Inclusion Criteria:  (ASA) grades I-II who were scheduled for spinal surgeries (intraspinal tumors resection, spondylolisthesis correction, traumatic spinal fractures fixation….etc)  Exclusion Criteria:  Patients aged less than 18 years, or with history of drug abuse, any pulmonary disease, preoperative motor deficit, history of epilepsy, pacemakers and cochlear implants, previous intracranial surgeries or needed to deepen anesthetic plane during surgery