P 13. Intersession reliability of cortical motor maps with navigated transcranial magnetic stimulation

Autor: A. Mante, R. Bathe-Peters, Stephan A. Brandt, A. Althoff, Sein Schmidt, Robert Fleischmann, M. Roennefarth
Rok vydání: 2013
Předmět:
Zdroj: Clinical Neurophysiology. 124:e70-e71
ISSN: 1388-2457
DOI: 10.1016/j.clinph.2013.04.092
Popis: Introduction Navigated transcranial magnetic stimulation (nTMS) is a non-invasive highly effective tool for mapping individual muscle representations in the motor cortex Julkunen et al., 2009 , Picht et al., 2011 . Optical navigation and model based estimates of intracortical target sites and stimulation strength suggest that nTMS should provide spatially more precise cartography than using external landmarks for defining a motor ‘hot-spot’. The remaining outstanding challenges are (a) a high inter-and intra-subject variability of motor evoked potentials (MEP) Schmidt et al., 2009 , Brasil-Neto et al., 1992 , (b) the extent to which anatomical mapping relative to the underlying gyrification is preferable and (c) hemispheric functional asymmetries possibly reflecting functional “lateralization”. These factors are particularly relevant in a clinical context, where typically cartography will be used with single pulses per stimulation location. Further, the definition of a representation “area” is strongly confounded by the variability of “fringe neurons” or overlapping cortical representations (Schieber and Hibbard, 1993) . Objectives The aim was to study the extent to which single pulse cartography can assure reproducible results. In the present analysis we focus on the concept of the “hot-spot”, i.e. point of maximum MEP and Center of Gravity (CoG). Materials and Methods 15 subjects were examined in two sessions by two different researchers. Stimulation was performed using a computer based navigated TMS system with a figure-of-eight-coil (eXimia, Nextim Ltd., Helsinki, Finland). Mapping of the FDI over both hemispheres was performed with perpendicular (fine) and changing (random) coil orientation with an average of 79 (±35.91) stimuli at 110% resting motor threshold. Margins were defined as scalp locations where a stimulus resulted in an MEP (Mortifee et al., 1994) . Results Stimulus location for the FDI-“hot-spot” in the dominant hemisphere showed a high intersession correlation (ICC: 81–87%). In the non-dominant hemisphere the ICC was lower (45–73%). There was no significant difference in ICC using intracortical instead of scalp stimulus location. Weighted “hot-spots” as expressed by the CoG showed a very high intersession reliability (ICC: 84–88%), the side of maximum MEP a rather poor intersession reliability (ICC: 9–72%). Perpendicular mapping was associated with significant higher test–retest correlation than random mapping (ICC for random mapping 22–38%). Conclusion • Stimulus locations (“hot-spots”) in the dominant hemisphere are more precise than in the non-dominant hemisphere. • Intracortical locations are not superior to scalp location for “hot-spot”-measurements. • Weighted “hot-spots” are more precise than maximal MEPs for “hot-spot”-definition and inter-rater reproducible. • Perpendicular mapping is clearly spatially more accurate than random mapping.
Databáze: OpenAIRE
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