What Causes Zero Sperm Motility While On Medication For Epilepsy?

Doctor , My husband has Epilepsy problem from last two years , earlier the seizures were very frequent but now from last March to till date he got one fit that too very mild,, but now his memory is very weak, secondly we were married from last 6 yrs, planning for baby, today only we have checked the his semen analysis report , motility is almost zero,,, is this the side effect of this medicine, kindly advice