What Causes Weakness, Difficulty With Balance And Blurred Vision?

I am enquiring about my mam who is having difficulty with balance and falling a lot. She has weakness along left side and legs very weak. She has had a ct scan which was clear and then an mri of head and spine with lumbar puncture also as signs wrre pointing to multiple sclerosis but these were all clear. Also she is havin blurred and double vision, headaches and general tiredness. The symptoms also seem to get worse as day progresses. Please help