What Causes Seizure And Dizzy Spells?

Here is my question.. My wife's brother had a seizure about a month back, they never were able to tell why he had a seizure he was going under for mouth work when it happen so they said it might of been from the meds they were using. Well today she had to go pick him up from school sick he is dizzy keeps falling into stuff.. Also is eyes look really weird from what she was explaining kind of not looking all there from his eyes.