Analysis Of Somatosensory Evoked Potentials Research Articles

Long Term Prognosis of Severe Traumatic Brain Injured Patients Using Acute Phase Neurophysiology Testing

Abstract INTRODUCTION Prognostic models for severe traumatic brain injury (sTBI) include initial Glasgow Coma Scale (GCS) score, pupillary response, and computerized tomography results in their computations; however, their predictive value is limited by confounding variables contributing to outcome and poor inter-rater reliability. Use of somatosensory evoked potentials (SSEPs) testing in the acute phase may provide additional objective data to improve prognostication in sTBI. METHODS Under an Institutional Review Board-approved protocol, prospective clinical and outcome data were collected from all severe TBI patients (GCS = 8) admitted to UPMC Presbyterian Hospital over a 5-yr period. SSEPs were obtained on post-trauma day 5 in patients who were not following commands. N9, N13, P14, N20, and P30 latencies are measured; central conduction time was defined as the delay between the P14 peak recorded at the C-2 electrode and the N20 peak recorded at the somatosensory cortex. Peak-to-peak amplitudes measured were of N20/P30 using Fz reference. Criterion for pathologic SSEP event was defined as either the reduction of the N20 amplitude below 50% of baseline or the in-crease of latency between P14 and N20 by 10%. SSEPs were graded as bilaterally absent, unilateral absence, bilateral delay > 23 ms, unilateral delay with normal, and bilateral normal latency. Functional outcome was prospectively collected at 12-mo follow-up, and included mortality and neurologic status as assessed by GOS. RESULTS A total of 145 patients were available for analysis. Median GCS was 6 (IQR 2), while median radiographic injury was a Marshall score 3 (IQR 2). Mean age was 38 ± 16 yr. Univariable ordinal logistic regression analysis of SSEP demonstrated significant ordinal prediction of outcome according to GOS; favorable outcome correlated with higher SSEP grading [OR = 1.66, 95% CI (1.29-2.13), P = .001]. A dichotomized model grouping higher/lower SSEP grading significantly predicted favorable/unfavorable outcomes, respectively [OR 4.69, 95% CI (2.36-9.32), P < .001]. CONCLUSION Graded somatosensory evoked potentials performed on postinjury day 5 following severe TBI predicted favorable versus unfavorable outcome at 1-yr post injury.

Time–Frequency Analysis of Somatosensory Evoked Potentials for Intraoperative Spinal Cord Monitoring

To evaluate the potential use of time-frequency analysis and its reliability in intraoperative somatosensory evoked potential (SEP) monitoring. One hundred ninety-one patients undergoing thoracic and/or lumbar spinal surgery were studied retrospectively. The SEP signals were recorded during different stages of surgery. Averaged SEP was analyzed by short-time Fourier transform. The main peak in the time-frequency interpretation of SEP was measured in peak power, peak time, and peak frequency. The variability of these parameters was compared with that of amplitude and latency during different stages of surgery. The reliability of these parameters was also compared in true-positive and false-positive cases. During different surgical stages for the posterior tibial nerve SEP, the intrasubject variability of peak power was found to be more stable than that of amplitude, while the intrasubject variability of peak time did not show any difference compared with that of latency. The peak frequency presented stable during surgery. Moreover, the true-positive SEP case showed that peak power may detect the potential injury earlier than amplitude does. The false-positive outcomes could be reduced by the proposed method. The SEP peak component was found stable and reliable during the different stages of surgery. For clinical application purpose, time-frequency analysis was suggested to be an additional monitoring method besides the conventional amplitude/latency measurement since it provided a more reproducible and prompt response to the potential injury in intraoperative SEP monitoring.

Connectivity Analysis of Somatosensory Evoked Potentials in Patients with Major Depression

Connectivity analysis was used to investigate the processing of intracutaneous stimuli and directed interactions within the pain matrix in patients with major depression (MD) and healthy controls (HCs), by means of frequency selective generalized partial directed coherence (gPDC). Eighteen patients with MD and 18 HCs underwent stimulations consisting of moderately painful intracutaneous electrical stimuli to the right and left middle fingers. Connectivity analysis was based on nine selected EEG electrodes. Stimulus-induced changes of the gPDC in a pre/post stimulus comparison and changes in the connectivity pattern in the post-stimulus condition were found. We could identify network changes correlating to the side stimulated, as well as differences between HCs and MD patients. These data support the suggestion that pain processing in response to noxious stimulation in MD patients is different compared to healthy controls, suggesting aberrant functional connectivity. Generalized partial directed coherence is shown to be a promising method to detect changes in connectivity in both within- and between-subject designs.

触覚刺激を用いた誘発脳波のフラクタル解析

触覚刺激を用いた誘発脳波のフラクタル解析

Analysis of Somatosensory Evoked Potentials by Tactile Board Stimuli Skin

Up to now, the analysis of the event-related potential has been carried out by the averaging method or the frequency analysis method. However, the averaging method is defective in that high-frequency off-phased components tend to cancel each other out and so detailed information may easily be lost. On the other hand, in the frequency analysis, time-axis information may easily be lost. In addition, in the past analysis of data, the amount of fluctuation represented by the 1/f power spectrum has been treated in its entirety as noise. Novertheless, nonlinear phenomena as represented by chaos of fractals indicate the possibility of quantification in numerical analysis. In this paper, the fractal analysis of event-related potential is carried out, and its results are used to examine fluctuational conditions in intellectual activity. In addition, peaks equivalent to N100 or P300 did not show up clearly. This is considered to be because fractal analysis is more suited to the detection of variations in the inducement amount rather than that of peaks.

Analysis of Somatosensory Evoked Potentials by Air-Puff Stimulated Skin

Title: Analysis of Somatosensory Evoked Potentials by Air-Puff Stimulated Skin | Keywords: Tactile sense, Fractal analysis, Potentials | Author: Hideto Ide, Satoki P. Ninomija, Satoshi Suzuki and Mariko F. Funada

Standard Curve and Correlation Analysis of Somatosensory Evoked Potentials

Standard Curve and Correlation Analysis of Somatosensory Evoked Potentials

Review of Acquisition and Analysis of Somatosensory Evoked Potentials

Review of Acquisition and Analysis of Somatosensory Evoked Potentials