Need help, my mother has severe dizines.

My mother has been experiencing symptoms like - severe dizziness, entire room feels like it's spinning all around, at that time she's unable to even move, head hurts and she even loses balance. Cannot get up at time of such episodes. And these incidents have now in last few months been happening more frequently, every 2-3 weeks , one or two episodes. She also feels ringing in her ears, loss of balance and head spinning. We also visited to an ENT to see if it was maybe an ear problem but the ent said it was fine, instead to ask a neurologist. So please help I am worried about my mother's health , as she is aged I do not want to take any chances. I am afraid it just should not be a tumor. Pls advise what can be the problem, and the solution?