Language mapping in healthy volunteers and brain tumor patients with a novel navigated TMS system: evidence of tumor-induced plasticity

Abstract

Objective: This article explores the feasibility of a novel repetitive navigated transcranial magnetic stimulation (rnTMS) system and compares language mapping results obtained by rnTMS in healthy volunteers and brain tumor patients.

Methods: Fifteen right-handed healthy volunteers and 50 right-handed consecutive patients with left-sided gliomas were examined with a picture-naming task combined with time-locked rnTMS (5-10 Hz and 80-120% resting motor threshold) applied over both hemispheres. Induced errors were classified into four psycholinguistic types and assigned to their respective cortical areas according to the coil position during stimulation.

Results: In healthy volunteers, language disturbances were almost exclusively induced in the left hemisphere. In patients errors were more frequent and induced at a comparative rate over both hemispheres. Predominantly dysarthric errors were induced in volunteers, whereas semantic errors were most frequent in the patient group.

Conclusion: The right hemisphere's increased sensitivity to rnTMS suggests reorganization in language representation in brain tumor patients.

Significance: rnTMS is a novel technology for exploring cortical language representation. This study proves the feasibility and safety of rnTMS in patients with brain tumor.

Keywords: Brain tumors; Hemispheric dominance; Language mapping; Language plasticity; Transcranial magnetic stimulation.