Limits...
Improved characterization of visual evoked potentials in multiple sclerosis by topographic analysis.

Hardmeier M, Hatz F, Naegelin Y, Hight D, Schindler C, Kappos L, Seeck M, Michel CM, Fuhr P - Brain Topogr (2013)

Bottom Line: TVEP was compared to conventional analysis (cVEP) with respect to reliability in HC, validity using descriptors of logistic regression models, and sensitivity derived from receiver operating characteristics curves.HC) and hON were more favorable using tVEP- versus cVEP-predictors.In combination with other EP modalities, tVEP may improve the monitoring of disease course in MS.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Hospital of the University of Basel, Petersgraben 4, 4031, Basel, Switzerland, martin.hardmeier@usb.ch.

ABSTRACT
In multiple sclerosis (MS), the combination of visual, somatosensory and motor evoked potentials (EP) has been shown to be highly correlated with the Expanded Disability Severity Scale (EDSS) and to predict the disease course. In the present study, we explored whether the significance of the visual EP (VEP) can be improved with multichannel recordings (204 electrodes) and topographic analysis (tVEP). VEPs were analyzed in 83 MS patients (median EDSS 2.0; 52 % with history of optic neuritis; hON) and 47 healthy controls (HC). TVEP components were automatically defined on the basis of spatial similarity between the scalp potential fields (topographic maps) of single subjects' VEPs and reference maps generated from HC. Non-ambiguous measures of latency, amplitude and configuration were derived from the maps reflecting the P100 component. TVEP was compared to conventional analysis (cVEP) with respect to reliability in HC, validity using descriptors of logistic regression models, and sensitivity derived from receiver operating characteristics curves. In tVEP, reliability tended to be higher for measurement of amplitude (p = 0.06). Regression models on diagnosis (MS vs. HC) and hON were more favorable using tVEP- versus cVEP-predictors. Sensitivity was increased in tVEP versus cVEP: 72 % versus 60 % for diagnosis, and 88 % versus 77 % for hON. The advantage of tVEP was most pronounced in pathological VEPs, in which cVEPs were often ambiguous. TVEP is a reliable, valid, and sensitive method of objectively quantifying pathological VEP in particular. In combination with other EP modalities, tVEP may improve the monitoring of disease course in MS.

Show MeSH

Related in: MedlinePlus

Topographic analysis I: generation of reference maps from healthy controls. a Conventional VEP (Oz–Fpz-electrode pair) from the grand mean VEP of all healthy controls. b Butterfly plot of the grand mean VEP of all healthy controls derived from 204 electrodes (average reference). c Grand mean VEP represented as a time series of topographic maps derived from the butterfly plot: time periods of quasi-stable topographies (“functional microstate”) are flagged by parentheses (for display, each five single topographic maps (=5 ms) are averaged). d Reference maps of single EP-components; from left to right, the “N75/N145”-, “P100”- and “P240”-maps are displayed and color-coded. Reference maps are the average of a group of topographic maps with high spatial similarity; N75 and N145 are represented as one reference map because of their overlapping spatial distribution of the electric potential on the scalp. e Butterfly plot as in (b) with additional color-coding according to the presence of a component during the time course of the EP, determined by the magnitude of spatial similarity of single topographic maps with one of the reference maps (fitting procedure, see text) (Color figure online)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection


getmorefigures.php?uid=PMC3921459&req=5

Fig1: Topographic analysis I: generation of reference maps from healthy controls. a Conventional VEP (Oz–Fpz-electrode pair) from the grand mean VEP of all healthy controls. b Butterfly plot of the grand mean VEP of all healthy controls derived from 204 electrodes (average reference). c Grand mean VEP represented as a time series of topographic maps derived from the butterfly plot: time periods of quasi-stable topographies (“functional microstate”) are flagged by parentheses (for display, each five single topographic maps (=5 ms) are averaged). d Reference maps of single EP-components; from left to right, the “N75/N145”-, “P100”- and “P240”-maps are displayed and color-coded. Reference maps are the average of a group of topographic maps with high spatial similarity; N75 and N145 are represented as one reference map because of their overlapping spatial distribution of the electric potential on the scalp. e Butterfly plot as in (b) with additional color-coding according to the presence of a component during the time course of the EP, determined by the magnitude of spatial similarity of single topographic maps with one of the reference maps (fitting procedure, see text) (Color figure online)

Mentions: In contrast to conventional analysis, in which the difference between the electric potentials at two electrodes is measured, topographic analysis relies on the distribution of the electric potential at the scalp (i.e. the topographic map) recorded from a multichannel electrode array. Instead of a voltage time series that forms a waveform for each electrode (Fig. 1a, b), the VEP is represented as a time series of topographic maps, as shown in Fig. 1c for the grand mean VEP of all healthy controls. The time series is characterized by time periods in which topographic maps have a stable and distinct distribution of the electric potential which varies only in intensity. These periods have been called functional microstates (Lehmann and Skrandies 1984; Brandeis and Lehmann 1986; Michel et al. 2001; Murray et al. 2008). Each microstate typically covers the period of a peak in the evoked potential waveform, i.e. what is traditionally called an evoked potential component.Fig. 1


Improved characterization of visual evoked potentials in multiple sclerosis by topographic analysis.

Hardmeier M, Hatz F, Naegelin Y, Hight D, Schindler C, Kappos L, Seeck M, Michel CM, Fuhr P - Brain Topogr (2013)

Topographic analysis I: generation of reference maps from healthy controls. a Conventional VEP (Oz–Fpz-electrode pair) from the grand mean VEP of all healthy controls. b Butterfly plot of the grand mean VEP of all healthy controls derived from 204 electrodes (average reference). c Grand mean VEP represented as a time series of topographic maps derived from the butterfly plot: time periods of quasi-stable topographies (“functional microstate”) are flagged by parentheses (for display, each five single topographic maps (=5 ms) are averaged). d Reference maps of single EP-components; from left to right, the “N75/N145”-, “P100”- and “P240”-maps are displayed and color-coded. Reference maps are the average of a group of topographic maps with high spatial similarity; N75 and N145 are represented as one reference map because of their overlapping spatial distribution of the electric potential on the scalp. e Butterfly plot as in (b) with additional color-coding according to the presence of a component during the time course of the EP, determined by the magnitude of spatial similarity of single topographic maps with one of the reference maps (fitting procedure, see text) (Color figure online)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3921459&req=5

Fig1: Topographic analysis I: generation of reference maps from healthy controls. a Conventional VEP (Oz–Fpz-electrode pair) from the grand mean VEP of all healthy controls. b Butterfly plot of the grand mean VEP of all healthy controls derived from 204 electrodes (average reference). c Grand mean VEP represented as a time series of topographic maps derived from the butterfly plot: time periods of quasi-stable topographies (“functional microstate”) are flagged by parentheses (for display, each five single topographic maps (=5 ms) are averaged). d Reference maps of single EP-components; from left to right, the “N75/N145”-, “P100”- and “P240”-maps are displayed and color-coded. Reference maps are the average of a group of topographic maps with high spatial similarity; N75 and N145 are represented as one reference map because of their overlapping spatial distribution of the electric potential on the scalp. e Butterfly plot as in (b) with additional color-coding according to the presence of a component during the time course of the EP, determined by the magnitude of spatial similarity of single topographic maps with one of the reference maps (fitting procedure, see text) (Color figure online)
Mentions: In contrast to conventional analysis, in which the difference between the electric potentials at two electrodes is measured, topographic analysis relies on the distribution of the electric potential at the scalp (i.e. the topographic map) recorded from a multichannel electrode array. Instead of a voltage time series that forms a waveform for each electrode (Fig. 1a, b), the VEP is represented as a time series of topographic maps, as shown in Fig. 1c for the grand mean VEP of all healthy controls. The time series is characterized by time periods in which topographic maps have a stable and distinct distribution of the electric potential which varies only in intensity. These periods have been called functional microstates (Lehmann and Skrandies 1984; Brandeis and Lehmann 1986; Michel et al. 2001; Murray et al. 2008). Each microstate typically covers the period of a peak in the evoked potential waveform, i.e. what is traditionally called an evoked potential component.Fig. 1

Bottom Line: TVEP was compared to conventional analysis (cVEP) with respect to reliability in HC, validity using descriptors of logistic regression models, and sensitivity derived from receiver operating characteristics curves.HC) and hON were more favorable using tVEP- versus cVEP-predictors.In combination with other EP modalities, tVEP may improve the monitoring of disease course in MS.

View Article: PubMed Central - PubMed

Affiliation: Department of Neurology, Hospital of the University of Basel, Petersgraben 4, 4031, Basel, Switzerland, martin.hardmeier@usb.ch.

ABSTRACT
In multiple sclerosis (MS), the combination of visual, somatosensory and motor evoked potentials (EP) has been shown to be highly correlated with the Expanded Disability Severity Scale (EDSS) and to predict the disease course. In the present study, we explored whether the significance of the visual EP (VEP) can be improved with multichannel recordings (204 electrodes) and topographic analysis (tVEP). VEPs were analyzed in 83 MS patients (median EDSS 2.0; 52 % with history of optic neuritis; hON) and 47 healthy controls (HC). TVEP components were automatically defined on the basis of spatial similarity between the scalp potential fields (topographic maps) of single subjects' VEPs and reference maps generated from HC. Non-ambiguous measures of latency, amplitude and configuration were derived from the maps reflecting the P100 component. TVEP was compared to conventional analysis (cVEP) with respect to reliability in HC, validity using descriptors of logistic regression models, and sensitivity derived from receiver operating characteristics curves. In tVEP, reliability tended to be higher for measurement of amplitude (p = 0.06). Regression models on diagnosis (MS vs. HC) and hON were more favorable using tVEP- versus cVEP-predictors. Sensitivity was increased in tVEP versus cVEP: 72 % versus 60 % for diagnosis, and 88 % versus 77 % for hON. The advantage of tVEP was most pronounced in pathological VEPs, in which cVEPs were often ambiguous. TVEP is a reliable, valid, and sensitive method of objectively quantifying pathological VEP in particular. In combination with other EP modalities, tVEP may improve the monitoring of disease course in MS.

Show MeSH
Related in: MedlinePlus