Introduction: Brain tumors in eloquent areas affect cortical excitability and function, and recent findings suggest they may also produce changes in excitability of the affected hemisphere regardless of location therein. These changes can be directly measured with transcranial magnetic stimulation (TMS) via the motor threshold (MT), where higher MT reflects lower excitation or greater inhibition. We examined children with brain tumor for pathological differences in cortical excitability between the normal and lesion hemispheres via change in motor threshold (DMT). Methods: 39 children (age 4.4 to 17.9 years, 32 right-handed) with newly diagnosed brain tumor (23 temporal, 3 frontal, 7 parietal) underwent motor mapping with TMS prior to surgical resection. 25 patients had left hemisphere tumors (66.7%); 9 had high grade tumors (23.1%). MTs were recorded in terms of TMS machine output (%), with significant ΔMT defined as variance >10%. Results: 22 of 39 patients (56.4%) had significantly different MT in the tumor hemisphere compared to the normal hemisphere. Of these, 10 (45.5%) had increased MT in the tumor hemisphere, while 12 (54.5%) had decreased MT in the tumor hemisphere. Patients with high grade tumor were more likely to have ΔMT (77.8%), and tumor hemisphere MT was more likely to be decreased (85.7%). Half of patients with low grade tumor had ΔMT, and tumor hemisphere MT was slightly more likely to be increased (60%). There was no significant effect of tumor-hemisphere hand dominance on ΔMT; of the 28 patients with hand-dominant tumor hemisphere, 14 (50%) had ΔMT. Conclusion: Pathological cortical excitability changes occur in some but not all children with brain tumor. In children with these pathological changes, tumor hemisphere excitability is sometimes increased and sometimes decreased. Further studies are needed for clarification. Particular attention should be paid to tumor type, grade, and contents, concurrent medications, and length of disease course prior to determination of excitability via TMS.
展开▼
