The present disclosure provides methods, systems, and instruments for the determination by a physician or medical professional whether a subject is experiencing or has recently experienced an overt HE episode and for grading overt HE episodes as well as methods, systems, instruments and tools for screening for overt HE episodes by a non-medical professional such as a caregiver. Also provided are methods of treating HE episodes and methods of monitoring HE episode treatment that incorporate these methods, systems, instruments, and tools.