My son for the last 2 weeks has had episode that last only for about a minute but he sometimes falls forward while sitting and then he turns his head to the left about every 10 seconds for a minute and then he stops,,,He seems to be tired after this episode. .I notice that he does it when he is tired....He is a brain cancer survivor and was dx in 2003 ..Any idea what this can be. He is on lamictal among other meds....Any ideas what it cold be....