Impairing Language Comprehension by Non-invasive Inhibition of the Inferior Frontal Gyrus in Brain Tumor Patients

Introduction: Language-eloquent brain tumors may induce functional reorganization. Traditionally, temporal areas were thought to be responsible for language comprehension. Nowadays, a more complex comprehension network is assumed. It is still unknown, however, which areas take over receptive language function if tumors impair language comprehension. Thus, we examined the relationship of receptive aphasia and the involvement of cortical left-hemispheric language sites during comprehension-based language mapping with navigated transcranial magnetic stimulation (nTMS).

Methods: Left-hemispheric nTMS-based language comprehension mapping was conducted in 15 glioma patients and 2 patients with metastasis (age=53.2 ± 15.7yrs, 7 female). Baseline performance during an auditory single-word comprehension task prior to stimulation determined the extent of comprehension deficit. Stimulation-induced comprehension disruptions per applied stimulations of cortical sites were documented as error rates. Correlational analyses between extent of receptive aphasia and stimulation-induced errors in language-eloquent cortical sites were performed.

Results: Extent of aphasia (baseline error rate=0.2 ± 0.2) correlated with higher error rates in pars opercularis (opIFG) and triangularis (trIFG) of left inferior frontal gyrus (both r=0.6, p=0.01). No significant association between aphasia and error rates in middle and posterior superior temporal, posterior middle temporal, angular, posterior and anterior supramarginal gyrus were substantiated (all r≤0.5, p>0.05).

Conclusion : Present results provide further evidence for higher involvement of opIFG and trIFG during language comprehension in brain tumor patients with poorer language comprehension skills. Whether this recruitment promotes language comprehension deficits or reflects compensational adaption processes and, moreover, which role the subcortical language network and other cortical language sites play, require further investigation.