Article
Intraoperative electrophysiological mapping of pyramidal tract fibers visualized by functional magnetic resonance and diffusion tensor imaging
Intraoperatives elektrophysiologisches Mapping der Pyramidenbahn unterstützt durch präoperative fMRI-und DTI-Bildgebung
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Authors
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A. Gharabaghi
- Klinik für Neurochirurgie, Universitätsklinikum Tübingen
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F. Kunath
- Klinik für Neurochirurgie, Universitätsklinikum Tübingen
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D. Freudenstein
- Klinik für Neurochirurgie, Universitätsklinikum Tübingen
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M. Erb
- Sektion für Experimentelle NMR des ZNS, Abteilung Neuroradiologie, Universitätsklinikum Tübingen
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W. Grodd
- Sektion für Experimentelle NMR des ZNS, Abteilung Neuroradiologie, Universitätsklinikum Tübingen
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M. Tatagiba
- Klinik für Neurochirurgie, Universitätsklinikum Tübingen
| Published: | May 4, 2005 |
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Outline
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Objective
The goal of this study was to use functional magnetic resonance (fMRI) and diffusion tensor imaging (DTI) to track fibers combined with intraoperative electrophysiological mapping to delineate subcortical motor pathways. This information was expected to guide tumor resection and to prevent surgical morbidity.
Methods
Ten patients with different intracranial lesions adjacent to the pyramidal tract received presurgical imaging with fiducial markers for intraoperative image guidance. MR images were acquired on a high-field 3.0 T scanner (Trio, Siemens, Erlangen). For the fMRI examination, EPI sequence. was used to image the whole brain volume in axial rotation. The patients performed motor tasks including repetitive contraction of the lips, flexion and extension of the fingers and toes, respectively.The reference anatomical sequence was a T1-weighted MPRANGE series.The DTI data was acquired with a EPI sequence with axial slices covering the brain from the pons to the vertex. Data sets were reconstructed, motion-corrected and re-aligned using SPM2 (Statistical Parametric Map, London). Fiber tracking was processed using DTiMap (Mori, Baltimore). Co-registration and 3D visualization of structural and functional information was performed with BrainVoyager QX (Brain Innovation, Maastricht). Electrophysiological mapping was performed using a bipolar probe (5mm spaced tip, pulse frequency 60 Hz, single pulse phase duration 1 ms, amplitude 2-15 mA, Ojemann Stimulator, Radionics, Burlington, MA) and multi-channel elektromyographic recording throughout the surgery.
Results
In all patients, the combination of reconstructed and fused fMRI and DTI data provided useful information concerning the topographical tumor interaction with the motor cortex and pyramidal tract. Intraoperative mapping confirmed the preoperative images and detailed the relationships between eloquent sites and tumor boundaries. Subcortical stimulations could be regularly applied along the procedure terminating further resections whenever eliciting motor responses. None of the patients showed additional permanent motor deficits after surgery.
Conclusions
The fusion of fMRI and DTI data is a helpful additional source of information concerning surgery around the descending motor tract. Subcortical electrophysiological mapping is essential in detecting functional pathways in the white matter. Thereby, this technique may serve as a tool to validate preoperative imaging which still remains limited by intraoperative brain shift.
