**Vignette 2. Functional Magnetic Resonance (fMRI)**

The functional Magnetic Resonance images are based on the changes in the oxygen levels in the blood related to an activity by the subject. It is an indirect measure of brain functionality since the equipment detects changes in signal intensity caused by vascular changes (demand for oxygen supply through the blood). Since the construction of the images depends on the use of complex mathematical algorithms, it is not possible to completely eliminate the noise sources that may occur, causing false positives, that is, activations in some brain region that are not real.


*BMI = body mass index; IV = intravenous; MEG = magnetoencephalography; MSI = magnetic source imaging.\*Motor function <2/5 or baseline naming/reading errors. From: Hervey-Jumper SL, Li J, Lau D, Molinaro AM, Perry DW, Meng L, et al. Awake craniotomy to maximize glioma resection: Methods and technical nuances over a 27-year period. J Neurosurg 2015;123:325–39.*

#### **Table 2.**

*Relative contraindications and solutions for awake craniotomy patients.*

### *Management of Brain Tumors in Eloquent Areas with Awake Patient DOI: http://dx.doi.org/10.5772/intechopen.95584*

In the same way, false positives can occur due to the pathology of the brain tissue itself due to the pathological vasculature.

It is currently one of the most common methods in cognitive neurosciences due to its safety in healthy subjects.

**Figure 5** shows motor paradigm during evaluation of a patient with a supratentorial glioma.

Other functional extension studies such as positron emission tomography (PET) or magnetoencephalography allow planning the procedure but none of them is superior to intraoperative cortical mapping, which is considered the gold standard**.**
