neonatal seizures

my son was born with seizures. MRI was normal. did not show anything abnormal. spinal fluid showed no infection. metabolic tests came back normal. blood tests were also fine. the only test we did not do is genetic testing which we are planning on doing very soon. he was put on kepra and phenobarbital. his seizures disappears for 3 or four days then they come back. we increase the does and they disappeare for 3 days and they come back. Can you tell me what is the next step. How can we stop the seizure?. until now , we have been to three hospitals. He is now in Cleveland Clinic and still the reason of the seizure is not known. What is the next step?