Suggest Medication For Seizure

Helo! I have been taking Keppra XR for approx.15 months, ( 1000 mg/day), when I was hosipitalized for partial seizure. Following numerous tests including a follow- up M.R.I. A reason could not be found for the condition and I have not had another event in over a year. My question is: What dose regiment shoul be followed in order to discontinue the medication safley.