Modern treatment of brain arteriovenous malformations using preoperative planning based on navigated transcranial magnetic stimulation: a revisitation of the concept of eloquence

BACKGROUND: Navigated transcranial magnetic stimulation (nTMS) provides a reliable identification of "eloquent" cortical brain areas. Moreover, it can be used for diffusion tensor imaging fiber tracking of eloquent subcortical tracts. We describe the use of nTMS-based cortical mapping and diffusion tensor imaging fiber tracking for defining the "eloquence" of areas surrounding brain arteriovenous malformations (BAVMs), aiming to improve patient stratification and treatment. METHODS: We collected data of BAVMs suspected to be in eloquent areas treated between 2017 and 2019, and submitted to nTMS-based reconstruction of motor, language, and visual pathways for the definition of the eloquence of the surrounding brain areas. We describe the nTMS-based approach and analyze its impact on patient stratification and allocation to treatment in comparison with the standard assessment of eloquence based on anatomical landmarks. RESULTS: Ten patients were included in the study. Preliminarily, 9 BAVMs were suspected to be located in an eloquent area. After nTMS-based mapping, only 5 BAVMs were confirmed to he close to eloquent structures, thus leading to a change of the score for eloquence and of the final BAVMs grading in 60% of patients. Treatment was customized according to nTMS information, and no cases of neurological worsening were observed. Radiological obliteration was complete in 7 cases microsurgically treated, and accounted for about 70% in the remaining 3 patients 1 year after radiosurgical treatment. CONCLUSIONS: The nTMS-based information allows an accurate stratification and allocation of patients with BAVMs to the most effective treatment according to a modern, customized, neurophysiological identification of the adjacent eloquent brain networks.