Abstract
Background
Transcranial magnetic stimulation (TMS) is being used in the pre-operative diagnostics of patients with tumors in or near the motor cortex. Although the main purpose of TMS in such patients is to map the functional areas of the motor cortex in spatial relation to the tumor, TMS also provides some numerical neurophysiological measurements of the functional status of the patient’s motor system. The aim of this paper is to provide reference values for these neurophysiological measurements from a large and varied clinical sample.
Methods
TMS was used in the pre-operative work-up of patients with various types of tumors in or near the motor cortex during a 3-year period. Data was collected prospectively in 100 patients, yet this is a post hoc report.
Results
Patient characteristics had no influence on the neurophysiological parameters. The response latency time was almost never different in the tumorous versus healthy hemisphere, so clinicians should be suspicious if they find interhemispheric differences for latency. A high interhemispheric ratio of resting motor threshold (RMT) or a low interhemispheric ratio of motor evoked potential (MEP) amplitude appear to suggest immanent deterioration of the patient’s motor status.
Conclusion
In addition to topographic cortical mapping, TMS also serves as a neurophysiological assessment of the functional status of the patient’s motor system. The results presented here provide clinicians with a set of reference values to contextualize findings in their own tumor patients. Further research is still needed to better understand the full clinical relevance of these neurophysiological parameters.
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Acknowledgments
This research was supported in part by a grant from the Berliner Krebsgesellschaft to Thomas Picht. We would like to thank Adela Castelló, MPH, MSc, and Michael Hanna, PhD, (both from Mercury Medical Research & Writing) for providing publication consulting (MH), statistical advising & analysis (AC, MH), and medical writing services (MH).
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Thomas Picht and Valerie Strack contributed equally to this paper.
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Picht, T., Strack, V., Schulz, J. et al. Assessing the functional status of the motor system in brain tumor patients using transcranial magnetic stimulation. Acta Neurochir 154, 2075–2081 (2012). https://doi.org/10.1007/s00701-012-1494-y
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DOI: https://doi.org/10.1007/s00701-012-1494-y