Could cte affect someone after a severe head injury from being hit by a car (in 1993 @ age 16), and if so, how would one be evaluated for it?

Too soon: It is too soon for the clinical symptoms of CTE to develop. If you are having cognitive impairment make an appointment with a neurologist.

Yes. See Neurologist: CTE is still in evolution as a diagnosis but 20 plus years from a head trauma is plenty of time for it to develop. If you have concerns see a neurologist ,preferably one who specializes in concussions and closed head injuries.

CTE: Any severe brain injury can lead to CTE. Start with neuro cognitive testing and mri. Hope that helps