P72. Impairment of non-invasive language mapping by lesion location a fMRI, rTMS, and DCS study

Abstract

Objective Language mapping by repetitive navigated transcranial magnetic stimulation (rTMS) is in-creasingly used and already replaces functional magnetic resonance imaging (fMRI) in some institutions for preoperative mapping of neurosurgical patients. However, some factors affect the concordance of both methods with the gold standard direct cortical stimulation (DCS). We therefore analyze the impairment of rTMS and fMRI by intraparenchymal lesions as compared to the results of DCS during awake surgery. Methods We performed language mapping in 27 patients with left-sided perisylvian lesions by DCS, rTMS, and fMRI using an object-naming task, and assigned the obtained language eloquent sites of each method to Corina’s cortical parcellation system (CPS). Subsequently, we calculated the receiver operating characteristics for rTMS and fMRI compared to DCS, and analyzed different subgroups with (W) and with-out (WO) lesion in the mapped areas. Results Within the W subgroup we revealed an overall sensitivity of 100% (WO: 100%), a specificity of 8% (WO: 5%), a PPV of 34% (WO: 53%), and a NPV of 100% (WO: 100%) for the comparison of rTMS with DCS. For the comparison of fMRI with DCS within the W subgroup we obtained an overall sensitivity of 32% (WO: 62%), a specificity of 88% (WO: 60%), a PPV of 56% (WO: 62%), and a NPV of 73% (WO: 60%). Conclusion With this study we were able to show that rTMS is less affected by a brain lesion than fMRI, particularly when performing mapping of language-negative cortical regions based on sensitivity and NPV. With this in mind, rTMS could be useful for the language mapping assessment prior to the gold standard DCS.