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Assessing Primary Motor Cortex Excitability and Excitability Modulation by Pairing Transcranial Magnetic Stimulation with Electromyography
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The motor-evoked potential threshold evaluated by tractography and electrical stimulation
Kyousuke Kamada1, Tomoki Todo, Takahiro Ota
1Department of Neurosurgery, Faculty of Medicine, The University of Tokyo, Japan. kamady-k@umin.ac.jp
Journal of Neurosurgery
|February 10, 2009
Summary
Diffusion tensor imaging tractography accurately maps corticospinal tract (CST) function. Direct fiber stimulation during surgery validated these DTI-based CST maps, showing reliable anatomical and functional correlation.
Area of Science:
- Neuroscience
- Neurosurgery
- Medical Imaging
Background:
- Diffusion tensor imaging (DTI) is a key neuroimaging technique.
- Tractography visualizes white matter pathways, including the corticospinal tract (CST).
- Validating DTI-based CST mapping in vivo is crucial for surgical planning.
Purpose of the Study:
- To validate the accuracy of DTI-based tractography for illustrating the CST.
- To correlate in vivo tractography with direct electrical stimulation mapping.
- To assess the reliability of DTI for mapping brain white matter connections.
Main Methods:
- Forty patients with brain lesions near the CST underwent surgery.
- Tractography-integrated neuronavigation was used to guide direct fiber stimulation.
- Motor evoked potentials (MEPs) were monitored during cortical and direct fiber stimulation.
Main Results:
- Direct fiber stimulation confirmed that DTI tractography accurately reflects CST function.
- Strong correlations were found between stimulus intensity and distance to the CST.
- A threshold of 1.8 mA was determined for CST electrical excitability.
Conclusions:
- DTI-based tractography is a reliable method for mapping white matter connections.
- Combining tractography with direct stimulation enhances CST identification during surgery.
- These techniques advance understanding of human CNS neural networks and higher brain functions.
