high sodium causing seizures? possible sodium channel gene defect?

My 5 year old son has had epilepsy for 3 years, seizures being controlled by keppra. The only time he's ever had multiple seizures in a day was before he was prescribed keppra.

He had a seizure November 28th 2012, and they increased his keppra dosage to 4.5ml twice daily (was 3.5ml). Then this past saturday he had 3 known seizures, possibly 5 because of postictal effects. He was admitted to the children's hospital because of this and also because his bloodwork showed high sodium.

Has anyone experienced seizures from high sodium? Wondering if we need to look into a sodium channel gene test?