Article
Neuronavigated rTMS of bilateral cerebral hand knobs before and after neurosurgical removal of unilateral cerebral tumors distant to the motor cortex
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Authors
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Alexander Hartmann
- Neurochirurgische Klinik und
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Joachim Spreer
- Radiologische Klinik, Kliniken der Stadt Köln Merheim, Universität Witten-Herdecke, Köln
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Friedrich Weber
- Neurochirurgische Klinik und
| Published: | June 2, 2015 |
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Outline
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Objective: To measure possible diaschitic effects of rTMS on hand motor area on electromyographic (EMG) response in tumors distant to the motor area and to evaluate if removal had effects on response.
Method: 18 patients with cerebral tumors underwent 2 rTMS studies. 1-2 days prior to and 5 -11 days post removal. Tumor localization was distant (> 20 mm) or close (< 20 mm) to the motor area. Localisation and extent of brain edema (BE) was determined by MRI (3D, T2). rTMS was performed using a robotic arm guided positioning of the 8-shaped coil. Coil and head were identified by an infrared camera. Position was correlated to the cortical surface by MRI. rTMS reponse was evaluated with EMG recording of latency (LA) and amplitude (AM) by surface electrodes of hand muscles. Magnetic hand knob stimulations (3 for each) for each muscle was done below 2 Tesla. Clinical control of muscle function was done by Movement ABC-2 test, the upper extremity part of NIHSS and the 1/5 paresis test.
Results: Before removal mean LA of all 3 muscles in the healthy hemispheres was 21.7 ms (+2.3, no difference to normal volunteers). Mean LA of the contralateral hand muscles stimulated over the tumor side was 22.5 ms (+ 4.8). AM varied significantly for both repetition of the rTMS intra- and interindividually. Stimulation resulted in EMG responses of more than one muscle. In patients with tumor and/or BE close to or at precentral motor cortex LA was prolonged compared to the contralateral healthy side, even in patients with normal muscle function. Again AM up to 5μV presented with a large variation. There was no correlation of LA and AM to clinical tests. Removal of the tumor did not result in change of the LA of the healthy side. Postoperative rTMS of the tumor-side resulted in shortening of LA only in a few patients with tumors or BE close to the motor cortex. There was no correlation of the change of LA and AM to the change of the clinical tests.
Conclusions: rTMS allows evaluation of the functional capacity of the corticospinal tract. Reliable positioning of the magnetic narrow focus coil is important. It is possible to stimulate the hand knob for singular muscles. However, due to the anatomical precentral superimposing always several muscles are stimulated. Cerebral tumors and surrounding BE have an effect on LA and AM only if they are located close to the hand knob. There is no correlation between changes of weakness and changes of electrophysiological parameters after tumor removal.
