Inclusion Criteria:  Adult patients who aged 20-70 years with ASA-PS 1-3, diagnosed of ossification of the posterior longitudinal ligament or cervical spondylotic myelopathy intraoperative neurophysiological monitoring.  Exclusion Criteria:  Tolerance or hypersensitivity to benzodiazepine or propofol Dependence or addiction to psychotropic drugs or alcohol Pregnant women, subjects who lack the ability to make decisions and susceptible to voluntary participation decisions