Neurosurgical resection of brain tumors presents a dilemma. While likelihood of reduction/delay or even elimination of tumor recurrence tends to improve with the increasing extent of resection, the immediate post-operative deficits will present in the case of disruption of viable tissue at or beyond the tumor margin. So the surgeon faces the question of how to maximize resection volume while minimizing impact on viable (and especially, eloquent, cortex). Generally, the term "eloquent" refers to those regions of cortex with particular functional specialization to subserve the neural processes underlying motor and language functions.Thus, presurgical mapping of brain function is especially critical to guide the surgical procedure with the goal of direct impact on short term (minimizing deficit) and long term (minimizing recurrence) outcome. Over the past two decades functional MRI has emerged as the primary technique to achieve such goals. That said, other pre-operative approaches may be complementary or even preferable in certain circumstances. These include magnetoencephalography (MEG) and transcranial magnetic stimulation (TMS).

This presentation will review the technique of fMRI and its applications, as well as practical considerations for performing successful fMRI in the pediatric population.

It will then delve into limitations of fMRI, especially consideration of neurovascular uncoupling and the potential for "false negative" findings.

It will address the potential for cortical reorganization, especially in pediatric brain, but also noting the possibility of "false positive" findings, common in the overzealous pursuit of evidence for cortical plasticity.

It will present the role of fMRI both in an integrated MRI examination, and in relation to MEG and TMS