMS) were collected from 23 patients prior to elective surgery. Resting‐state EEG spectral power ratio (SPR) served as a measure of integrity of neural circuits. TMS–EEG metrics of plasticity (TMS‐plasticity) were used as indicators of brain capacity to respond to stressors. Presence or absence of delirium was assessed using the confusion assessment method (CAM). We included individuals with no baseline clinically relevant cognitive impairment (MoCA scores ≥21) in order to focus on subclinical neurophysiological measures. Results In patients with no baseline cognitive impairment ( N  = 20, age = 72 ± 6), 3 developed post‐surgical delirium (MoCA = 24 ± 2.6) and 17 did not (controls; MoCA = 25 ± 2.4). Patients who developed delirium had pre‐surgical resting‐state EEG power ratios outside the 95% confidence interval of controls, and 2/3 had TMS‐plasticity measures outside the 95% CI of controls. Conclusions Consistent with our proposed conceptual framework, this pilot study suggests that non‐invasive and scalable neurophysiologic measures can identify individuals at risk of post‐operative delirium. Specifically, abnormalities in resting‐state EEG spectral power or TMS‐plasticity may indicate sub‐clinical risk for post‐surgery delirium. Extension and confirmation of these findings in a larger sample is needed to assess the clinical utility of the proposed neurophysiologic markers, and to identify specific connectivity and plasticity targets for therapeutic interventions that might minimize the risk of delirium.
    Type of Medium: Online Resource
    ISSN: 0002-8614 , 1532-5415
    URL: Issue
    URL: Article
    DOI: 10.1111/jgs.v71.1
    DOI: 10.1111/jgs.18072
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2040494-3
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  • 3
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    Performance of Spectrogram-Based Seizure Identification of Adult EEGs by Critical Care Nurses and Neurophysiologists
    Ovid Technologies (Wolters Kluwer Health) ; 2017
    In:  Journal of Clinical Neurophysiology Vol. 34, No. 4 ( 2017-07), p. 359-364
    Details
    In: Journal of Clinical Neurophysiology, Ovid Technologies (Wolters Kluwer Health), Vol. 34, No. 4 ( 2017-07), p. 359-364
    Abstract: Continuous EEG screening using spectrograms or compressed spectral arrays (CSAs) by neurophysiologists has shorter review times with minimal loss of sensitivity for seizure detection when compared with visual analysis of raw EEG. Limited data are available on the performance characteristics of CSA-based seizure detection by neurocritical care nurses. Methods: This is a prospective cross-sectional study that was conducted in two academic neurocritical care units and involved 33 neurointensive care unit nurses and four neurophysiologists. Results: All nurses underwent a brief training session before testing. Forty two-hour CSA segments of continuous EEG were reviewed and rated for the presence of seizures. Two experienced clinical neurophysiologists masked to the CSA data performed conventional visual analysis of the raw EEG and served as the gold standard. The overall accuracy was 55.7% among nurses and 67.5% among neurophysiologists. Nurse seizure detection sensitivity was 73.8%, and the false-positive rate was 1-per-3.2 hours. Sensitivity and false-alarm rate for the neurophysiologists was 66.3% and 1-per-6.4 hours, respectively. Interrater agreement for seizure screening was fair for nurses (Gwet AC1 statistic: 43.4%) and neurophysiologists (AC1: 46.3%). Conclusions: Training nurses to perform seizure screening utilizing continuous EEG CSA displays is feasible and associated with moderate sensitivity. Nurses and neurophysiologists had comparable sensitivities, but nurses had a higher false-positive rate. Further work is needed to improve sensitivity and reduce false-alarm rates.
    Type of Medium: Online Resource
    ISSN: 0736-0258
    URL: Article
    DOI: 10.1097/WNP.0000000000000368
    RVK:
    XA 10000
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2017
    detail.hit.zdb_id: 2065729-8
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  • 4
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    Absence of early epileptiform abnormalities predicts lack of seizures on continuous EEG
    Ovid Technologies (Wolters Kluwer Health) ; 2012
    In:  Neurology Vol. 79, No. 17 ( 2012-10-23), p. 1796-1801
    Details
    In: Neurology, Ovid Technologies (Wolters Kluwer Health), Vol. 79, No. 17 ( 2012-10-23), p. 1796-1801
    Type of Medium: Online Resource
    ISSN: 0028-3878 , 1526-632X
    URL: Article
    DOI: 10.1212/WNL.0b013e3182703fbc
    RVK:
    XA 10000
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2012
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  • 5
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    Successful aging after elective surgery II : S tudy design and methods
    Wiley ; 2023
    In:  Journal of the American Geriatrics Society Vol. 71, No. 1 ( 2023-01), p. 46-61
    Details
    In: Journal of the American Geriatrics Society, Wiley, Vol. 71, No. 1 ( 2023-01), p. 46-61
    Abstract: The Successful Aging after Elective Surgery (SAGES) II study was designed to increase knowledge of the pathophysiology and linkages between delirium and dementia. We examine novel biomarkers potentially associated with delirium, including inflammation, Alzheimer's disease (AD) pathology and neurodegeneration, neuroimaging markers, and neurophysiologic markers. The goal of this paper is to describe the study design and methods for the SAGES II study. Methods The SAGES II study is a 5‐year prospective observational study of 400–420 community dwelling persons, aged 65 years and older, assessed prior to scheduled surgery and followed daily throughout hospitalization to observe for development of delirium and other clinical outcomes. Delirium is measured with the Confusion Assessment Method (CAM), long form, after cognitive testing. Cognitive function is measured with a detailed neuropsychologic test battery, summarized as a weighted composite, the General Cognitive Performance (GCP) score. Other key measures include magnetic resonance imaging (MRI), transcranial magnetic stimulation (TMS)/electroencephalography (EEG), and Amyloid positron emission tomography (PET) imaging. We describe the eligibility criteria, enrollment flow, timing of assessments, and variables collected at baseline and during repeated assessments at 1, 2, 6, 12, and 18 months. Results This study describes the hospital and surgery‐related variables, delirium, long‐term cognitive decline, clinical outcomes, and novel biomarkers. In inter‐rater reliability assessments, the CAM ratings (weighted kappa = 0.91, 95% confidence interval, CI = 0.74–1.0) in 50 paired assessments and GCP ratings (weighted kappa = 0.99, 95% CI 0.94–1.0) in 25 paired assessments. We describe procedures for data quality assurance and Covid‐19 adaptations. Conclusions This complex study presents an innovative effort to advance our understanding of the inter‐relationship between delirium and dementia via novel biomarkers, collected in the context of major surgery in older adults. Strengths include the integration of MRI, TMS/EEG, PET modalities, and high‐quality longitudinal data.
    Type of Medium: Online Resource
    ISSN: 0002-8614 , 1532-5415
    URL: Issue
    URL: Article
    DOI: 10.1111/jgs.v71.1
    DOI: 10.1111/jgs.18065
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2040494-3
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  • 6
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    EEG Functional Connectivity is a Weak Predictor of Causal Brain Interactions
    Springer Science and Business Media LLC ; 2020
    In:  Brain Topography Vol. 33, No. 2 ( 2020-03), p. 221-237
    Details
    In: Brain Topography, Springer Science and Business Media LLC, Vol. 33, No. 2 ( 2020-03), p. 221-237
    Type of Medium: Online Resource
    ISSN: 0896-0267 , 1573-6792
    URL: Article
    DOI: 10.1007/s10548-020-00757-6
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2020
    detail.hit.zdb_id: 2015003-9
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  • 7
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    The probability of seizures during EEG monitoring in critically ill adults
    Elsevier BV ; 2015
    In:  Clinical Neurophysiology Vol. 126, No. 3 ( 2015-03), p. 463-471
    Details
    In: Clinical Neurophysiology, Elsevier BV, Vol. 126, No. 3 ( 2015-03), p. 463-471
    Type of Medium: Online Resource
    ISSN: 1388-2457
    URL: Article
    DOI: 10.1016/j.clinph.2014.05.037
    Language: English
    Publisher: Elsevier BV
    Publication Date: 2015
    detail.hit.zdb_id: 1499934-1
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  • 8
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    High Risk for Seizures Following Subarachnoid Hemorrhage Regardless of Referral Bias
    Springer Science and Business Media LLC ; 2014
    In:  Neurocritical Care Vol. 21, No. 3 ( 2014-12), p. 476-482
    Details
    In: Neurocritical Care, Springer Science and Business Media LLC, Vol. 21, No. 3 ( 2014-12), p. 476-482
    Type of Medium: Online Resource
    ISSN: 1541-6933 , 1556-0961
    URL: Article
    DOI: 10.1007/s12028-014-9974-y
    Language: English
    Publisher: Springer Science and Business Media LLC
    Publication Date: 2014
    detail.hit.zdb_id: 2176033-0
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  • 9
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    Interrater Reliability of Expert Electroencephalographers Identifying Seizures and Rhythmic and Periodic Patterns in EEGs
    Ovid Technologies (Wolters Kluwer Health) ; 2023
    In:  Neurology Vol. 100, No. 17 ( 2023-04-25), p. e1737-e1749
    Details
    In: Neurology, Ovid Technologies (Wolters Kluwer Health), Vol. 100, No. 17 ( 2023-04-25), p. e1737-e1749
    Abstract: The validity of brain monitoring using electroencephalography (EEG), particularly to guide care in patients with acute or critical illness, requires that experts can reliably identify seizures and other potentially harmful rhythmic and periodic brain activity, collectively referred to as “ictal-interictal-injury continuum” (IIIC). Previous interrater reliability (IRR) studies are limited by small samples and selection bias. This study was conducted to assess the reliability of experts in identifying IIIC. Methods This prospective analysis included 30 experts with subspecialty clinical neurophysiology training from 18 institutions. Experts independently scored varying numbers of ten-second EEG segments as “seizure (SZ),” “lateralized periodic discharges (LPDs),” “generalized periodic discharges (GPDs),” “lateralized rhythmic delta activity (LRDA),” “generalized rhythmic delta activity (GRDA),” or “other.” EEGs were performed for clinical indications at Massachusetts General Hospital between 2006 and 2020. Primary outcome measures were pairwise IRR (average percent agreement [PA] between pairs of experts) and majority IRR (average PA with group consensus) for each class and beyond chance agreement (κ). Secondary outcomes were calibration of expert scoring to group consensus, and latent trait analysis to investigate contributions of bias and noise to scoring variability. Results Among 2,711 EEGs, 49% were from women, and the median (IQR) age was 55 (41) years. In total, experts scored 50,697 EEG segments; the median [range] number scored by each expert was 6,287.5 [1,002, 45,267] . Overall pairwise IRR was moderate (PA 52%, κ 42%), and majority IRR was substantial (PA 65%, κ 61%). Noise-bias analysis demonstrated that a single underlying receiver operating curve can account for most variation in experts' false-positive vs true-positive characteristics (median [range] of variance explained ( JOURNAL/neur/04.03/00006114-202304250-00004/inline-formula1/v/2023-08-29T031927Z/r/image-tiff ): 95 [93, 98] %) and for most variation in experts' precision vs sensitivity characteristics ( JOURNAL/neur/04.03/00006114-202304250-00004/inline-formula2/v/2023-08-29T031927Z/r/image-tiff : 75 [59, 89]%). Thus, variation between experts is mostly attributable not to differences in expertise but rather to variation in decision thresholds. Discussion Our results provide precise estimates of expert reliability from a large and diverse sample and a parsimonious theory to explain the origin of disagreements between experts. The results also establish a standard for how well an automated IIIC classifier must perform to match experts. Classification of Evidence This study provides Class II evidence that an independent expert review reliably identifies ictal-interictal injury continuum patterns on EEG compared with expert consensus.
    Type of Medium: Online Resource
    ISSN: 0028-3878 , 1526-632X
    URL: Article
    DOI: 10.1212/WNL.0000000000201670
    RVK:
    XA 10000
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 2023
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  • 10
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    Physiological consequences of abnormal connectivity in a developmental epilepsy
    Wiley ; 2015
    In:  Annals of Neurology Vol. 77, No. 3 ( 2015-03), p. 487-503
    Details
    In: Annals of Neurology, Wiley, Vol. 77, No. 3 ( 2015-03), p. 487-503
    Abstract: Many forms of epilepsy are associated with aberrant neuronal connections, but the relationship between such pathological connectivity and the underlying physiological predisposition to seizures is unclear. We sought to characterize the cortical excitability profile of a developmental form of epilepsy known to have structural and functional connectivity abnormalities. Methods We employed transcranial magnetic stimulation (TMS) with simultaneous electroencephalographic (EEG) recording in 8 patients with epilepsy from periventricular nodular heterotopia and matched healthy controls. We used connectivity imaging findings to guide TMS targeting and compared the evoked responses to single‐pulse stimulation from different cortical regions. Results Heterotopia patients with active epilepsy demonstrated a relatively augmented late cortical response that was greater than that of matched controls. This abnormality was specific to cortical regions with connectivity to subcortical heterotopic gray matter. Topographic mapping of the late response differences showed distributed cortical networks that were not limited to the stimulation site, and source analysis in 1 subject revealed that the generator of abnormal TMS‐evoked activity overlapped with the spike and seizure onset zone. Interpretation Our findings indicate that patients with epilepsy from gray matter heterotopia have altered cortical physiology consistent with hyperexcitability, and that this abnormality is specifically linked to the presence of aberrant connectivity. These results support the idea that TMS‐EEG could be a useful biomarker in epilepsy in gray matter heterotopia, expand our understanding of circuit mechanisms of epileptogenesis, and have potential implications for therapeutic neuromodulation in similar epileptic conditions associated with deep lesions. Ann Neurol 2015;77:487–503
    Type of Medium: Online Resource
    ISSN: 0364-5134 , 1531-8249
    URL: Issue
    URL: Article
    DOI: 10.1002/ana.v77.3
    DOI: 10.1002/ana.24343
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2037912-2
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