What is epilepsy and why it comes? first my husband got this problem(he faint and was unconsious for one time)?

when he was 17 years age after 4 year medication he was well and he did his engineering and MBA too. But now he is 40 and he was suffering from negitive thoughts so went to Dr., and after CT scan we came to know it is epilepsy. Why it has come again could any body suggest a good Dr in Gurgaon for this problem.