Seizure type symptoms and conditions

My 6 year old son has had all of these more or less. He has been on Singulair for about 5 months. We took him off last Friday when he started having seizures. It is only now that we are connecting the things he has complained about. He is still going through testing but everytime a test is done it is negative. He is in perfect health. The dr.s are stumped. What happens is, he smells a wierd smell. Then he sees lights. After this he has a bad headache and becomes weak so he lays down. Shortly thereafter he stiffens and starts shaking his arms and legs while clinching his hands. He also grunts and makes a buzzing sound and appears as though he only breathes out. the dr.s say it is not seizures but movement disorder and if it is Singulair it should be out of his system within 3 days... He is still having the seizure type fits and its been a week since we took him off singulair. He is still losing his temper and having horrible dreams as well. Cat scan was normal, EEG was normal, blood work is ok, they want to do an MRI but does this sound familiar to anyone?