Electroencephalography / Brain Death / Humans / Ultrasonography / INTENSIVE CARE / Oscillations / Meta Analysis / Systematic review / Clinical Sciences / Transcranial Doppler / Public health systems and services research / Intensive Care Medicine / Flow Pattern / Sensitivity and Specificity / Brain Damage / Oscillations / Meta Analysis / Systematic review / Clinical Sciences / Transcranial Doppler / Public health systems and services research / Intensive Care Medicine / Flow Pattern / Sensitivity and Specificity / Brain Damage