The GABRD 659 G > A polymorphism may play an important role in the susceptibility of JME and LGS and this polymorphism may also increase the duration of postictal period in JME patients but may decrease the duration of seizure in LGS patients.
Considering response to valproic acid, there is no significant difference in familial versus sporadic cases of JME, whereas history of absences and older age at the onset of grandmal seizures, decrease the probability of being excellent responders in this syndrome.