Train-of-four monitoring is routinely performed during spine surgery by stimulation of the ulnar nerve. Furthermore motor evoked potentials (MEPs) are routinely used in intraoperative neuromonitoring to assess the whole motor pathway from the cortical level down to the distal muscle. During anesthesia MEPs are routinely evoked by transcranial electrical stimulation with single or short train stimuli. In clinical practice even though full muscle relaxation of the hand by NMBA can be observed, utilizing the TOF test, remaining muscle tonus can be observed at the paraspinal musculature during spine surgery.