High resolution passive speech mapping in dominant hemisphere glioma surgery

Background. Intraoperative brain mapping is one of the most critical stages of neurosurgical intervention in the eloquent area of the cerebral cortex. Traditionally direct cortical electrical stimulation is used for these purposes, but it can lead to seizures and loss of consciousness that makes it impossible to continue the procedure. Moreover, it significantly changes the surgery plan, especially in case of speech mapping during awake craniotomy. The study objective is to create a setup for intraoperative eloquent cortical areas passive mapping, and to compare informativity and safety of passive and active speech mapping. Materials and methods. We have created and tested a mobile device for high-resolution mapping of the Broca’s area that uses the analysis of the desynchronization processes in high-gamma oscillations in 64 micro-contact grid electrode for electrocorticography during awake craniotomy when patient pronounces the objects and actions. Results. We found precise coincidence for localization of the Broca’s area, determined by analyzing of bioelectric signal obtained from the electrocorticography and cortical mapping performed by bipolar direct cortical stimulation using Penfield method. Conclusion. The passive cortical speech mapping expands the potentialities of neurosurgical operations in the eloquent area of the brain and can increase the number of patients for whom this study is achievable. Further studies needed to evolve algorithms and sets of stimuli to expand the list of functional zones that can be mapped passively.