I am sorry to read all of your posts regarding loved ones having seizures.
My Mum is the one with Alzheimers but my husband has seizures as a result of 2x surgeries and treatment for a brain tumour 11 yrs ago.
Absolutley horrendous to witness one, especially a grand mal ( tonic clonic ) seizure.

From over the years I have learnt that any thing wether its from surgery, TIA's, prior strokes, interaction of medications, any physical deformity of the brain can cause a seizure.
Even a resulting infection or UTI, even if on anti seizure meds can cause a seizure.

Initially 11 yrs ago my husband was put on Epilim ( Sodium Valproate).
His dosage was increased every time he had a seizure until he was on the absolute maximum. In 2011 he had not had a seizure or even a partial seizure since 2007, when a bladder infection resulted in a tonic clonic seizure. He was asleep in bed at the time.
His Neurologist decreased his Epilim and added Lamictal ( Lamogatrine) he has not had a seizure since.