An apparatus for monitoring changes in symptoms of a patient is described. The apparatus includes a display for displaying information to a patient; a processing system configured to output to the display at least one of audio, video or both audio and video stimuli for eliciting a reaction in the patient; an audio and video capture device for capturing audio, video or both audio and video recordings of the patient performing an action as the stimuli is output by the display; a computer vision processor configured to determine from the audio, video or both audio and video recordings, one or more reactions of the patient in response to the stimuli and during a first period of time immediately after presentation of the stimuli to the patient, wherein the first period of time is less than 250 milliseconds.