Phase reversal is a technique used in intraoperative neuromonitoring, particularly during surgeries involving the brain or spinal cord. Identifying the central sulcus of the brain by detecting a change in the phase (direction) of electrical activity recorded from electrodes placed on the cortex during electrical stimulation signifies the transition from sensory to motor areas of the brain. In spinal surgeries, phase reversal can help identify specific nerve root functions by observing the change in electrical activity direction. This technique is crucial for accurately mapping the functional areas of the brain or spinal cord, enabling surgeons to preserve critical neurological functions while performing surgery. Phase reversal provides precise guidance for surgical interventions, reducing the risk of postoperative deficits and enhancing patient outcomes.