**3.2. Intraoperative monitoring**

Monitoring consists of the surveillance of the functional state(s)/structure(s) that is(are) being monitored for all or most of the surgical action, given the risk of iatrogenic injury [9].

Therefore, the duration of monitoring is considerably greater than in the case of mapping, and it usually lasts as long as the surgery itself. This condition naturally requires more dramatic changes than those used for mapping, beyond the modification of anaesthesia.

The objectives in this case are not just the functional identification but also the preservation of functional integrity, which can be compromised by many medical/surgical procedures, ranging from problems related to tissue perfusion (for example, by actively inducing hypo‐ tension or bleeding) to inadvertent surgical injuries such as the placement of spatulas.

In general, neurophysiological monitoring is widely employed in oncological or vascular neurosurgery.
