What Causes Hemifacial Spasms?

My husband around 48 yrs old is having hemifacial spasm for last 3 years. It started as eye twitching and gradually the left side upto the lips. He consulted a doctor who prescribed Tegrital 200(morning) and 300(evening), pacetane, atilam, folvite for last 3 yrs. At the starting time with medicine, it was minimize but now from last one month it is continuously twitching. At the time of anger, anxiety or tension it started continuously and sometime it stopped or minimize automatically. The doctor has suggested botox injection but we don t want to go for it. He is also taking medicine like Nebicip-5 for BP. Is our treatment right or anything else u suggested.