During the sedation protocol, cortical electroencephalographic monitoring with the cortical electrodes will be continuously recording. Other physiologic data obtained clinically (including, but not limited to, vital signs, arterial wave forms, laboratory values, video EEG) will be subject to review and data collection for correlation with occurrence of SD. This data is obtained as part of standard of care and stored in a departmental server in an anonymous fashion. Clinical video EEG will be obtained on the majority of patients (if not all patients) as part of standard multimodal monitoring. This video will be reviewed to look for any external stimuli that might induce cortical spreading depressions.