It call comes down to watching the patient’s eyes as he/she watches the music video. This comes from Gizmag:
Brain injuries are complicated things and even now not fully understood. Researchers at the NYU Langone Medical Center have completed a study that suggests eye tracking technology may be able to help locate and determine the extent of brain injuries as well as monitor recovery. The key to this method is its simplicity – the required eye tracking analysis can be achieved while patients watch music videos for a few minutes.
Thanks to its relative simplicity, the method can be applied to head trauma or blast injury to assess brain injury quickly. Its potential use in triage marks it as useful, especially given that current techniques often do not pick up some kinds of injury.
Read more here.