What Causes Weakness In Legs Of An Epilepsy Patient?

Hi My mother has sudden loss of both legs and falls - with no prior warning. She always hits her head. When she gets up, she feels dizzy, a little confused about how she fell and says she sees black. Currently, my mother has been diagnosed as having: depression, migraines, mild epilepsy. She also has a benign cyst in the brain and does very little physical movement on a daily basis. Doctors have been unable to determine the cause of her falls, but they are getting more frequent. Any advice would be appreciated.