Nephew 17 Years Old - Woke Up Yesterday Not Feeling

Nephew 17 years old - woke up yesterday not feeling well. Complaint is brain feels odd - unsteady and difficult to walk. Went ER they did not do a CT scan but did find he was low on potassium and gave him IV- and bag of potassium. He has high b/p but they said his b/p was ok. Vit. B checked said that was ok. They sent him home after begging it just keep him to monitor. Now still having same issue no improvements.