Article
Phase asynchrony of motor evoked potentials in brain tumour patients
Gestörte Phasensynchronisierung bei motorisch-evozierten Potentialen von Hirntumorpatienten
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Authors
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Kathrin Machetanz
- University of Tübingen, Department of Neurosurgery, Tübingen, Deutschland
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Alberto L. Galotti
- Vita-Salute University, Department of Neurosurgery and Stereotactic Radiosurgery, Mailand, Italien
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Maria T. Leao Tatagiba
- University of Tübingen, Department of Neurosurgery, Tübingen, Deutschland
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Marina Liebsch
- University of Tübingen, Department of Neurosurgery, Tübingen, Deutschland
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Leonidas Trakolis
- University of Tübingen, Department of Neurosurgery, Tübingen, Deutschland
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Sophie Wang
- University of Tübingen, Department of Neurosurgery, Tübingen, Deutschland
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Alireza Gharabaghi
- University of Tübingen, Department of Neurosurgery, Tübingen, Deutschland
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Marcos Tatagiba
- University of Tübingen, Department of Neurosurgery, Tübingen, Deutschland
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Georgios Naros
- University of Tübingen, Department of Neurosurgery, Tübingen, Deutschland
| Published: | June 4, 2021 |
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Outline
Text
Objective: Motor-evoked potentials (MEPs) after navigated transcranial magnetic stimulation (nTMS) are mirroring the status of the complete human motor system, far beyond corticospinal integrity. Classic time domain features of MEPs (e.g. peak-to-peak amplitudes and onset latencies) exert a high inter-subject and intra-subject variability. Frequency domain analysis might help to resolve or quantify disease-related MEP changes, e.g. in brain tumor patients. The aim of the present study was to describe the time-frequency representation of MEPs in brain tumor patients, its relation to clinical and imaging findings and the differences to healthy subject.
Methods: This prospective study enrolled 12 healthy subjects and 29 consecutive brain tumor patients (with and without an apparent paresis) who underwent a nTMS mapping. Resulting MEPs were evaluated in the time series domain (i.e., amplitudes and latencies). After transformation to the frequency domain using a Morlet wavelet approach, event-related spectral perturbation (ERSP) and inter-trial coherence (ITC) were calculated and compared to results of the diffusion tensor imaging (DTI).
Results: MEPs were projecting to a frequency band between 30 and 300 Hz with a local maximum around 100 Hz for both healthy subjects and patients. Despite no significant differences in the standard time series characteristics, there was ERSP reduction for higher frequencies (>100 Hz) in patients in contrast to healthy subjects. This deceleration of the MEPs was mirrored in an increase of the inter-peak MEP latencies. Patients with an apparent paresis showed an additional disturbance in ITC in these frequencies. There was no correlation between the CST integrity (as measured by DTI) and the MEP parameters.
Conclusion: The present study demonstrates how time-frequency analysis could provide additional information about the MEP and the status of the corticospinal system in brain tumor patients. This first evaluation indicates that brain tumors might affect cortical physiology and the responsiveness of the cortex to TMS resulting in a temporal dispersion of the corticospinal transmission.
