7 year old with abnormal EEG but not classic for absence seizure

My son had an abnormal EEG in September after the teacher felt he was "spacing out".  The EEG overall was abnormal but not classic for absence seizure (something about a 3/second spike?).  I don't have a copy of the report but the abnormal activity occurred in the left parietal area from what I was told.  After meeting with a pediatric neurologist to discuss the results, they said they could not rule out seizures but it was unlikely (not classic signs).  They recommended a 24 hour in patient hospital stay with continuous video EEG to be certain and they also offered MRI.  Since they leaned away from the seizure possibility, I opted for an MRI instead first.  He was sedated yesterday and had the MRI but I am on pins and needles waiting for results.  He also suffers from frequent headaches-and some of them are possibly migraine level (my husband and I as well as our other two children have all had migraine history).  His vision and hearing have been tested and are normal.  He has inattention issues and we have tried stimulant medications a year ago, but they did not help and he lost too much weight so we discontinued.  What are the possibilities of an abnormal EEG if its not seizure disorder?  And what can the MRI diagnose?