For The Last 10 Days Or So My Healthy, Very

For the last 10 days or so my healthy, very athletic and physically fit 16 year old son has had sporadic slurred speech, loss of balance and suddenly using wrong words. I immediately thought drugs or alcohol but have noticed the problem at all times of the day from waking up in the morning to times where he has not been out of my sight for hours. I don't think it is drugs or alcohol. The slurred speech in not every word but often. I had never noticed any of these symptoms before. Could it be a medical condition?